Jobs for the
buoys The impact of impacts
Where is North?
Tracking our ancestors
The carbon age
Planet Earth Autumn 2010
FEATURES 10 The impact of impacts Could sulphide deposits help find life on Mars?
30 Mysteries of the blue ocean Not a watery desert after all.
12 Current thinking
32 Website rocks Geology for the people.
Fine-tuning ocean observations.
14 Agave – biofuel of the future? New energy crops for arid climates. 16 Where is North? Tracking the shifts in the Earth’s magnetic field. 18 Reading nature’s barcode River sediments and climate history. 20 The carbon age How a new, portable sensor is shedding light
on the carbon cycle.
22 COVER STORY Jobs for the buoys New tools to monitor the English Channel. 24 Tracking our ancestors Fossil footprints reveal how we evolved. 26 Hot off the press Hands-on geologists make miniature planets. 28 When politics and science come face to face From Ethiopian volcanoes to Westminster.
NERC scientists: we want to hear from you Planet Earth is always looking for interesting NERC-funded science for articles and news stories. If you want to see your research in the magazine, contact the editors to discuss. Please don’t send in unsolicited articles as we can’t promise to publish them. We look forward to hearing from you. Planet Earth is the quarterly magazine of the Natural Environment Research Council. It aims to interest a broad readership in the work of NERC. It describes new research programmes, work in progress and completed projects funded by NERC or carried out by NERC staff. Some of this work may not yet have been peer-reviewed. The views expressed in the articles are those of the authors and not necessarily those of NERC unless explicitly stated. Let us know what you think about Planet Earth. Contact the editors for details.
Front cover: Autonomous buoy, see page 22.
Editors: Adele Rackley, 01793 411604, email@example.com Tom Marshall, 01793 442593, firstname.lastname@example.org
Science writer: Tamera Jones, 01793 411561, email@example.com Design and production: Candy Sorrell, firstname.lastname@example.org Available as an e-magazine at: www.nerc.ac.uk/publications/planetearth/
THE CONSEQUENCES OF CLIMATEGATE
The consequences of
he reviews of the Climategate affair, which centred on emails taken from the University of East Anglia’s Climate Research Unit (CRU), have submitted their findings, and enough time has passed that we can reflect on these events and what we should learn from them. It’s worth pointing out that all three inquiries have exonerated CRU researchers of any serious misconduct. There were problems with working practices at the CRU, but its scientists’ professional integrity was fully confirmed and the inquiries found no evidence of research being manipulated to support the idea that human activities are changing the climate. It’s clear that the supposed scandal got much more attention from the media than the conclusions of the independent reviews. Some members of the public who haven’t followed the story closely may have been left with the impression of serious wrongdoing where there was none. There is no doubt the affair has reduced public trust in climate science and climate scientists. It’s important that scientists regain this trust. In part this will involve trying harder to communicate what we do more clearly. But we also need to be more willing to engage in debate with critics, and to demand that the so-called sceptics make it clear what credible, published evidence they have to back up their assertions – usually there is little or none. Too often, researchers have left the sceptics’ claims unchallenged, and this has made it seem that there is genuine doubt over whether or not the climate is changing, and that scientists have no answers to the charges made against them.
Some of these reflect misconceptions about what science is like. Research involves a huge amount of challenge from peers; it is not a cosy club – more like a bear pit. The climate scientists themselves are sceptics. By contrast, many self-proclaimed sceptics seem willing to accept anything they read that downplays the evidence of human-induced climate change or casts climate science in a bad light, no matter how thin the evidence for it is. The fact that this material nevertheless gets spread so widely is largely due to the vast number of blogs and other websites now covering the subject. We know the blogosphere will continue to exist and be influential, and in many ways this surge of interest in climate science is a healthy development. But not all claims are equally credible. Without professional quality control we can have no basis for establishing new knowledge – and, yes, professional here means other trained scientists. Some people have challenged the principle of peer review, in which new research is evaluated by other scientists with expertise in the same field. They argue it leads to group-think and the suppression of dissenting views. But the peer-review process is at the heart of how we test the credibility of new science. It is also central to how research councils decide what to fund. Without it, society has no way of telling good science from bad. The problem, again, is trust – people have to be confident in the scientists doing the peer reviewing. One way of rebuilding this trust is for researchers to do more to engage the public with their work.
Alan Thorpe Chief Executive, NERC
Taxpayers pay for most of the science NERC funds, so they have a stake in the results and we have a duty to communicate the science in an accessible way at all stages in the process. Scientific data should be openly available, after the researchers have had a reasonable period – normally two years from the end of data collection – in which to examine their results and draw inferences. NERC runs several data centres
ensuing media debate. For example, it was not emphasised that the CRU data is only a small part of climate science, albeit an important one, and that no mistakes had been found in the published work based on it. This made it easy for the opponents of global warming to blow the CRU emails out of all proportion and portray all climate science as flawed. The media’s default option still seems to be a one-on-one
Research involves a huge amount of challenge from peers; it is not a cosy club – more like a bear pit. where we require our researchers to place their data for general access. We are doing more than ever to get the scientists whose work we fund to think harder about how that work will benefit society as a whole. And we are making unprecedented efforts to involve the public in our science from the start through dialogue to inform the research process. It’s also vital that scientists get better at dealing with the media. Journalists said the science community went silent when Climategate broke. Maybe so, but perhaps this was partly because scientists saw at once that the story wasn’t really about science at all, but about particular scientists and how they conducted their research. Many in the research community didn’t feel comfortable commenting on that. This may be understandable, but unfortunately it meant that vital points were missing from the
confrontation between scientist and sceptic, as if the evidence for both positions was similar in quantity and quality. And too often, the same few scientists are asked for interviews again and again; it would be better if the public could see the true diversity of the research community. Scientists must do more to communicate the fact that research is a human activity subject to human emotions and failings. They also need to get better at putting their points across in plain, succinct English. These changes are badly needed, because we have much further work to do to communicate the complexities and uncertainties of climate science. Climategate has been a difficult experience for many in the field, but perhaps if it helps bring about changes in areas like these, the affair may turn out to have served a useful purpose after all.
Planet Earth Autumn 2010
DAILY UPDATED NEWS www.planetearth.nerc.ac.uk
News Chemicals make young burying beetles beg for food
IT’S NOT just birds that respond to the begging cries of their offspring. Burying beetles do too. But burying beetle larvae grow up in complete darkness and can’t see their parents – so how do they know when to beg? It turns out they are responding to chemicals on the mother’s body. Burying beetles are so named because they lay their eggs in the soil near the carcass of a small bird or mammal which they’ve buried to provide food for their larvae. But sometimes this rotting flesh isn’t enough for the hungry larvae, which beg their parents for regurgitated carrion. ‘We wanted to understand what the costs of begging to burying beetle larvae were. To do this, we had to stimulate begging,’ explains Dr Per Smiseth from the University of Edinburgh, who led the research, published in Behavioral Ecology. When they put a dead burying beetle parent next to its offspring, they were surprised to see the larvae begged for hours. They
Planet Earth Autumn 2010
couldn’t have been relying on behavioural cues, which led the researchers to think the trigger may be chemical. ‘In the same beetle, there’s some evidence that females discriminate between their male partner and intruders because of differences in the hydrocarbons in the insects’ cuticles,’ says Smiseth. So the researchers washed some female parents in a solvent to strip the hydrocarbons away and found that larvae begged less towards these washed parents than toward unwashed females. ‘We’re not sure at the moment exactly what the chemical is, but we think it’s probably hydrocarbon,’ says Smiseth. The researchers are keen to take their work further. ‘We want to see if there’s a difference between males and females. Females are the primary care-givers, but larvae might respond to males in the same way they respond to females. We just don’t know right now,’ adds Smiseth.
Kinder Eggs throw light on mongoose traditions SCIENTISTS have shown for the first time that wild banded mongooses pass foraging traditions down to the next generation. Individual mongoose pups learn one of two different foraging techniques from an older relative, called an escort. Once pups learn a technique, they stick to it throughout their lives, say the researchers. There’s growing evidence to show that culture is not exclusively human. For example, chimps use twigs to fish for ants and orangutans use sponges to soak up water. But until now there’s been no evidence to show that these methods are passed on to the next generation through cultural transmission. ‘You need experiments to see how the techniques are passed on,’ explains Dr Corsin Müller. He was a member of the University of Exeter when he authored the research, published in Current Biology, but is now at the University of Vienna. While studying wild banded mongooses in Queen Elizabeth Natural Park, Uganda, Müller noticed that mongooses use one
of two techniques to crack foods with a hard shell. They either use their teeth or hurl them at a hard surface. To test whether techniques would be passed on to pups, Müller filled Kinder Egg plastic containers with rice and fish. With no pups around, the scientists gave adult mongooses the filled Kinder Egg and saw that some used the biting technique to open it and some used the throwing technique. Others used both. Then the researchers allowed the pups to watch their escorts open the Kinder Egg. When the pups had reached juvenile age, Müller and his team tested their responses to a filled Kinder Egg and found that the young mongooses copied the technique they saw their escorts use. And they continued to use this technique as adults. ‘What’s interesting is that when people think about traditions, they usually think about one population showing one type of behaviour. But what we’ve shown is that there are two behavioural variants in the same group,’ says Müller.
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News Signs of asteroid impact turn out to be fungus TINY black spheres, previously seen as evidence that a catastrophic asteroid impact caused a little ice age, are actually charred fungus, according to new research. So ideas about what caused the Younger Dryas stadial, a cold period which began around 12,900 years ago, need to be revised. The impact theory was partly based on the discovery of carbon ‘spherules’, tiny black spheres up to a millimetre across that were found in sediment layers deposited around this time. Researchers have argued that these formed in the intense heat of wildfires triggered when a comet or asteroid either hit the Earth or exploded in its atmosphere. These fires supposedly raged across vast areas, stretching from coastal California across North America to Europe. The idea was that only these continent-wide infernos could have created carbon spherules in such numbers, and only an asteroid impact could have ignited such a conflagration. But a recent paper in Geophysical Research Letters suggests that the spherules are really just fungal sclerotia – compact balls of hardened tissue produced by certain fungi. These are common worldwide, in both modern and ancient soils. The 12,900-year-old spherules, found in Californian sediment samples, have indeed been blackened by fire. But through experiments in the lab the research team showed that they had only been exposed to comparatively low temperatures. The reflectivity of the spherules’ glossy black surface suggests they couldn’t have been higher than around 450°C. A continent-wide conflagration would almost certainly be far hotter – perhaps 800°C – and would have destroyed the sclerotia or at least burned out their distinctive honeycomb-like
internal structure. ‘They are clearly fungal from their morphology,’ comments Professor Andrew C Scott, a palaeobotanist at Royal Holloway, University of London, lead author of the paper.
Warmer climate may have wiped out the cave lion
CAVE LIONS probably became extinct across Europe and Asia 14,000 years ago because a warmer climate drastically reduced the availability of their favourite hunting grounds. As the climate warmed around 14,700 years ago, forests and shrubs steadily replaced the open, steppe-like environment that had dominated for thousands of years, reducing the amount of clear space for the lion to hunt in. The cave lion roamed the plains of Europe, northern Asia and Alaska and north-west Canada from around 60,000 years ago until about 14,000 years ago. From the numerous fossils dated from the same period, scientists know that the lion’s preferred prey were probably bison, reindeer, horse, giant deer and musk ox. Before this research, many scientists thought the cave lion (Panthera spelaea) may have died out because it slowly ran out of food after its prey went extinct. ‘We’ve pretty much ruled this out now,’ explains Professor Tony Stuart from Durham University, who led the research.
Most of the cave lion’s likely prey survived for thousands of years after the cave lion went extinct. Stuart and his colleague Professor Adrian Lister from London’s Natural History Museum report in Quaternary Science Reviews how they compiled 111 carbon dates of cave lion bones or teeth from museums in Europe, Russia and North America. Their results suggest the cave lion went extinct around about the same time across Europe and northern Asia. The most recent date came from a cave lion skeleton found in France which died about 14,141 years ago. They found the youngest bones, from Alaska and the Yukon region, dated back to 13,300 and 13,800 years ago. Other researchers have argued that the arrival of humans on the cave lion’s patch may have contributed to its extinction, but so far there’s no strong evidence for this. ‘What is clear is that as the climate changed the environment, this had a big effect on everything,’ says Stuart.
Earth’s oldest mantle discovered SCIENTISTS have found rocks formed from what they think may be Earth’s oldest mantle reservoir – a 4.5-billion-year-old remnant of the primordial material that made up the planet not long after it condensed out of clouds of space dust. The discovery, published in Nature, has important implications for our understanding of the Earth’s early history. ‘This is such an exciting discovery, because this mantle reservoir could well be parental to all of the mantle reservoirs we recognise today in volcanic rocks around the world,’ says Dr Pamela Kempton, one of the paper’s
authors who analysed some of the rock samples while at the NERC Isotope Geosciences Laboratory in Keyworth. She has since moved to become Head of Research at the Natural Environment Research Council. The 60-million-year-old rocks, found on Baffin Island and West Greenland in the Canadian Arctic, preserve the chemical signature of the mantle reservoir deep within the Earth from which they formed. How this remnant of primordial mantle has persisted since the planet formed is a mystery, but one possibility is that the reservoir is kept isolated at the centre of an eddy in the mantle, like the still air in the eye of a very slow hurricane. The research also suggests the Earth may have started to take on its present form earlier than previously thought. The rocks have higher ratios of the element neodymium (Nd) than chondrites – stony meteorites that are believed to represent the same kind of material the Earth formed out of. These higher ratios were produced by the radioactive decay of an isotope of samarium that became extinct within a couple of hundred million years after the Earth formed, so this difference must have arisen very early in the planet’s history. This could mean that the assumption that the Earth formed out of similar stuff to chondritic meteorites is wrong – meaning we need to rethink large areas of geology. Or, it could mean that the Earth began to differentiate – to change from a mass of primordial matter into a more structured form with crust, mantle and core – very early in its history. The creation of a crust and core would have depleted the mantle of certain elements. This is the explanation the researchers favour. If we assume the early Earth began this irreversible differentiation within the first hundred million years or so of its life, we can explain the discrepancy between chondrites and today’s mantle.
