Interstitial Water Chemistry of Mangrove Sediments, Kerala

Vertical concentrations of salinity, Eh, pH, total alkalinlty, NO₂^-, NO₃^-,NH₄⁺, PO₄^3-,SiO₂, Fe, Mn, Na and K in interstitial water as well as sediment organic carbon and CaCO₃, from three different mangrove areas, bordering the Vembanad estuary, the largest backwater system along the southwest coast of India have been studied The selected three mangrove locations are not only kilometers a part but also differ vastly m physico-chemical environment themselves - namely a fresh water one (cores I and 2) a brackish (core 3) and a saline mangrove area (core 4) Relatively, lower Eh values are measured in fresh water mangrove sediments than the brackish/saline cores pH and K show a decreaseing trend with depth whereas alkalinity, NH₄⁺,PO₄^3-, Si0₂, Fe, Mn and Na ~ncreases ysternatlcally donward The lower limit of oxic zone in fresh water enviroment is very much compressed than in the brackish and saline regions, where a larger oxic zones preval NO₂^- and NO₃^- concentrations after an lnitial Increase (up to approximately 10 cm in cores 1 and 2) and (1 8 crn in core 3 and 4) decrease sharply lndicating nitrificatoon fo llVertical concentrations of salinity, Eh, pH, total alkalinlty, NO₂^-, NO₃^-,NH₄⁺, PO₄^3-,SiO₂, Fe, Mn, Na and K in interstitial water as well as sediment organic carbon and CaCO₃, from three different mangrove areas, bordering the Vembanad estuary, the largest backwater system along the southwest coast of India have been studied The selected three mangrove locations are not only kilometers a part but also differ vastly m physico-chemical environment themselves - namely a fresh water one (cores I and 2) a brackish (core 3) and a saline mangrove area (core 4) Relatively, lower Eh values are measured in fresh water mangrove sediments than the brackish/saline cores pH and K show a decreaseing trend with depth whereas alkalinity, NH₄⁺,PO₄^3-, Si0₂, Fe, Mn and Na increases systematically donward The lower limit of oxic zone in fresh water enviroment is very much compressed than in the brackish and saline regions, where a larger oxic zones preval NO₂^- and NO₃^- concentrations after an lnitial Increase (up to approximately 10 cm in cores 1 and 2) and (1 8 crn in core 3 and 4) decrease sharply lndicating nitrificatoon fo owed by denitnficatio PO₄^3-, Fe, Mn, NH₄⁺, K and alkalinity production are more in fresh water mangroves than brackish/ saline mangroves indicating gatherd degradation of organic matter under higher anoxic condition.