Capacity achievement and fate of primary production at the ecosystem scale

This section is concerned with the estimation of the capacity of phytoplankton-based systems to fix carbon, how much of that capacity is realised in terms of primary product assembled and how much of that is, in turn, processed into the biomass of its consumers, including at higher trophic levels. This is no new challenge, the questions having been implicit in the earliest investigations of plankton biology. The stimulus to pursue them has varied perceptibly over this period, beginning with the objective of understanding the dynamics of biological systems thitherto appreciated only as steady states. From the 1970s, advances in satellite observation have greatly enhanced the means of detecting planetary behaviour and function, while, at the other end of the telescope (as it were), revolutionary changes in understanding how fixed carbon is transferred among ecosystem components have greatly enhanced the interpretation of the sophisticated techniques available for their remote sensing. In the 1990s, study of the fluxes of materials between atmosphere and oceanic systems and the means by which they are regulated has acquired a fresh urgency, born of the need to understand the nature and potential of the ocean as a geochemical sink for anthro-pogenically enhanced carbon dioxide levels.

These researches help to substantiate the following account, even though it is approached through a hierarchical sequence of integrals of capacity, from those of organelles to metapopula-tions of plankters stretching across oceans. Moreover, although the productive potential is shown to be vast, plankton biomass remains generally very dilute and broadly stable, and has remained so despite recent increases in atmospheric CO2 partial pressures, and it is also argued that the current flux of carbon through this rarefied catabolic system is probably as rapid as it can be.

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