Planet Earth Autumn 2010
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News Most detailed map of Earth’s gravity revealed ESA - GOCE High Level Processing Facility
IN JUNE scientists unveiled the most detailed map yet of the Earth’s gravity, using data generated by the European Space Agency’s GOCE satellite, launched in March 2009. GOCE stands for Gravity field and Ocean Circulation Explorer. The satellite flies in the edge of the Earth’s atmosphere at a height of 254.9km and measures tiny differences in gravity at many points around the Earth. The map shows the Earth’s ‘geoid’ – or which parts of our planet have a greater gravitational pull than others because of the different rocks they’re made of. If you turned this map into a globe, it would look like a partially blown-up football, with peaks representing strong gravity and troughs showing weaker gravity. But if you placed a much smaller ball anywhere on this squashy football, it wouldn’t move – even if it was on a slope – because gravity would be exactly the same all over it. Because the Earth is the shape of a squashed ball, gravity is stronger at the poles than at the equator.
Before GOCE was launched, scientists knew that gravity is stronger around Greenland than around the Indian Ocean for example. But ‘the current geoid models are largely based on ground measurements, which of course is difficult in inaccessible parts of the planet,’ says Dr Helen Snaith from the National Oceanography Centre in Southampton.
So the new map is telling scientists much more about places where it’s difficult to do ground research, like the Himalayas, the Andes and Antarctica. The geoid model that GOCE has generated also represents the shape the world’s seas would be if there were no winds, tides or currents. This means scientists can subtract the geoid from real measurements of sea-surface height
to work out how winds, tides and currents affect ocean circulation. ‘Until now, the best maps we had were on the 400 to 500 kilometre scale. GOCE’s resolution is focused down to 150 kilometres. Most ocean currents are around this width or smaller, so we’re going to get a lot more detail about currents with this map,’ explains Snaith.
Plastics found in the seas around Antarctica MAN-MADE plastics have found their way to the most remote and inaccessible waters in the world off the coast of Antarctica. The seas around continental Antarctica are the last place on Earth scientists have looked for plastic, mainly because they’re so difficult to get to. ‘We were going to the Amundsen Sea onboard the RRS James Clark Ross to collect biological specimens for the first time ever, and were well placed to look for plastics at the same time,’ explains David Barnes from the British Antarctic
Planet Earth Autumn 2010
Survey, who led the research. Barnes linked up with other researchers, from Greenpeace’s MV Esperanza and ice patrol vessel HMS Endurance, to look for one of the most abundant and persistent scourges of the global ocean – floating debris. They found that plastic rubbish was most common compared with debris made from metal, rubber or glass. They report in Marine Environmental Research how they found fishing buoys and a plastic cup in the Durmont D’Urville and Davis seas of east Antarctica, and fishing buoys and plastic packaging from the Amundsen Sea
in western Antarctica. They found no evidence of natural debris like branches, shells or plants. There are no scientific research stations or other bases anywhere near the Amundsen Sea, suggesting the plastic debris must have got there via ocean currents. The researchers also sampled seabed sediments around Antarctica for minute degraded plastics. Plastic fragments have found their way as far as South Georgia in the South Atlantic, so the researchers were surprised to find no evidence of fragments in seabed
sediments around the continent. ‘The possibility of tiny pieces of plastic reaching the seafloor is especially worrying, because the continental shelves around Antarctica are dominated by suspension feeders, which are essentially at the bottom of the food chain,’ says Barnes. ‘But what’s really worrying about plastics getting to Antarctica, apart from aesthetics, is the fact that they can carry non-native animals. We don’t have this problem in Antarctica yet, but with warming seas, they stand a much better chance of surviving,’ he adds.
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News Birds strengthen social bonds when they sense trouble MAORI warriors use the haka to bond before battle. Now it seems that birds also demonstrate bonding behaviour when they think they might have trouble with the neighbours. Scientists know that social birds become closer immediately after conflict with other groups, but until now little was known about how the risk of future conflict influenced animal behaviour. Dr Andy Radford of the University of Bristol studied green woodhoopoes to see if they acted differently when faced with possible territorial conflict. These birds live in small groups in permanent territories; conflict between groups is frequent close to territorial boundaries, and allopreening – when one bird preens another – is an important part of group behaviour. The groups typically consisted of a dominant breeding pair and up to six subordinate ‘helpers’. Radford watched the birds in the river valleys of the Eastern Cape Province, South Africa. He noted the length of periods of selfpreening and allopreening, which individuals in the group were involved, and where in the territory the birds were when the preening took place. His results, published in Biology Letters, show that both the frequency of allopreening within the group, and the amount of time the birds spent doing it, increased when the group was at the edge of its territory, where conflict with neighbouring groups is likelier. Radford found the biggest increase was in the amount of preening given by the dominant birds to the helpers in the group. This ‘affiliative’ behaviour is likely to reassure subordinates
Chris van Rooyen
and increase closeness within the group, ensuring the birds all stick together if battle ensues. Surprisingly, when this behaviour was observed there had been no visual or vocal evidence of other woodhoopoe groups for at least an hour. This suggests that, rather than bonding in response to an immediate threat, the birds’ behaviour was in anticipation of a possible future threat. ‘It would be wrong to say this behaviour is firm evidence for forward planning in birds,’ says Radford, ‘but it is very exciting to have seen this link between potential intergroup conflict and current intragroup behaviour in the wild.’
Unique social structures could explain the menopause HUMAN females aren’t the only ones to go through menopause – some whale species also go through a similar ‘change’, and the unique structure of human and whale societies might be responsible, say scientists. Short-finned pilot whales stop breeding when they get to around 36 years, but can live until they’re 65. Killer whales stop having young when they reach about 48 years of age, but often live up to 90 years. This is in line with the socalled grandmother hypothesis, which suggests that by stopping having children early and then helping their existing offspring survive and reproduce, women still benefit by helping to pass on their genes. Among our ancestors, a woman would move to wherever her mate lived. Initially she’d be completely unrelated to members of her new ‘group’, and so would have no incentive to help them reproduce. But by having children, as she aged, she became more related to them. Then it made evolutionary sense to stop having children and help her younger relatives bring up their children. Among mammals, however, it’s unusual for the female to move away from the family she was born into – it’s usually the male that leaves his family group. Mammals with this type of social structure don’t go through a menopause, but continue breeding until they die. Elephants, for example, breed well into their sixties.
‘We were puzzled by this and wanted to understand why you don’t get grandmothers in other long-lived cooperative species,’ says Dr Rufus Johnstone from the University of Cambridge, lead author of the research, which is published in the Proceedings of the Royal Society B. Johnstone and his colleague Dr Michael Cant from the University of Exeter describe how they applied a model of relatedness – or kinship dynamics – to the two species of whale which go through menopause. They found a similar pattern of increased relatedness with age to the one seen in humans. In killer and pilot whale societies both males and females stay with their family groups, but males leave temporarily to mate with females from other family groups, called pods. This means that females are born into a pod which doesn’t contain their father. But as they get older and have young of their own they become more related to other pod members. So it makes sense for older female pilot and killer whales to stop breeding and instead help the younger members of their families raise their offspring. ‘This helps explain why of all the long-lived mammals, menopause has only evolved in humans and toothed whales,’ says Johnstone. ‘It would be good to look into the social structures of whale species we don’t know much about to see how well our theory stacks up,’ he adds.
Planet Earth Autumn 2010
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News Ocean circulation is a key factor in deglaciation MOST SCIENTISTS think that fluctuations in ocean circulation are linked to changes in climate. Now they’ve found evidence linking those fluctuations to temperature increases so extreme they can end an ice age. The Atlantic Meridional Overturning Circulation (AMOC) carries tropical surface waters northwards, and brings cold, North Atlantic deep water (NADW) southwards to mix with deep waters originating in the Antarctic. When ocean circulation is strong, heat is moved efficiently from the tropics to the poles. When circulation is weak the poles become colder. Scientists think that during particularly cold periods in the last ice age (so-called Heinrich Stadial events) the AMOC weakened significantly. A stronger AMOC is
associated with warmer phases. A team of researchers, led by Dr Stephen Barker from Cardiff University, believe the link is so strong that deglaciation may only happen when the AMOC shifts from weak to strong. Models predict that when the AMOC strengthens after an interval of weak circulation, it doesn’t just return to its ‘normal’ extent but it gets stronger than before – it ‘overshoots’. These changes can have extreme effects. During the Bølling-Allerød (B-A) warm phase, 14,600 years ago, temperatures rose by 9°C over the course of just a few decades. To find evidence that this increase was indeed linked to an overshoot, the scientists looked at a sediment core from the South Atlantic Ocean, and related changes in the core to the abrupt
temperature changes observed in the surface ocean and in ice cores from Greenland. Their results are published in Nature Geoscience. The radiocarbon content and preservation of carbonate shells in the sediments indicate that the waters over the sample site during the B-A period have all the characteristics of NADW. This suggests an overshoot did happen, because it means that NADW was carried much deeper than normal, pushing the older southern waters
out of the way. These results are particularly significant because they show the AMOC overshooting to well beyond its present-day state. And when overshoots occur, the effects on surface temperature are extreme. And such extreme changes aren’t just geological phenomena. ‘Humans were around in northwest Europe when some of these events happened,’ Barker adds. ‘I’d love to know what they made of such massive climate change.’
Birds prefer non-organic wheat BIRDS prefer conventionally grown grain over organic when given the choice. This doesn’t mean that organic foods are bad, say researchers; the birds probably just find the more protein-rich conventional seed more satisfying. The findings come from the first of a set of long-term experiments by Dr Ailsa McKenzie of Newcastle University. ‘The difference between organic and conventionally grown seeds is not a matter of taste – it takes time for the birds to tell one from the other,’ she says. McKenzie and Newcastle colleague Dr Mark Whittingham offered a group of 12 canaries a choice of organic and conventionally
Planet Earth Autumn 2010
grown wheat seeds, then patiently counted how many times the birds pecked at each bowl. ‘Overall the birds preferred conventional grain over organic,’ says McKenzie. During the experiment the canaries chose the non-organic wheat 66 per cent of the time. As the days passed and the birds learned the difference between the two foods, their preference for conventional wheat increased. Over the next two winters they repeated the experiment in 47 gardens across Newcastleupon-Tyne and Northumberland, measuring how much organic and non-organic grain was eaten daily from two feeders. As before, the birds preferred the conventionally grown seed. But how do the birds tell the difference between grain from
organic farms and wheat grown with the help of fertilisers and pesticides? ‘It’s not the taste, because the preference takes time to develop,’ says McKenzie. So it must be something innate to the grain. Wheat from conventionally fertilised crops often has more protein. ‘It is likely that after a while, the birds begin to sense that conventional wheat has more protein,’ she says, adding that maybe they find this proteinrich diet more satisfying. To test if the birds can learn to spot high-protein wheat, the team went back to the lab. They chose two types of wheat grown in the same conventional farm, but
treated with different amounts of fertiliser. The only difference between these types of nonorganic grain was that the overfertilised crop had more protein. ‘The canaries ate less lowprotein than high-protein wheat throughout the trial,’ says McKenzie, who reported the results in the Journal of the Science of Food and Agriculture.
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News Ocean currents ended last ice age THE LAST ICE AGE came to a stop soon after carbon dioxide levels in the atmosphere started to rise about 18,000 years ago. Now researchers have found the possible location of a carbon dioxide leak from the Southern Ocean around Antarctica that helped speed up the process. ‘The Southern Ocean is one of the areas where deep and cold water surfaces,’ explains lead author Dr Luke Skinner, an earth scientist from the University of Cambridge. ‘This deep water is rich in carbon dioxide, which can be released when the water comes in contact with the atmosphere.’ ‘Our results show that during the last ice age, around 20,000 years ago, carbon dioxide dissolved in the deep water circulating around Antarctica was locked away for two or three times longer than today,’ says Skinner. The findings, published in Science, are the first direct evidence that the time carbon spends in the deep ocean increased substantially during the last glacial period. This helped to keep atmospheric carbon dioxide levels low and the world in a deep freeze. Skinner and colleagues discovered the link in the shells of tiny bottom-dwelling micro-organisms called foraminifers. They compared the carbon-14 in the shells, which was absorbed from the water where the foraminifers lived, with the carbon-14 in the atmosphere at the time. The difference let the team work out how long the CO2 in the deep water had been locked away from the atmosphere. ‘We found that water sitting deep in the Southern Ocean was older during the last ice age,’ says Skinner. This confirms the suspicion that ocean circulation drives at least part of the changes in atmospheric carbon dioxide between glacial and interglacial times. But the mechanisms for this are still uncertain. ‘Our guess at this point is that changes in sea-ice extent were crucial in letting the winds stir up the ocean around Antarctica, and effectively lift water to the sea surface as a result,’ Skinner says.
