Atmospheric nitrous oxide fluxes from mangrove sediments

Although the marine environment is recognized as a net source of nitrous ox ide to the atmosphere, current global budgets appear to underestimate the m arine source of this radiatively active gas. Mangrove forests occupy a sign ificant fraction of the tropical land/sea interface and receive high inputs of terrestrial nitrogen. Anthropogenic activities increase nitrogen input to mangrove sediments thereby enhancing microbial nitrogen metabolism. Elev ated rates of nitrous oxide flux might therefore be expected, Our experimen tal determinations of nitrous oxide flux from mangrove sediments yield rate s of between 0.12 and 7.8 mu mol N2O m(-2) h(-1); values which are between 2 and 135 times greater than those reported previously for intertidal estua rine sediments. Nitrous oxide yield from these sediments varies greatly in response to both the magnitude and chemical nature of the sediment nitrogen source. Rates appear to be greater when reduced nitrogen is the dominant s ubstrate and nitrification is the main source of nitrous oxide compared to sediments where nitrate and nitrite predominate and nitrous oxide arises fr om microbial denitrification. (C) 1999 Elsevier Science Ltd. All rights res erved.