Variation in thermal trait and plankton assemblage pattern induced by coal power plant discharge in river Ganga

Thermal pollution in the riverine resources is an important issue due to its potential threat concern towards aquatic organisms. Though the thermal pollution effect on the planktonic community is well studied in the coastal thermal plant, little is available in freshwater stretches of river ecosystems. The goal of the current study was to ascertain the impact of thermal discharge from a coal-fired power station on the planktonic population and water quality along the spatial and temporal dimensions of a tropical river Ganga River. Thermal discharge led to a thermal gradient with an increase in water temperature in the river near the discharge point. The effect of temperature elevation was more profound in winter than the summer. The results showed that the dissolved oxygen and chlorophyll content was lower (1.46 and 1.34 times, respectively) near the thermal discharge point particularly in the winter as compared to summer. A total of 28 phytoplankton genera from 9 classes were identified among which 5 and 3 genera are dominated in winter and summer, respectively. The thermal discharge resulted in 1.34 times reduced chlorophyll content at the source in the winter, whereas no effect was observed in the summer. However, the diversity and abundance of plankton were found to be more closely connected to seasonal variation than to the thermal gradient. This study inferred that the plankton assemblage pattern at the thermal discharge point in the tropical river was more influenced by seasonal variation than the thermal discharge. Further studies are required on other aquatic biota for a comprehensive understanding of the effect of thermal pollution on river health status.