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Imagine the oceans as an underwater world with a crew of quirky characters lurking in the depths. This book is your essential guide to the mysterious guys who are waiting to make a splash. Praise for BIOLOGY: “Fresh, sassy, and smart.” Children’s Literature
Praise for HUMAN BODY: “Science reading doesn’t come much more fun.” Booklist
Praise for THE PERIODIC TABLE: “[An] inviting ready reference.” Bulletin of the Center for Children’s Books An ALA/YALSA Quick Pick
Praise for PHYSICS: “Handy as a supplement to a physics curriculum.” School Library Journal
Praise for ROCKS
AND
MINERALS:
“A refreshing change of approach.” Booklist www.basherbooks.com $8.99 US $9.99 CAN
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First published 2012 by Kingfisher an imprint of Macmillan Children’s Books a division of Macmillan Publishers Limited 20 New Wharf Road, London N1 9RR Basingstoke and Oxford Associated companies throughout the world www.panmacmillan.com ISBN 978-0-7534-3344-7 Consultant: Dr Frances Dipper Designed and created by Basher www.basherbooks.com Text written by Dan Green Dedicated to Dave (master chicken), Ness and Leela Text and design copyright © Toucan Books Ltd 2012 Based on an original concept by Toucan Books Ltd Illustrations copyright © Simon Basher 2012 All rights reserved. No part of this publication may be reproduced, stored in or introduced to a retrieval system or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the prior written permission of the publisher. Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. 987654321 1TR/0412/WKT/UNTD/140MA
A CIP catalogue record for this book is available from the British Library. Printed in China Note to readers: the website addresses listed above are correct at the time of going to print. However, due to the ever-changing nature of the internet, website addresses and content can change. Websites can contain links that are unsuitable for children. The publisher cannot be held responsible for changes in website addresses or content, or for information obtained through a third party. We strongly advise that internet searches should be supervised by an adult.
CONTENTS Introduction Water World Ocean Motion Shoreline Gang Reef Chillin’ Open-water Crew Deep-down Dandies Chilly Chaps Ocean Explorers Index Glossary
4 6 16 28 50 68 88 98 114 124 126
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First published 2012 by Kingfisher an imprint of Macmillan Children’s Books a division of Macmillan Publishers Limited 20 New Wharf Road, London N1 9RR Basingstoke and Oxford Associated companies throughout the world www.panmacmillan.com ISBN 978-0-7534-3344-7 Consultant: Dr Frances Dipper Designed and created by Basher www.basherbooks.com Text written by Dan Green Dedicated to Dave (master chicken), Ness and Leela Text and design copyright © Toucan Books Ltd 2012 Based on an original concept by Toucan Books Ltd Illustrations copyright © Simon Basher 2012 All rights reserved. No part of this publication may be reproduced, stored in or introduced to a retrieval system or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the prior written permission of the publisher. Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. 987654321 1TR/0412/WKT/UNTD/140MA
A CIP catalogue record for this book is available from the British Library. Printed in China Note to readers: the website addresses listed above are correct at the time of going to print. However, due to the ever-changing nature of the internet, website addresses and content can change. Websites can contain links that are unsuitable for children. The publisher cannot be held responsible for changes in website addresses or content, or for information obtained through a third party. We strongly advise that internet searches should be supervised by an adult.
CONTENTS Introduction Water World Ocean Motion Shoreline Gang Reef Chillin’ Open-water Crew Deep-down Dandies Chilly Chaps Ocean Explorers Index Glossary
4 6 16 28 50 68 88 98 114 124 126
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Introduction Oceans Welcome to the Big Blue – an endless expanse of water that covers most of planet Earth. A million mysteries lurk within these murky depths: creatures living here have to prevent salt drying out their bodies; there’s only light for the first 100–200 m; temperatures plummet beneath the waves; pressure rises with depth; and sound travels great distances. You’ve got it – this is one weird, watery realm. The most recent tally of all ocean life counted 230,000 species, with at least four times that still awaiting discovery. Your guide to this alien environment is Captain Jacques Cousteau (1910–1997). This clever Frenchman was an eccentric and a pioneering explorer, scientist, filmmaker, author and inventor of the aqualung (phew!). He made 120 TV documentaries and wrote more than 50 books – his work revealed the hidden underwater world. Jacques was one of the first to think about how humans can harm ocean life and what we can do to protect this eyeballachingly amazing environment. The ocean is so vast, this book can only dip a toe beneath the surface, but what are you waiting for? Come on in, the water’s lovely! 4
Jacques Cousteau
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Introduction Oceans Welcome to the Big Blue – an endless expanse of water that covers most of planet Earth. A million mysteries lurk within these murky depths: creatures living here have to prevent salt drying out their bodies; there’s only light for the first 100–200 m; temperatures plummet beneath the waves; pressure rises with depth; and sound travels great distances. You’ve got it – this is one weird, watery realm. The most recent tally of all ocean life counted 230,000 species, with at least four times that still awaiting discovery. Your guide to this alien environment is Captain Jacques Cousteau (1910–1997). This clever Frenchman was an eccentric and a pioneering explorer, scientist, filmmaker, author and inventor of the aqualung (phew!). He made 120 TV documentaries and wrote more than 50 books – his work revealed the hidden underwater world. Jacques was one of the first to think about how humans can harm ocean life and what we can do to protect this eyeballachingly amazing environment. The ocean is so vast, this book can only dip a toe beneath the surface, but what are you waiting for? Come on in, the water’s lovely! 4
Jacques Cousteau
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Chapter 1 Water World
Our planet is very special indeed. It’s the only one in the entire Solar System that has liquid water on its surface. In fact, almost three-quarters of this mighty orb is covered in oceans and seas. It makes you wonder why anybody decided to call it “Earth” in the first place, since any Noddy can see that it’s mainly water! So take this rare opportunity to meet the wet, wild Water World crew. You’ll encounter mountains higher than anything on dry land, trenches deeper than Everest is high and mindblowingly huge plains. And let’s not forget the salt-stained captain of them all – Ocean! Just wade this way… 6
Ocean
Seas
Mid-ocean Ridge
Trench
Zones
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Chapter 1 Water World
Our planet is very special indeed. It’s the only one in the entire Solar System that has liquid water on its surface. In fact, almost three-quarters of this mighty orb is covered in oceans and seas. It makes you wonder why anybody decided to call it “Earth” in the first place, since any Noddy can see that it’s mainly water! So take this rare opportunity to meet the wet, wild Water World crew. You’ll encounter mountains higher than anything on dry land, trenches deeper than Everest is high and mindblowingly huge plains. And let’s not forget the salt-stained captain of them all – Ocean! Just wade this way… 6
Ocean
Seas
Mid-ocean Ridge
Trench
Zones
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Ocean Water World This salty fellow covers 66% of the Earth’s surface Makes up almost three-quarters of the planet’s hydrosphere The hydrosphere is all water in, on and around the planet
I am the blue-eyed giant, reaching far and wide across the planet’s surface. Gaze into my depths and you’ll see wonders and mysteries that will blow your mind! My great volume acts as a sink for the Sun’s energy. I soak up its rays, helping to keep Earth warm and affecting its climate. My currents drive the globe’s wind patterns. Though I have just one body, I am subdivided into five mammoth oceans. The biggest is Pacific, which stretches majestically between the Americas, Asia and Australia. Atlantic – the saltiest ocean – reaches from Europe to the Americas. Warm Indian Ocean hugs the east coast of Africa up to India, while frigid Southern Ocean wraps around Antarctica. Lastly, small, frozenover Arctic Ocean sits all a shiver at the North Pole. Brrr!
