Interannual changes in zooplankton of the canals of the Volga delta in the spring-summer period

Abstract

Research conducted in 2011–2014 revealed the main trends in structural and quantitative changes in zooplankton in the Volga delta channels in low-water years compared to middle-water years. It has been shown that in dry years, zooplankton is characterized by a decrease in species richness and high quantitative development of juvenile stages of Copepoda. In a mid-water year, zooplankton is characterized by a high total and specific species richness, an average individual mass of Crustacea, in the spring – a high biomass of Cladocera, in the summer – a decrease in the abundance and biomass of Cladocera, an increase in the quantitative characteristics of Rotifera, and among ecological groups – the proportion of floating organisms. The formation of zooplankton is influenced by a complex of factors, among which, at different times, are the volume of runoff, water level, the rate of its rise, the period of standing and the value of the maximum level, temperature conditions, the duration of the flood, the water content of the floodplain, control by juveniles fish.

Keywords

• hydrological regime
• weather conditions
• control of juvenile fish
• species richness
• quantitative characteristics