Some regularities in zooplankton distribution in the Baltic Sea by regions

Abstract

Based upon the material for 1960-1974 period, the distribution of total abundance of crustacean plankton and separate species by the regions of the Baltic Sea (Sothern, Eastern, North-Eastern and Northern) are examined. The influence of temperature and phosphates on the distribution of zooplankton is shown. In spring zooplankton abundance is to a great extent conditioned by temperature, therefore plankton abundance in Southern regions is always higher. In summer food supply is of great importance. In the years of average phosphorus content (6-9 mg · l -¹) and of mean and high zooplankton abundance the tendencies to form reverse relations between zooplankton abundance in separate regions and phosphate quality in the active layer may be observed. More often heightened zooplankton abundance in summer is noted in the Eastern region. In autumn zooplankton abundance by regions equalizes. The productivity of species-filtrates is under the influence of phosphate content.