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Continental shelves (Ecosystems of the World, Vol. 27)
Ocean & Shoreline Management 12 (1989) 101-104
B o o k Review
Continental Shelves (Ecosystems of the World, Vol. 27). Edited by H. Postma and J. J. Zijlstra, Elsevier Science Publishers, Amsterdam. 1988. 406 pp. Price: Dfl.360. ISBN 0 444 42609 4; US$189.50.
This book is the latest volume in the series Ecosystems of the World. It follows a closely related volume (Vol. 26), Estuaries and Enclosed Seas (Ketchum, 1983), and comes at a time when the global importance of continental shelves is being highlighted in a number of different ways. Even though continental shelves occupy only some 7.6% of total ocean area, their economic importance far outweighs their rather limited size. For example, roughly 90% of the world's fisheries yield is harvested on continental shelves. Anthropogenic activities that include navigation, commercial fishing, waste disposal, oil and gas exploitation, aggregate dredging and the interests of the military, call for a sound knowledge base concerned with the physical and biological characteristics and processes of continental shelves. Indeed, the editors express the hope that the publication of this volume will give an impetus to increased research on the subject of continental shelves. The first seven chapters of this volume provide a generalised overview of the geological, physical and chemical characteristics of shelf systems. There are parallel discussions about the various sub-systems of a biological nature, including planktonic forms, benthos and fish. Another chapter examines the flow of energy through the continental shelf system. The final four chapters take the form of case-studies: the shelf ecosystems being the Arctic (the Barents Sea), the Tropics (the Gulf of Thailand) and the temperate zone (the North Sea in Europe) and the north-west Atlantic shelf off the US east coast. The editors point out that these regions were chosen because of the comprehensive knowledge available for them. It seems that few really detailed studies have been made of tropical regions, although the shelf off Thailand is a relatively well studied one. 101 Ocean & Shoreline Management (12) (1989)----~ 1989 Elsevier Science Publishers Ltd, England. Printed in Northern Ireland
102
Book review
The 18 authors contributing to this volume are all experts in this important area of research, many of them serving on the staff of fisheries centres or other scientific institutions. Clearly, they have been able to draw not only on their own research experience but also on some of the other work carried out by those institutions. Collectively, this represents a substantial body of knowledge pertaining to one of the most important ecosystems in the world. The following section describes the Contents of this volume: 1. Introduction (H. Postma, J. J. Zijlstra) 2. Physical and Chemical Oceanographic Aspects of Continental Shelves (H. Postma) Periodic water movements. Residual currents. Stratifications. UpweUing and downwelling. Fronts. The fate of chemical elements. Summary. 3. An introduction to the Geology of Continental Shelves (D. Eisma). Extent and origin of continental shelves. Sea-level changes. Bottom sediment patterns. Sediment transport on the shelf. Geotechnical properties of shelf sediments. Summary. 4. Plankton Characteristics (V. Smetacek) Basic processes of pelagic ecosystems. Distinguishing features of continental shelves. Organisms of the shelf plankton. Regional and temporal considerations. Acknowledgements. 5. Characteristics of the Benthic Fauna (D. S. McLusky, A. D. McIntyre) Structure of the benthic communities. Methods of study. Dynamics of the ecosystem. Variations with latitude. Economic aspects. 6. Fish Populations and Fisheries (G. D. Sharp) Setting the scene. Neritic habitats. Neritic fish populations. Environments, lifehistory patterns and observed variations. Scales of productivity and dispersion in the marine ecosystem. Geographic variations of the neritic zone. Dominant ambient influences on the neritic regime. The habitat matrix. Ecosystem perturbations and longterm processes. Conclusions. 7. The flow of energy in Marine Ecosystems, with special reference to the Continental Shelf (D. H. Cushing) Methods. The forms of production. The quantities produced. The transfer of energy. Conclusions. 8. The North Sea Ecosystem (J. J. Zijlstra) Topography. Hydrography. Nutrients. Phytoplankton. Zooplankton. Benthos. Fish and fisheries. Conclusions. 9. The Continental Shelf Ecosystem off the Northeast Coast of the United States (K. Sherman et al.) Bathymetry. Hydrography.
Book review
10.
11.