In brief Ecologist snaps up photography prizes Cardiff University’s Adam Seward has won two of the five awards in this year’s British Ecological Society photographic competition. Adam was doing fieldwork in Fair Isle when he took the photographs of a puffin (Fratercula arctica) and wheatears (Oenanthe oenanthe) to scoop the Ecology in Action and Student categories. NERC supported his visit to Britain’s most remote inhabited island as part of his PhD. No stranger to photographic fame, Adam’s work has been widely published and he was highly commended in the prestigious European Wildlife Photographer of the Year competition in 2009.
Bioblitz on into autumn Building on the success of the summer Bioblitz events, the Bristol Natural History Consortium (BNHC) is coordinating a further series of mini events on university campuses around the country, and NERC scientists will be on hand to help. Details are on the BNHC website, www.bnhc.org.uk/home/bioblitz, and you can keep up to date on Twitter @BioBlitzUK and Facebook BioBlitzUK. Snakes in dramatic decline Snake populations around the world have declined sharply over the last 22 years, and Britain’s smooth snake Coronella austriaca is among the species showing the sharpest drop. Scientists think a change in habitat quality – like a reduction in the prey available – rather than habitat loss, could be to blame. ‘It’s too coincidental for snakes from so many countries to be going through the same steep decline. There has to be a common cause,’ says Dr Chris Reading from the Centre for Ecology & Hydrology, who led the research published in Biology Letters. Open Data From January 2011 NERC will make the environmental data in its Data Centres freely available without restrictions on use. This is to increase the openness and transparency of the research process, and to encourage the development of new and innovative uses for these data. To help support this, NERC will require environmental data collected from the activities it funds to be made openly available within two years of their collection. These are just a couple of the changes that NERC will make with the introduction of its new Data Policy. The policy will be launched in October and will come into force in January 2011. See the NERC website, www.nerc.ac.uk, for more information.
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News Antarctica’s enigmatic Gamburtsev Subglacial Mountains unveiled NEW IMAGES of the Gamburtsev Subglacial Mountains (GSM) were presented at the International Polar Year conference in Oslo in June, showing the features of this enigmatic mountain range in unprecedented detail. Scientists from the British Antarctic Survey (BAS) were part of the seven-nation Antarctica’s Gamburtsev Province project (AGAP), which has completed an airborne survey of 20 per cent of this previously unexplored area. The images clearly show the GSM’s high-relief, alpine-style landscape, and the profiles show that the valleys were carved by rivers as well as ice. ‘It’s likely that the valleys were initially eroded by rivers, which points to the fact that the mountains were there long before the ice began to form, about 35 million years ago,’ says Dr Kathryn Rose of BAS. ‘As temperatures fell, glaciers formed on the highest peaks and followed the path of the existing drainage system.’ But the fact that the mountain peaks have not been eroded into plateaus suggests the ice sheet could have formed relatively quickly. Amazingly, the radar also showed there’s liquid water under the ice. Scientists had to endure surface temperatures of around -30°C during the survey, but the temperature under the ice is as high as -2°C. ‘This is because the ice acts like a blanket,’ says BAS’s Dr Tom Jordan. It traps geothermal heat and its immense pressure causes
Perspective view of GSM’s peaks and valleys.
water to melt at lower temperatures than it does at the surface, so the water can exist as liquid at the base of the ice. Studying this subglacial environment will help scientists understand how the region’s climate has changed – and how the ice has responded – over tens of thousands of years. ‘Meltwater from one place is moving through the system and seems to be freezing back onto the base of a different part of the ice sheet. This new process hasn’t been taken into account in previous ice-sheet studies,’ adds Jordan. Another key finding is that the mountains are not volcanic. The researchers found signs of ancient tectonic fabric – areas of rock that have been pushed together or slid past each other. Today the GSM aren’t close to the edge of a tectonic plate, so these readings provide important clues to their age: ‘significantly more than 500 million years old’, says Jordan.
Old males rule the roost even as sex-drive fades OLD MALE chickens can still rule the roost even when their sex drive and ability to fertilise eggs nose-dive with age. This leads to disastrous results for hens. Being monopolised by an impotent rooster means they’ll lay many more infertile eggs than if they’d mated with a younger model. ‘What we’re seeing is an evolutionary battle between what’s good for roosters and what’s good for hens,’ says Dr Rebecca Dean from Oxford University, co-author of the study published in Current Biology. Dean and her co-authors looked at a natural population of domestic chickens (Gallus gallus domesticus) to study various components of
Planet Earth Autumn 2010
reproductive success like sperm count, sex drive and how well old roosters’ sperm swim. ‘We wanted to find out how different components of male reproductive success affect roosters’ overall fertility as they age. But also how this impacts on females within groups,’ explains Dean. The researchers found that, compared with their younger competitors, older roosters had a lower sex drive, were more likely to fire blanks and produced fewer sperm of lower quality. But they were surprised to find that if old roosters were faced with just a few young competitors in groups with plenty of females, they were just as likely to rule the roost as younger males. And in groups
dominated by an old rooster, females lay lots of infertile eggs. When there are plenty of young males around, though, old roosters were much less likely to become dominant. ‘To females, dominant roosters suggest good genes. But the fact that they can still be dominant while being infertile is bad news for hens,’ says Dean. ‘At the moment, we don’t know if females can detect whether or not older roosters are infertile.’ What isn’t clear is whether hens get any benefit at all from mating with older males. ‘There are still many questions we’re keen to answer,’ says Dean.
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News Archaeologists find Britain’s oldest house THE REMAINS of what’s thought to be the oldest house in Britain have been found at Star Carr, near Scarborough, near traces of an ancient lake. Archaeologists at the Universities of York and Manchester say the 3.5m-diameter circular dwelling dates from at least the early mesolithic period – 8500BC. It was last used just after the last ice age, when glaciers had retreated from much of Europe but sea levels hadn’t yet risen enough to cut Britain off from the Continent. The house is older than the previous record-holder, at Howick in Northumberland, by at least 500 years. The people who lived there were hunter-gatherers, pioneers who were colonising this landscape not long after the glaciers’ retreat had made it habitable again. ‘This changes our ideas of the lives of the first settlers to move back into Britain after the end of the last ice age’, says Dr Chantal Conneller of the University of Manchester, one of the directors of the project. ‘We used to think they moved around a lot and left
little evidence. Now we know they built large structures and were very attached to particular places in the landscape.’ She adds that her whole team of 12 people managed to squeeze into the space available, so it could have sheltered a relatively large group. Excavations also revealed a wooden platform or trackway that could have let people cross the boggy terrain to reach the lake. It’s made from wood that could be as much as 11,000 years old. The archaeologists found 18 post holes around the edge of the house, which probably held vertical posts supporting its roof, and a central fireplace. This kind of structure, or larger versions of it, is common 500-1000 years later, but this is the first known example from the early mesolithic. The archaeologists think there could be more structures nearby. English Heritage has signed an agreement with the farmers who own the land at Star Carr to help protect the remains. It is now investigating whether a largerscale dig is needed to recover more information before it’s lost for ever.
Artist’s impression of mesolithic hunter-gatherers at a temporary camp near Star Carr. From an original drawing by Alan Sorrell.
Africa’s national parks not working properly NUMBERS of zebras, giraffes, lions and other large mammals have plummeted by a staggering 59 per cent across Africa’s national parks since the 1970s, according to the first-ever study of the parks’ effectiveness. The likeliest explanation is overhunting and changing habitats, both of which are driven by fast-expanding human populations. Africa’s national parks cover five million square kilometres and are meant to play a vital role in defending some of the best-known species on the planet. But, until now, no one has looked in detail at whether or not they work. Ian Craigie, who led the research during his PhD at the University of Cambridge, and colleagues from the Zoological Society of London collected data for 583 mammal populations from 78 Protected Areas. They found
the steepest declines in large mammals in western Africa, while the only region in which populations grew was in the south of the continent. Their report is published in Biological Conservation. ‘Southern African parks are much better funded than parks across the rest of Africa. They have more staff and so are better at defending against poachers and other threats,’ explains Craigie. ‘There’s generally a good correlation between good management and a lower risk of threats like hunting.’ Craigie is keen to emphasise that ‘many creatures like rhino and wild dog only exist in the national parks. If it wasn’t for these parks, the situation might be far worse.’ ‘In most parks, managers know their jobs. They know what’s happening, but they don’t have the resources to deal with it,’ he adds.
Planet Earth Autumn 2010
The impact of impacts In remotest Arctic Canada, scientists are discovering that life can exploit the harshest of conditions on our planet – not the Arctic winter, but the aftermath of a massive meteorite collision. Could traces of life be found in this sort of area on Mars too? Adrian Boyce and John Parnell tell us more.
Fragments of rock in the soil zone, Haughton impact structure, where iron sulphides are weathered to rustycoloured sulphate minerals. Analysing these is valuable as an analogue for exploration on the highly oxidised martian surface, where sulphates are widespread.
Planet Earth Autumn 2010
isaster movies like Deep Impact with comets colliding catastrophically with Earth inevitably involve the extinction of ‘life as we know it’. And just ask the dinosaurs how big an influence meteorite impacts have on survival prospects on our planet! But, that doesn’t mean that all life is destroyed by impacts. Far from it – our recent research is providing evidence that some bacteria may actually thrive in the thermal spring systems these events leave behind. These bugs leave behind distinctive chemical traces, and we may be able to find similar traces in the impact craters of Mars. Discussions are under way to develop instruments for future Mars landers to do just that. The Haughton impact crater lies in the wilderness of the Canadian High Arctic on Devon Island – the largest uninhabited island on Earth. Nearly 40 million years ago, a meteorite two kilometres across crashed into Earth, leaving behind a 23km-wide crater in the bedrock and causing serious damage over an area of 50km2. It melted stone and formed what are known as impact ‘breccias’ – a tell-tale pattern of smashed rocks. In fact the movies exaggerate only slightly. These asteroids do strike with enormous speed (more than 10km a second). On impact, much of this energy dissipates into the rocks around as heat, generating temperatures of thousands of degrees centigrade. The rocks the meteorite encountered were mainly ancient carbonates, around 470 million years old, but they also contained thick beds of sulphate salts, called gypsum. These are the remnants of ancient seas and lakes that dried up, of which there are many examples through geological time. The sulphates around the Haughton crater were broken up and even melted by the impact. In some areas they were dissolved by the scalding water circulating around the newly formed underground fractures and voids – a natural mechanism called a hydrothermal system that cools the Earth after such events. This system lasted for around 10,000 years –
THE IMPACT OF IMPACTS
Researchers carry out sampling in the Haughton impact structure breccias.
this sounds a long time to us, but in geological time is just the blink of an eye. The occurrence of sulphate also sparks an intriguing possibility. Sulphate is at the heart of one of the oldest and most important biological metabolic functions on Earth – bacterial sulphate reduction. Just as we metabolise oxygen and organic matter to produce carbon dioxide, so sulphate-reducing bacteria (SRB) metabolise sulphate and organic matter and produce hydrogen sulphide, a chemical with a characteristic rotten-egg smell that makes it a favourite ingredient in stink bombs.
Of microbes and meteorites
Detlev Van Ravenswaay /Science Photo Library
SRB can live only where there is no oxygen, so they are generally found in soils, mud on the seabed, or even deep in the Earth in what scientists have called the deep biosphere. Wherever there’s sulphate, organic matter and no oxygen you’re likely to find SRB activity – even at extreme temperatures. Much of the hydrogen sulphide they produce escapes into the atmosphere, but some of it combines with iron in the surrounding rocks and mud to produce iron sulphide minerals. Most commonly these are pyrite – fool’s gold – but also another compound called marcasite. Both minerals are abundant in cracks and fissures in the Haughton impact breccia, deposited by the flowing hydrothermal waters. However, there are other natural processes that can make iron sulphides with no need for living things. So, how could we tell that SRB were responsible if all this happened many millions of years ago?
We looked at the precise chemical make-up of 25 samples of iron sulphide from all over the crater, and found a distinctive chemical signature, very different from that which can arise without the presence of life. Atoms of the same chemical element come in different varieties, called isotopes. All atoms of an element have the same number of protons – that’s why they’re the same element. But the number of neutrons in the atom varies. Some kinds of sulphur have more neutrons than others, and we found that the split between different sulphur isotopes in the Haughton crater sulphides could have arisen only through the activity of microbes. SRB much prefer the slightly lighter sulphur-32 isotope to the heavier sulphur-34 variety, so the sulphides they produce contain lots more sulphur-32 than sulphur-34. This isn’t the case with sulphides that form naturally. So, there’s little chance this isotopic signature could have been produced by a non-biological process – the difference between the starting sulphates and the eventual sulphides is just too great. Furthermore, we have found that when this ‘bacteriogenic’ sulphide is oxidised back to sulphate by exposure to the weather at the surface, there is very little change from the original sulphide isotopic value. This means that even these sulphate minerals retain the tell-tale sulphur isotopic signature after weathering. Among those planetary bodies nearby which are thought most likely to harbour life are Mars and Europa, one of Jupiter’s moons. It also seems that their surfaces are rich in sulphates, left behind from the gases given off by
ancient volcanoes. This abundance has fuelled speculation that simple life on Mars could set energy from the transformation of sulphur compounds – sulphur metabolisms are thus a credible component of life on Mars. Areas of Mars that are thought to be rich in sulphate have already been identified as priority targets in the search for life. Our new observations of widespread sulphide precipitation, mediated by bacteria, in impact breccias in a sulphate-rich terrain, indicate that martian sulphur minerals in impact crater settings should be strong candidates for sulphur isotopic analysis, and that the next missions to return to Mars should aim to gather such samples. A programme has also started to develop a mass spectrometer system to do the analysis via laser-based instruments on a lander. It may be that the answer to the question of whether there is life out there could be just a laser zap away.
