author(s)
Kalpana Srivastava, Sandeep Mishra, Hari Om Verma, Venkatesh R Thakur, DN Jha, Absar Alam and BK Das

abstract
The present study analyses the long term seasonal changes in the Ganga river plankton communities at Kanpur during the period of 2002-2020. River Ganga at Kanpur is passing through multiple stressors like pollution, climate change, habitat alteration, eutrophication and various anthropogenic activities, since a long period. This was reflected by the abundant growth of various taxonomic groups of phytoplankton and zooplankton. Degradation of plankton quality was noticed by the reduction in Bacillariophyceae and increase in Chlorophyceae, with the lapse of time from 2002-2017 and 2018-2020 improvement in water quality was observed. A sudden increase in Myxophyceae was recorded after the construction of barrage in above Kanpur area during 2014 and 2015. A comparison with 1966 data indicated that river depth, temperature, Chloride, Silica, hardness and turbidity exhibited major differences in the past fifty years and impacted plankton community structures. Species shift was observed from time to time as Synedra, Melosira, Cyclotella, Fragilaria, Nitzschia, Asterionella were dominant diatoms but their order of dominance varied. Similarly, in Green algae, the present dominance of Chloroccoccales (Ankistrodesmus, Scenedesmus, and Pediastrum), replaced the dominance of Zygnemales (Spirogyra, Mougeotia-in 1966). In recent years (2018-2020) improvement in plankton, quality is evidenced by a gradual increase of Bacillariophyceae and reduction in Chlorophyceae.