Phytoplankton diversity of two floodplain lakes (pats) of Manipur, northeastern India

Phytoplankton communities of Utra and Waithou pats (floodplain lakes) of Manipur, studied during November 2002 - October 2004, revealed 62 and 61 species, and indicated monthly richness between 27-45 (38 � plus or minus 4) and 32-46 (39 � plus or minus 4) species respectively with distinct qualitative importance of Chlorophyta (29 � plus or minus 4 and 28 � plus or minus 3 species). Phytoplankton (154 � plus or minus 31 n/l and 164 � plus or minus 34 n/l) comprised between 43.8 � plus or minus 3.0 % and 41.5 � plus or minus 3.0 % of net plankton abundance respectively of these two lakes. Chlorophyta (115 � plus or minus 23 n/l and 113 � plus or minus 21 n/l), the dominant quantitative component (74.4 � plus or minus 4.1% and 67.5 � plus or minus 4.8%), indicated importance of the demids. Bacillariophyta (33 � plus or minus 9 n/l and 37 � plus or minus 12 n/l) formed sub-dominant group, and Dinophyta > Euglenophyta > Chrysophyta showed very low densities. Various abiotic factors registered relatively limited influence on richness and abundance of phytoplankton as well as on abundance of individual groups in Utra Pat than in Waithou Pat. Multiple regression depicted higher cumulative influence of fifteen abiotic factors on the stated biotic parameters in these pats. Both richness and abundance of Phytoplankton recorded significant monthly variations, showed insignificant temporal variations between two lakes and followed indefinite annual patterns in each pat. Phytoplankton communities of the sampled pats are characterized by higher species diversity, higher evenness and lower dominance.