Coupling of the Limnetic and Brackishwater Plankton Crustaceans in the Curonian Lagoon (Baltic Sea)

Abstract

The impact of salinity to crustacean zooplankton was studied in the Curonian lagoon, characterised by rapid and unpredictable salinity changes in the range from 0 up to nearly 8 PSU. It was hypothesised, that in the case of high spatio-temporal unstability of the salinity gradient, the zooplankton within the gradient should be simply the sum of limnetic and brackishwater assemblages with structural and quantitative characteristics changing according to the ratio of brackish and fresh water mixing. It was concluded, that the impact of changing salinity to the plankton crustaceans is rather controversial. The noticeable increase in species number and heterogeneity of the lagoon zooplankton was observed due to brackish water intrusions, nevertheless, the gradient zone is obviously unfavourable for representatives of both limnetic and brackishwater assemblages, leading to decreasing density and changes in structural characteristics.