Spatio-temporal variability of mesozooplankton from the Gulf of Gdańsk (Baltic Sea) in 1999-2000

The spatio-temporal variability of mesozooplankton in the Gulf of Gdańsk was studied using samples collected in the western part of this basin every month in the 1999-2000 period. The investigation indicated that the qualitative composition of zooplankton was typical of this area and was comprised of Copepoda, Cladocera, Rotatoria, Appendicularia, and meroplankton. Acartia bifilosa and Temora longicornis were present permanently, while Cladocera, Acartia tonsa, Centropages hamatus, Eurytemora sp., the genus Keratella, as well as Mollusca and Balanus improvisus larvae exhibited clear preferences for warmer months. Acartia longiremis, Pseudocalanus elongatus, and Fritillaria borealis were encountered in the cooler season (from November to April). Synchaeta spp. dominated among Rotatoria and Polychaeta larvae among meroplankton. The presence of Brachionus calyciflorus indicated the presence and influence of riverine water from the Vistula.