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Preface
This fifth edition has been completely updated, rearranged and largely rewri en to reflect the current state of our knowledge, with revised figures and the addition of many colour photographs. A considerable amount of new and additional materials has been integrated into each chapter, and a new chapter on nekton has been added. The book provides the materials essential to any student undertaking courses or modules in marine ecology, marine biology and related topics. It also provides information, ideas, reading lists and references from which particular topics can be pursued in greater detail and additional materials sought. Were he with us today, I hope that Ronald Tait, who wrote the first edition (1968) and for whom I updated the third edition into a fourth expanded edition, would feel that his original aim of presenting marine ecology as a coherent science has been retained. This science of marine ecology must now firmly take into account human impacts on the planet and the ocean. Impacts continue to increase both in type and intensity and have become a part of marine ecology and of the processes that drive marine ecosystems and therefore must also be a part of the study of marine ecology.
Acknowledgements
Frances Dipper would like to thank the following friends, colleagues and organisations for providing photographs and other illustrative materials for this book: Peter Barfield, Sarah Bowen, Fiona Crouch, Marc Dando, David Fenwick, Keith Hiscock, Alison Hitchens, David John, Daniel Jones, Robert Irving, Paula Lightfoot, MBA, MBARI, NASA, Paul Naylor, NOAA, NOC, Rob Spray, Elizabeth Wood and Dawn Watson. Photographs were also sourced from Shu erstock, Alamy and Wikipedia. All photographs are credited in the figure captions. Uncredited photographs are the author’s. She would also like to thank Professor Stephen Hawkins for his encouragement in undertaking this project and for helpful suggestions on content and organisation.
Introduction
Just over 70% of our planet is covered by water, and with the exception of a tiny 3% or so of freshwater (in all its forms including ice), this is all saltwater ocean. While the seabed provides a hugely varied and expansive place to live, it is the immense volume of water above it that provides most of the living space on Earth. Although we will never know for certain the exact environment (or environments) where life first began, most evidence points to somewhere in a salt-rich ocean. Whether this was in warm shallow seashore pools or, as some scientists now postulate, around deep-sea hydrothermal vents, the ocean is certainly where it flourished and diversified before finally emerging onto land.
Many different elements are involved in the study of marine ecology, which can be defined as the study of relationships between organisms, their surroundings and each other. At the base of it all are marine species. However, to gain anything like a full understanding of marine species, it is also necessary to look at them within the context of the habitats and whole ecosystem in which they live. An analogy might be made to the very commonwealth game of cricket. It would be impossible to understand the game without knowing the way the cricket ground is laid out and the rules by which the individuals play. An introductory explanation of what an ecosystem is and the elements within it is given here to start readers along the route to an understanding of marine ecology.
1 Ecological definitions
Ecosystem: An ecosystem is the all-encompassing term that brings together all the elements of the system, both living and nonliving, along with the flow of energy through the system. The activities which comprise species lives are dependent upon and closely
controlled by their external circumstances, by the physical and chemical conditions in which they live and the populations of other organisms with which they interact. In turn the activities of organisms have effects on their surroundings, altering them in various ways. Organisms, therefore, exist only as parts of a complex entity made up of interacting inorganic and biotic elements, to which we apply the term ecosystem.
• Abiotic elements: physical and chemical
• Biotic elements: living organisms, their populations and communities
• Energy in and out: starting with input of solar energy from the sun primarily through photosynthesis, but chemosynthesis can be important in some habitats such as hydrothermal vents and anoxic water and mud (see Section 7.4.6). Energy is transferred through the ecosystem, by movements of materials within and between organisms, mainly through the agencies of feeding, growth, reproduction and decomposition. An ecosystem is therefore essentially a working, changing and evolving sequence of operations, powered (mainly) by solar energy. Energy flows through ecosystems and material is cycled within them.
The ecosystem concept can be applied at different scales which may encompass one other. The ocean can be considered an ecosystem itself, the ocean or marine ecosystem, but the concept is more usually used for ecologically recognisable entities within the ocean ecosystem, such as estuaries and lagoons, the seashore, coral reefs and their adjacent waters. Ecosystems can be open, such as the pelagic zone of the open ocean, or semienclosed as in estuaries or highly enclosed such as saline lagoons.
Habitats: Habitats are essentially the area and environment in which populations and communities of organisms live. Using similar examples as for the ecosystem concept above – the marine habitat is the saltwater environment in which the marine life is found (vs the
freshwater habitat or the terrestrial habitat), the seashore habitat is where intertidal organisms live. Habitat is by no means purely physical and chemical. A kelp forest habitat has both abiotic and biotic elements, including the kelp itself.
