Biological diversity of plankton communities in the south-east of the Baltic Sea

Abstract

In this investigation, we used the data on hydrobiological and hydrochemical observations (phyto- and zooplankton, nutrients), which were obtained from the monthly (AprilOctober) research cruises in the Baltic Sea and its lagoons (Curonian and Vistula) in 20022010. For the analysis of species diversity, Shannon index (H) and its relation to different abiotic characteristics of the aquatic environment was used. The obtained results have shown that many factors influence the formation of biological diversity, which manifest themselves in different ways at different times. The H Index is apparently not related to the level of the trophy of a water body. A decrease and increase in ecosystem diversity occur under the influence of abiotic factors and through trophic relationships, and it is an adaptive characteristic of the ecosystems. This is what ensures the stability of the ecosystems in the seasonal and interannual aspects at the existing level of trophies. These results also clearly indicate that during analysis it is very important to consider the time scale of the processes for a selected period of averaged data and, as a rule, the nonlinear feature of correlative dependences.