Abundance & distribution of aquatic benthic macro-invertebrate families of river Ganga and correlation with environmental parameters.

Bio-monitoring freshwater bodies using macro-invertebrates is an excellent way to detect biological water quality. Organic contamination in aquatic settings is well indicated by benthic macro-invertebrates. The use of macro-invertebrates to bio-monitor freshwater bodies is an effective method for determining biological water quality. Benthic macro-invertebrates are excellent indicators of organic pollution in aquatic environments. In the present study, the distribution of pollution-sensitive and pollution-tolerant families of benthic macro-invertebrates from 33 different locations along the Ganga River in Uttarakhand, Uttar Pradesh, Bihar, and West Bengal was studied. Benthic macro-invertebrates collected from different studied locations were identified up to family level and it was observed that a total of 15 pollution-sensitive families belong to four taxonomic orders, while eight pollution-tolerant families come from two taxonomic orders. Several moderately tolerant families have also been observed, but in this paper the distribution of only pollution-sensitive and pollution-tolerant families is presented as they reflect the extreme states of organic pollution. In the majority of locations, the pollution-sensitive Ephemeroptera family Ameletidae predominated. Likewise, the pollution-tolerant families Chironomidae (order-Diptera) and Naididae (order-Oligochaeta) dominated the Ganga River locations. Besides, the relationship between macro-invertebrate diversity and physicochemical factors (pH, water temperature, and dissolved oxygen) was investigated, and 3D surface distribution maps were displayed for qualitative interpretation. The correlation coefficients for all parameters were found to be positive. Macro-invertebrate pollution indices for bio-monitoring are based on community impacts and assist in evaluating the success of action plans to prevent industrial and anthropogenic pollution that contributes to the Ganga.