Respiration in Aquatic Ecosystems

P.A Del Giorgio & P.J. leB. Williams ( Eds ). Oxford University Press , Oxford, New York , 2005 , ISBN 0-19-852709-8 ( hardback; GBP 80.00 ), ISBN 0-19-852708-X ( softback; 39.95 ), 315 pp .

Soon after Winkler introduced his method to determine oxygen concentrations in water in 1888, this method was applied to determine oxygen consumption by aquatic organisms. Over the first part of the 20th century, the focus was clearly on determining the photosynthetic activity of autotrophic organisms, and dark bottle incubations were essentially only performed to obtain estimates of net photosynthetic activity. Respiration, as the main process besides primary production in aquatic systems, first received attention in the 1960s. Since then, respiration measurements have been performed on a wide range of organisms and on benthic and pelagic systems. So, why is there a need for a book dealing exclusively with respiration, something one expects to be covered in every good textbook of various scientific disciplines ranging from physiology to systems ecology?

This question is answered right away in the first chapter of the book, which outlines the history of respiration measurements in aquatic systems. The answer is: because traditionally much more weight has been put on estimating production. Phytoplankton and bacterial production are routinely assessed in systems ecology; methods to determine them are sensitive and fairly straightforward. Determining respiration rates is less easy to perform and requires longer incubation times because the methods are less sensitive. It might be our anthropocentric point of view to focus more on production rather than on loss terms such as respiration. The vivid discussions over the last decade on whether or not large parts of the ocean are net heterotrophic highlight the need for a stronger focus on respiration, which is a major parameter determining global carbon cycling. Our data set on respiration is only a small fraction of the data we have acquired on production.

This book aims at covering all the major aspects of respiration in aquatic systems, from freshwater and estuarine to marine systems, with a focus on the pelagic realm, although the benthos is covered in two chapters as well. All the chapters are written by experts in the particular field. The 14 chapters are rather uniformly arranged with an outline of the chapter at the beginning, followed by the body of text and references at the end of each chapter.

First, the biogeochemical background of oxygen respiration is provided, followed by a chapter on anaerobic microbial respiration. These first two chapters provide an excellent overview of the physiology and biochemistry of respiration in organisms. They are followed by a detailed overview of the respiratory processes in phytoplankton, differentiating between dark and light processes. Tables and figures provide an overview of all the oxygen-consuming reactions occurring in aquatic photolithotrophs. Next to phytoplankton respiration, the respiration of aquatic protists is covered in the context of their energy metabolism, including both aerobic and anaerobic respiration. This chapter also includes a methodology section on measuring respiration rates, for example with microelectrodes, and a detailed description of factors influencing respiration rates such as oxygen tension, temperature and food availability. Metazooplankton respiration is covered in the subsequent chapter, which spans from methodological aspects in measuring zooplankton respiration rates to the latitudinal trends and depth variations in zooplankton respiration.

Whole system respiration is covered in the following chapters, starting with freshwater wetlands. The carbon dioxide and methane balance is described in detail, with a focus on different types of wetlands from northern bogs and fens to tropical swamps. The metabolism of lakes is described next, both of the water column and the underlying sediments. Relationships between respiration and dissolved organic carbon content, phosphorus load and phytoplankton biomass are presented in figures, as is the global relation between temperature and benthic and pelagic respiration, with a specific focus on the importance of lakes in the global carbon balance. A thorough analysis of the data set available on estuarine respiration has been compiled, covering all climate zones. Probably the largest data set on respiration rates exists for marine surface waters. The authors of this chapter have done a tremendous job in compiling existing information; they summarize it in illustrative tables and figures covering virtually all aspects of surface water respiration, ranging from growth yield estimates of individual groups of organisms to global estimates of marine surface water respiration. Particularly useful in this chapter are the detailed calculations presented in boxes. This format should have been used throughout the book, although a number of chapters do use it to provide additional in-depth information. This approach would have made some of the calculations easier to follow. The chapter on respiration of the meso- and bathypelagic realm of the ocean clearly indicates the lack of knowledge on reliable respiration rates for the dark realm of the ocean. It summarizes existing, scattered respiration measurements and, due to the scarcity of data, the authors constrain dark ocean respiration by examining the lateral and vertical input of dissolved and particulate organic carbon into the deep ocean; they use apparent oxygen utilization to constrain dark ocean respiration rates. Given the scarcity of direct respiration measurements for the largest oceanic subsystem, the authors have put substantial effort into collecting information on parameters ultimately determining respiration in the dark ocean. Thus, despite the general lack of data here, we obtain a rather holistic picture of the magnitude of dark ocean respiration in the various parts of the world's ocean.

In contrast to the previous chapter, the chapter on respiration in coastal benthic systems can rely on a large data set. The differences in the carbon balance between salt marshes, reefs, mangroves, sea grasses and unvegetated sediments are shown. Suboxic respiration in the water column is dealt with in a separate chapter. The largest suboxic region in the world's ocean is the oxygen minimum zone, most pronounced in the northern Arabian Sea. The main biogeochemical processes involved in the processes of suboxic respiration are described, focusing particularly on nitrogen cycling. A chapter on modeling respiration – ranging from individual functional groups like phyto-, bacterio-, and zooplankton to global models – and a concluding chapter on the global importance of respiration in aquatic systems round up the most detailed book on the market at present on respiration in aquatic systems. The final chapter presents a truly global perspective on respiration.

The book is generally very well illustrated and each chapter provides tables and figures summarizing existing knowledge. The subject index allows searching for information on specific topics.

The book provides an excellent overview on all aspects of respiration, whereby the main focus is clearly put on oxygen. I found this book ideal as reading material for students’ classes and courses in aquatic ecology and biological oceanography at the undergraduate but particularly at the graduate level. For environmental scientists from a variety of disciplines ranging from aquatic ecologists to biogeochemists, it provides a thorough synthesis of the current knowledge on respiration and of the factors determining it on an organismic as well as on a systems level. This is one of the books that should be on the shelf of every environmental scientist.