103
Primary productivity. Nutrients. Zooplankton. Benthos. Fish fauna of the New England shelf region. Fish biomass and yield. Production in different trophic levels of northwest Atlantic shelf ecosystems. Possible explanations for production differences. The Barents Sea (O Dragesund, J. Gjosaeter) Boundaries and bottom topography Hydrography. Nutrient salts. Phytoplankton. Zooplankton. Benthos. Fish. Interrelations of the ecosystem of the Barents Sea. The Gulf of Thailand (D. Menasveta, V. Hongskul) General characteristics. Living resources. Resource management. Summary and conclusions.
The presentation of the 11 chapters is clear, and the standard of the figures and photographs commendable. This is not surprising in the 27th Volume of a consistently well prepared series, and it will no doubt be followed by other quality publications. The editors highlight a number of 'problems' or 'gaps' in our present knowledge of continental shelves. For instance, while the ecological and other linkages between shelves and coastal bays, lagoons and estuaries are reasonably well established, the oceanward boundaries of shelves (geology apart) are more difficult to specify accurately, if only because of the irregular nature of the exchanges between shelf and ocean water. 'Complicated hydrographic patterns influence the behaviour of marine organizers in a way that is still poorly understood.' Again, besides the problem of properly defining an ecosystem, 'our knowledge about the functioning of shelf ecosystems as a whole is still very restricted and it seems doubtful whether we have identified all major processes and energy pathways. Only in a few ones, all situated in temperate regions, sufficient information seems available to venture a tentative construction of the energy flow through the system, from primary producers up to fish production. However, even in those few cases, the general ideas about major processes and pathways have been changing rapidly in the last decade and it seems likely that future studies will again modify the picture. At present one of the difficulties is that according to present knowledge the energy budget in the ecosystem seems to be a rather tight one, whereas other information often indicated that food is hardly a limiting factor.' (Postma and Zijlstra 1988). It follows that certain of the energy-flow models are currently inadequate to explain some major changes observed in the North Sea and in the George's Bank area. Have these resulted from climatic variations, excessive fishing or some other kind of human interference? The editors draw the general conclusion that, at the present time, the
104
Book review
communities of very few continental shelves have been examined in every detail; that research in this subject area needs to be expanded. Notwithstanding this, this new volume embodies valuable knowledge of shelf ecosystems, and is to be welcomed as an important addition to continental shelf literature. It is bound to provide much interest, and not simply in the biological and physical field. I. P. JoHiffe
B o o k Review
Continental Shelves (Ecosystems of the World, Vol. 27). Edited by H. Postma and J. J. Zijlstra, Elsevier Science Publishers, Amsterdam. 1988. 406 pp. Price: Dfl.360. ISBN 0 444 42609 4; US$189.50.
This book is the latest volume in the series Ecosystems of the World. It follows a closely related volume (Vol. 26), Estuaries and Enclosed Seas (Ketchum, 1983), and comes at a time when the global importance of continental shelves is being highlighted in a number of different ways. Even though continental shelves occupy only some 7.6% of total ocean area, their economic importance far outweighs their rather limited size. For example, roughly 90% of the world's fisheries yield is harvested on continental shelves. Anthropogenic activities that include navigation, commercial fishing, waste disposal, oil and gas exploitation, aggregate dredging and the interests of the military, call for a sound knowledge base concerned with the physical and biological characteristics and processes of continental shelves. Indeed, the editors express the hope that the publication of this volume will give an impetus to increased research on the subject of continental shelves. The first seven chapters of this volume provide a generalised overview of the geological, physical and chemical characteristics of shelf systems. There are parallel discussions about the various sub-systems of a biological nature, including planktonic forms, benthos and fish. Another chapter examines the flow of energy through the continental shelf system. The final four chapters take the form of case-studies: the shelf ecosystems being the Arctic (the Barents Sea), the Tropics (the Gulf of Thailand) and the temperate zone (the North Sea in Europe) and the north-west Atlantic shelf off the US east coast. The editors point out that these regions were chosen because of the comprehensive knowledge available for them. It seems that few really detailed studies have been made of tropical regions, although the shelf off Thailand is a relatively well studied one. 101 Ocean & Shoreline Management (12) (1989)----~ 1989 Elsevier Science Publishers Ltd, England. Printed in Northern Ireland
102
Book review