Ocean Area of all oceans: 360 million km2 Volume of all oceans: approximately 1.3 billion km3 Average depth of the oceans: 3790 m 8
9
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Ocean Water World This salty fellow covers 66% of the Earth’s surface Makes up almost three-quarters of the planet’s hydrosphere The hydrosphere is all water in, on and around the planet
I am the blue-eyed giant, reaching far and wide across the planet’s surface. Gaze into my depths and you’ll see wonders and mysteries that will blow your mind! My great volume acts as a sink for the Sun’s energy. I soak up its rays, helping to keep Earth warm and affecting its climate. My currents drive the globe’s wind patterns. Though I have just one body, I am subdivided into five mammoth oceans. The biggest is Pacific, which stretches majestically between the Americas, Asia and Australia. Atlantic – the saltiest ocean – reaches from Europe to the Americas. Warm Indian Ocean hugs the east coast of Africa up to India, while frigid Southern Ocean wraps around Antarctica. Lastly, small, frozenover Arctic Ocean sits all a shiver at the North Pole. Brrr!
Ocean Area of all oceans: 360 million km2 Volume of all oceans: approximately 1.3 billion km3 Average depth of the oceans: 3790 m 8
9
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Seas Water World Large areas of salt water connected to the ocean Can be cut off from the ocean completely (e.g. Caspian Sea) These bodies include gulfs, inlets, passages and bays
Ahoy there! We are Ocean’s little friends. Our boots may be smaller and take less to fill, but we’re an important part of Earth’s fascinating saltwater story. The difference between us and Ocean is that we are often surrounded by land (although almost always with a channel to our expansive pal). Our names suggest adventure and romance. Take Celebes, in the western Pacific, with its stunning coral reefs and notorious pirates, or North Atlantic Sargasso – the only sea with no land coasts. Surrounded on all sides by swift Atlantic currents, Sargasso’s water is calm, deep blue and crystal clear. Migrating eels journey here to lay their eggs below the abundant floating seaweed that also shelters young turtles from predators on the prowl.
Seas Largest sea: Philippine Sea (surface area: 5,177,762 km2) Amount of salt in 1 litre of seawater: 35 g Proportion of Earth’s biomass in the oceans: over 90 % 10
11
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Seas Water World Large areas of salt water connected to the ocean Can be cut off from the ocean completely (e.g. Caspian Sea) These bodies include gulfs, inlets, passages and bays
Ahoy there! We are Ocean’s little friends. Our boots may be smaller and take less to fill, but we’re an important part of Earth’s fascinating saltwater story. The difference between us and Ocean is that we are often surrounded by land (although almost always with a channel to our expansive pal). Our names suggest adventure and romance. Take Celebes, in the western Pacific, with its stunning coral reefs and notorious pirates, or North Atlantic Sargasso – the only sea with no land coasts. Surrounded on all sides by swift Atlantic currents, Sargasso’s water is calm, deep blue and crystal clear. Migrating eels journey here to lay their eggs below the abundant floating seaweed that also shelters young turtles from predators on the prowl.
Seas Largest sea: Philippine Sea (surface area: 5,177,762 km2) Amount of salt in 1 litre of seawater: 35 g Proportion of Earth’s biomass in the oceans: over 90 % 10
11
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Zones Water World Marine environments found at different depths in the ocean Light, water temperature and water pressure vary per zone Some form of life can be found in each of the zones
As well as covering area, Ocean also has depth, and that’s where we come in. From surface to floor, we change in character the lower we go. At the top is the sunlit zone. Sufficient light to allow plants to thrive penetrates about 100–150 m, which means that 90 per cent of all ocean life either resides or feeds here. Below this, the twilight zone has the merest hint of blue light. It’s extremely cold and the water pressure is crushing. No plants live here, just hungry carnivores. Lower still, the midnight zone stretches to the near-freezing muddy plains of the ocean floor, home to bottom feeders and witching-hour predators. Finally, there’s the impressively deep abyssal zone (up to 6000 km) and the hadal zone, where Trench plunges way down, as low as you can go.
Zones Sunlit zone (aka epipelagic zone): 0–200 m Twilight zone (aka mesopelagic zone): 200–1000 m Midnight zone (aka bathypelagic zone): 2000–4000 m 12
13
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Zones Water World Marine environments found at different depths in the ocean Light, water temperature and water pressure vary per zone Some form of life can be found in each of the zones
As well as covering area, Ocean also has depth, and that’s where we come in. From surface to floor, we change in character the lower we go. At the top is the sunlit zone. Sufficient light to allow plants to thrive penetrates about 100–150 m, which means that 90 per cent of all ocean life either resides or feeds here. Below this, the twilight zone has the merest hint of blue light. It’s extremely cold and the water pressure is crushing. No plants live here, just hungry carnivores. Lower still, the midnight zone stretches to the near-freezing muddy plains of the ocean floor, home to bottom feeders and witching-hour predators. Finally, there’s the impressively deep abyssal zone (up to 6000 km) and the hadal zone, where Trench plunges way down, as low as you can go.
