Coastal salt marshes store large amounts of carbon but the magnitude and patterns of greenhouse gas (GHG; i.e., carbon dioxide (CO₂) and methane (CH₄)) fluxes are unclear. Information about GHG fluxes from these ecosystems comes from studies of sediments or at the ecosystem‐scale (eddy covariance) but fluxes from tidal creeks are unknown. We measured GHG concentrations in water, water quality, meteorological parameters, sediment CO₂ efflux, ecosystem‐scale GHG fluxes, and plant phenology; all at half‐hour intervals over 1 year. Manual creek GHG flux measurements were used to calculate gas transfer velocity (k ) and parameterize a model of water‐to‐atmosphere GHG fluxes. The creek was a source of GHGs to the atmosphere where tidal patterns controlled diel variability. Dissolved oxygen and wind speed were negatively correlated with creek CH₄ efflux. Despite lacking a seasonal pattern, creek CO₂ efflux was correlated with drivers such as turbidity across phenological phases. Overall, nighttime creek CO₂ efflux (3.6 ± 0.63 μmol/m²/s) was at least 2 times higher than nighttime marsh sediment CO₂ efflux (1.5 ± 1.23 μmol/m²/s). Creek CH₄ efflux (17.5 ± 6.9 nmol/m²/s) was 4 times lower than ecosystem‐scale CH₄ fluxes (68.1 ± 52.3 nmol/m²/s) across the year. These results suggest that tidal creeks are potential hotspots for CO₂ emissions and could contribute to lateral transport of CH₄ to the coastal ocean due to supersaturation of CH₄ (>6,000 μmol/mol) in water. This study provides insights for modeling GHG efflux from tidal creeks and suggests that changes in tide stage overshadow water temperature in determining magnitudes of fluxes.

中文翻译：

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温带盐沼潮汐溪中的二氧化碳和甲烷排放

沿海盐沼储存大量碳，但温室气体（GHG；即二氧化碳（CO ₂）和甲烷（CH ₄））通量的大小和形式尚不清楚。来自这些生态系统的温室气体通量的信息来自沉积物研究或生态系统范围内的（涡度协方差），但来自潮汐小溪的通量是未知的。我们测量了水中的GHG浓度，水质，气象参数，沉积物CO ₂流出，生态系统规模的GHG通量和植物物候学；一年内每半小时间隔一次。手工进行的小溪温室气体通量测量用于计算气体传输​​速度（k）并参数化水-大气温室气体通量模型。这条小溪是大气中温室气体的来源，潮汐模式控制了狄尔变异性。溶解氧和风速与小溪CH ₄外排负相关。尽管缺乏季节性模式，但小溪CO ₂流出与诸如物候期浑浊的驱动因素相关。总体而言，夜间小溪CO ₂排放量（3.6±0.63μmol/ m ² / s）至少是夜间沼泽沉积物CO ₂排放量（1.5±1.23μmol/ m ² / s）的至少两倍。Creek CH _4的流出量（17.5±6.9 nmol / m ² / s）比生态系统规模的CH ₄低4倍全年通量（68.1±52.3 nmol / m ² / s）。这些结果表明，潮汐小溪是潜在的CO ₂排放热点，并且由于水中的CH ₄过饱和（> 6,000μmol/ mol），可能有助于CH ₄向沿海海洋的横向运输。这项研究为模拟潮汐小溪的温室气体排放提供了见识，并指出在确定通量大小时，潮汐期的变化使阴影水温过高。