MORE INFORMATION Dr Adrian Boyce is manager of the NERC Isotope Community Support Facility at the Scottish Universities Environmental Research Centre. Professor John Parnell is Chair in Geology and Petroleum Geology at the University of Aberdeen. Email: email@example.com. FURTHER READING Parnell, J, Boyce, A et al (2010). Sulfur isotope signatures for rapid colonization of an impact crater by thermophilic microbes. Geology, 38, 271-74.
Planet Earth Autumn 2010
Current thinking Fine-tuning ocean observations When we think about the oceans and their role in Earth’s climate, we tend to think of big features like the Gulf Stream and the impact of Arctic melt water. But oceanographers know that the devil is in the detail. Roz Pidcock tells us how her research expedition to Iceland took ocean observation to new depths.
reen plants are the basis of the food chain in the ocean, just as they are on land. Microscopic floating algae, called phytoplankton, photosynthesise and remove carbon dioxide (CO2) from the atmosphere, just like the plants in your garden. This makes them important for regulating climate because as the phytoplankton die and sink down to the bottom, they transfer carbon from the surface ocean to the deep sea, where it can be stored away for many thousands of years. But what controls this photosynthesis? One important factor is how much of the main nutrient for phytoplankton growth – nitrate (NO3) – is available in the water. Phytoplankton live in about the top 50 metres of the water column – typically the depth to which sunlight penetrates. When they grow in very large numbers, such as in spring when there’s plenty of light and food around, they can quickly use up all the readily available nitrate. That’s where my fieldwork comes in. I am studying ocean features called eddies and filaments. Eddies are circular, rotating currents up to 100 kilometres (around 60 miles) wide, which are found throughout the world’s oceans. They usually form where two bodies of water with different densities meet, for example, in the north-west Pacific where the cold Oyashio current coming down from the Arctic meets the warmer Kuroshio current flowing in from the south.
Planet Earth Autumn 2010
Giant stirring spoons Eddies act like giant spoons, stirring up the water to depths of hundreds of metres. As eddies turn, ribbon-like filaments form at their edges, just like you see when you stir milk into a cup of tea. These filaments can be stretched many tens of kilometres in length, but may be just 1000 metres across. The longer they stretch, the narrower they become. Eddies and filaments can be very efficient at supplying nitrate to phytoplankton, because their horizontal circulation is accompanied by vertical motion that brings deep water up to the surface. Because it has been below the sun-lit layer and beyond the reach of the phytoplankton, this water is high in nitrate. Computer models and observations have shown that eddies can contribute a significant amount of the total nutrients needed each year in some parts of the ocean. And over the last decade, as models have become more refined, they have begun to show that the filaments may be at least as important as the eddies. Clever computer models are all very well, but actual observations of nutrient supply within filaments are in short supply. This is partly because of the limited sensitivity of the equipment available to measure nitrate, and also because until recently, most in-situ studies have focused just on the eddies. So, in summer 2007, we set off towards Iceland aboard RRS Discovery, to try to redress the balance.
Eddies and filaments in the Iceland Basin We took two crucial pieces of kit with us, one of which – an ultra-violet (UV) nitrate sensor – had been specially developed at the National Oceanography Centre in Southampton. Nitrate absorbs UV light at certain wavelengths, so by shining it through the water and measuring how much comes out the other side, we can calculate how much nitrate is present. But until now nitrate sensors have only really been effective where concentrations are high and where changes in concentration are sharply contrasted (for example, as you move away from high-nutrient coastal water into the open ocean). But filaments involve much smaller changes in concentration and appear and disappear relatively quickly over short distances. Small concentration differences are still important as they may contribute to significant vertical transport of nitrate when combined with fast upward movement of water. So we developed the SUV-6, a nitrate sensor that uses a series of prisms rather than fibre optics, making it about ten times more sensitive than its predecessors. The SUV-6 was deployed within our other piece of equipment – SeaSoar. This small, computer-controlled vehicle was towed behind Discovery carrying a number of different sensors. It travelled repeatedly in V-shaped profiles, from the surface to a specified depth
SeaSoar on deck.
When two currents (in this case the Oyashio and Kuroshio currents) collide, they create eddies. Phytoplankton become concentrated along the boundaries of these eddies, tracing out the motions of the water.
and back up again, measuring temperature, salinity, chlorophyll fluorescence, oxygen and light intensity, every second. SeaSoar has been used many times to survey the physical characteristics of eddies, but this was the first time it had carried a nitrate sensor that could also take accurate measurements every second, at the same time as the physical measurements. We were very excited about what it might reveal.
could tell how the water was moving, how fast, and how much vertical water movement was taking place. But the really good bit came when we looked at the simultaneous nitrate measurements from the SUV-6. These enabled us to calculate the amount of nitrate being transported at every point in our 3-D grid. For the first time, instead of just using a few individual profiles to infer nitrate transport over the whole eddy, we were able to work with a continuous dataset, meaning our calculations were far more accurate than has been possible in the past. These unique results mean we can investigate how the nitrate moves around relative to different parts of the eddy – its spatial variability. And, because we carried out four similar surveys over the course of four weeks, we can also study the temporal variability – how the spatial patterns change with time. We can also calculate the overall nitrate transport at a particular depth for the whole eddy feature, to see if there is an overall upward or downward flux, or movement, of nitrate, and how big it is. This is important to understand how the eddy feature as a whole contributes to phytoplankton growth in the upper sunlit layer
Eddies can contribute a significant amount of the total nutrients needed each year in some parts of the ocean. Despite giving up a large part of our survey time to avoid a lively tropical storm, we identified our target: a pair of eddies, each about 50 kilometres in diameter. We could see on satellite images that there were several filaments associated with this eddy pair. We towed SeaSoar along nine parallel tracks, each around 100 kilometres long, which crossed the eddies from east to west. Four days later, at the end of the survey, we had a very detailed 3-D picture of the temperature and salinity of the eddies, and after some complex calculations we
of the ocean. Finally, and most excitingly for us, we can make an accurate assessment of the vertical movement of nitrate associated with any point inside a filament, to test the models’ suggestion that transport within filaments is just as important as within the main eddy.
So what next? We are still analysing the results from our trip to the Iceland Basin. But we already know for sure that integrating SUV-6 into SeaSoar has created a powerful tool for studying the role of eddies and filaments in supplying nutrients to ocean plants. More surveys like ours will dramatically increase our understanding of oceanic processes. Direct observations of eddies and filaments will help make ocean models increasingly realistic and improve our understanding of the role of oceans in climate-change predictions.
FURTHER INFORMATION Roz Pidcock is a PhD student at the National Oceanography Centre in Southampton. Email: firstname.lastname@example.org www.noc.ac.uk FURTHER READING Pidcock, R et al, A novel integration of an ultra-violet nitrate sensor on-board a towed vehicle for mapping open ocean submesoscale nitrate variability. Journal of Atmospheric and Oceanic Technology, August 2010
Planet Earth Autumn 2010
AGAVE Biofuel of the future? Traditionally grown for tequila and fibre, agave could also become an important source of energy in the dry regions where it thrives. Andrew Leitch, Theodosios Korakianitis and Manuel Robert describe their teamâ€™s efforts to investigate this plant groupâ€™s energy potential.
Planet Earth Autumn 2010
he trend towards replacing fuels derived from oil with cleaner renewable ones generated from living organisms is a very attractive proposition, but itâ€™s full of potential problems that need to be addressed in detail. Recent events in the Gulf of Mexico make biofuels even more relevant, in the light of the environmental problems associated with the oil industry. But we need to make the new methods as efficient and environmentally friendly as possible, and to find the right strategy for different regions of the world so that new fuels are economically competitive. Producing new fuels locally would reduce the very high costs of transporting them from one place to another and the risks of contaminating the environment. Also, crops used to produce biofuels must not affect the production of food or alter its markets. This has already happened to Zea mays (maize) production in the Americas, where demand for maize as a biofuel, food and fodder crop led to higher prices. All this means we will need more than one strategy to satisfy an energyhungry world while taking account of the threat of climate change, the market laws of price competition and the specific needs of different countries. Agaves could play an important role. For many years, these plants have been a source of products including sugars for producing alcoholic drinks like tequila, and hard fibres such as henequen and sisal for making products including ropes, twine and bags. But these same raw materials could become an important source of biofuels, whether bioethanol or biodiesel. Agaves are perennial plants that produce large leaves in a rosette form. Their size and lifespan vary enormously between species, from 20 to 200cm in height and between 8 and 30 years old. Cultivated agaves
AGAVE – BIOFUEL OF THE FUTURE?
Russell Gordon/DAS FOTOARCHIV./Still Pictures
benefit from adequate water from rain, but most are well adapted to arid conditions, and tolerate high temperatures and water shortages. This means they can be grown on land that would not be suitable for other purposes, and where soils are easily degraded by disturbance. It is not clear whether these plants can become an economically competitive alternative source of biofuels, but their biomass and growth characteristics make it worth looking into the possibility, particularly given the dry conditions that climate change may create in many parts of the world. How to exploit the plant depends on the type of agave and the final product aimed for. Alcohol is made by fermenting the sugars stored in the plant’s ‘bole’, or stem, after many years of growth, while biodiesel could be produced using fast pyrolysis, burning the biomass harvested regularly from fibrous agave leaves. The most efficient alcohol-producing agave is Agave tequilana Weber, best known as the blue agave from which tequila is made. The industry generates an average of 120 tons of boles per hectare every six years, from which 20,000 litres of tequila (46 per cent alcohol) are produced. One of the most important questions is how to transport the raw material to the processing plants. This calls for small facilities near the industry’s centres of operation. This is nothing new; in Germany, hundreds of small plants that make methane from agricultural waste are being strategically placed near farms, and the production facilities of companies that use fast pyrolysis to generate crude biodiesel are all found near where the crops are grown. Agaves produce considerable biomass, though not nearly as much as annual crops. A key advantage would be that no new planting is needed, and it takes relatively little work to maintain existing or new plantations. It is also possible to use waste leaves left by the tequila industry, or the stems and short fibre Harvesting agave leaves on a sisal plantation in Tanzania.
discarded during henequen or sisal production. This might not generate very much biodiesel, but it would not require any extra expenditure on establishing and running new plantations, or on fuel to move products long distances. Another alternative for biofuel production has already been implemented in Tanzania – a plant that makes biogas from the controlled fermentation of the liquid waste generated when leaves are decorticated – their outer layers removed and their fibres extracted. The gas, methane, is burnt on site to generate electricity. This in turn powers the decorticating plant and the small town nearby. Any that is left over is sold to the national network. The best fuel will be suitable for combustion engines. We now need to examine different species and varieties of agave to determine how best to produce biofuels for this use. We will soon be seeking funding to let us select fuel production processes, engine materials and fuel mixtures suitable for combustion engines, taking into consideration engine performance and the emissions of agave-derived biofuels.
Improving the crop
Ron Giling/Lineair/Still Pictures
The main problem when considering agaves for industrial purposes is that they have not been studied in detail. There are many taxonomical studies, classifying different agave species according to where they fit into the wider group, but only a small number of papers have been published on functional aspects of their biology such as genetics, biochemistry and physiology. We have made a start on this study by analysing the genome organisation of commercially grown agave species and generating physical and genetic maps. These maps can be used to find agave lines most suitable for using targeted breeding to create new varieties with particular desired characteristics, using strategies already well developed in breeding new varieties of other crops. However, most agaves spread vegetatively through rhizomes – underground root-stalks. This is an advantage when producing planting material, as this can be done simply by taking cuttings. But it presents us with a challenge for genetic improvement, as it’s hard to combine the genes of two different plants by breeding them. So far, the only successful
programme to genetically improve agaves was carried out in Tanzania during the first half of the twentieth century. Then, it took George Lock around 30 years to produce a family of hybrids that produce long fibre. We hope to make progress more quickly than that. New, more efficient and faster-growing varieties will be needed, and we plan to use new molecular techniques, such as the use of genetic markers to help selectively breed plants with desired characteristics, together with new methods to grow plant tissues efficiently. These advances will shorten the time needed to generate new plant materials. A programme for the genetic improvement of Agave tequilana using these techniques is already under way in Mexico. However, much more work is needed. The best way to use agaves will depend on the special circumstances of the place where they will be grown, and a combination of options may be called for. However, since agaves have not been genetically improved in a consistent way, the most important initiative to consider is a large-scale, long-term programme for the selection and generation of new agave types that will be more suitable for biofuel production. Even using the best modern genetic techniques, this process of selective breeding will be long and difficult. But in the end it could provide us with new and useful sources of renewable, carbon-neutral energy that can thrive in hot, dry conditions. It could be grown across large tracks of land that currently have little agriculture, or only subsistence farming, and often limited conservation value. This means the industry doesn’t just offer cleaner energy; it could also bring wealth to people who suffer from extreme poverty.
MORE INFORMATION Andrew Leitch is Professor of Plant Genetics and Theodosios Korakianitis is Professor and Chair of Engineering, both at Queen Mary University of London. Dr Manuel Robert is a member of the biotechnology department of the Centro de Investigación Científica de Yucatán in Mexico. Email: email@example.com, firstname.lastname@example.org or email@example.com. FURTHER READING Korakianitis, T, Namasivayam, A, and Crookes, RJ, (2010). Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions. Progress in Energy and Combustion Science, doi:10.1016/j.pecs.2010.04.002. Robert, ML, Lim, KY, Hanson, L, Sanchez-Teyer, F, Bennett, MD, Leitch, AR and Leitch, IJ (2008). Wild and agronomically important Agave species (Asparagaceae) show proportional increases in chromosome number, genome size, and genetic markers with increasing ploidy. Botanical Journal of the Linnean Society, 158, 215-22.