Zones Sunlit zone (aka epipelagic zone): 0–200 m Twilight zone (aka mesopelagic zone): 200–1000 m Midnight zone (aka bathypelagic zone): 2000–4000 m 12
13
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Mid-ocean Ridge
Trench Water World
Water World A chain of young mountains that form new ocean floor Longest-known mountain range in the Universe Tall peaks (seamounts) form mid-ocean islands
Tall and broad of shoulder, I have underwater peaks that dwarf those on land. Seamounts rear up from my ridges, sometimes breaking the surface to form islands and reefs. My ranges are connected to each other and I have a very unique skill. Hot and volcanic, I pump out lava to make new ocean crust as part of a process that slowly pushes the continents apart.
Mid-ocean Ridge
Length of mid-ocean ridge mountain chain: over 65,000 km Thickness of ocean crust: 1 to 2 km Tallest seamount: Mauna Kea, Hawaii (10,203 m from ocean floor to summit) 14
Deepest, darkest and coldest part of the ocean Great ditches where ocean crust is dragged back into Earth Only three submersibles have ever been this deep
Trench
I am the lowest of the low, a ditch marking where Earth has dragged the ocean floor down into its hungry interior. My deep gullies and fissures plunge suddenly and steeply, thousands of metres below the ocean floor. With headcrushing pressures and water temperatures barely above freezing, humans know more about the surface of the Moon than they do about me.
Ocean’s deepest point: 10,924 m (Challenger Deep, Mariana Trench) Height of Mount Everest: 8848 m Proper name for the trench zone: hadal zone 15
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Mid-ocean Ridge
Trench Water World
Water World A chain of young mountains that form new ocean floor Longest-known mountain range in the Universe Tall peaks (seamounts) form mid-ocean islands
Tall and broad of shoulder, I have underwater peaks that dwarf those on land. Seamounts rear up from my ridges, sometimes breaking the surface to form islands and reefs. My ranges are connected to each other and I have a very unique skill. Hot and volcanic, I pump out lava to make new ocean crust as part of a process that slowly pushes the continents apart.
Mid-ocean Ridge
Length of mid-ocean ridge mountain chain: over 65,000 km Thickness of ocean crust: 1 to 2 km Tallest seamount: Mauna Kea, Hawaii (10,203 m from ocean floor to summit) 14
Deepest, darkest and coldest part of the ocean Great ditches where ocean crust is dragged back into Earth Only three submersibles have ever been this deep
Trench
I am the lowest of the low, a ditch marking where Earth has dragged the ocean floor down into its hungry interior. My deep gullies and fissures plunge suddenly and steeply, thousands of metres below the ocean floor. With headcrushing pressures and water temperatures barely above freezing, humans know more about the surface of the Moon than they do about me.
Ocean’s deepest point: 10,924 m (Challenger Deep, Mariana Trench) Height of Mount Everest: 8848 m Proper name for the trench zone: hadal zone 15
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Chapter 2 Ocean Motion
With most of the planet covered in slippy-slidey water, this is a world in motion. Wave transports energy across the oceans, as seawater is pushed hither and thither by the wind. It is here that you’ll find Water Current trying out a few turbulent tricks. Meanwhile, the Moon pulls Earth’s surface towards it, creating two bulges as it orbits, and these force moonstruck Tide to rise and fall. Of course, the big player in this great game is Ocean Current. In shifting warm water around the planet, this stirrer and mixer of vast water masses also drives the world’s Weather Systems. What a com-“motion”! 16
Wave
Tide
Ocean Current
Weather Systems
Tidal Current
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Chapter 2 Ocean Motion
With most of the planet covered in slippy-slidey water, this is a world in motion. Wave transports energy across the oceans, as seawater is pushed hither and thither by the wind. It is here that you’ll find Water Current trying out a few turbulent tricks. Meanwhile, the Moon pulls Earth’s surface towards it, creating two bulges as it orbits, and these force moonstruck Tide to rise and fall. Of course, the big player in this great game is Ocean Current. In shifting warm water around the planet, this stirrer and mixer of vast water masses also drives the world’s Weather Systems. What a com-“motion”! 16
Wave
Tide
Ocean Current
Weather Systems
Tidal Current
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Chapter 3 Shoreline Gang
The shallow-water zones surrounding Earth’s landmasses are a mere drop in the ocean’s total volume, but they supply more than 90 per cent of our seafood. Young fish stay here until they’re big enough to venture out into open water. Closer in, the shore is licked by waves and washed by tides to create a range of different habitats – from sandy beaches, rocky shores and cliffs, to vast mudflats and mangroves. This place is teeming with creatures who are submerged one moment and stranded without water the next. Take a look in any rock pool and you’ll find a very special crew scuttling away from you! 28
Seaweed
Seashells
Sea Slug
Sea Anemone
Sea Urchin
Prawn
Barnacle
Crab
Lobster
Seahorse
Mudskipper
Marine Iguana
Dugong
Shore Birds
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Chapter 3 Shoreline Gang
The shallow-water zones surrounding Earth’s landmasses are a mere drop in the ocean’s total volume, but they supply more than 90 per cent of our seafood. Young fish stay here until they’re big enough to venture out into open water. Closer in, the shore is licked by waves and washed by tides to create a range of different habitats – from sandy beaches, rocky shores and cliffs, to vast mudflats and mangroves. This place is teeming with creatures who are submerged one moment and stranded without water the next. Take a look in any rock pool and you’ll find a very special crew scuttling away from you! 28
Seaweed
Seashells
Sea Slug
Sea Anemone
Sea Urchin
Prawn
Barnacle
Crab
Lobster
Seahorse
Mudskipper
Marine Iguana
Dugong
Shore Birds
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Chapter 4 Reef Chillin’
The whole reef community depends on the health of lovely Coral – a fragile habitat increasingly endangered by environmental change. A riot of colour, coral reefs play host to some pretty wild scenes. Life is a carnival, with nearly a quarter of the world’s marine species either living on the reef or simply chillin’ out down here. The reefs themselves are alive – inhabited by tiny coral polyps – and their towering structures provide a home for a bewildering parade of marine life. Corals prefer warm, sunlit waters, but some hardy reef colonists try out the deep, dark and cold northern waters (now that’s chillin’!). 50
Coral
Sea Fan
Sponge
Starfish
Reef Tenders
Reef Hunters
Moray Eel
Ray
Blue-ringed Octopus
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Chapter 4 Reef Chillin’
The whole reef community depends on the health of lovely Coral – a fragile habitat increasingly endangered by environmental change. A riot of colour, coral reefs play host to some pretty wild scenes. Life is a carnival, with nearly a quarter of the world’s marine species either living on the reef or simply chillin’ out down here. The reefs themselves are alive – inhabited by tiny coral polyps – and their towering structures provide a home for a bewildering parade of marine life. Corals prefer warm, sunlit waters, but some hardy reef colonists try out the deep, dark and cold northern waters (now that’s chillin’!). 50
Coral
Sea Fan
Sponge
Starfish
Reef Tenders
Reef Hunters
Moray Eel
Ray
Blue-ringed Octopus
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Coral Reef Chillin’ Soft-bodied house-building animals called polyps Their hard, stone houses offer protection from predators Some corals make reefs that can live for thousands of years
We live in high-rise colonies, all crammed in on top of one another. Our white, calcium carbonate apartments might be a squeeze, but there’s always plenty of clear, unpolluted water, good light and warmth. What’s known as a “coral head” is actually a vast colony of colourful, genetically identical polyps, each only a few millimetres across. Many hands make light work and there is no shortage of labour here. Most of us build slowly and steadily, but we are master masons. For proof just look at the Great Barrier Reef – you can see it from space! We operate a strict one-polyp, one-house policy with nutrients piped in via a system of canals. We’ve also teamed up with algae, who take energy from the Sun and provide us with food.
