MEPS 145:179-193 (1996)  -  doi:10.3354/meps145179

This paper describes an approach to determine, using a small number of food-web or hydrodynamic variables, the partitioning of phytoplankton production among 3 carbon fluxes, i.e. remineralization within the euphotic zone, food-web transfer, and sinking to depth of organic particles. In order to do so, the flows of biogenic carbon in the marine pelagic environment are reduced to 5 broad pathways, which are ordered along a continuum of decreasing export relative to primary production. At one end of the continuum, ungrazed phytoplankton is exported to depth and, at the other, biogenic carbon is remineralized within the bacteria-microzooplankton loop. In the present paper, export of biogenic carbon from the euphotic zone includes food-web transfer of primary production and downward flux of particulate organic carbon (POC) into deep waters. A simple model and data from the literature lead to the conclusions that: (1) the export characteristics of pelagic ecosystems are largely determined by the size structure of primary production and the matching (or, conversely, segregation) between primary production and grazing and (2) total export from the euphotic zone is a function of the delivery of mechanical energy to the upper water column whereas the partitioning of total export between food-web transfer and sinking of POC is controlled by temporal variations in depth of the surface mixed layer. Food-web transfer is significant for marine resources and sinking of POC may contribute to the regulation of climate change (sequestration at depth of biogenic carbon).

Carbon flux · Oceans · Phytoplankton production · Size · Matching · Food web · Hydrodynamics