A Review of Measurements of Respiration Rates of Marine Plankton Populations

Abstract

The biological cycle in the oceans may be viewed to be comprised of two fundamental processes: photosynthesis and respiration. The introduction by Steemann Nielsen of the 14C-technique for measuring planktonic photosynthesis has enabled this particular process to be extensively and easily studied. As a consequence there is now a considerable body of data available of measurements of plankton photosynthesis. This contrasts with respiration for which there are still remarkably few direct measurements. Although the processes of respiration and photosynthesis may be regarded to be in balance and essentially equal on the oceanic scale, food chain processes cause them to be separated both in space and time. In contrast to photosynthesis, planktonic respiration may be expected to occur throughout the water column. Thus in any one situation, respiration cannot be taken to be simply equal to photosynthesis but needs to be measured independently. Furthermore respiration is not restricted to a single group of organisms but common to all. Thus the study of respiration is inherently more complex and extensive than photosynthesis from both the trophodynamic and geographical points of view. The distribution of respiration between the major planktonic groups (net zooplankton, microzooplankton, heterotrophic microorganisms, algae) will give insight into the trophic structure of the planktonic community. The vertical distribution of respiration in the water column can given accounts of the export to and fate of the products of phytoplankton photosynthesis in the deeper parts of the ocean.