Abstract
The impact of anthropogenic disturbances on water quality parameters, diversity of macrophytes and benthic macro fauna of Abesan River, Lagos, Nigeria is reported. Some Physico-chemical and biological assessment were carried out at three sampling stations located at downstream (AR-1), midstream (AR-2) and upstream (AR-3) with different levels of disturbance. Results of measured physico-chemical parameters showed that there was no significant difference (P > 0.05) in temperature, total acidity and chloride values between the sampling stations. Although, Total solids, conductivity, DO, Sulphate, BOD and COD were significantly higher (P < 0.05) at Stn.AR-1 than at Stns. AR-2 and AR-3, all physico-chemical parameters measured were within the limits of the Lagos State Environmental Protection Agency (LASEPA) and the World Health Organization (WHO) regulatory standards except for high COD concentration in downstream station. Aquatic vegetation (macrophyte) diversity was relatively abundant at upstream and downstream stations, suggesting possible impact of human activities on macrophyte diversity at midstream station where highest level of disturbance occurred. Chironomid larvae were the most abundant invertebrate fauna found in all three sampling stations but more abundant at sampling station AR-2 which corresponds to point of effluent entry to river where human activities is most intense. There is evidence that anthropogenic activities impact on the water quality of Abesan River. Biotic indices such as Sorensenen’s Index of Similarity and Margalef Index show that Abesan River is lightly polluted. The implications of these results and the need to monitor the water quality of Abesan River are highlighted.
Highlights
In the face of global environment change uncertainties, fore-knowledge on how anthropogenic activities impact on rivers and the biota they support is of importance to freshwater biologist
AR-2 and AR-3, all physico-chemical parameters measured were within the limits of the Lagos State Environmental Protection Agency (LASEPA) and the World Health Organization (WHO) regulatory standards except for high Chemical Oxygen Demand (COD) concentration in downstream station
Bottom sediments at stn.AR-1 is of coarse sandy particles, whereas, stn.AR-2 is muddy clay mixed with sand particles and decaying plant materials
Summary
In the face of global environment change uncertainties, fore-knowledge on how anthropogenic activities impact on rivers and the biota they support is of importance to freshwater biologist. In Africa, the bane of water bodies is the paucity of information relating to them and Abesan River is not an exception. Limnological studies in West Africa especially Lagos has concentrated on large water bodies such as the Lagos Lagoon [3,4,5] and River Sasa [6] there are many small rivers which study would make significant contribution to our knowledge of tropical aquatic ecosystems and the impact of anthropogenic activities on them [6,7]. The river is used daily by the rural folks and communities for washing, bathing, drinking, cooking and spiritual activities. It receives run-off water and effluents from nearby manufacturing industries. The foregoing points to the inadvertent introduction of pollutants into Abesan River, which could impact on the water quality as well as availability and distribution of benthic macrofauna
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