Plankton communities of a subtropical reservoir of Meghalaya (NE India)

Abstract

Nongmahir reservoir, studied during June, 1995 - May, 1996, shows subtropical nature and soft-alkaline waters characterized by low electrolyte concentration, moderate transparency, unsaturated dissolved oxygen and low nutrient concentrations. Net plankton indicate 17 species of phytoplankton and 28 species of zooplankton, and lower abundance (164 ± 77 n/l) with predominance of phytoplankton (109 ± 94 n/l). The latter exhi bit quantitative dominance of chlorophyta (83 ± 99 n/l) and sub-dominant role of cyanophyta> bacillariophyta > chrysophyta > dinophyta. Zooplankton (55 ± 26 n/l) depict copepoda> cladocera and poor densities of rotifera > rhizopoda. Temporal variations of planktonic communities are discussed with special reference to community similarities, abundance, species diversity, dominance and evenness as well as their relationships with abiotic and biotic factors. Remarks are made on trophic status of the reservoir.