PHYTOPLANKTON COMMUNITIES OFA FLOODPLAIN LAKE OF THE BRAHMAPUTRA RIVER BASIN, UPPER ASSAM B. K.
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Authors
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B. K. Sharma
Department of Zoology, North-Eastern Hill University, Permanent campus,
Umshing, Shillong - 793 022, Meghalaya
Abstract
Phytoplankton (52 species; Bacillariophyceae > Chlorophyceae >
Cyanophyceae > Euglenophyceae = Dinophyceae) of Samuajan heel, a tropical
floodplain lake, registered identical mean annual richness (30 ± 4 species) in
littoral and limnetic regions and depicted 33.3 - 77.2 % and 31.4 - 81.1 %
community similarities respectively. Their abundance ranged between 137 ±
54 nil in littoral (Bacillariophyceae > Chlorophyceae) and 122 ± 45 nil
(Chlorophyceae > Bacillariophyceae) in limnetic communities, comprised
about 46% of net plankton and indicated winter peaks. This study depicted
moderate species diversity, high evenness and low dominance of
phytoplankton; species diversity showed significant direct correlation with
richness and evenness and an inverse relationship with dominance.
Phytoplankton showed significant positive relationship with transparency
and silicate and negative with water temperature, rainfall, chloride and
nitrate. Multiple regression revealed that ten abiotic factors accounted for
> 80 - 98% of density variations of phytoplankton and the dominant groups.
AN OVA depicted trends of significance in abundance of the biotic communities
analysed.
Keywords: Phytoplankton, floodplain lake, Brahmaputra basin, abundance,
ecology
