Abstract

The current study evaluated the ecohydrological interactions of macrobenthic community and the trophic state of the Hirakud Reservoir. According to the computed values of weighted arithmetic water quality index (WAWQI), the reservoir represented a mesotrophic state with "good to excellent" water quality, particularly during the monsoon and post-monsoon seasons. However, during the monsoon, the water fell into the "poor to very poor" category. Seasonal heterogeneity was noted in the macrobenthos characteristics, with the monsoon season (848 ind.m-2) showing the highest quantitative spectrum. Ecological functional groups − SC/SH (46%) were the major contributors to the total macrobenthic population. A total of 25 taxa of macrobenthos were recorded with Gastropoda was the chief contributor. Species Melanoides tuberculata, Filopaludina bengalensis, Tarebia granifera and T. lineata were consistently present throughout the seasons suggested that these species were highly tolerant of seasonality and other environmental disturbances. The ordination analysis stated that sediment variables such as water depth, clay (%), available-N, available – P and sediment organic carbon were the major influencing variables for abundance and distribution of macrobenthos in the Hirakud reservoir. Because of the constant inflow of water from the main river, Mahanadi, which inhibits the settling of finer particles at the bottom, the reservoir's sediment was primarily sandy (44–82%). The baseline data from the current study on Hirakud Reservoir will be useful in developing management recommendations for fisheries and water quality monitoring.