Nitrous oxide in mangroves and surrounding waters of the Andaman islands

Abstract

Trace gases such as NO CH and CO directly affect global newlineclimate change NO though found in trace quantities have greater impact due newlineto its longer residence time and higher radiative forcing This study aids in a newlinebetter understanding of NO emissions from coastal margins especially from newlinemangrove forests and the surrounding creek waters which are not well newlinedocumented Most of our understanding of coastal biogeochemical processes newlineis from studies in temperate areas and very few targeted studies have been newlinemade in tropical zones Dissolved NO and nutrient concentrations and fluxes newlinein three mangroves and transects from the Andaman Islands were estimated newlineIn the present study the spatial transects did not show seasonality newlinebut still the NO emission was high when the temperature was high Likewise newlinethe water column showed more potential for nitrification than denitrification newlineas there was positive correlation between nitrous oxide and dissolved oxygen newlineand ammonium The dissolved NO followed the tidal mechanism where the newlinehighest concentrations always occurred at tidal minima in all the tidal sites newlineDissolved NO in Wright Myo and Kalighat mangroves did not exhibit a newlinedistinct seasonal variation although the wet seasons of August 2005 and 2006 newlineshowed comparatively higher concentrations than in the dry seasons newlineThe average denitrification rate was 954Mm from all seasons newlineand locations put together The flux nitrous oxide measured through other newlinemethods is higher than already reported through denitrification and so the newlinemangrove sediments of Andaman Islands account for denitrification rates and newlinethe surrounding waters are thought to be a potential system for nitrification newlinerather than denitrification newlineThe NO emission rates from Andaman mangroves varied between newline0161 and 302 and#956;mol NO m with an annual average of 5341391and#956;mol newlineNO m yr This was extrapolated for the entire mangrove cover of newlineAndaman to give 15576 g yr of NO from the mangrove sediments and newline24958 g yr of NO from the mangrove creek waters newline newline