Anthropogenic impact on environmental variables and macroinvertebrates community of River Eme, South-East, Nigeria

Abstract

Macroinvertebrates are good bioindicators of water quality and ecosystem health and are often used to study anthropogenic effect on aquatic ecosystems. Consequently, some environmental variables and macroinvertebrates of Eme river were studied to understand the impact of human activities on this socio-economically important ecosystem. Six stations (reflecting different anthropogenic activities) along the reaches of the river were sampled and analyzed monthly from December, 2017 to November, 2018 using standard methods. The results showed that water temperature varied from 22.00, station 1 to 28.5oC, station 6, turbidity (0.50-9.40 NTU, station 4), flow velocity (0.21, station 1-0.85m/s, station 3), pH (4.30, station 2-6.30, station 1), electrical conductivity (45.20, station 2-168.40µS/cm, station 5), dissolved oxygen (1.60, station 4-6.10mg/l, stations 3 and 4), biochemical oxygen demand (0.80-4.30mg/l, station 4), nitrate (1.10, station 3-5.6mg/l, station 4) and phosphate (0.40, station 3-4.6mg/l, station 4). Flow velocity, electrical conductivity, biochemical oxygen demand, nitrate and phosphate varied significantly between stations (p<0.05). A total of 584 individuals from 5 taxonomic groups and 23 species of macroinvertebrates were recorded. Aquarius remigis was the most abundant species (8.7%). The macroinvertebrate community was dominated by tolerant and very tolerant species, such as Aquarius remigis, Caridina africana, Pseudocloen sp. nymph, Hydrometra sp and Belostoma sp. The dominance of tolerant species, high turbidity, biochemical oxygen demand, nitrate and phosphate values and low dissolved oxygen values are strong indications of anthropogenic effect. It is suggested that adequate management attention should be paid to the river in order to prevent further deterioration.