Structural indicators of zooplankton in the shardara reservoir (Kazakhstan) and the main influencing factors

The Shardara reservoir is located in southernmost Kazakhstan, in the zone of intensive farming and industrial development. Zooplankton and basic parameters of the environment have been studied in the summer of 2015. Zooplankton was represented by 60 species. The average abundance of the community amounted to 92.9 thous. specimens m^-3, with biomass of 966.0 mg m^-3. Copepods and rotifers dominated. The Shannon index values were equal to 2.24 bit specimen^-1and 1.23 bit mg^-1. The average individual mass of a specimen reached 0.0082 mg. Nonparametric and multivariate analysis of the data showed that macrophytes, nitrates, total nitrogen, organic polyphosphates, and copper favorably influenced Rotifera. Possible reasons for a positive relationship between quantitative indicators of Cladocera and zinc content are discussed. The main negative factors for Copepoda were organic polyphosphates, nitrites, total nitrogen, cadmium, and lead. Decrease in the Shannon index values under the influence of cadmium, ammonium, HCCH isomers is associated with increased dominance of Acanthocyclops trajani in the contaminated areas. There was no significant impact of heavy metals and pesticides on most of the structural indicators of zooplankton which can be due to the complex nature of contamination of the reservoir.