Coral Coral types: massive, branching, columnar, encrusting and plates Deepest-living coral: Lophelia (3000 m) Largest coral reef: Great Barrier Reef (2600 km long) 52
53
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Coral Reef Chillin’ Soft-bodied house-building animals called polyps Their hard, stone houses offer protection from predators Some corals make reefs that can live for thousands of years
We live in high-rise colonies, all crammed in on top of one another. Our white, calcium carbonate apartments might be a squeeze, but there’s always plenty of clear, unpolluted water, good light and warmth. What’s known as a “coral head” is actually a vast colony of colourful, genetically identical polyps, each only a few millimetres across. Many hands make light work and there is no shortage of labour here. Most of us build slowly and steadily, but we are master masons. For proof just look at the Great Barrier Reef – you can see it from space! We operate a strict one-polyp, one-house policy with nutrients piped in via a system of canals. We’ve also teamed up with algae, who take energy from the Sun and provide us with food.
Coral Coral types: massive, branching, columnar, encrusting and plates Deepest-living coral: Lophelia (3000 m) Largest coral reef: Great Barrier Reef (2600 km long) 52
53
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Sea Fan
Sponge
Reef Chillin’
Reef Chillin’
Flexible, non-reef-forming coral rooted to a hard surface This flattened spray of colour is related to the sea anemone Has stinging cells that snare tiny creatures Fan-tastically elegant and brightly coloured, I am the peacock of the sea. But beware, my flashy whips spell danger for some. Like my cousins, Jellyfish, Coral and Anemone, I’m a stinger. (Why else would they call me Gorgonian, after mythical Medusa, who had biting snakes for hair?) Inhospitable you might think, but I provide safe harbour for tiny goby fish and seahorses.
Sea Fan
Scientific name: Gorgonacea Number of species: at least 500 Distribution: shallow, tropical waters, especially Caribbean and Indo-Pacific 54
Structurally one of the simplest multicellular animals that exists Attaches to hard surfaces and grows into weird shapes Has no stomach, so filters food from the water through pores
Sponge
Chillax dude! I keep things cool by not being overly complicated. What more do you need in life than a body full of holes and channels awash with lovely cool water helped along by microscopic hairs? I use currents to bring me food particles suspended in the water. Plus, I am one of Earth’s great regenerators. Oh yeah, chop me up into pieces and I can regroup – simple pleasures…
Scientific name: Porifera Number of species: about 5000 Volume of water passing through a sponge: up to 20,000 times its volume, daily 55
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Sea Fan
Sponge
Reef Chillin’
Reef Chillin’
Flexible, non-reef-forming coral rooted to a hard surface This flattened spray of colour is related to the sea anemone Has stinging cells that snare tiny creatures Fan-tastically elegant and brightly coloured, I am the peacock of the sea. But beware, my flashy whips spell danger for some. Like my cousins, Jellyfish, Coral and Anemone, I’m a stinger. (Why else would they call me Gorgonian, after mythical Medusa, who had biting snakes for hair?) Inhospitable you might think, but I provide safe harbour for tiny goby fish and seahorses.
Sea Fan
Scientific name: Gorgonacea Number of species: at least 500 Distribution: shallow, tropical waters, especially Caribbean and Indo-Pacific 54
Structurally one of the simplest multicellular animals that exists Attaches to hard surfaces and grows into weird shapes Has no stomach, so filters food from the water through pores
Sponge
Chillax dude! I keep things cool by not being overly complicated. What more do you need in life than a body full of holes and channels awash with lovely cool water helped along by microscopic hairs? I use currents to bring me food particles suspended in the water. Plus, I am one of Earth’s great regenerators. Oh yeah, chop me up into pieces and I can regroup – simple pleasures…
Scientific name: Porifera Number of species: about 5000 Volume of water passing through a sponge: up to 20,000 times its volume, daily 55
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Chapter 5 Open-water Crew
Over half of the world’s surface is open water, far away from the shore and a long way from the seafloor. Most things live in the top 200 m or so, lit by the Sun. They congregate where upwelling currents bring nutrients in from the deep. This is a good place to live, protected from the worst of the Sun’s radiation, which can interfere with DNA. There is no fear of drying out, either – temperature extremes that occur on land do not arise here, and creatures are surrounded on all sides by the chemicals and food needed to sustain life. The result is a diverse range of open-water inhabitants. Ready for a dip? 68
Plankton
Jellyfish
Fast Fish
Sea Turtle
Blue Whale
Porpoise and Dolphin
Great White Shark
Humboldt Squid
Seabirds
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Chapter 5 Open-water Crew
Over half of the world’s surface is open water, far away from the shore and a long way from the seafloor. Most things live in the top 200 m or so, lit by the Sun. They congregate where upwelling currents bring nutrients in from the deep. This is a good place to live, protected from the worst of the Sun’s radiation, which can interfere with DNA. There is no fear of drying out, either – temperature extremes that occur on land do not arise here, and creatures are surrounded on all sides by the chemicals and food needed to sustain life. The result is a diverse range of open-water inhabitants. Ready for a dip? 68
Plankton
Jellyfish
Fast Fish
Sea Turtle
Blue Whale
Porpoise and Dolphin
Great White Shark
Humboldt Squid
Seabirds
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Plankton Open-water Crew Microscopic drifters called phytoplankton and zooplankton Burst into life in spring, turning parts of the ocean green Phytoplankton is the ocean’s main source of plant food
Green and serene, we are members of an entire world of microscopic plants and animals that float free in the ocean. All we need for life is light, clean water and food. Some of us are super-tiny plants known as phytoplankton (say “fye-toe-plank-ton”). Soaking up the Sun’s rays, we produce half of the world’s oxygen. Floating alongside, gorging on our veggie buffet, are billions of microscopic beasts such as jellyfish, crustaceans, snails, squid and fish larvae. This zooplankton (say “zoo-plank-ton”) makes a great snack in itself, snaffled by a host of nightmarish creatures who ascend from the deep after sundown. Together we attract forage fish, jellyfish, basking sharks and seabirds, as well as seals, sea lions and whales. You could say we are the ocean’s biggest attraction!
