Importance of microzooplanktonic crustaceans in the coastal food chain: Bay of Marennes-Oléron, France

Abstract

Modelling biological processes in marine ecosystems requires a good knowledge of the relationships between the different compartments of the ecosystems. Microzooplanktonic crustaceans are often neglected in field feeding studies, due to the difficulties in identification and to their small size. In coastal areas, difficulties are enhanced by the great quantities of particulate organic matter in the water column. Euterpina acutifrons is the major component of the zooplankton community in the Bay of Marennes-Oléron (south-west France) during the algal spring bloom (nauplii strongly dominate the copepod community). The grazing impact of the copepod Euterpina acutifrons (microzooplanktonic and mesozooplanktonic fractions) on the algal standing stock was estimated in the Marennes-Oléron Bay during this period by means of both laboratory experiments and field data. The results suggest that grazing pressure of the microzooplanktonic stages was similar to the pressure exerted by the mesozooplanktonic ones, underlining the significant role of small copepod stages in marine systems in terms of grazing impact. Our results indicate that the daily grazing pressure exerted by the whole population is quite low in the Marennes-Oléron Bay (about 15 % of the algal standing stock).