Planet Earth Autumn 2010
The Earth’s magnetic field. The magnetic poles are shown as red lines. Magnetic field lines (orange) can be seen emerging from the south magnetic pole and converging at the north magnetic pole, which is offset from the geographic north pole (blue lines) by eleven degrees. Mark Garlick/Science Photo Libarary
To go north, you just follow your compass towards magnetic north, right? Not quite. Geophysicists have to work hard so we can continue to navigate with map and compass. Susan Macmillan and Tom Shanahan describe how the UK magnetic repeat station network helps.
Where is North? T
o find your way using a magnetic compass with a map, you need to know the difference between magnetic north and map north. This difference is called ‘grid magnetic angle’, and in the UK it is derived from a model of the Earth’s magnetic field, which is updated every year. The variation
in grid magnetic angle reflects changes in the Earth’s magnetic field arising from sources in the Earth’s fluid outer core. We don’t yet understand these changes well enough to make good forecasts, so we need to monitor them continuously. Some of the data we need has been provided by an important, UK-wide network of magnetic survey stations that has been operating since the early 20th century. At these ‘repeat stations’, very accurate measurements are made of the magnetic field strength and direction over a whole day,
every few years, at exactly the same place. The readings are influenced by different sources of magnetism (see explanations to the right) and all these need to be carefully considered when making and processing magnetic field observations. For example, in the UK the horizontal direction of the main field is currently changing by about 0.2° each year. But we can also see this much variation between sites just a few metres apart because of variations in the crustal fields. Taking repeated measurements at exactly the same spot lets us measure the core magnetic field signal without the risk of distortions from changes in the crustal field. Likewise, variations in the magnetosphere surrounding the Earth cause the overall magnetic field to fluctuate by about 0.2° each day in the UK, and by considerably more during a magnetic storm. During a storm in October 2003 the magnetic field direction was observed in the UK to change by over 5° in six minutes. Fortunately these variations are short-lived compared to those from the core. We measure them at the three UK magnetic observatories, and can then subtract them from the repeat station data. Having processed and modelled the data,
Planet Earth Autumn 2010 Pasieka/Science Photo Libary
WHERE IS NORTH?
MAGNETIC FIELD SOURCES n
The Earth’s magnetic field mostly arises from the motions of fluid in the Earth’s outer core region, and changes slowly with time.
Weaker fields from magnetic material in local rocks (the ‘crustal field’) vary significantly over the surface of the Earth – often aiding geological interpretation – but not so much with time.
The Earth’s magnetosphere – where the planet’s magnetic field interacts with charged particles from space – causes variations in the observed magnetic field. These are affected by the Sun’s activity, and are relatively rapid compared to those from the core.
we can update the magnetic charts. We can see that the correction we need to apply to a compass bearing to convert it to a map bearing – and vice versa – varies both in space and in time. The models are then used to supply the Ordnance Survey with the magnetic north data they need for their maps.
East is least, west is best The earliest observations of the geomagnetic field in the UK were made in and around London in the late 16th century. At that time magnetic north was east of map north. However it was not until the early 20th century that we had a genuine repeat station network covering the whole of the UK with sites that could be revisited at regular intervals. Several magnetic surveys were made before this, though. Perhaps the most noteworthy were the efforts of Major Edward Sabine between 1834 and 1838. At that time, magnetic north was more than 20° west of map north. Later he was to declare that this survey ‘deserves to be remembered as having been the first complete work of its kind planned and executed in any country as a national work, coextensive with the limits of the state or country, and embracing the three magnetic elements’.
Sabine also pointed out that such surveys are able ‘by their repetition at stated intervals to supply the best kind of data for the gradual elucidation of the laws and source of the secular change in the distribution of the Earth’s magnetism’. These early magnetic surveys were major undertakings, given the delicate but sizeable instruments available at that time and the challenges of travelling across the country. Nowadays the instruments used are a ‘fluxgate-theodolite’, allowing us to measure the direction of the magnetic field, and a ‘proton precession magnetometer’, for measuring its strength. We determine the direction of true north using a north-seeking gyroscope. Each site is marked by a buried slab of concrete, and detailed site plans allow us to set up our equipment in exactly the same place each time. The data we get from these stations can also help us understand the crustal magnetic field. By measuring the magnetic field at the same locations very accurately over long periods of time, we should be able to distinguish between the different types of crustal magnetisation. This can be either ‘remanent magnetisation’, which is ‘embedded’ in rocks
when they form, or ‘induced magnetisation’, which rocks take on when exposed to the Earth’s ambient magnetic field. As the core field changes with time, there should also be small changes in the crustal magnetic field if there is induced magnetisation present – although detecting these very small signals in measurements that contain signals from a variety of sources is quite a challenge. But for the foreseeable future, the main and most crucial application of the data is likely to be navigation. You’ll be making use of magnetic field data next time you use a map and compass to find the next destination. However it’s also used whenever something needs to be set up to point in a precise direction with the help of a compass. This includes everything from aligning sundials and satellite dishes, to making sure mosques face towards Mecca.
MORE INFORMATION Dr Susan Macmillan and Tom Shanahan are members of the BGS geomagnetism team. Email: firstname.lastname@example.org or email@example.com. FURTHER READING Jackson A, Studies of crustal magnetic anomalies of the British Isles. Astronomy & Geophysics, 2007.
Planet Earth Autumn 2010
Reading nature’s barcode The sediment left behind by rivers forms a unique record of the climate, written in sand and gravel. But we’re only starting to understand how to examine it in detail. Arjan Reesink reports on words of river history that have never been read before. Exposed dunes on a bar in the Paraná River, Argentina.
Histories of climatic change are found in river deposits just as the effects of ice ages are found in deep ice cores. They’re just a bit smaller.
Planet Earth Autumn 2010
s rivers gradually shift across the landscape over decades and centuries, they leave behind deposits of sand and gravel with a remarkable diversity of internal layering. The texture of these river deposits is dominated by inclined layers of sediment, sorted according to size by the action of the water. Don’t be tempted to believe this is all just plain sand. Repeated sorting and re-sorting of the sand ultimately builds a vast record of river history, cryptically written in a natural barcode that has been the same since the dawn of time. Can we decipher the response of rivers to climate change from this barcode? Mostly hidden from sight by the water, ripples, dunes and sandbars slowly migrate downstream over riverbeds. The downstream slopes of these features on the river bed get
steeper and steeper until they collapse under their own weight. Miniature avalanches of sand generate thin, inclined layers as each feature advances along the river bed. Until recently, noone was crazy enough to count these avalanches as well as the little ripples that migrate over the edge of larger dunes. But the exercise pays off; little ripples generate their own unique pattern as they tumble over the edge of the larger dune slope. And it isn’t just ripples tumbling over the edge of dunes. Many different types, sizes and shapes of bedforms – features of the riverbed landscape – are found superimposed on one another. Each combination of bedforms can be produced only by a limited set of flow conditions, and each such combination has its own signature. Changes in river flow are recorded as changes in the layering of the sediment.
READING NATURE’S BARCODE
Different types of strata in a single trench through a sandbar on the South Saskatchewan River, Canada.
The climate controls each river’s temperament and behaviour, and this is one of the reasons why we need to understand climate change. Rivers in flood are serious natural hazards, and the number and size of floods change with the climate. Sure, we can use temperature and precipitation data and make models of how river discharge and behaviour will change. But why don’t we look more carefully at the river records themselves? If climate controls a river’s behaviour, and this in turn controls the river’s sedimentary record, then river records are proxies of the ancient climate. Histories of climatic change are found in river deposits just as the effects of ice ages are found in deep ice cores. They’re just a bit smaller. Many paleoclimatologists, spoiled with deep-sea, lake and ice cores, would argue the archive preserved in rivers is incomplete and fragmented. Honestly, do I dare compare river deposits to ice cores? Of course no records of temperatures over thousands of years will be identified from river deposits. The information in river beds is more subtle than that. If ice cores are like a chronological story, river deposits are more like jumbled-up words and torn-out pages. If it really was easy, it would have been done already. The careful experimentation needed to start translating the barcode means long hours spent in a gloomy basement with air compressors, air-pumps and propeller-pumps singing in deafening harmony. Circulating water and sand in an experimental setting allows us to observe and measure river processes without having to wait for the right flow conditions. Testing the validity of these experimental results requires going outside and shovelling
truckloads of sediment from natural rivers. The sedimentary structures can be seen in rock cliffs but are easier to place in the context of the landscape when they are exposed by trenches dug in river bars. The coarser sand crumbles faster as the trench face dries and this makes the structures visible. The fieldwork thus ranges from making sketches in a local quarry in a sunny breeze to drop-offs on a sandbar hours from civilization in the middle of the Cumberland Marshes: a blank spot on the Canadian map. Good data often come from the strangest places.
Decoding the river bed What new knowledge has this given us? By carefully controlling the flow of water in an experimental setting, we have developed a dictionary to let us translate these natural barcodes. For example, we now know that ripples on dunes form layers with reasonably constant cross-sections that are separated by thin, fine-grained layers. Ripples exist on dunes only in very gentle flows, when turbulence only occasionally affects the sediment. In real life this means that ripples exist on dunes in a very narrow range of flow conditions and when dunes are being replaced by ripples after the peak of a flood has passed. Ripple-ondune layering tells us about how the river has flowed. A set of a single dune with evidence of superimposed ripples represents a short segment of time; it is like a single word describing a historical event. On a larger scale, we can look at the inclined layers along the length of sandbars to describe their history of movement. Dunes form on bars, and bars move fast, when there is a lot of water flowing in the river. Ripples form on bars, and
Different types of strata exposed by scraping the surface of a bar on the Paraná River, Argentina.
bars move more slowly, in medium flows. And during low flows bars emerge and water flows around them, reshaping their edges. Repeated floods eventually create recurring cycles of structures. So sets formed by sandbars are like pages of text describing historical events. We have only just begun to realise that we can get detailed information from river deposits. It is almost as if we have never read the contents of the chapters, only the summaries. We inferred the contents from these summaries, but were we right? River deposits are built through cycles of repeated sorting of sediment, driven by dynamic interactions between the flow of water and the river bed, and ultimately subject to the river’s temperament. They are the product of changes in their environment and as such make up a vast record of information about the ancient climate. It is cryptically written in a natural barcode, but it is there for anyone who wants to translate it. Besides now being able to read nature’s barcode, the most illuminating aspect of this study is perhaps the realisation that science can still be pushed forward simply using a shovel. MORE INFORMATION Dr Arjan Reesink is currently a post-doctoral researcher on NERC’s Rio Paraná project at the Universities of Brighton and Birmingham. Email: firstname.lastname@example.org The Rio Paraná project focuses on the dynamics of one of the world’s largest rivers; see also www.brighton.ac.uk/parana
Planet Earth Autumn 2010
The carbon age In a radiocarbon laboratory in Scotland, researchers came up with a new portable kit to sample carbon dioxide using a clay sieve. Mark Garnett tells us how they’ve taken this technique to some remote places, and how it’s shedding new light on CO2.
The new portable equipment.
Planet Earth Autumn 2010
hen I tell people I do research in a radiocarbon laboratory, a common response is, ‘Oh right, like radiocarbon dating the Turin shroud?’ Radiocarbon dating is a valuable technique for dating objects of historical and archaeological importance, but it’s also a powerful tool in the quest to understand our environment. In particular, because it deals with an isotope of the element carbon, radiocarbon analysis can tell us about processes that are fundamental both to life on Earth and to our climate. Radiocarbon analysis was pioneered over 60 years ago, and the technique continues to be improved. At the NERC Radiocarbon Facility (Environment) in East Kilbride we have come up with new techniques for collecting CO2 for radiocarbon analysis. This is the story of these new sampling systems, some of their applications and the insights they have provided. CO2 is important to many processes that occur on Earth, a component of our planet’s atmosphere and, in terms of climate change, one of the most important greenhouse gases. Plants use CO2 from the atmosphere for growth, through photosynthesis. Most of the CO2 they absorb will at some stage return to the atmosphere, but crucially, the time it spends
locked away can vary from less than a day to millions of years. For example, carbon fixed by a plant during photosynthesis will cycle through it very rapidly and may be returned to the atmosphere as the plant ‘breathes’. Alternatively, carbon that sits in a plant’s tissues is likely to end up in the soil when the plant dies, and depending on the rate of decomposition it can stay there for decades or even millennia. In extreme cases, some carbon fixed by plants millions of years ago is only now being released, as we burn fossil fuels. The rate that carbon cycles through these various routes before returning to the atmosphere as CO2 has a critical influence on its concentration in the atmosphere. This is because the amount of carbon in the Earth’s atmosphere (mostly as CO2) is small compared to that in the oceans and on land. This is where radiocarbon dating comes in. It tells us how long carbon has remained in a particular pool (soil, for example) and, therefore, the rate that it cycles through that pool. Measuring the radiocarbon in the CO2 leaving the carbon pool can show us directly the average age of the gas entering the atmosphere. All this is possible because carbon naturally occurs in three slightly different forms (isotopes). Two are ‘stable’, while the third – radiocarbon – is ‘unstable’, because it’s
THE CARBON AGE
Collecting soil respired carbon dioxide from Arctic tundra for radiocarbon analysis.
