Chemistry of specialized coastal environments a case study of Alappuzha mud banks southwest coast of India

Abstract

The west coast of India experiencing the southwest monsoon from newlineJune to September has a profound influence on the biogeochemistry of the newlinesoutheastern Arabian Sea. The inclement weather during this period is newlinecharacterised by the high availability of fishes in the nearshore waters, but newlinethe trawl ban (45 days) imposed by the government prevents any kind of newlinefishing from this region. Thus, the southwest monsoon has a devastating newlineeffect on the livelihood of the coastal community engaged in fishing. newlineHowever, certain coastal stretches along the southwest coast are found to newlinedevelop unusually calm waters known as mud banks (chakara), enabling newlinethe fishermen to take their country crafts into the sea, where they get newlineplenty of fish. The reason that mud banks facilitate smooth fishing newlineoperations has gained much popularity in the country since there are no newlineother places along the west coast of India from where fishing is possible newlineduring monsoon. newlineMud banks are generally reported in coastal areas adjacent to river newlineembayment s following the deposition of a large amount of silt brought newlineby rivers. In contrast, the fact that Alappuzha mud banks are located far newlineaway from any river entrance is quite surprising for its formation. History newlineof Alappuzha mud banks dates back to 1678, though knowledge about newlinethese mud banks and their functions remains incomplete. The present newlinestudy aims to examine the hydrochemistry of Alappuzha mud banks and newlineits impact on the geochemical characteristics on a seasonal and interannual newlinescale.The significance of this study is that formation of these mud banks newlineare concurrent to the intense upwelling along the southwest coast of India newlineduring monsoon. Therefore, the calm mud banks form an ideal site newline(mesocosm) to study the upwelling (hypoxia) induced changes in a newlineproductive coastal environment.The variations in temperature, salinity, newlinedissolved oxygen and nutrients (N, P and Si) can explain the dynamics of newlineupwelling in the nearshore waters. The characteristic feature of mud bank newlineis the presence of think fluid mud layer