Zooplankton community of the upper riches of the Izhora river (the Baltic Sea basin) under the long-term anthropogenic impact

In the conditions of increasing anthropogenic load on ecosystems it is particularly relevant to study the peculiarities of aquatic community changes due to the influence of adverse factors. To assess the state of water bodies, zooplankton organisms are used as environmental bioindicators. For each water body it is important to estimate the intensity and duration of exposure to adverse factors. On the example of the Izhora river (Leningrad region, Baltic Sea basin) influenced by industry and agricultural production for a long time, zooplankton community was studied in 2014. The results were compared to those of 1970s, at that the scheme and methods of sampling were the same. It was shown that throughout the study region the population and biomass of rotifers and crustaceans significantly decreased (more than 100 times). The reduction of the populations alongside with the disturbance of their structure is the signs of supressed zooplankton communities. As the degree of pollution increases and species composition is depleted, the variety of food types decreases. The analysis of the trophic structure of crustaceans (considering the food types) carried out in 2014 as well as the use of saprobity index allowed estimating the quality of river water (on a plot of 26 km) as “moderately polluted” by organic matter. At the same time, there were signs indicative of toxic pollution. In the course of the study it was stated that the zooplankton community of the Izhora river continues to experience the significant adverse effects.