Abstract

Lakes, important ecosystems of great value to humans are prone to pollution from autochthonous and allochthonous sources; the latter include various anthropogenic stresses that disturb the complex interactions and self purification capacity of aquatic ecosystems. The physical and chemical factors influencing aquatic ecosystems decide as well their biological diversity, of which the macroinvertebrates are the focus of this study. The diversity and abundance of aquatic macroinvertebrates might vary at the inlets and outlets of urban lakes depending upon the pollution levels and purification capacity of the lake ecosystems as such. The current study, carried out in 17 spatially well distributed lakes in around Bangalore city explores macroinvertebrate diversity and abundance at the inlets and outlets of these lakes, in relation to physico-chemical parameters of the water. The samples were collected from the inlets and outlets of the lakes concerned and macro-invertebrate diversity studied. The results of one way ANOVA pointed out that no significant differences (P < 0.05) were found between the macroinvertebrate communities of inlets and outlets of all the lakes studied, indicating high degree of pollution beyond the self cleansing powers of the lakes. The first axis of principle component analysis accounted for 25.69 % of the overall variance and was most heavily weighted on the variables pH, total hardness, dissolved oxygen, and nitrate. Canonical component analysis ordination for 27 aquatic genera in 17 lakes  with 14 environmental variables show that phosphate, nitrate and pH played more decisive roles in the macroinvertebrate diversity and assemblage of Bangalore lakes.

Keywords: Lake biodiversity, Macroinvertebrate, ecosystem, functional feeding group, environmental parameters