Tidal dynamics and rainfall control N2O and CH4 emissions from a pristine mangrove creek



[1] Dissolved CH4, N2O, O2, and inorganic nitrogen nutrients (NH4+, NO3 and NO2) were measured over tidal cycles in pristine Wright Myo mangrove creek waters during dry and wet seasons. Dissolved CH4 and N2O showed no seasonality (dry season; 491 ± 133 nmol CH4 l−1, 9.0 ± 2.3 nmol N2O l−1, wet season; 466 ± 94 nmol CH4 l−1, 8.6 ± 1.3 nmol N2O l−1). Creek water dissolved gas and inorganic nitrogen distributions reflect sediment porewater release during hydrostatic pressure drop toward low water. Creek water CH4 emission was suppressed by oxidation during rainfall, consistent with changes to dissolved nitrogen speciation, although N2O emissions were unaffected. Scaling up emissions flux estimates from mangrove creek waters and intertidal sediment gives worldwide mangrove emissions ∼1.3 × 1011 mol CH4 yr−1 and 2.7 × 109 mol N2O yr−1; mangrove ecosystems are thus small contributors to coastal N2O emissions but could dominate coastal CH4 emissions. Comparing our data with mangrove CO2 fluxes, mangrove ecosystems could be small net contributors of atmospheric greenhouse gases.