Spatio temporal variation of Phytoplankton in relation to physicochemical parameters along Mahanadi estuary & inshore area of Paradeep coast, north east coast of India in Bay of Bengal

Abstract

Percentage contribution of each group of phytoplankton was in the order of: Diatom > Cyanobacteria & Chlorophyceans > Dinoflagelles. Out of all, only three species <em>(Asterionellopsis glacialis</em>, <em>Nitzschia</em> sp. and <em>Thalassiothrix longissima)</em> contributed more than 50% to the total phytoplankton population. Abundance varied from115 nos.ml^-1 to 555 nos.ml^-1 which is 8 times more than the earlier studies made in the coast of Odisha. Significant variations is also observed in physicochemical parameters viz., salinity, dissolved oxygen (DO), nitrites (NO₂–N), nitrates (NO₃-N), Ammonia (NH₃-N), Phosphate (PO₄-P), silicate (SiO₄-Si) . By analyzing the N:P ratio, in the samples of the study area, it was observed that nitrogen is the limiting factor for phytoplankton. The similarity and group average clustering (Bray Curtis) divide the area in to two distinct phytoplankton groupings with their location of sampling as (A) low salinity and high turbidity and (B) high salinity. Higher species diversity (H’= 2.6-3.0) and higher equitability in plankton flora (J’=0.8-0.9) were observed in estuarine monitoring points having lower levels of anthropogenic influence (BOD=1.2-1.9 mg L^-1).