Plankton Smallest plankton: picoplankton (0.0002 to 0.02 mm: bacteria, small protists) Largest plankton: megaplankton (2 to 20 cm: some seaweed and jellyfish) Spring bloom: term for rapid growth of phytoplankton as the oceans warm up 70
71
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Plankton Open-water Crew Microscopic drifters called phytoplankton and zooplankton Burst into life in spring, turning parts of the ocean green Phytoplankton is the ocean’s main source of plant food
Green and serene, we are members of an entire world of microscopic plants and animals that float free in the ocean. All we need for life is light, clean water and food. Some of us are super-tiny plants known as phytoplankton (say “fye-toe-plank-ton”). Soaking up the Sun’s rays, we produce half of the world’s oxygen. Floating alongside, gorging on our veggie buffet, are billions of microscopic beasts such as jellyfish, crustaceans, snails, squid and fish larvae. This zooplankton (say “zoo-plank-ton”) makes a great snack in itself, snaffled by a host of nightmarish creatures who ascend from the deep after sundown. Together we attract forage fish, jellyfish, basking sharks and seabirds, as well as seals, sea lions and whales. You could say we are the ocean’s biggest attraction!
Plankton Smallest plankton: picoplankton (0.0002 to 0.02 mm: bacteria, small protists) Largest plankton: megaplankton (2 to 20 cm: some seaweed and jellyfish) Spring bloom: term for rapid growth of phytoplankton as the oceans warm up 70
71
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Jellyfish Open-water Crew Free-swimming, brainless wonder – the largest kind of plankton One of four different classes of related stinging animals Some tiny fish hide from predators behind jellyfish tentacles
A jelly-belly dancer, I am a silent and deadly menace of the ocean. I float rather than swim, pulsing softly like a heartbeat, going wherever the ocean currents take me. I am simplicity itself. I don’t have a central nervous system, let alone a brain, and I breathe through my skin, so there’s no need for complicated gills. I might be 90 per cent water, but I’m no drip! My trailing tentacles are lined with spring-loaded, venom-tipped spears that fire into the body of anything that happens to get tangled in my tentacles. In some of us, this “curtain of death” is powerful enough to kill a human. Like my photoplankton cousins, I bloom in the right conditions. My microscopic larvae suddenly mature into full jellies, creating a swarm of hundreds of thousands of beautiful blobs.
Jellyfish Most deadly jellyfish: box jellyfish Longest tentacles: lion’s mane jellyfish (up to 120 m) Distribution: worldwide/all oceans 72
73
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Jellyfish Open-water Crew Free-swimming, brainless wonder – the largest kind of plankton One of four different classes of related stinging animals Some tiny fish hide from predators behind jellyfish tentacles
A jelly-belly dancer, I am a silent and deadly menace of the ocean. I float rather than swim, pulsing softly like a heartbeat, going wherever the ocean currents take me. I am simplicity itself. I don’t have a central nervous system, let alone a brain, and I breathe through my skin, so there’s no need for complicated gills. I might be 90 per cent water, but I’m no drip! My trailing tentacles are lined with spring-loaded, venom-tipped spears that fire into the body of anything that happens to get tangled in my tentacles. In some of us, this “curtain of death” is powerful enough to kill a human. Like my photoplankton cousins, I bloom in the right conditions. My microscopic larvae suddenly mature into full jellies, creating a swarm of hundreds of thousands of beautiful blobs.
Jellyfish Most deadly jellyfish: box jellyfish Longest tentacles: lion’s mane jellyfish (up to 120 m) Distribution: worldwide/all oceans 72
73
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Fast Fish Open-water Crew Friction-free fish that move like bullets through the water Marlin and swordfish swim alone; others, like tuna, form shoals These guys do everything on the move – even rest
Just you try to catch a glimpse of us as we flit past with a flash and a twinkle. Ruling the open ocean and built for lightning speed, we are obsessed with streamlining. We are like sleek torpedoes. Our eyes are flush with our bodies and we have stiff, narrow fins that we can tuck back into hollow slots. Anything that causes drag is out – too many scales, for example. Some of our fastest crew – marlin, sailfish and swordfish – have rapier-like noses that really “slice” through the water! Many of us group together in vast schools. We love to eat herring and need awesome control to catch them as they swirl in the water. We have a line of extra-sensitive cells running down each side of the body, and this stops us crashing into each other as we give chase.
Fast Fish Fastest fish: Indo-Pacific sailfish (bursts of 110 km/h) Tuna migration: about 10,800 km yearly, from western Atlantic to Mediterranean Time taken to cross the Atlantic Ocean: 119 days (bluefin tuna) 74
75
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Fast Fish Open-water Crew Friction-free fish that move like bullets through the water Marlin and swordfish swim alone; others, like tuna, form shoals These guys do everything on the move – even rest
Just you try to catch a glimpse of us as we flit past with a flash and a twinkle. Ruling the open ocean and built for lightning speed, we are obsessed with streamlining. We are like sleek torpedoes. Our eyes are flush with our bodies and we have stiff, narrow fins that we can tuck back into hollow slots. Anything that causes drag is out – too many scales, for example. Some of our fastest crew – marlin, sailfish and swordfish – have rapier-like noses that really “slice” through the water! Many of us group together in vast schools. We love to eat herring and need awesome control to catch them as they swirl in the water. We have a line of extra-sensitive cells running down each side of the body, and this stops us crashing into each other as we give chase.
