Anthropogenic Drivers Shift Diatom Dominance–Diversity Relationships and Transparent Exopolymeric Particles Production in River Ganga:Implication for Natural Cleaning of River Water

We studied the relationships among diatom biodiversity,transparent exopolymeric particles (TEP) and water quality at the confluences of four tributaries of River Ganga (Yamuna, Assi, Varuna and Gomti)during low flow. Diatom abundance changed with concurrent shifts in water chemistry with dominance–diversity curves markedly skewed from a log-normal pattern. Canonical correspondence analysis segregated chloride-loving and calcifilous species from N- and P-favoured taxa. Despite pollution-induced reduction of diatom diversity, TEP production continued to rise plausibly due to dominance transference of TEP producers. However, with further increase in nutrient pollution, TEP declined. Since TEP enhances sedimentation removal of carbon, nutrients and heavy metals, the present study confirms one of the fundamental mechanisms that underline the self-purification capacity of River Ganga and has relevance from a biodiversity/river conservation perspective.