Populations: The multitude of organisms living within any habitat or ecosystem does not live randomly but are structured into interacting groups. A population of a particular species consists of individuals living in the same area, such that they can interbreed. In the ocean the ‘same area’ may be a particular depth zone as well as a geographical area. The population of a wanderer such as the Leatherback Turtle (Dermochelys coriacea) may be sca ered over many thousands of miles. Sponges, seaweeds and other sessile (fixed) organisms may also have a sca ered population, through the drifting of their planktonic larval stages. In slow-moving benthic animals with eggs that hatch directly into juveniles, such as some gastropod molluscs, several different populations may be present within just a small area.
Communities: Populations of different species live together in the same area and habitat and interact in many interdependent ways. Together they make up communities of species suited to living under the conditions prevailing in that habitat. Many will be dependent on one another for food and living space, but there will also be competition – both within populations of a species and among populations of different species. Although many features of the marine environment are virtually uniform over wide areas, different parts of the ocean are populated by different communities of organisms. Marine ecological studies aim to discover what these differences are and why they exist and to evaluate the factors responsible.
Biodiversity: Biological diversity or biodiversity is defined by the Convention on Biological Diversity 1992 (cbd.int/convention) as: ‘the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems’.
In terms of biodiversity, the oceans win in that they have a greater number of phyla and classes than either the freshwater or terrestrial habitat, with 39% of phyla endemic (unique) to the oceans (Costello and Chaudhary 2017). However, these authors calculate that only about 16% of named species are marine, partly a reflection of the difficulties in accessing the marine environment, but also due to the amazing diversification of flowering plants, arthropods and fungi on land. Accessing the data on named marine species is now relatively easy through the global database known as WoRMS (World Register of Marine Species). This currently contains nearly 240,000 accepted marine extant species (WoRMS Editorial Board, 2021).
Species: The classical understanding of the term ‘species’ is one of a natural populations of individuals, which are interbreeding or could interbreed, but cannot do so with other such groups (they are ‘reproductively isolated’). This is often called the ‘biological species concept’ of a species. This is a useful guide but is by no means universally applicable, particularly with regard to microorganisms such as bacteria that do not undergo sexual reproduction in the usual sense. There is continued useful scientific debate over the ‘species problem’ bringing in other concepts including morphological, evolutionary and genetic (Hey, 2001).
2 Studying the ocean
There are obvious problems of working in the ocean environment, to which we have no easy access. Our view and knowledge of the oceans is naturally constrained by how we sample it. At the same time, new methods are continually being developed and remote sensing is allowing us to ‘see’ under the surface as never before. The continued development of the next generation of remotely operated vehicles, autonomous underwater vehicles, manned submersibles and other techniques such as marine telemetry (see Sections 7.5 and 8.4.2), is opening up the way to a much greater understanding of even the deepest parts of the ocean. Back in the laboratory, the rapid development of metagenomics – the analysis of environmental samples for genetic material – is allowing detection of marine
bacteria and other microorganisms in true forensic style, without the difficult and time-consuming need to culture them. The fundamental importance of these unseen microorganisms in ocean processes is now becoming obvious. Experimental ecology is playing an increasingly important role in our understanding of marine ecology and is now providing vital information with respect to conservation and management in the light of climate change. The accessibility of coastlines and shores makes these the focus for such work. Hawkins et al. (2020) review rocky shores as test systems for experimental ecology.
To evaluate the interactions between organisms and their environment, both oceanographic and biological data are required. Oceanographic data relate to the inorganic parameters of the environment, including measurements of water movement, temperature, composition, illumination and depth and the nature of the sea bo om. Biological data relate to the distribution, numbers, activities and relationships of organisms in different parts of the ocean.
3 Structure of this book
This book is divided into nine chapters and while cross-references are made between chapters, each can be read and used on its own and in any order. The first and second chapters provide an overview of the physical and chemical ocean environment. This is the hugely varied terrain that we would see if the water were drained away and the equally varied ‘waterscape’ of seawater itself. These environmental parameters obviously have significant effects on shaping the ecology and distribution of marine organisms and their responses and adaptations to aspects such as pressure, light and ocean currents are integrated into these chapters. The third chapter covers the vitally important processes of organic production and cycling, concentrating mainly on primary production.
The middle chapters cover major marine ecosystems, habitats and communities, arranged to reflect the lifestyles of the component organisms. Chapters 4 and 5 address pelagic (open-water) systems
and cover plankton and nekton, respectively. Chapters 6 and 7 address benthic (seabed) systems, covering the intertidal (seashore) and subtidal (subli oral and deeper), respectively. Rocky shores, sediment shores, estuaries, tropical shores and coral reefs are all covered.
Information on the impacts of human activities on marine ecosystems and species is integrated throughout the book. However, the final two chapters tackle major environmental impacts, including climate change, ocean acidification and overfishing; why and how they are occurring and the ways in which they can and are being mitigated. A knowledge of these issues is now essential to the understanding of marine ecology. The chapter on sea fisheries and aquaculture also integrates descriptions of fishing methods, with the vulnerabilities of specific targeted groups, such as sharks. Key elements of fishery research and stock management are also described.