Fast Fish Fastest fish: Indo-Pacific sailfish (bursts of 110 km/h) Tuna migration: about 10,800 km yearly, from western Atlantic to Mediterranean Time taken to cross the Atlantic Ocean: 119 days (bluefin tuna) 74
75
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Chapter 7 Chilly Chaps
Locked in ice for much of the year, the seas around Earth’s poles are parky places. Their chilly inhabitants have to be on their toes to stop freezing their paws, fins and flippers off! That is why this lot are a blubbery crew, with layers of fat beneath the skin to keep them toasty in the cold water. You might think that the going would be too tough in these high latitudes, that animals would go in search of a more comfortable climate, but upwelling waters loaded with vital nutrients and yearly blooms of plankton keep the larders full and the living good. The Chilly Chaps are here to make a splash! 98
Sea Ice
Ice Shelf
Krill
Icefish
Narwhal
Killer Whale
Walrus, Seal and Sea Lion
Polar Bear
Penguin
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Chapter 7 Chilly Chaps
Locked in ice for much of the year, the seas around Earth’s poles are parky places. Their chilly inhabitants have to be on their toes to stop freezing their paws, fins and flippers off! That is why this lot are a blubbery crew, with layers of fat beneath the skin to keep them toasty in the cold water. You might think that the going would be too tough in these high latitudes, that animals would go in search of a more comfortable climate, but upwelling waters loaded with vital nutrients and yearly blooms of plankton keep the larders full and the living good. The Chilly Chaps are here to make a splash! 98
Sea Ice
Ice Shelf
Krill
Icefish
Narwhal
Killer Whale
Walrus, Seal and Sea Lion
Polar Bear
Penguin
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Sea Ice
Ice Shelf Chilly Chaps
Chilly Chaps Ice that is made when seawater freezes Formed at both poles, it makes up the polar ice packs “Fast ice” sticks to the coastline; “drift ice” floats about
I’m a drifter – I like to go with the floe. I appear when it gets cold enough for seawater to freeze. As it does so, it loses some of its salt content. Ice is less dense than liquid water, so I float on top of the sea, changing size with the seasons. I balloon in winter and shrink with the summer melt. With each passing year there’s less of me about as the world’s oceans heat up. Shame!
Freezing point of seawater: –1.8 ºC Total area of polar ice pack: 15,600,000 km2 Thickness of pack ice: 1 to 4 m 100
Sea Ice
Floating platform of ice that juts out into the sea Made of compressed snow, the ice is fresh water Large pieces of shelf snap off to float free as icebergs
Ice Shelf
I’m totally frigid – a cold shoulder is all you’ll get if you nestle up to me. Unlike my bro, Sea Ice, I form on land from snow that gets compressed into glaciers. I slip down to the shore as glacier ice and end up jutting out into the sea like a quiff of frozen water. Being compressed makes my ice denser than normal ice and so almost 90 per cent of me floats beneath the surface. Feel the chill!
Thickness of sheet: 100 to 1000 m Largest existing iceberg: Iceberg B-15; 295 km long, 37 km wide An iceberg caused the Titanic to sink on her maiden voyage in 1912 101
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Sea Ice
Ice Shelf Chilly Chaps
Chilly Chaps Ice that is made when seawater freezes Formed at both poles, it makes up the polar ice packs “Fast ice” sticks to the coastline; “drift ice” floats about
I’m a drifter – I like to go with the floe. I appear when it gets cold enough for seawater to freeze. As it does so, it loses some of its salt content. Ice is less dense than liquid water, so I float on top of the sea, changing size with the seasons. I balloon in winter and shrink with the summer melt. With each passing year there’s less of me about as the world’s oceans heat up. Shame!
Freezing point of seawater: –1.8 ºC Total area of polar ice pack: 15,600,000 km2 Thickness of pack ice: 1 to 4 m 100
Sea Ice
Floating platform of ice that juts out into the sea Made of compressed snow, the ice is fresh water Large pieces of shelf snap off to float free as icebergs
Ice Shelf
I’m totally frigid – a cold shoulder is all you’ll get if you nestle up to me. Unlike my bro, Sea Ice, I form on land from snow that gets compressed into glaciers. I slip down to the shore as glacier ice and end up jutting out into the sea like a quiff of frozen water. Being compressed makes my ice denser than normal ice and so almost 90 per cent of me floats beneath the surface. Feel the chill!
Thickness of sheet: 100 to 1000 m Largest existing iceberg: Iceberg B-15; 295 km long, 37 km wide An iceberg caused the Titanic to sink on her maiden voyage in 1912 101
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Krill Chilly Chaps Shrimp-like crustaceans related to crabs and lobsters Like living in swarms of hundreds of millions of animals Main food source for a great many sea animals
Life is tough when you’re snack food for half the animals in the ocean. We stick together in brain-boggling numbers, keeping a sharp lookout for whales, penguins, squid, seals and many, many fish. Although we swim at just 5 to 10 cm per second, we snap our tails when threatened and fire through the water – we’re the ultimate fast food! We spend our days avoiding predators, shivering in the cold and dark, 100 m below the surface. By night we rise up as a vast cloudy mass to feed on microscopic phytoplankton. We have the largest biomass of any single creature on Earth – more than double that of humans and rivalled only by copepods (mini crustaceans to you). We’re tiny, but hugely important and, without us, life in the cold southern seas simply wouldn’t survive.
Krill Scientific name: Euphasia superba Average size: 5 cm Distribution: Antarctic ocean 102
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Krill Chilly Chaps Shrimp-like crustaceans related to crabs and lobsters Like living in swarms of hundreds of millions of animals Main food source for a great many sea animals
Life is tough when you’re snack food for half the animals in the ocean. We stick together in brain-boggling numbers, keeping a sharp lookout for whales, penguins, squid, seals and many, many fish. Although we swim at just 5 to 10 cm per second, we snap our tails when threatened and fire through the water – we’re the ultimate fast food! We spend our days avoiding predators, shivering in the cold and dark, 100 m below the surface. By night we rise up as a vast cloudy mass to feed on microscopic phytoplankton. We have the largest biomass of any single creature on Earth – more than double that of humans and rivalled only by copepods (mini crustaceans to you). We’re tiny, but hugely important and, without us, life in the cold southern seas simply wouldn’t survive.
