Monitoring and current state of plankton and benthic fauna of an oligotrophic reservoir (Urozero, Southern Karelia)

Abstract

This article presents research findings on the current state of zooplankton and zoobenthos communities in Urozero (Prionezhsky District, Republic of Karelia). The study examined the aquatic fauna of the reservoir, which is weakly affected by anthropogenic factors and has the status of a state hydrological natural monument of regional significance. The study conducted an analysis of the qualitative and quantitative composition, assessed the species diversity of zooplankton and zoobenthos, and examined the structure of dominant species and their percentage ratio in samples from the littoral and profundal zones. The analysis of the studies showed that, in terms of the development of zooplankton and macrozoobenthos and low nutrient levels in the water, Urozero can be characterized as an oligotrophic reservoir with favorable habitat conditions for aquatic organisms.The saprobity index (Pantle and Buck) for zooplankton ranged from 1.20 to 1.36, while the Shannon index ranged from 2.68 to 2.96 bit/ind., which is typical of oligosaprobic water bodies. Biotic indices calculated using macrozoobenthos indicators confirm the saprobity level of the Urozero reservoir. Specialized indices (Goodnight-Whitley, Mayer, and Balushkina) characterize the reservoir as moderately polluted. Assessing the characteristics of planktocenosis and benthocenoses in reservoirs under conditions of increasing anthropogenic impacts is a relevant task for research aimed at short- and long-term monitoring of water bodies, especially those in areas close to protected areas. The results obtained can be used for comprehensive environmental monitoring of such water bodies.