Winter distribution of phytoplankton and zooplankton around some sandbanks of the Belgian coastal zone

Abstract

The distribution of phytoplankton and zooplankton around three sandbanks (Gootebank, Westhinder and Buitenratel sandbank) off the Belgian Coast was investigated in February 1994. The abundance of phytoplankton taxa was significantly different between the sandbanks. Community analysis using TWINSPAN resulted in a clear separation of clusters corresponding to the different sandbanks. The zooplankton community analysis, on the contrary, showed a rather indistinctive division of the sandbank stations. This was due to the omnipresence of three dominant copepod species (Temora longicornis, Pseudocalanus elongatus and Centropages hamatus). When these species were excluded from the analysis, a clearer distinction between the different sandbanks was found. The observed differences in phyto- and zooplankton species distribution could be explained by the position of the sandbanks. Westhinder is positioned further from the coast than Buitenratel, while Gootebank has an intermediate position. Buitenratel and Gootebank harbour typical coastal plankton communities, while the plankton community over Westhinder is clearly influenced by the Atlantic current penetrating the southern North Sea from the English channel. More phyto-benthic species were found at Buitenratel than at Gootebank, probably because of its limited depth. Thus, the Belgian coastal zone, which is considered as one box in most spatial descriptions of the North Sea plankton, in fact harbours heterogeneous plankton communities at the end of winter.