Krill Scientific name: Euphasia superba Average size: 5 cm Distribution: Antarctic ocean 102
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Penguin Chilly Chaps Chubby Antarctic seabird, fully adapted to life at sea Has a streamlined body, flipper wings and heavy bones Incredibly powerful and balletic swimmer
I have you fooled! I’m no cute bird in a dinner jacket, but an agile, two-tone ninja. OK, so I get in a bit of a flap out of the water, but what do you expect? I’m squat, I waddle and I can’t fly. Get me in the water, though, and I’ll adeptly go in for the krill! I’m a tough old thing, coming in to land on breakers that would snap a ship in two. Fortunately I bounce off the rocks! My dark top/light belly combo makes me hard to spot in the water. Thick, matted feathers and a blubbery layer keep me warm in freezing seas. When it comes to incubating eggs, none do it better than the male Emperor, who balances an egg on his feet for over two months. Hundreds of them huddle together to keep warm in vicious Antarctic storms. That’s male bonding for you!
Penguin Largest penguin: Emperor penguin (up to 1.1 m tall) Diving speed: 6 to 12 km/h Distribution: southern hemisphere (mainly Antarctica) 112
113
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Penguin Chilly Chaps Chubby Antarctic seabird, fully adapted to life at sea Has a streamlined body, flipper wings and heavy bones Incredibly powerful and balletic swimmer
I have you fooled! I’m no cute bird in a dinner jacket, but an agile, two-tone ninja. OK, so I get in a bit of a flap out of the water, but what do you expect? I’m squat, I waddle and I can’t fly. Get me in the water, though, and I’ll adeptly go in for the krill! I’m a tough old thing, coming in to land on breakers that would snap a ship in two. Fortunately I bounce off the rocks! My dark top/light belly combo makes me hard to spot in the water. Thick, matted feathers and a blubbery layer keep me warm in freezing seas. When it comes to incubating eggs, none do it better than the male Emperor, who balances an egg on his feet for over two months. Hundreds of them huddle together to keep warm in vicious Antarctic storms. That’s male bonding for you!
Penguin Largest penguin: Emperor penguin (up to 1.1 m tall) Diving speed: 6 to 12 km/h Distribution: southern hemisphere (mainly Antarctica) 112
113
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Chapter 8 Ocean Explorers
These intrepid explorers demonstrate some of the ways in which humans investigate and exploit the oceans. Life should be a beach for these adventurers – there are still many regions that are largely unexplored – but it seems these guys have a beef with the blue stuff. While 3000 robot probes surface every ten days to beam ocean data back to base, we are whisking food out of the water faster than it can be replaced. Meanwhile, no end of muck floats about, fouling open water and coastlines across the globe. And then there’s ocean warming, the greatest threat of all. This could be the time to bail... 114
Diving
Submersible
Pollution
Fishing
Oil Rig
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Chapter 8 Ocean Explorers
These intrepid explorers demonstrate some of the ways in which humans investigate and exploit the oceans. Life should be a beach for these adventurers – there are still many regions that are largely unexplored – but it seems these guys have a beef with the blue stuff. While 3000 robot probes surface every ten days to beam ocean data back to base, we are whisking food out of the water faster than it can be replaced. Meanwhile, no end of muck floats about, fouling open water and coastlines across the globe. And then there’s ocean warming, the greatest threat of all. This could be the time to bail... 114
Diving
Submersible
Pollution
Fishing
Oil Rig
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Index P
Character entries are bold
AB
IJ
Anglerfish 89 Barnacle 37, 39, 78 Blue-ringed Octopus 62, 66 Blue Whale 78
Icefish 104 Ice Shelf 101 Jellyfish 54, 70, 72, 76
C Coral 10, 50, 52, 54, 58, 60 Cousteau, Jacques 4 Crab 36, 38, 39, 40, 41, 48, 64, 66, 96, 102
D Diving 116 Dolphin 80, 106 Dugong 46
FG Fast Fish 74 Fishing 116, 122 Great White Shark 82, 106
H Hagfish 92 Humboldt Squid 84 Hydrothermal Vent 96 124
KL Killer Whale 105, 106 Krill 78, 102, 108 Lobster 38, 40, 41, 96, 102
M Marine Iguana 45 Mid-ocean Ridge 14 Moray Eel 62 Mudskipper 44
N Narwhal 105
O Ocean 6, 8, 10, 12, 14, 15, 20, 24, 26, 28, 38, 56, 70, 72, 76, 78, 80, 94, 100, 119, 120 Ocean Current 8, 16, 24, 26, 72, 120, 122 Oil Rig 119
Penguin 86, 102, 108, 112 Plankton 42, 70, 72, 90, 98, 102, 120 Polar Bear 105, 110 Pollution 120 Porpoise 80 Prawn 36, 38
R Ray 64 Reef Hunters 60 Reef Tenders 58, 60
S Sea 6, 10, 18, 20, 22, 24, 38, 98, 119, 120, 122 Sea Anemone 34, 36, 40, 54, 58 Seabirds 70, 76, 86, 112, 120 Sea Cucumber 94 Sea Fan 54 Seahorse 42, 54 Sea Ice 100, 101, 105, 110 Seal 70, 102, 106, 108, 110 Sea Lion 70, 106, 108 Seashells 32, 39, 56, 86 Sea Slug 34
Sea Turtle 76 Sea Urchin 37, 94 Seaweed 10, 30, 37, 44, 45, 76 shark 58, 60, 70, 76, 82 Shorebirds 48 Sponge 34, 37, 55, 58 squid 66, 70, 84, 102, 105 Starfish 37, 56, 94 Submersible 15, 118
T Tidal Current 16, 22, 24 Tide 16, 20, 28, 39, 44 Trench 6, 12, 15, 118 Tripod Fish 89 turtle 19, 76, 122
W Walrus 108 Wave 16, 18, 22, 28, 32, 39, 41 Weather Systems 10, 16, 26 whale 39, 70, 78, 102, 105, 106
Z Zones 12, 39, 88
125
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Index P
Character entries are bold
AB
IJ
Anglerfish 89 Barnacle 37, 39, 78 Blue-ringed Octopus 62, 66 Blue Whale 78
Icefish 104 Ice Shelf 101 Jellyfish 54, 70, 72, 76
C Coral 10, 50, 52, 54, 58, 60 Cousteau, Jacques 4 Crab 36, 38, 39, 40, 41, 48, 64, 66, 96, 102
D Diving 116 Dolphin 80, 106 Dugong 46
FG Fast Fish 74 Fishing 116, 122 Great White Shark 82, 106
H Hagfish 92 Humboldt Squid 84 Hydrothermal Vent 96 124
KL Killer Whale 105, 106 Krill 78, 102, 108 Lobster 38, 40, 41, 96, 102
