Comparative assessment of physico-chemical conditions and zooplankton diversity of Anambra River in Anambra State, Nigeria

An assessment of Physico-chemical parameters and zooplankton diversity of Anambra River in Anambra State was conducted for a period of eight months from February 2021-September 2021. Water samples were collected from three sampling stations of the river every month in sterilized containers during the course of the study. The study stations are Umueri (S1), Anam (S2) and Otuocha (S3). The samples were analysed for both Physico-chemical attributes and zooplankton diversity. Zooplankton species were determined following standard procedures. A total of twenty three species of zooplankton were encountered in Anambra River. The abundance of zooplankton in Anambra was in the order: Protozoa (28.57%) > Crustacea (27.14%) > Insecta (26.67%) > Rotifera (17.62%). There were 66, 79 and 65 zooplanktons recorded for Station 1 (S1), Station 2 (S2) and Station 3 (S3) respectively in Anambra River. 8 zooplankton species cut across the 3 stations while 1(Lacane species), 2(Chaoborus species and Microcodon species) and 1(Sphaerophysa species) species were unique to Station 1 (S1), Station 2 (S2) and Station 3 (S3), respectively. Anambra River recorded high diversity indices value for Cruataceans = 1.779 and least value for Rotifera = 0.6365. The physico-chemical attributes of the river were investigated by measuring the degree of correlation with the plankton diversity. The zooplankton diversity of the river correlated significantly (p<0.05) with physico-chemical parameters. The result revealed a deterioration of water quality of the river due to industrial, commercial and anthropogenic activities. The status of zooplankton diversity of Anambra River was low indicating that the river is highly polluted and the water chemistry has direct effect on plankton diversity. Rotifera showed less number of zooplankton abundance in most of the sites in the river. Nutrient enrichment of the river, as a result of farming activities, industries, discharge of domestic wastes and effluents, has altered the structure of zooplankton community of the river. There is need for urgent management and conservation strategies to protect and restore the water quality of the river.