Structural Indicators of Zooplankton in the Shardara Reservoir (Kazakhstan) and the Main Influencing Factors

Özet

The Shardara reservoir is located in southernmost Kazakhstan, in the zone of intensive farming and industrialdevelopment. Zooplankton and basic parameters of the environment have been studied in the summer of 2015. Zooplanktonwas represented by 60 species. The average abundance of the community amounted to 92.9 thous. specimens $m^{-3}$, withbiomass of 966.0 mg $m^{-3}$. Copepods and rotifers dominated. The Shannon index values were equal to 2.24 bit $specimen^{-3}$and1.23 bit $mg^{-1}$. The average individual mass of a specimen reached 0.0082 mg. Nonparametric and multivariate analysis of thedata 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. Themain negative factors for Copepoda were organic polyphosphates, nitrites, total nitrogen, cadmium, and lead. Decrease in theShannon index values under the influence of cadmium, ammonium, HCCH isomers is associated with increased dominance ofAcanthocyclops trajani in the contaminated areas. There was no significant impact of heavy metals and pesticides on most ofthe structural indicators of zooplankton which can be due to the complex nature of contamination of the reservoir.