Evaluation of cycling patterns of dissolved oxygen in a tropical lake as an indicator of biodegradable organic pollution

Dissolved oxygen cycling patterns in a tropical lake (Weija Lake) were show n to be useful as a potential indicator of biodegradable organic pollution, by dosing with liquid malt to give an additional organic burden of 2.5 and 5.0 mg l(-1) TOC, and monitoring the DO values continuously for 140 h. The se loadings were added to water columns (in tubes) suspended from a raft in a lake in south-east Ghana. The addition of organic pollution burden to th e lake water produced two main effects: the mean DO value was lowered, and the amplitude of the DO cycle decreased as organic loading increased from 2 .5 to 5.0 mg l(-1) TOC. There was also an indication of heterotrophic respi ration associated with organic inputs for the 5.0 mg l(-1) added TOC sugges ting a P/R ratio of well below 1.0. Taking the results of a DO cycling comp uter model together with those from the lake raft experiments, it can be co ncluded that dissolved oxygen cycles can be a good indicator of biodegradab le organic pollution load. (C) 1999 Elsevier Science B.V. All rights reserv ed.