Impact of Effective Light Climate on Periphyton in the Nutrient Impacted River Ganges

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Usha Pandey
Jitendra Pandey


Anthropogenic releases in large regulated rivers are overriding their organic load assimilation capacity and ability to rejuvenate. Effective light penetration in such water bodies are constrained by trade-off between organic load and benthic oxygen supply.We investigated the impact of light climate, as influenced by dissolved organic carbon (DOC) and phytoplankton shading effect, on periphyton biomass accrual in Ganges during summer low flows. Periphyton chlorophyll a decreased with increasing growth of phytoplankton and DOC. Periphyton biomass showed significant negative correlation with DOC (R2=0.9483; p less than 0.0001) and phytoplankton biomass (R2=0.9251; p less than 0.0001) and positive correlation with Secchi depth (R2=0.9506; p less than 0.0001). Among taxonomic divisions, Chlorophyta, with 24-60% of total standing stock, showed higher biomass at sites characterized by moderate nutrients and DOC levels. Cyanophyta (39-74%) contributed large fraction at eutrophic sites and Bacillariophyta (2-5%) at moderately eutrophic sites. Cyanophycean alga Phormidium appeared dominant at sites enriched in nutrients. The study indicated that light attenuation driven by DOC and phytoplankton is leading to erode benthic primary producers and redistribution of taxonomic divisions in Ganges, which may, by implication, entail a similar shift in the trophic cascades.

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Pandey U, Pandey J. Impact of Effective Light Climate on Periphyton in the Nutrient Impacted River Ganges. IJPE [Internet]. 31Oct.2016 [cited 11Apr.2021];2(1 and 2):59-8. Available from:
Review Article