Benthic responses to sedimentation of phytoplankton on the Belgian Continental Shelf

The Belgian Continental Shelf (BCS), located in the nutrient enriched Southern Bight of the North Sea, is characterised by a high levels of primary production and algal biomasses (Lancelot et al., 1987; Rousseau, 2000). Phytoplankton dynamics displays strong seasonal patterns with diatom blooms initiating the succession in February-March and the main spring bloom composed of diatoms and Phaeocystis in April-May (Rousseau et al., 2002; 2008). At that time, Phaeocystis colonies can contribute up to 99% of the autotrophic biomass in the pelagic realm (Hamm & Rousseau, 2003). Phytoplankton summer blooms are mainly composed of diatoms which last as late as end October (Rousseau et al., 2008). Although the bulk of phytoplankton production is mostly remineralized in the water column after the bloom (Rousseau et al., 2000), still 24% is deposited on the sediment of the BCS, 65% of it being under the form of Phaeocystis colonies (Lancelot et al., 2005).