Nutrient conditions and chironomid productivity in Kolkata, India: assessment for biomonitoring and ecological management

The chironomid diversity in the water bodies are useful indicators of the nutrient and environmental states. A spatial scale analysis on the relative abundance of the chironomid species in the context of selected nutrient indicators like organic carbon (C), potassium ions (K+), nitrate (NO3¯), and phosphate (PO42¯) of the water bodies was assessed to justify the use of chironomids in environmental biomonitoring. Analysis of a sample of 90 data from eight different ponds of Kolkata, India, revealed the presence of 11 chironomid species in different relative densities. The chironomid immature productivity was found to be positively correlated with C and PO42¯ of the water bodies, while no definite significant correlation was observed for K+, NO3¯. Based on these nutrients and the productivity of chironomids the ponds could be distinguished from one another. The abundance of three species of chironomid midges, Chironomus striatipennis, Chironomus circumdatus and Kiefferulus calligaster were prominent in all the water bodies. Cluster analysis showed that these species were highly correlated in their abundance contrast to others. The correspondence analysis showed distribution of the chironomid species to differ against the variance of nutrients. The results are supportive of the use of chironomid larvae in biomonitoring and ecological restoration of urban water bodies, through monitoring the nutrient status and the chironomid species assemblage. In this instance the chironomid species C. striatipennis, C. circumdatus and K. calligaster can specifically act as indicator of the nutrient state of the ponds.