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Seasonal variations in the water quality of six tropical micro and meso-tidal estuaries, central west coast of India
The seasonal nutrient dynamics were investigated in four rivers having micro-tidal range (Terekhol, Chapora, Sal, Talpona) and compared with two rivers of meso-tidal range (Zuari and Mandovi), along the central west coast of India. The rainfall and freshwater discharge, during the wet season, led to salinity stratification of the water columns at these river mouths. The nutrient concentrations in all the rivers were higher during the wet season as compared to the dry season due to considerable land runoff. Based on the estuarine mixing diagrams of the nutrient with respect to the salinity, the meso-tidal rivers showed greater flushing capacity and acted as corridors for the nutrient passage between the estuary and the open ocean. On the other hand, amongst the micro-tidal rivers, the Terekhol and Chapora seemed to retain the nutrients, while the Talpona R. did not show the presence of nutrient sink or source. The Sal R. was observed to be eutrophic with high nutrients and acted as a source of phosphorus and nitrogen. Thus, the present study clearly illustrates the important role played by minor river estuaries in modifying the nutrient concentrations during their transport from the rivers to the coastal waters and vice versa.
MF17181 Accepted 07 February 2018
© CSIRO 2018