Spatio-temporal distribution and production of calanoid copepods in the central Baltic Sea

Abstract

The aim of our study was the exploration of species-specific distribution and production patterns of dominant copepods in the Central Baltic Sea (Bornholm Basin). Spatio-temporal distribution, egg and secondary production were studied by means of net-sampling and egg production experiments from April to August 1999. Vertical and horizontal distribution patterns appeared to be linked with each other and were primarily species-dependent. Both Acartia spp. and Temora longicornis preferentially inhabited the upper 30 m of the water column and the shallower marginal regions of the Bornholm Basin. In contrast, the C4–5 and C6 of Pseudocalanus spp. preferentially inhabited the halocline region (50–70 m) and the deep central part of the area. Observed differences in horizontal distribution among these three copepods appear to result from different depth preferences and depth-dependent water circulation patterns. Egg production rates (EPR) clearly exhibited seasonal differences with maximum EPR in May and minimum EPR in July. Mean EPR was significantly different between species, being highest in Acartia spp. and lowest in Pseudocalanus spp. The variability in EPR was related to differences in hydrography and modelled food environment.