Sampling chambers had to be tied down to cope with the high winds and exposed conditions.
radioactive and decays as it emits radiation. So its concentration declines over time relative to its stable counterparts, and measuring the relative proportions of the carbon isotopes in a material forms the basis of carbon dating. In addition, nuclear weapon tests in the mid20th century produced a rapid but temporary global increase – a ‘spike’ – of radiocarbon in the atmosphere which can be tracked throughout the carbon cycle. This spike lets us date very recent materials, which can’t be done using conventional carbon dating. Our challenge was to develop a sampling system that researchers could use in remote field sites. Although a few milligrams of carbon are enough for analysis, in most cases the concentration of CO2 in the actual samples is extremely small – typically a suitable sample would require 5-10 litres of air. Transporting such volumes in gas sample bags or glass flasks would be impractical. Alternative methods such as cryogenic purification – where CO2 is separated from other gases in air by cooling in liquid nitrogen at -196°C – are also impractical, not to mention potentially hazardous in the field.
Sieving the carbon Thanks to earlier work by researchers at the East Kilbride lab, we knew the key was a zeolite molecular sieve. Zeolite is a rather unimpressive looking clay material which has remarkable properties. Firstly, it contains a uniform network of tiny pores which allow small molecules (including CO2) to pass through but exclude larger molecules. Secondly, at room or field temperatures this molecular sieve attracts certain molecules to its surface – a process called adsorption – and the type we use strongly adsorbs CO2. This means that, when we pump air through the molecular sieve, all the CO2 is trapped within its pores. Crucially for a system that has to be used in the field, it has a high surface area so only a small amount of molecular sieve is needed to collect a suitable sample. When heated to several hundred degrees celsius back in
the lab, the sieve releases the stored gas. These characteristics make it ideal for our purposes. Our system also uses an infra-red gas analyser, which measures CO2 concentration in the air being sampled so we can estimate when a big enough sample has been collected. It needs no external power supply and can be easily transported and operated by one person. Developing the system has had huge benefits. For example, in the NERC-funded International Polar Year ABACUS project it was used to work out the age of CO2 produced from decomposing soil in birch forest and tundra heath (where cold temperatures prevent tree growth). To collect the samples required daily hikes over many miles of tundra, and sampling chambers had to be tied down to cope with the high winds and exposed conditions (fortunately they escaped the attention of the numerous passing reindeer). Results showed that, although these soils contain carbon that is hundreds of years old, most of the CO2 emitted from the soil surface had been fixed from the atmosphere within the last decade or so. There was also evidence for much faster carbon cycling in the forest compared with the tundra heath. This will have implications for the overall rate of carbon emissions if forest replaces heath in these regions, which may be occurring due to global warming. The system has also helped investigate CO2 emissions from UK peatlands, which contain vast stores of carbon. One surprise was that deep-rooted plants act as conduits for greenhouse gases dissolved deep in the peat. We know that plants like sedges help transport methane to the peat surface, but it was news to scientists that they provide a similar service for CO2 that’s hundreds of years old. And by connecting the sampling system to a floating chamber, we managed to collect and date CO2 coming from the surface of peatland streams. Surprisingly, radiocarbon results show that this CO2 can be ancient; derived either directly from deep bedrock weathering or, potentially, from
CO2 taken in by plants more than a thousand years ago. As if this isn’t enough, a whole new range of possible applications have emerged since we developed the technique so it could also be used as a ‘passive sampler’. This means that we simply rely on the CO2 molecules’ own kinetic energy to get them to the molecular sieve – no pump required. So the sieve only needs to be exposed to the atmosphere being sampled to get sufficient CO2 before it’s returned to the lab for analysis. This is particularly helpful in remote and inaccessible locations – for example, in Arctic Sweden we managed to collect CO2 from underneath the snow during winter for the first time – completing a whole year’s sampling without a break. The soil carbon emitted during the winter (a significant proportion of the annual total) proved to be of a similar age to emissions during the growing season. This isn’t the end of the story though. There are even more possibilities for applying both sampling systems, and the study of fossil-fuel emissions could be a particularly fruitful one. Because of its extreme age there is no radiocarbon in fossil fuel, so if we can’t detect any radiocarbon our samples must be very old (at least 50,000 years old). Our sampling methods could be used to quantify how much of the CO2 in the atmosphere comes from fossil fuel, helping us understand the impact of fossil-fuel burning on global warming. It could also be used to test for CO2 leakage from carbon capture and storage facilities, helping maximise the contribution they make to reducing our carbon emissions. FURTHER INFORMATION Dr Mark Garnett is deputy head of the NERC Radiocarbon Facility (Environment), hosted by the Scottish Universities Environmental Research Centre, East Kilbride, email: email@example.com Development of the sampling system was supported by the NERC Radiocarbon Facility and a NERC CEH studentship (Susie Hardie) based at the Scottish Universities Environmental Research Centre, East Kilbride, and CEH Lancaster.
Planet Earth Autumn 2010
buoys Jobs for the
Two bright yellow, 7m-tall buoys, bristling with sensitive instruments, are providing scientists with an unprecedented amount of detail about the English Channel. Dr Tim Smyth, manager of the data buoy project at Plymouth Marine Laboratory (PML), tells Kelvin Boot about his favourite new toys.
cientists have been sampling the English Channel for more than a century, investigating its biology and chemistry and monitoring its tides and currents. The Channel is a complex environment, yet in many ways is representative of coastal seas around the UK. The western Channel, off Plymouth, is especially interesting as it is here that oceanic and coastal waters meet â€“ an ideal area to monitor long-term changes brought about by rising sea temperatures, for example, or shorter term as the seasons come and go. Such information helps us understand the health of the sea, how it behaves and what affects it. But getting the information has never been straightforward. Until recently, the only way we could collect data was to visit the sampling sites on our research vessel to take a range of physical measurements, such as temperature, salinity and optics or to obtain biological samples directly from the water for analysis back at the laboratory. At best we managed this on a weekly basis, but itâ€™s a highly weather-dependent activity so there were no guarantees. And while such long-term data has proved invaluable in helping us understand longer-term trends and
Planet Earth Autumn 2010
JOBS FOR THE BUOYS
therefore large-scale changes in the Channel, it left a serious gap in our understanding of what is happening on a daily or even hourly timeframe. The deployment in 2009 of our two shiny new buoys, at the imaginatively named sampling sites L4 and E1, marked a significant advance in both the quality of the information and the ease with which we could get it. The buoys are autonomous – they send us their data automatically almost as soon as it’s recorded, enabling us to fill in the gaps between the weekly boat-collected samples. The buoys are part of the Western Channel Observatory, which combines routine in-situ sampling with modelling and remote sensing. Between them they cover a range of conditions. At around 7 nautical miles off Plymouth, L4 is close enough to shore to tell us about inputs from the local estuaries. E1 is sampling in very different conditions, 25 nautical miles offshore on the open continental shelf, where there is more of an oceanic character, so the two datasets provide a comparison of the impact and timings of any changes taking place. So apart from being new, what makes these buoys so special? They carry an impressive array of equipment powered by a combination of solar and wind energy. This variety of instrumentation – which we’ll look at later – and their flexibility make the buoys unique. But their other star quality is their ruggedness. This is crucial because conditions in the English Channel are harsh, with waves up to 6m, strong winds and a high volume of boat traffic. In short it’s hostile and busy, causing serious logistical problems for long-term buoy deployments. Standard environmental monitoring buoys used around the world would simply not be up to it, so we went back to the drawing board to create something new. We worked with Plymouth company Hippo Marine to design and build the new buoys to withstand the Channel’s tough conditions, while enabling the equipment to take the sensitive measurements needed. Integral to the design is a ‘moon pool’ – an enclosed column of water at the centre of the buoy which enables the instruments to be lowered into the sea and remain submerged and working while being completely protected. Each of the buoys weighs around 3.5 tonnes and requires 6 tonnes of anchorage to keep it in place. To add to the challenge, they also have to be kept on station and facing in a constant direction, to ensure the solar panels are oriented efficiently and the optics equipment is unshaded. It hasn’t all been plain sailing. We really were
The possibility of a 7m buoy running amok in one of the world’s busiest shipping lanes was not to be contemplated lightly. at the mercy of the elements when it came to getting the buoys to their stations, and on more than one occasion the deployment mission had to be aborted as the weather deteriorated. Tethering the buoys was also quite a challenge – the possibility of a 7m buoy running amok in one of the world’s busiest shipping lanes was not to be contemplated lightly, as we’d learned from experience. Even with all its heavy-duty tethering, the L4 buoy decided to make a break for a nearby beach during a test run in 2008. Following this the entire system was refined and improved, so our buoys can hopefully stand up to anything the Channel will throw at them in the years to come.
Down to the detail We can use the long-term data collected by boat to establish a baseline for studying how humans are affecting the oceans and the planet through climate change. For example, changes in temperature affect ocean chemistry and cause variations in the make-up of the biota – the plant and animal life. With the buoys now fully operational, we also have high-frequency, small-scale data, which lets us look at shortterm changes and see how they in turn affect the longer-term trends. All this gives us a much greater understanding of our coastal waters. Take plankton blooms, for example, which can appear within hours and spread and die within days. Blooms are important because they may concentrate food fish, for example, which could be a boon to fishermen – or concentrate toxins – ‘red tides’ that are a threat to shellfisheries. So we need to understand what causes these blooms and why a particular species appears one year and maybe not the next. Small changes in the physics or chemistry of the sea may hold some of the answers, but it is likely to be a complex combination of factors. Our sensors are measuring temperature, salinity, nitrate levels, sediment concentrations
and chlorophyll. They also measure coloured dissolved organic material, which can ‘stain’ the water, reducing the amount of light available for photosynthetic phytoplankton and interfering with satellite readings of things like sea-surface temperature and phytoplankton concentration. There’s even a weather station and camera on board. By studying these factors we can begin to understand how changes in the environment, temperature and nutrient availability, for example, affect the marine ecosystem on an hourly basis, giving us the potential for predicting the onset of phytoplankton blooms. The L4 buoy has already given us information on the influence on phytoplankton of freshwater surges resulting from flood conditions in the River Tamar. These ‘freshening’ events brought extra nitrates into the sea from river run-off, and resulted in blooms at a time when conditions were otherwise unsuitable for accelerated plankton growth. We’d had our suspicions about this for many years but until now had not been able to recover any evidence on our weekly sampling visits. Put this small-scale detail together with PML’s expertise in ecosystem modelling, remote sensing, and our existing weekly in-situ observations, and you get some very useful insights into what is happening in the English Channel. This level of detail will directly support decisions about the sustainable management of our coastal and shelf waters. Not only that, but as different questions about the chemistry and physics of the sea arise and new methods of study are developed, our buoys are flexible enough to accommodate new instruments to provide the data needed to respond. One could be forgiven for thinking that the data buoys’ hourly readings, combined with broad-scale satellite readings, would make boat visits redundant. This is not the case; we still need other readings and water samples for analysis in the lab, because the deeper water column still eludes the satellites and the data buoys’ instruments. But before 2009 we had only part of the story: now we have boat, buoy and satellite working together to give us the complete picture. FURTHER INFORMATION The buoys were funded through NERC’s Oceans 2025 initiative, which is implemented through seven leading UK marine centres. www.oceans2025.org Dr Tim Smyth is manager of the data buoy project at PML. Email: firstname.lastname@example.org Kelvin Boot is science communicator at PML. Email: email@example.com Western Channel Observatory www.westernchannelobservatory.org.uk
Planet Earth Autumn 2010
New techniques let scientists analyse ancient footprints to understand how our forebears’ physiques and lifestyles changed over time. Matthew R Bennett, Robin Huw Crompton and Sarita Amy Morse describe recent breakthroughs in the science of fossilised movement.
key part of being human is our ‘bipedal’ posture – we walk upright on two legs. The development of bipedalism was a critical stage in our evolution. Another was the later transition from early habitual bipeds such as Australopithecus africanus, made famous by the skeleton ‘Lucy’, to more modern humans like Homo erectus and Homo sapiens, which were, and are, endurance walkers and runners. Our ancestors’ ability to walk efficiently influenced how they foraged and hunted for food, how they gathered raw materials for tools and how they migrated across the globe. But despite more than a century of research, our understanding of the modern foot is still relatively poor, and our knowledge of our ancestors’ feet is even more uncertain. The foot is a complex structure of 22 bones held in place by a lattice of soft tissue. It interfaces with the ground to create pressures which decelerate, balance and accelerate the body during walking and running. Little wonder this complex machine has not given up its secrets easily. Fossil foot bones are rarely found with skeletons of known species, and the fossil record is fragmentary. When we do find part of one of our ancient ancestors’ feet, it has usually been badly chewed by scavengers. And fossil foot bones rarely give a definite indication of how our early ancestors walked, since they act
Planet Earth Autumn 2010
through a series of complicated soft tissues which are rarely preserved – from ligaments to the outer skin – so they interact only remotely with the ground.
