Community Structure of Macrobenthic Fauna in Achenkovil River, Southern-Western Ghats, Kerala, India

A study on the water quality parameters and community structure of the macrobenthic fauna was carried out in the Achenkovil river basin, Kerala. Nine sampling sites were selected for the study and the macrobenthic fauna was collected using Van Veen Grab (0.025m2). Both the water and sediment samples were collected bimonthly and seasonally. Fourteen water quality parameters were analyzed to monitor the influence of water quality on the community structure of macrobenthos. The maximum mean value for DO and silicate was in station 1 (S1). The water temperature, BOD, turbidity, conductivity, TDS, salinity, alkalinity, hardness, pH, nitrate, and phosphate have their maximum value in the downstream stretches of the river. A total of 3563 macrobenthic individuals belonging to 8 orders, 32 families, 32 genera, and 32 species were collected and identified. Among the macrobenthic community, the order Ephemeroptera showed the maximum abundance (860 Ind/m²) and minimum for Zygoptera (63 Ind/m²). Station S1, part of a pristine forest region, is characterized by rich benthic diversity and abundance. The pollution-sensitive taxa such as Ephemeroptera, Plecoptera, and Trichoptera were the dominant members of the community structure in S1. Their presence is an indication of good water quality. The midstream and downstream segments of the river are facing severe anthropogenic stress. An increase in the abundance of pollution-tolerant organisms such as Chironomids in the midstream and downstream segments of the river is an indication of deteriorating water quality. The diversity, distribution, and abundance of the macrobenthic community were highly influenced by the variations in water quality due to various natural as well as anthropogenic impacts.