Pristine mangrove creek waters are a sink of nitrous oxide.

ABSTRACT: Nitrous oxide (N2O) is an important greenhouse gas, but large uncertainties remain in global budgets. Mangroves are thought to be a source of N2O to the atmosphere in spite of the limited available data. Here we report high resolution time series observations in pristine Australian mangroves along a broad latitudinal gradient to assess the potential role of mangroves in global N2O budgets. Surprisingly, five out of six creeks were under-saturated in dissolved N2O, demonstrating mangrove creek waters were a sink for atmospheric N2O. Air-water flux estimates showed an uptake of 1.52?±?0.17??mol?m(-2)?d(-1), while an independent mass balance revealed an average sink of 1.05?±?0.59??mol?m(-2)?d(-1). If these results can be upscaled to the global mangrove area, the N2O sink (~2.0?×?10(8)?mol?yr(-1)) would offset ~6% of the estimated global riverine N2O source. Our observations contrast previous estimates based on soil fluxes or mangrove waters influenced by upstream freshwater inputs. We suggest that the lack of available nitrogen in pristine mangroves favours N2O consumption. Widespread and growing coastal eutrophication may change mangrove waters from a sink to a source of N2O to the atmosphere, representing a positive feedback to climate change.

SUBMITTER: Maher DT 

PROVIDER: S-EPMC4864614 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature