The comparative estimation of phytoplanktonic, microphytobenthic and macrophytobenthic primary production in the oceans

Abstract

The contributions of the planktonic unicellular algae [phytoplankton), the benthic unicellular algae [microphytobenthos) and the benthic multicellular algae (macrophytobenthos) to the primary production of the world ocean are evaluated, together with the respective limitations regarding data, concepts and methods. The use of “free-water” methods (e.g. in situ oxygen or CO2 budgets) is recommended in complement to the more specific measurements on enclosed organisms. For phytoplankton, a previous estimate of 30 . lo9 t C y-’ is retained as a minimal estimate. Earlier estimates of the world benthic production have been based on indirect calculations; revised estimates are suggested here which still lack precision but rely on the actual measurements available at present. Primary production of the micro- and macrobenthic algae amount to 50 and 375 g C m-? y-’ respectively as averages for the whole photic layer they can colonize, and total 2.9 . 10‘ t C y-’ for the world ocean. Thus, benthic algae contribute some 10% of the total marine primary production. On the continental shelf alone, the contributions of benthic and planktonib algae are commensurate and nearly equivalent.