M Marine Iguana 45 Mid-ocean Ridge 14 Moray Eel 62 Mudskipper 44
N Narwhal 105
O Ocean 6, 8, 10, 12, 14, 15, 20, 24, 26, 28, 38, 56, 70, 72, 76, 78, 80, 94, 100, 119, 120 Ocean Current 8, 16, 24, 26, 72, 120, 122 Oil Rig 119
Penguin 86, 102, 108, 112 Plankton 42, 70, 72, 90, 98, 102, 120 Polar Bear 105, 110 Pollution 120 Porpoise 80 Prawn 36, 38
R Ray 64 Reef Hunters 60 Reef Tenders 58, 60
S Sea 6, 10, 18, 20, 22, 24, 38, 98, 119, 120, 122 Sea Anemone 34, 36, 40, 54, 58 Seabirds 70, 76, 86, 112, 120 Sea Cucumber 94 Sea Fan 54 Seahorse 42, 54 Sea Ice 100, 101, 105, 110 Seal 70, 102, 106, 108, 110 Sea Lion 70, 106, 108 Seashells 32, 39, 56, 86 Sea Slug 34
Sea Turtle 76 Sea Urchin 37, 94 Seaweed 10, 30, 37, 44, 45, 76 shark 58, 60, 70, 76, 82 Shorebirds 48 Sponge 34, 37, 55, 58 squid 66, 70, 84, 102, 105 Starfish 37, 56, 94 Submersible 15, 118
T Tidal Current 16, 22, 24 Tide 16, 20, 28, 39, 44 Trench 6, 12, 15, 118 Tripod Fish 89 turtle 19, 76, 122
W Walrus 108 Wave 16, 18, 22, 28, 32, 39, 41 Weather Systems 10, 16, 26 whale 39, 70, 78, 102, 105, 106
Z Zones 12, 39, 88
125
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Glossary Alga (pl. algae) A simple, non-flowering plant, without proper roots, stem or leaves; often single-celled. Amphibious A creature that can live in and out of water. Biomass The total mass of animals (or plants) in an area, zone or habitat. Bivalve A type of mollusc, encased in two hinged shells (e.g. oyster, mussel, clam, scallop), which attaches to rocks with a soft foot. Blowhole A breathing hole, or nostril, on top of the head of a whale, dolphin or porpoise. Blubber The layer of insulating fat under the skin of sea mammals and birds. Brachiopod An invertebrate whose soft body is protected by two hinged shells, which attaches to rocks with a stalk. Cartilage A tough and flexible connective tissue; some fish have skeletons made from cartilage. Cephalopod Octopus, squid and cuttlefish; a predatory mollusc with large eyes and tentacles surrounding a beaked mouth; squirts a cloud of inky fluid to confuse its predators. Chelonian A group of reptiles that includes the turtle family, tortoises and terrapins. Clutch The group of eggs produced by a reptile. Colony A community of animals living close together. Continent Earth’s main blocks of land (Africa, Asia, Antarctica, Asia, Europe, North and South America). 126
Copepod A small crustacean, living as plankton; the most numerous animal on Earth. Crustacean A subaqua invertebrate with eight or more jointed legs (e.g. crab, lobster, barnacle and copepod). Cyclone Wind that moves in a circular motion towards an area of low pressure. Detritus The messed-up rubble fragments of wrecked and destroyed materials. Echinoderm A marine invertebrate with a hard skeleton, tube feet and a body shape based on a five-pointed star (e.g. starfish, sea urchin and sea cucumber). Floe A sheet of floating ice. Gastropod A mollusc with a large muscular “foot” and a spiral shell (e.g. sea snail and whelk). Herbivore An animal that feeds only on plants. Hermaphrodite An animal with both male and female sexual organs. Hydroid A tiny aquatic invertebrate with a tube body and a ring of stinging tentacles around the mouth. Invertebrate An animal without a backbone. Latitude An imaginary line that divides Earth horizontally – high latitudes are zones near the poles; low latitudes are near the Equator. Mammal A warm-blooded animal, often with hair, that gives birth to live young. Maw An old-fashioned word for mouth. 127
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Glossary Alga (pl. algae) A simple, non-flowering plant, without proper roots, stem or leaves; often single-celled. Amphibious A creature that can live in and out of water. Biomass The total mass of animals (or plants) in an area, zone or habitat. Bivalve A type of mollusc, encased in two hinged shells (e.g. oyster, mussel, clam, scallop), which attaches to rocks with a soft foot. Blowhole A breathing hole, or nostril, on top of the head of a whale, dolphin or porpoise. Blubber The layer of insulating fat under the skin of sea mammals and birds. Brachiopod An invertebrate whose soft body is protected by two hinged shells, which attaches to rocks with a stalk. Cartilage A tough and flexible connective tissue; some fish have skeletons made from cartilage. Cephalopod Octopus, squid and cuttlefish; a predatory mollusc with large eyes and tentacles surrounding a beaked mouth; squirts a cloud of inky fluid to confuse its predators. Chelonian A group of reptiles that includes the turtle family, tortoises and terrapins. Clutch The group of eggs produced by a reptile. Colony A community of animals living close together. Continent Earth’s main blocks of land (Africa, Asia, Antarctica, Asia, Europe, North and South America). 126
Copepod A small crustacean, living as plankton; the most numerous animal on Earth. Crustacean A subaqua invertebrate with eight or more jointed legs (e.g. crab, lobster, barnacle and copepod). Cyclone Wind that moves in a circular motion towards an area of low pressure. Detritus The messed-up rubble fragments of wrecked and destroyed materials. Echinoderm A marine invertebrate with a hard skeleton, tube feet and a body shape based on a five-pointed star (e.g. starfish, sea urchin and sea cucumber). Floe A sheet of floating ice. Gastropod A mollusc with a large muscular “foot” and a spiral shell (e.g. sea snail and whelk). Herbivore An animal that feeds only on plants. Hermaphrodite An animal with both male and female sexual organs. Hydroid A tiny aquatic invertebrate with a tube body and a ring of stinging tentacles around the mouth. Invertebrate An animal without a backbone. Latitude An imaginary line that divides Earth horizontally – high latitudes are zones near the poles; low latitudes are near the Equator. Mammal A warm-blooded animal, often with hair, that gives birth to live young. Maw An old-fashioned word for mouth. 127