At the end of each chapter is a list of further reading suggesting more detailed texts, for example on some of the habitats and ecosystems described in Chapters 6 and 7. The Oxford University Press ‘Biology of Habitats’ series of books is particularly useful in this respect as is Raffaelli and Hawkins (1996). The short bibliography below will also be useful for additional study of marine ecology, marine biology and adjacent fields, such as biological oceanography and oceanography.
Further reading
Begon and Townsend, 2021 Begon M, Townsend CR. Ecology From Individuals to Ecosystems 5th edition Wiley-Blackwell 2021;844. Dipper, 2016 Dipper FA. The Marine World A Natural History of Ocean Life Princeton University Press (Wild Nature Press) 2016;554.
Kaiser et al., 2011 Kaiser MJ, et al. Marine Ecology: Processes, Systems and Impacts 2nd edition Oxford University Press 2011;501. Lalli and Parsons, 1997 Lalli CM, Parsons TR. Biological Oceanography: An introduction 2nd edition Oxford: Elsevier,
Bu erworth-Heinemann; 1997;314.
Parsons et al., 1984 Parsons TR, Takahashi M, Hargrave B. Biological Oceanographic Processes 3rd edition Pergamon Press 1984; (ebook: Elsevier 2016).
C H A P T E R 1
The physical structure of oceans
Abstract
This chapter describes the major physical features, depth zones and seabed composition of the ocean. It starts with the topography of coastlines and beaches and then covers the varied terrain of the continental shelf, abyssal plains, mid-ocean ridges and trenches. Plate tectonics and its role in configuring the ocean basins and continents are explained. The open water pelagic division, where plankton and nekton are found and the seabed, (benthic division) are described along with each division’s depth zones. The major types of sediment covering the ocean floor are categorized, including those of terrigenous and pelagic origin, polymetallic nodules and oil-bearing deposits. Survey methods for seabed depth and bathymetry and for sediment sampling are summarized.
This chapter sets the ecological scene by describing some of the major physical features and zones of the ocean. Some appreciation of the physical marine environment is essential to understand the distribution and ecology of marine communities and organisms. The major oceans and seas, all of which are connected, are shown in Fig. 1.1 and depth and area statistics are shown in Table 1.1. In the deepest parts, the seabed lies more than 10,000 m from the surface
and the average depth of the ocean is about 3700 m. Although marine organisms are unevenly distributed, they occur throughout this vast three-dimensional environment and have been sampled or seen even in the deepest places. Recent introductory oceanography texts to which the student can refer for more detailed information are given at the end of this chapter.
FIGURE 1.1 Major oceans and seas of the world. (1) Bering Sea; (2) Beaufort Sea; (3) Caribbean Sea; (4) Sargasso Sea; (5) Greenland Sea; (6) North Sea; (7) Baltic Sea; (8) Mediterranean Sea; (9) Red Sea; (10) Barents Sea; (11) Arabian Gulf; (12) Arabian Sea; (13) Bay of Bengal; (14) Timor Sea; (15) South China Sea; (16) Sea of Japan; (17) Sea of Okhotsk; (18) Coral Sea. From Dipper, F A , 2016 The Marine World: A Natural History of Ocean Life Princeton University Press (Wild Nature Press), 544pp. Courtesy Marc Dando and Wild Nature Press.
Approximate statistics for major oceans and seas.
4080 10,803 Mariana Trench
3646 8486 Puerto Rico Trench
Sunda (Java) Trench
Eurasia Basin
Sandwich Trench
Seas Notes
Skagerrak
Off Gotland
1480
(inc. Black and Azov Seas)
2200
Calypso Deep
Cayman Trench
Red
South China
500 2500 Central trough
3,700,00 1419 5016 West of Luzon, DK
Notes: Not surprisingly, ocean statistics vary according to their source The area varies according to the exact ocean boundaries used by the calculating agency In this table, area and depths for oceans and for the Mediterranean are from the NOAA’s National Geophysical Data Centre (Eakins and Sharman, 2010) Data for other seas are from various sources that do not refer to specific surveys and may be less accurate
Source: Modified from Dipper, F.A., 2016. The Marine World. A Natural History of Ocean Life. Wild Nature Press. Courtesy Wild Nature Press.
1.1 Physical features and topography
An accurate and complete map of the ocean floor showing its immensely varied terrain of flat plains, mountain chains, trenches, shelves and other fascinating features is not yet available. New features, including large seamounts, are still being discovered. However, full details of all the known depth contours and named features such as ridges and fracture zones, seamounts, basins and ocean trenches are shown on the GEBCO World Map, which can be downloaded and printed or details can be viewed online (h p://www.gebco.net). They also provide access to a gaze eer of undersea feature names.
Major topographical features have been mapped over many decades, using soundings in the early years and through sonar from the 20th century onwards. The geographical positions of 53
important main features are shown and listed in Fig. 1.2, and the main types (such as ridges and basins) are described in the following sections (1.1–1.6).
