REGULATION OF VERTICAL EXPORT OF PARTICULATE ORGANIC-MATTER FROM THE EUPHOTIC ZONE BY PLANKTONIC HETEROTROPHS IN EUTROPHICATED AQUATIC ENVIRONMENTS

Different scenarios of remineralization response by planktonic heterot rophs on increasing primary production are presented. The consequences of these response patterns for the vertical export of particulate org anic matter from the euphotic zone and productivity indexes are discus sed. Reference is made to existing data and algorithms regarding prima ry production and vertical export of carbon from the euphotic zone. Th e response patterns of planktonic heterotrophs to increasing primary p roduction most likely to be found in eutrophicated aquatic environment s are indicated. The transport of particulate organic matter to depth in limnic as well as marine environments, as a fraction of a given rat e of phytoplankton production, seems to depend on the structure and fu nction of the prevailing planktonic food webs. It is suggested that he rbivore control of suspended biomass along gradients of increasing nut rient supply results in decreasing carbon supply to bottom water and s ediments. Carnivory probably reverses this trend, giving rise to incre ased carbon export. This conclusion has crucial consequences for inves tigating pelagic-benthic coupling, currently also a priority in eutrop hication studies. Zooplankton orientated programmes will be a necessar y component of future investigations of eutrophication in aquatic envi ronments.