Fossilised motion We believe human footprints provide a better record of our ancestors’ feet than foot bones – a record of ‘fossilised motion’ formed as they walked across soft ground. The prints directly record the forces our forebears applied to the ground to balance and propel their bodies. Our team is a collaboration between field
animal footprints were thought to be rare in the geological record – freak occurrences of sedimentary preservation, with each one holding a rare glimpse of locomotive behaviour. But we’re coming to realise that footprint sites probably aren’t so scarce; it’s just that they haven’t been properly identified and analysed before. The oldest and most famous ancient footprints are at Laetoli in Tanzania, made some 3.75 million years ago by an ancestor similar to ‘Lucy’ (Australopithecus africanus). Last year we published in Science details of the second-oldest human footprint site, found in northern Kenya, dating from 1.5 million years ago. We think these footprints were made by Homo erectus, one of the first of our ancestors capable of long-distance walking and running. Comparing these sites and prints will help us understand the transition in locomotive style between species of Australopithecus and Homo. There are also other more recent human footprint sites around the world, and lots still to be discovered, with prints made by Homo sapiens in diverse settings like coastal mudflats, caves and layers of volcanic ash. These sites help us understand the data on ‘fossil locomotion’ from ancient footprints. For example, some team members have just
We believe that human footprints provide a better record than foot bones of our ancestors’ feet. scientists at Bournemouth University led by Professor Matthew Bennett, who have expertise in excavating and recording footprints, and experts in biomechanical modelling at the University of Liverpool under Professor Robin Crompton. Our goal is to meld field science with computational analysis and simulation to reveal the fossilised motion of our ancestors. Until relatively recently, human and
TRACKING OUR ANCESTORS
Matthew Bennett and the team scanning footprints at Ileret, Kenya.
returned from Namibia, where one of the richest footprint sites in the world recently came to light. The site contains many human trails and a plethora of animal prints including elephants, giraffe, buffalo, cattle, goats/sheep and a range of birds. The site is in a large dune field, and each day the team used quad bikes to reach it – a former mudflat over which the dunes have migrated. The footprint surfaces are only exposed for a few years at a time as they are revealed and then covered again by the mobile dunes. The site’s age will not be known until the results of our dating programme are completed later this year, and it is probably only a few thousand years old. But it contains important information to help us interpret ancient footprints, since the prints reveal the subtle influence of the surface they are made in. In one case there is a trail of more than 70 prints formed by an individual walking across a shallow channel and mudflat. The individual prints vary in their anatomy and with the type of sediment they were made in, particularly its moisture content. Adding sites with different properties to our database of knowledge is crucial if we want to understand the patterns of foot pressure caused by different styles of locomotion and foot anatomy. The team will also be returning to northern Kenya and the second-oldest footprint site in the coming year to continue excavating these ancient prints.
3-D scans of a human footprint from Formby, UK (left), c3500 years old, and one of the prints from the quarry at Valsequillo, Central Mexico.
Capturing the information held in a footprint has long involved casting it in a medium like latex or plaster, a destructive process that does not readily provide quantitative data that we can analyse objectively. Our team has pioneered the use of an optical laser scanner to capture footprints in the field. Mounted on a custom-made rig which controls light and dust levels, the laser scanner provides digital elevation models of individual prints that are accurate to less than a millimetre. The scans record each print, preserving them for the scientific community even if these fragile sites with their prints erode in future. More importantly, the scans provide the basis for statistical analysis of print anatomy. One of our goals is to develop objective methods for interpreting footprints. First, we needed to be able to tell for sure whether or not a mark in the ground is really a human footprint. Working at controversial sites in Mexico, and closer to home in South Wales, we have developed a simple numerical test using scans of footprints of various ages and species, formed in different materials. Objectivity is critical, especially as prints within a single trail may vary from one another; we need a way of effectively determining what the mean print looks like, eliminating the bias associated with the interpretation of individual prints. Professor Crompton’s team did some
lateral thinking and realised that methods used to analyse chemical patterns in the brain are also ideal for comparing footprints. They have developed a new approach which lets us calculate an ‘average’ footprint from a whole trail, and then compare it statistically to other print populations. This lets us objectively compare prints made by different species at different times and helps develop models of how human locomotion has evolved. For example, the technique has helped resolve a 30-year debate over the Laetoli footprints, showing they were made not by a creature that walked with bent hips and knees, but by a more modern version with a gait not so far from our own. Studying these footprints has greatly improved our knowledge of our ancestors. We can more accurately place them on the map chronologically, see what fauna they interacted with – even make them walk through computer modelling. We can’t research our forebears’ feet directly, but our work may ultimately mean the prints they left behind are just as good. MORE INFORMATION Matthew Bennett is Professor of Environmental & Geographical Sciences at Bournemouth University. Robin Huw Crompton is Professor in the Institute of Ageing and Chronic Disease at the University of Liverpool. Sarita Amy Morse is a student of the anthropology department at Rutgers, State University of New Jersey. Email: firstname.lastname@example.org
Planet Earth Autumn 2010
Hot off the press Signs of the forces that shaped the Earth’s surface are all around us; to the trained eye, each rocky outcrop tells a story about how the landscape developed over millions of years. But when it comes to understanding what’s going on in the hot depths hundreds of kilometres below, or how the planet first condensed out of celestial dust, things get trickier. Tom Marshall reports.
rofessor Bernie Wood carefully fits a tiny sliver of sample material into a giant piece of machinery hulking to one side of his lab, tucked towards the rear of Oxford University’s Earth Sciences faculty building. It’s a delicate business. One mistake and he’ll know about it only when he removes his sample several hours later and finds something broke under the strain. Wood and his team want to understand problems like how the Earth and the other planets of the solar system formed, and how our planet’s core then separated from its silicate mantle when the planet was still young. They go about finding out by feeding mineral samples into huge machines to compress them. Biggest of all is the multi-anvil press; it applies hundreds of thousands of times the pressure at the Earth’s surface for several hours, while creating scorching heat with an electrical current. It’s a unique, custom-built piece of kit. As well as replicating the conditions deep inside the Earth, it can supply enough pressure to turn graphite into diamond. There are only a few working in the UK – apart from the one at Oxford, there are others in earth sciences departments at Bristol, UCL, Edinburgh and Cambridge. The team makes a lot of its own equipment. Experimental petrologists have to be good in the workshop; their equipment needs bespoke components that you can’t buy on the high street, and the whole team can wield a mean lathe when the situation calls for it. ‘We build
Planet Earth Autumn 2010
HOT OFF THE PRESS
most of the parts for our machines ourselves,’ says postdoctoral researcher James Tuff. ‘This is very much hands-on, make-your-own-rocks geology.’ At the heart of the press is a cubic arrangement of tungsten carbide cubes – the ‘anvils’. Each is missing a corner. Powdered samples are encased in an octahedral medium designed to transmit pressure and fitted with a tiny graphite or semi-conducting heating element together with a thermocouple that records what happens as the heat and pressure mount; the octahedron fits snugly into the gap left at the centre of the cube of cubes by their missing corners. Once activated, the hydraulic press bears down with a load of up to 1000 tonnes, and the anvils transmit this load into the sample along each of its faces. It’s compressed from all sides at once, while an electric current heats up the furnace element to thousands of degrees. A thick outer metal ring would protect those nearby if anything gave way under the titanic pressure. Once pressurised, each sample may be left for several hours, then allowed to decompress to relieve the pent-up stress within the anvils. Sometimes everything works; sometimes the heating element burns out, or one of the anvils breaks, or something else goes wrong, and everything must be repeated. But this kind of work, known as experimental petrology, has laid the foundations on which much of our modern understanding of geology is built. Professor Wood’s group’s current research is to recreate the conditions under which Earth accreted – formed out of clouds of dust in space – as well as those still found deep beneath our feet, with a combination of precision engineering and brute force. Seismologists can tell a lot about the Earth’s interior from how sound moves through it, and we get clues to its chemical make-up from samples brought to the surface by drilling or tectonic movements. But experimental petrology is the only way to test theoretical models of the deep Earth and understand how minerals behave in extreme conditions. ‘The deepest borehole we have (Russia’s Kola superdeep borehole) only goes down about 12km,’ explains postdoctoral researcher Jon Wade. ‘But the mantle begins far beneath that and the core-mantle boundary doesn’t start until 2900km down. So our knowledge of the deep Earth is mostly inferred from seismic data or from rare rocks brought to the surface by tectonic and volcanic activity. Using experimental techniques we can often test many of these inferences.’
False-colour image of the results of a run on the multi-anvil press at pressures equivalent to 800km beneath the Earth’s surface, taken using a scanning electron microscope. The circular shape in the middle is perovskite, a silicate mineral thought to be dominant in the lower mantle; the yellow spots are iron.
The team use their press to simulate conditions down to around 660km deep – around where the upper and lower mantles meet. At this depth, the pressure is around 20 gigapascals – some two hundred thousand times the pressure at the surface – and the temperature around 2000°C. Other presses exist that can simulate even deeper conditions, but at these depths the discipline comes up against the physical limits of the materials. ‘The problem is that to work with reasonable samples at this kind of depth, you need an absolutely enormous press,’ Wood explains. ‘Beyond certain depths, you just can’t build a machine that can compress the sample
That’s because the elements in the material of the primitive Earth were divided up unequally when it separated into its present parts. Rock-loving, or ‘lithophile’, elements were concentrated disproportionately in the silicarich mantle, while metal-loving ‘siderophile’ elements mostly ended up in the iron core. More than 99 per cent of the Earth’s total gold supply is locked up in its core, for example. This is why gold is so rare and valuable. Otherwise, there would be enough in the upper Earth to cover the planet’s surface to a depth of nearly half a metre. This process is called ‘partitioning’, and scientists are striving to understand the chemical and thermodynamic processes involved. They rely on the decay of radioactive elements into other ‘daughter’ elements with differing preferences for either the rocky mantle or metallic core to shed light on the timescales over which the planet formed. But to test how element partitioning varies within a growing planet experimentally takes huge temperatures and pressures. Hence the presses. Experimental data has let Wood and his team build models that simulate partitioning far more accurately than was previously possible. By running experiments and carefully controlling pressure and temperature, they can begin to understand the conditions under which the Earth’s core must have formed. ‘You don’t get the current concentration of, say, nickel and cobalt unless you assume equilibration of metal and silicate at very high temperatures and pressures,’ Wade says. ‘So we know that the core and mantle must have reached equilibrium at the base of an ocean of magma around 700 kilometres deep.’ The results don’t just apply to Earth’s history; they shed light on how all planets formed, condensing out of clouds of gas and gradually separating into core, mantle and crust. Samples go into the press as homogeneous powder; under the forces and temperatures they face there they swiftly divide into their component parts, forming metallic core and silicate mantle. ‘We want to find the effects of temperature, pressure and chemistry on the components of planetary formation,’ says Wood. ‘Each sample we work with is like a simulated planet a few millimetres across,’ explains Tuff. ‘You’ve got a metallic core surrounded by silicates, and we’re subjecting them to conditions that they may well have experienced when the Earth was being formed.’
Each sample we work with is like a simulated planet a few millimetres across. enough.’ Alternative approaches, like using diamond anvils, can take more pressure, but have their own drawbacks.
Little planets One of the greatest challenges for experimental petrologists is understanding how the Earth formed, and how the elements were divided between its core, mantle and crust. We know the overall chemical make-up of the Earth; it’s similar to the mix of elements found in meteorites known as carbonaceous chondrites. These are made of the same primitive stuff that formed all the solar system’s planets. But the breakdown of the Earth’s mantle doesn’t match that of the meteorites – for instance, in comparison to chondrites, Earth’s silicate mantle has less iron and nickel.
Planet Earth Autumn 2010
When politics and science come
face to face
Relations between the worlds of science and politics are rarely straightforward. Former NERC policy intern David Ferguson (above) tells us just how tricky, and how important, the relationship can be.
Planet Earth Autumn 2010
olicy-makers want definite answers, scientists prefer probabilities; the evidence says one thing, the political ideology another. Such scenarios are all too common. The recent volcanic ash crisis is a good example of scientific advice being subject to intense outside pressures, and also how such advice can have profound economic and social implications. Science-based high-tech industries are increasingly important to the UK economy. How far is the government responsible for developing such sectors? How can they know which fields will be economic winners? Where is the dividing line between the responsibilities of the public and private sectors in creating the technology and jobs of tomorrow? The House of Commons Select Committee on Science and Technology (S&T) is one of the main forums where questions like these are publicly debated. The committee comprises a cross-party group of UK MPs with a broad remit to investigate scientific issues across government, and it often acts as referee to public disputes on scientific issues. The committee’s regular public meetings routinely bring together research scientists, policy-makers and regulators, who give their views and account for their actions on an array of science-related topics. As a NERC PhD policy intern at Westminster I recently got the chance to experience the committee’s work at first hand. You might reasonably ask why anyone would swap their research into volcanism in northern Ethiopia for a suit and the corridors of Whitehall. But I’ve always been interested in what happens to science beyond the laboratory door. When the NERC parliamentary internship came up I grabbed the chance to see for myself. Fortunately the Ethiopian volcanoes at least stayed quiet while my attention was diverted!
