Changes in bacterioplankton and zooplankton communities in response to Covid-19 forced lockdown at dolphin surfacing sites in the River Ganga

Abstract

The spread of Covid-19 has reduced human intervention in aquatic ecosystems, which has shown a discernible improvement in air and water quality. Ganges River, being a historical, economic and cultural icon of India providing multiple ecosystem services as industrial, provisioning, regulatory and cultural services, constitutes an important habitat for Gangetic Dolphin (Platanista gangetica). The surfacing of dolphins in Ganga river is patchy and unpredictable. The present study unravels 25 different chemical, microbiological, biological and meta-genomics of most abundant bacteria at dolphin surfacing sites in Ganges water during October 2017 February 2018 and January 2021 to elicit the impact of Covid-19 lock down at the Garhmukteshwar (28.7601°N, 78.1437°E) stretch in Hapur district of Uttar Pradesh, India. The most abundant bacteria at dolphin surfacing site was Bacillus subtilis in February 2018 which was replaced by Aeromonas sp. in January 2021. The zooplankton community was dominated by rotifers during pre-Covid period however the dominance pattern recorded a shift towards larger herbivorous crustacean species during Covid −19 lock down. Overall bacterial count decreased whereas Chl a level increased during the lock down. The total zooplankton abundance did not show a significant difference, but relative proportion of larger herbivorous crustacean zooplankton increased in January 2021 samples. The present results convincingly establish effects of shutdown on chemical, metagenomics and biological components of the riparian ecosystem and the information of micro to mesoplanktonic community may be useful for characterizing dolphin surfacing sites, enhancing existing water quality monitoring efforts and also for human epidemiological studies associated with recreational use of Ganga water.