PHYTOPLANKTON NUTRIENT DYNAMICS OF TWO LENTIC HABITATS IN EASTERN INDIAPARTHA TALUKDAR, AMIT SWARNAKAR AND RUMA PALAbstract In the present investigation we studied seasonal fluctuations in composition and community structure of micro-phytoplankton in relation to the environmental drivers from two lentic habitats. The phytoplankton nutrient dynamics from two different ecological niches are represented as one industrial wastewater pond (Pond-I) and the other domestic pond, also used for fish production (Pond-II). The phytoplankton productivity was determined in terms of chlorophyll content for both the ecosystems and their diversity was determined by species diversity, richness and evenness index. The results indicated that major nutrients influenced the seasonal phytoplankton population together with temperature and pH of the water bodies. More productivity (mg/L) in relation to chlorophyll (Chl.) was recorded in Pond-I (31.71) compared to Pond-II (10.12), especially in winter period. Wide seasonal variation in nutrient concentrations (mg/L) were recorded for both sites, showing much higher levels of total nitrogen (nitrate 2.9-30.72, ammonium nitrogen 0.2-8.6 ), phosphate (0.37-1.89), and silicate (9.1-46.8) in Pond I, compared to that of pond II (nitrate 0.6-10.1, ammonium nitrogen 0.01-0.27, phosphate 0.005-0.11 and silicate 1.3-7.5). Dominant microplanktonic flora of wastewater pond was represented by members of Chlorophyceae, mainly the genera Actinastrum and Kirchneriella, whereas in Pond-II the Cyanobacterial genus, Aphanocapsa was the dominant one. The species richness was higher in wastewater fed pond showing blooming of Kirchneriella lunaris in winter. Multivariate statistical analysis especially Principal Component Analysis (PCA) showed the possible relationships between productivity and other abiotic and nutrient variables like nitrate and silicate, and moderately with phosphate and ammonium nitrogen availability. In conclusion, it was found that the seasonal cycle of production and succession was majorly controlled by temperature, transparency, BOD, DO, nitrate and phosphate for pond-I while only temperature and pH played important role in pond-II. |