Aquatic Insects as Pollution Indicator-A Study in Cachar, Assam, Northeast India

A seasonal study on water and aquatic insects of one oxbow lake (Satkorakandi anua) and one floodplain lake (Magura haor) of Cachar, Assam was conducted. Environmental variables of water, diversity, and density of aquatic insects were estimated by standard methods. In the oxbow lake, dissolved oxygen values were found to be lower than that of the floodplain lake. The pH of water was found below the acceptable limit of BIS in post-monsoon in oxbow lake, and in most of the seasons in floodplain lake. Other variables were within the permissible limit. The Biological Monitoring Working Party (BMWP) and BMWPTHAI scores computed on the basis of tolerance level of the aquatic insects to organic pollution revealed poor water condition in all the sites and seasons in anua while in haor water condition was found moderate in some seasons of the year. Different biotic indices, correlation coefficients, canonical correspondence analysis were computed and the role of aquatic insects as pollution indicator has been discussed in the paper.