The role of rotifer in water quality improvement in a fishpond

Abstract

Rotifers are common in fresh and brackish water bodies, in coastal areas of the seas, and can be an effective tool for analyzing the state of the environment. The ability of rotifers to adapt to unfavourable environmental conditions has been considered in the course of studying the species composition of rotifers in a fish pond near Moscow under the conditions of the supply of organic artificial food for fish and changes in the temperature regime of water. During the period of increased temperature of the water (21-25 °C) and decrease in the concentration of dissolved oxygen from the surface to the bottom layers of water from 3.8 to 0.2 mgO/L in early July, Asplanchna priodonta helvetica , Brachionus angularis angularis and Brachionus calyciflorus dominated in the pond (98-100 % of the abundance and 99-100 % of the biomass of rotifers). During the period of elevated temperatures, the turbidity indices in the upper layer (0.2-0.5 m) were an order of magnitude lower than those in the deeper layers of the reservoir. Bacteria and tiny particles served as food for rotifers. The temperature of 18-25 °C was favourable for the development of B. angularis angularis in the fish pond. At a temperature of 18 °C, its abundance reached 1,500 ind./L (70 % of the abundance of rotifers). In August, when the temperature of the water column decreased from 20 to 18 °C, the biomass of A. priodonta helvetica changed from 0.3 to 9.5 mg/L (99 % of the biomass of rotifers). Polyarthra vulgaris dominated among small rotifers. During the period of low temperatures, the biomass of rotifers increased to 20 mg/L; its basis was A. priodonta helvetica. Rotifers are able to adapt to conditions of high organic input in a wide range of temperatures and participate in the restoration of water quality in a fish pond.