Phytoplankton Diversity of a Subtropical Reservoir of Meghalaya State of Northeast India

Abstract

The littoral and limnetic phytoplankton of ‘soft and de-mineralized water’ in the Nongmahir reservoir of Meghalaya state of northeast India (NEI) reveal a fairly diverse assemblage of a total of 52species, depict a higher richness of Chlorophyta and desmids, and record a speciose constellationof 51 species per sample. Phytoplankton form a dominant quantitative component of net planktonand indicate the differential spatial dominance of important groups. Bacillariophyta > Chlorophytaindicate dominance in the littoral region and Chlorophyta records dominance in the limnetic region. Staurastrum spp. > Cosmarium spp. are important in the two regions. Seventeen ‘specialist’species collectively contribute to phytoplankton abundance in the littoral (87.9±6.9%) and limnetic(91.6±3.3%) regions and the rest depict a ‘generalist’ nature. Phytoplankton records moderatespecies diversity and variations of dominance and evenness. The spatial monthly variations of composition, richness, similarities, abundance, diversity indices and influence of individual abiotic factors are hypothesised to differences in habitat heterogeneity amongst the two regions. The CCAregisters 78.36 and 78.95% cumulative influence of 10 abiotic factors on the littoral and limneticphytoplankton assemblages, respectively. Our results highlight distinct temporal variations of diversity parameters in comparison with the preliminary survey of June 1995–May 1996. This study isan important contribution to phytoplankton diversity of the reservoirs of India and the subtropicalreservoirs in particular.