Diurnal variation of plankton in Nawagaon wetland of Chhattisgarh.

Abstract

Nawagaon wetland situated on Mahanadi river basin in Raipur District of Chhattisgarh, has 82.12 ha water spread area. Diurnal variation of plankton was studied in the wetland during summer, monsoon and winter seasons at 6, 12, 18 and 24 hrs. Phytoplankton biomass showed summer peak at 6 hrs (330 u l-1) with the dominance of Myxophyceae. Monsoon (180 u/l) and winter (410 u l-1) peaks for phytoplankton were at 12 hrs and 18 hrs, respectively with the dominance of Chlorophyceae. Seasonally, phytoplankton biomass was maximum during winter while the degree of variation was relatively higher during summer. Diurnal variation of zooplankton had indicated summer peak at 6 hrs (50 u l-1), monsoon (170 u l-1) and winter (80 u l-1) peaks at 24 hrs. Among zooplankton, crustaceans were found to be more sensitive towards environmental changes as compared to rotifers. Rotifers were observed in the surface water regardless of the illumination while crustaceans were adapted to low light intensity, however their abundance varied accordingly. The study points out that light and temperature may be regulating the biotic fluxes in the environment. Observation of morning and evening abundance of phytoplankton evidenced that the change of illumination in either direction constituted the effective stimulus to upward movement of the plankton. Continuous presence of some taxa viz. Phormidium of Myxophyceae, Pediastrum and Tribonema of Chlorophyceae, Synedra and Navicula of Bacillariophyceae and Brachionus of Rotifera at 6, 12, 18 & 24 hrs, revealed their resistance towards changing environmental fluxes of the wetland.