Occurrence and Deleterious Effects of Algal Blooms Associated With Some Pollutants in Three Man-Made Lakes

Abstract

Associations of plankton genera, some of which are known to be potentially harmful and indicative of pollution stress in surface waters were studied alongside some of their corresponding physico-chemical parameters, in three man-made lakes (reservoirs) over a period of 18 months in Ibadan, Nigeria. These lakes receive sewage effluents and agricultural run-offs. Two of these, Lakes Awba and Main are sites of drinking water abstraction. Bloom-forming algal families found in association included members of the phytoplankton class Chlorophyceae: (Pediastrium spp and Spirogyra spp.), the Bacillariophyceae which included Synedra, Melosira and Nitzschia species and potentially toxin-producing genera of the class Cyanophyceae (Microcystis, Anabaena, Aphanizomenon and Lyngbya). The plankton exhibited significant correlations with pH, temperature, total suspended solids, dissolved oxygen, carbon dioxide, nitrate-nitrogen and ammonium-nitrogen at various seasons of the year. An altered physico-chemistry of large areas of the lake and a total absence of aquatic life in some highly polluted parts were recorded in the study. Reports from lake users were recorded, of contaminated bad tasting water unfit to drink, unpalatable fish and skin infections, all indicators of the far-reaching effects algae can have on fresh water supplies. This paper calls for more frequent and thorough monitoring of such resources Keywords: Sewage, Bloom–forming algae, pollution, water quality parameters, agricultural run-offs, eutrophic, harmful algal bloomsTropical Freshwater Biology Vol. 17 (1) 2008: pp. 53-72