Littoral Benthic Macroinvertebrates as Indicators of Impact in Four Urban Lakes of Coimbatore, India.

Research Area and Question:

Littoral Benthic Macro invertebrate community composition, abundance, and diversity reflect the nature and environmental quality of lakes. The presentstudy was carried out to assess the impact on four lakes of Coimbatore, which are facing varying degree of anthropogenic pressure using littoral benthic macro invertebrate abundance.

Objectives and Methodology:

Benthic macro-invertebrate samples were collected in triplicates from littoral zones (depth 0-0.5 m) from 3 sites in each lake during February 2009 by using Van Veen’s Grab sampler with surface area of 0.0318 m2. At each sampling site, from where benthic samples were collected, water samples were also collected and analysed for varies physio-chmeical parameters to estimate Water Quality Index (WQI). Taxonomic identification was done upto family level and the total number of individuals in each family were counted and recorded.

Results:

Highest taxa richness was seen in Kurchi lake (17 families), followed by Perur Chinakulam lake (14 families) and Ukkadam lake (13 families). Shannon Wiener diversity for macro-invertebrates was highest in Chinnakulam lake (H=2.2531) followed by Perur lake (H=2.0771), Kurchi lake (H=2.0636) and Ukkadam lake (H=1.2141). WQI was highest in Ukkadam lake (123, highly polluted), followed by Kurchi lake (97), Chinnakulam lake (84) and Perur lake (75).

Discussion:

The results shows that based on diversity indices Ukkadam lake is found to be highly impacted from anthropogenic pressures followed by Kurchi, perur and Chinnakulam. This is again confirmed by WQI in all lakes. In the case of Chinnakulam the WQI reflects a t temporary impairment in water quality, habitat suitability for benthos because of the seasonal inflows. This lake is facing relatively reduced anthropogenic pressure except for certain temporary inflows and wastes. The study also indicates the urgent requirement of mitigation measures in these lakes to contain further degradation.