Both houses of Parliament have to scrutinise the government’s activities, and one of the key tools in this work is the select committee, a subject-specific group of Members with statutory powers to investigate and question government ministers and public figures on their policies, actions and intentions. The S&T Committee tackles a particularly large array of subjects, from the fiscal management of UK research councils and the licensing of stem-cell research to the culture of ‘evidence-based policy’ within Whitehall – any topic with a scientific dimension is open to its investigation. Without firm ties to any one government department, the committee is free to navigate almost the entire policy landscape. While I was in Westminster I took part in a number of inquiries, including several ad hoc investigations launched in response to emerging events. Some of these were particularly relevant to NERC science, such as the impact of potential spending cuts on UK research budgets, the global regulation of geoengineering (an inquiry held jointly with a US Congress committee) and the disclosure of emails from the Climatic Research Unit at the University of East Anglia (the so-called ‘Climategate’ affair). The focal point of a committee’s weekly diary is the evidence session. During these public meetings, witnesses come to Westminster to answer questions and make statements. Over the course of my three-month internship, more than 35 witnesses appeared in front of the S&T Committee, representing a cross-section of those who fund, regulate, use and carry out science. The sessions varied from informationgathering to direct interrogations of someone’s actions or views, and the tone differed accordingly. It was fairly common to have some
WHEN POLITICS AND SCIENCE COME FACE TO FACE
quite animated exchanges – though these were mostly reserved for sparring with politicians, well versed in the artful avoidance of difficult issues. I quickly learned that a hostile question can be very effective against a seasoned government minister but is liable to send most (though not all) academics into a rambling panic. The evidence from these sessions forms the basis of the committee’s reports; official documents published by the House of Commons and presented to the government, which has an obligation to respond. As my internship coincided with the last months of the parliamentary session, there was a push to achieve as much as possible before the election. For the committee and its staff this meant a non-stop schedule of drafting reports, public evidence sessions, press briefings and oftenlengthy private meetings to debate the details of inquiries and their final reports. One of my main tasks was to help draft a report on the committee’s impact since its inception in 1966. The Legacy Report was the last report published by the committee before the 2010 general election. Facing an uncertain future, the committee was understandably keen to highlight the benefits of its work. I had to trawl the parliamentary archives for committee documents and talk to former members to get their perspective, which gave me a great overview of the contribution the committee has made. During all this I still found time to ‘tweet’ updates on my Westminster life (on the ‘microblogging’ website Twitter). Though I did have to exercise a certain degree of discretion, to avoid breaking press embargoes or breaching
There’s a huge and under-exploited opportunity for research scientists to get out of the lab. the trust of being included in private parliamentary discussions. Beyond their primary responsibilities, NERC interns are also encouraged to experience as much of Westminster life as possible and have access to most of the Westminster estate. Between committee meetings and report writing I managed to
fit in a visit to a theatrical Prime Minister’s Questions; several science-policy related debates and seminars held around Westminster; a tour up the clock tower (with earplugs included) to hear Big Ben strike midday; and plenty of Westminster’s favourite pastimes – spotting famous MPs and ministers in the canteen and coffee shop and guessing the party affiliation of groups of young researchers in the House of Commons bar. How will science scrutiny fare in the new Parliament? When the House of Commons is disbanded prior to a general election, so too are all of its attendant committees, and they, like their respective members, have no guarantee of surviving the electoral process. As my internship came to an end, the committee members and their staff had no idea if the final report of that parliamentary session would also be the committee’s very last. As it turned out, the committee was reestablished, and is now chaired by Labour MP Andrew Miller. As it retains only one of its former members, though, it’s likely to have a very different character from its predecessor.
My experience has certainly broadened my perspective on the role of science in wider society, and the value of original research in developing good policy. Equally enlightening was seeing how scientific research can become highly politicised – as with climate science currently. Such debates need engaging and charismatic scientists who can clearly communicate the scientific viewpoint. I also saw that there’s a huge and underexploited opportunity for research scientists to get out of the lab. Anyone can submit written evidence to a parliamentary committee inquiry, and those with relevant expertise may be invited to give evidence directly to Parliament. If scientists don’t speak up on issues relevant to them, someone else can, and probably will.
FURTHER INFORMATION David Ferguson is a volcanology student at the Department of Earth Sciences, University of Oxford. Email: email@example.com Thanks to Chris Tyler, Xameerah Malik and Glen McKee at the House of Commons, and to NERC for funding the internship.
Planet Earth Autumn 2010
Mysteries of the
blue ocean Scientists used to think the open ocean was a watery desert. Now we’re starting to understand the diversity of life there and the profound influence it has on our climate. Types of plankton that were once dismissed turn out to play a vital role in the carbon cycle. Dave Scanlan and Mike Zubkov explain.
Microscope image of a 3μm alga of the class Prymnesiophyceae. Green areas are caused by genetic markers tailored to this group; the cell’s nucleus fluoresces red.
Planet Earth Autumn 2010
ife in the oceans evokes a plethora of images – from whales and shoals of tropical fish to spectacular coral reefs and even monsters of the deep. But although these might be the most amazing and colourful of marine spectacles, it is the abundant microscopic life beneath the waves that ultimately drives all the biogeochemical cycles of the oceans and hence of our planet. The sunlit portion of the ocean, the so-called photic zone, is where carbon is ‘fixed’ – turned into an organic form that living things can use – by photosynthesis, so it is critical to the global carbon cycle. At the core of the marine food chain tiny phytoplankton, fated to move around the globe at the whim of ocean winds and currents, are the major fixers of carbon dioxide (CO2), levels of which have increased markedly over the last 100 years because of human emissions. To get an idea of how important these organisms are on a global scale, remember that 40 per cent of the CO2 fixed on Earth occurs in marine systems, and 75 per cent of this is fixed in the open ocean. We should remember that this is just the current thinking, though. Up until the late 1970s the open oceans were thought of as biological deserts, and we knew little of the abundance and diversity of microbes that are now known to exist there. Within the last 30 years we have identified and characterised the two main genera of cyanobacteria, Prochlorococcus and Synechococcus, often misleadingly called ‘blue-green algae’ because they photosynthesise like plants. Because of this, we have begun to radically rethink how marine food webs function. Depending on the exact structure of this picophytoplankton community (that is, phytoplankton a few micrometres (μm) in size) and its diversity, the ocean’s whole food web may shift from one state to another. For example, dominance of the very small Prochlorococcus (0.6μm) may indicate that mineral elements are being recycled very efficiently and that very little organic carbon is sinking down from sunlit waters, while dominance of the larger Synechococcus (1μm) may show that more organic carbon is sinking because mineral nutrients are being recycled less efficiently.
MYSTERIES OF THE BLUE OCEAN
Peeking into the microbial black box Until now, these cyanobacteria have been thought to dominate carbon fixation in the open ocean. However, the photic zone also has a high biomass of small eukaryotic phytoplankton – that is, photosynthesising plankton with a complex cellular structure – which are capable of CO2 fixation. The eukaryotic phytoplankton community has long been a ‘black box’ – we have known little of its composition or of its contribution to CO2 fixation. It is only by determining how much CO2 these different groups fix into biomass that we can get a full understanding of the Earth’s carbon cycle. Ascertaining this contribution has been a thorny problem for biological oceanographers for decades. However, using flow cytometry – a technique borrowed from medical research that can physically separate (and hence ‘sort’) cells
west Africa. This suggests they play a key role in global CO2 fixation, though this needs to be confirmed by widespread sampling from other parts of the world’s oceans – our Atlantic Meridional Transect research is under way. One of the best-known prymnesiophytes is Emiliania huxleyi, a species that can form extensive blooms in some regions and is characterised by its chalk-like shell of calcium carbonate, the so-called coccolith. The prymnesiophytes we observed in our study, however, are likely not calcified as shown both by examination under the microscope and by flow cytometry. This reinforces the idea that these prymnesiophytes include previously undiscovered groups. It is likely that some of the organic carbon of these prymnesiophytes and other eukaryotic phytoplankton eventually sinks down from the photic zone to the deep ocean, rather than being returned to the atmosphere as CO2. Given their clear importance in this marine ‘biological carbon pump’, it is crucial that we discover the factors that control the growth of small eukaryotes in the oceans. Certainly, being able to make more accurate predictions of the effects of global warming on our planet will probably depend on what we learn about carbon cycling by these organisms. Mathematical models for predicting CO2 drawdown by the oceans are currently quite simple, yet the biology may be much more complicated. For instance, it is wrong to assume that the salty waters of the sea are uniform throughout. Light penetrates only the top 200 metres of the ocean, and during the summer months the water column becomes stratified, separating the nutrient-rich deeper waters from the windmixed surface layer. Microbial activity quickly depletes the nutrients in the surface waters, and specific niches become defined: surface waters that are high in light but low in nutrients, and deep waters that have little light but are rich in nutrients. We now know that such environments favour specific genotypes or ‘ecotypes’ that are adapted for life in these different niches and have different cell-specific CO2 fixation rates. We need to take this into account when evaluating the ocean’s CO2 sequestration and productivity. The future offers much. Picophytoplankton
Picophytoplankton may not be the most visible of the sea’s inhabitants but they are vital, fuelling much of the global marine production of biomass. based on their size and fluorescence properties – we have now been able to measure how much CO2 is being fixed by different phytoplankton groups. Analysing samples collected from surface waters during a research cruise aboard RRS Discovery in the subtropical and tropical north-east Atlantic Ocean we discovered that eukaryotic phytoplankton actually fix significant amounts of CO2, contributing up to 44 per cent of the total, despite being a thousand times less abundant than cyanobacteria. This is probably because eukaryotic phytoplankton cells, although still small, are considerably bigger than cyanobacteria. Two groups of eukaryotes were distinguished by flow cytometry, ‘EukA’ cells being more abundant but smaller than ‘EukB’ cells. Molecular techniques revealed that EukB were mostly photosynthetic organisms called prymnesiophytes, most of which have never been cultured in the laboratory. Many of these are probably previously unknown species. These prymnesiophytes accounted for as much as 38 per cent of CO2 fixation in the (sub)tropical north-east Atlantic Ocean, off the coast of
A water sampler being launched from the RRS Discovery.
may not be the most visible of the sea’s inhabitants but they are certainly vital, fuelling much of the global marine production of biomass. Indeed, it was not so long ago that oceanographers missed these tiny cells simply because they were too small to be caught in the large pore-size meshes traditionally used to collect phytoplankton samples. But without them, the oceans really would be watery deserts, and our world would be a very different place. Just how important they really are may become even more apparent in the coming years. MORE INFORMATION Dave Scanlan is Professor of Marine Microbiology at Warwick University. Professor Mike Zubkov is a member of the marine biogeochemistry and ecosystems group at the National Oceanography Centre. Email: firstname.lastname@example.org or email@example.com FURTHER READING Jardillier, L, Zubkov, MV, Pearman, J, Scanlan, DJ (2010). Significant CO2 fixation by small prymnesiophytes in the subtropical and tropical northeast Atlantic Ocean. The ISME Journal: International Society for Microbial Ecology. doi:10.1038/ismej.2010.36
Planet Earth Autumn 2010
Website rocks Geology for the people Need information about the Earth beneath your feet? Seeking nourishment for budding young scientific minds? Looking for photos of the landscape around you? Now there’s one place to find them all: the British Geological Survey’s ‘OpenGeoscience’ website. Richard Hughes sells it to us.
aunched in early December 2009, OpenGeoscience is unique. It gives visitors access to their choice of a wide range of geological data, searchable maps, high quality photographs, Key Stage 1-3 resources, in-house software applications, and an open archive of BGS reports and published papers. What’s more, for most users it’s free. The site’s flagship is access to street-level-resolution geological mapping for the whole of the UK – the first service of its kind in the world. Visitors can access the maps through a purpose-built ‘UK geology viewer’, which allows them to zoom into their area of interest and view the geology against a topographical (landscape) map or satellite image backdrop. Click on the map and detailed geological information will appear before your eyes. More technical users can export the dataset to a KML file (a file type used to display geographic data in a geo-browser) and look at it on GoogleEarth, or view it as a web map service. The image library – GeoScenic – has more than 50,000 modern and historical images from BGS’s archives, which you can search by theme, collection, or even the name of your town or village. It’s proving extremely popular with teachers as a way of illustrating their lessons. Then there’s the ‘popular geology’ resources, which include BGS’s highly successful schools seismology project, and a ’download and cut-out’ model of the ash-producing Icelandic volcano Eyjafjallajökull. While it’s simple for the user, there’s some sophisticated software working hard behind the scenes. Because the maps can be delivered via KML files and web map services it’s possible to ‘mash’ them with data from entirely different sources. Mash-up applications have real scientific value. A good example is the recent map of the land-cover history and surface geology of East Anglia since the Domesday Book, which was based on BGS superficial and offshore geology, selected land-cover data, administrative and geographic boundaries from Ordnance Survey OpenData, and global coastline data from the US National Oceanic and Atmospheric Administration (see www.giscloud.com/map/3186/medievalfenlands/land-cover-history).
Planet Earth Autumn 2010
The response to OpenGeoscience has been astonishing. The launch got widespread media coverage – even knocking the Copenhagen climate summit off the BBC Science and Environment website’s top spot at one point. On launch day our map server was delivering over 1,000 files per second, and the BGS website received three times its regular traffic during that month. But why? There are lots of reasons, some of them fairly obscure to the average visitor. The geospatial information industry likes it because web mapping demonstrates the usefulness of web standards applications. The European Commission approves because it complies with the INSPIRE environmental information directive, now part of UK law. The research and education sectors like it because of the free resources it puts at their disposal. Dr Steve Drury, Senior Lecturer in Remote Sensing at the Open University, foresees the website will become ‘a kind of “GoogleRock” for a great many people’. The public likes OpenGeoscience because it brings information about UK geology into their homes in a way that’s just not been possible before. And BGS likes OpenGeoscience too. The website has raised the visibility of BGS and NERC science and that’s always a good thing. But its success also demonstrates that there’s a nation of users out there hungry for online information about their ‘place’. Try it for yourself, and find out what’s beneath your feet.
FURTHER INFORMATION Richard Hughes is Director of Information and Knowledge Exchange at BGS. Email: firstname.lastname@example.org Access OpenGeoscience at: www.bgs.ac.uk/opengeoscience and tell us what you think. Email: email@example.com
Screen shots from the GeoScenic website at
Planet Earth Autumn 2010