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

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. 53-7

Metal Distribution and Bioaccumulation in Water and Fish of a Tropical Lake

A study was conducted to investigate the metal (copper, zinc and manganese) concentrations in the surface water and fish of a man-made lake receiving agricultural and domestic effluents in Ibadan, Nigeria. The lake (Main Lake, IITA) is a site of drinking water abstraction and the major water source for the surrounding agricultural research farms. Factor analysis indicated that copper was an important contributor to the total variance observed in the lake, being involved in Factor 1 of the 6-factor model. Significant differences occurred in the copper and manganese levels of the organs of Oreochromis niloticus at P< 0.05 and P< 0.01 respectively and in manganese levels of Sarotherodon. galilaeus at P< 0.05. Significant differences did not occur in Lates niloticus and Synodontis nigrita organs. Bioaccumulation factors from water to fish muscles were highest for manganese ranging from 4.56-10.56; zinc from 1.83-5.67 and copper from 1-1.8. These factors showed that despite the low levels of these metals in surface water, there may be an onset of bioaccumulation in some of the fishes. This work contributes to the baseline data on the presence and effects of metals in African freshwaters and could aid future plans for the control of toxic build-up in our aquatic environments. Keywords: Metal, concentrations, lake, bioaccumulation, water, fish and IITATropical Freshwater Biology Vol. 17 (1) 2008: pp. 81-9