Characteristics of geochemical fractions of phosphorus and its bioavailability in sediments of a largest brackish water lake, South Asia

Abstract

The spatio-temporal distribution of geochemical fractions of phosphorus and its bio-availability for Asia's largest brackish water lake has been carried out. One way ANOVA analysis revealed that both iron bound phosphorus (Fe-P) (p<0.05, n=360) and calcium bound phosphorus (Ca-P) (p<0.05, n=360) showed a significant variation on a spatio-temporal scale which may be attributed to pH and salinity of overlying water column. Pearson's correlation matrix revealed that sediment texture played a major role in the quantification of phosphorus species. The relationship between Ca-P and Ca was not established for the sediments of the lake Chilika, which suggested its authigenic origin. The concentration of bio-available phosphorus (BAP) in different sectors of the lake varied in the order of northern sector (45.64%)>central sector (42.22%)>outer channel (36.63%)>southern sector (29.27%) of total phosphorus (TP). This is supported by the fact that bioavailable P is comparatively higher in the freshwater zone than in the brackish water zone. The principal component analysis (PCA) revealed a good relationship between dissolved phosphate concentrations of water column with benthic population density. It showed that TP availability in the sediment of the lake is mostly bounded with Al, Fe and organic matter (OM). Positive association of total carbon (TC), total nitrogen (TN) and OM with negatively loading of Eh indicates towards the fact that, deposition of TN and TC is largely governed by OM availability in sediment.