Interaction among macrobenthic molluscan diversity of river Ganga and ecological variables by using multivariate indices.

Ganga river is one of the important water bodies harbouring different aquatic communities especially sedentary benthic organisms. We determined several macrobenthic molluscan faunas including 24 species comprising of 18 gastropods and 6 bivalves. The maximum species diversity with a value of 2.08 was recorded during monsoon, whereas the species richness was found to be highest (0.809) during winter. To determine the correlation between the physicochemical parameters of water, sediment and macrobenthic organisms, we have employed the canonical correspondence analysis (CCA) for middle, lower and estuarine stretches of river Ganga. The water CCA components, CCA1 and CCA2, explained 48.64%, 47.01%, 45.11% (p = 0.568, 0.019 and 0.417) and 18.11%, 26%, 23.9% (p = 0.98, 0.292 and 0.978) between the environmental parameters and macrobenthos correlation, respectively. Similarly, the CCA components for soil showed a percentage of 41.82%, 41.58%, 24.73% in CCA1 (p = 0.156, 0.026 and 0.922) and the CCA2 revealed a percentage value of 24.23%, 25.58%, 23.59% (p = 0.446, 0.174 and 0.488) of the mentioned parameters. The present study explored a dual relationship between the organisms and environmental factors according to their abundance and distribution pattern. [ABSTRACT FROM AUTHOR]