The 18 authors contributing to this volume are all experts in this important area of research, many of them serving on the staff of fisheries centres or other scientific institutions. Clearly, they have been able to draw not only on their own research experience but also on some of the other work carried out by those institutions. Collectively, this represents a substantial body of knowledge pertaining to one of the most important ecosystems in the world. The following section describes the Contents of this volume: 1. Introduction (H. Postma, J. J. Zijlstra) 2. Physical and Chemical Oceanographic Aspects of Continental Shelves (H. Postma) Periodic water movements. Residual currents. Stratifications. UpweUing and downwelling. Fronts. The fate of chemical elements. Summary. 3. An introduction to the Geology of Continental Shelves (D. Eisma). Extent and origin of continental shelves. Sea-level changes. Bottom sediment patterns. Sediment transport on the shelf. Geotechnical properties of shelf sediments. Summary. 4. Plankton Characteristics (V. Smetacek) Basic processes of pelagic ecosystems. Distinguishing features of continental shelves. Organisms of the shelf plankton. Regional and temporal considerations. Acknowledgements. 5. Characteristics of the Benthic Fauna (D. S. McLusky, A. D. McIntyre) Structure of the benthic communities. Methods of study. Dynamics of the ecosystem. Variations with latitude. Economic aspects. 6. Fish Populations and Fisheries (G. D. Sharp) Setting the scene. Neritic habitats. Neritic fish populations. Environments, lifehistory patterns and observed variations. Scales of productivity and dispersion in the marine ecosystem. Geographic variations of the neritic zone. Dominant ambient influences on the neritic regime. The habitat matrix. Ecosystem perturbations and longterm processes. Conclusions. 7. The flow of energy in Marine Ecosystems, with special reference to the Continental Shelf (D. H. Cushing) Methods. The forms of production. The quantities produced. The transfer of energy. Conclusions. 8. The North Sea Ecosystem (J. J. Zijlstra) Topography. Hydrography. Nutrients. Phytoplankton. Zooplankton. Benthos. Fish and fisheries. Conclusions. 9. The Continental Shelf Ecosystem off the Northeast Coast of the United States (K. Sherman et al.) Bathymetry. Hydrography.
Book review
10.
11.
103
Primary productivity. Nutrients. Zooplankton. Benthos. Fish fauna of the New England shelf region. Fish biomass and yield. Production in different trophic levels of northwest Atlantic shelf ecosystems. Possible explanations for production differences. The Barents Sea (O Dragesund, J. Gjosaeter) Boundaries and bottom topography Hydrography. Nutrient salts. Phytoplankton. Zooplankton. Benthos. Fish. Interrelations of the ecosystem of the Barents Sea. The Gulf of Thailand (D. Menasveta, V. Hongskul) General characteristics. Living resources. Resource management. Summary and conclusions.
The presentation of the 11 chapters is clear, and the standard of the figures and photographs commendable. This is not surprising in the 27th Volume of a consistently well prepared series, and it will no doubt be followed by other quality publications. The editors highlight a number of 'problems' or 'gaps' in our present knowledge of continental shelves. For instance, while the ecological and other linkages between shelves and coastal bays, lagoons and estuaries are reasonably well established, the oceanward boundaries of shelves (geology apart) are more difficult to specify accurately, if only because of the irregular nature of the exchanges between shelf and ocean water. 'Complicated hydrographic patterns influence the behaviour of marine organizers in a way that is still poorly understood.' Again, besides the problem of properly defining an ecosystem, 'our knowledge about the functioning of shelf ecosystems as a whole is still very restricted and it seems doubtful whether we have identified all major processes and energy pathways. Only in a few ones, all situated in temperate regions, sufficient information seems available to venture a tentative construction of the energy flow through the system, from primary producers up to fish production. However, even in those few cases, the general ideas about major processes and pathways have been changing rapidly in the last decade and it seems likely that future studies will again modify the picture. At present one of the difficulties is that according to present knowledge the energy budget in the ecosystem seems to be a rather tight one, whereas other information often indicated that food is hardly a limiting factor.' (Postma and Zijlstra 1988). It follows that certain of the energy-flow models are currently inadequate to explain some major changes observed in the North Sea and in the George's Bank area. Have these resulted from climatic variations, excessive fishing or some other kind of human interference? The editors draw the general conclusion that, at the present time, the
104
Book review
communities of very few continental shelves have been examined in every detail; that research in this subject area needs to be expanded. Notwithstanding this, this new volume embodies valuable knowledge of shelf ecosystems, and is to be welcomed as an important addition to continental shelf literature. It is bound to provide much interest, and not simply in the biological and physical field. I. P. JoHiffe