Coastal lagoons are important nutrient filters and carbon sinks but may release large amounts of methane (CH4) to the atmosphere. Here, we hypothesize that eutrophication and population density will turn coastal lagoons into stronger methane emitters. We report benthic fluxes from 187 sediment cores incubated from three of the largest European lagoons suffering persistent eutrophication. Methane fluxes were mainly driven by sediment porosity, organic matter, and dissolved inorganic carbon (DIC) fluxes. Methane was always supersaturated (250–49,000%) in lagoon waters leading to large, variable emissions of 0.04–26 mg CH4 m−2 d−1. Combining our new dataset with earlier estimates revealed a global coastal lagoon emission of 7.9 (1.4–34.7) Tg CH4 yr−1 with median values of 5.4 mg CH4 m−2 d−1. Lagoons with very highly populated catchments released much more methane (223 mg CH4 m−2 d−1). Overall, projected increases in eutrophication, organic loading and population densities will enhance methane fluxes from lagoons worldwide.

中文翻译：

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富营养化和城市化增加了沿海泻湖的甲烷排放


沿海泻湖是重要的营养物过滤器和碳汇，但可能会向大气中释放大量甲烷 (CH4)。在这里，我们假设富营养化和人口密度将使沿海泻湖变成更强的甲烷排放源。我们报告了 187 个沉积物核心的底栖通量，这些沉积物核心来自欧洲三个最大的泻湖，遭受持续的富营养化。甲烷通量主要由沉积物孔隙度、有机质和溶解无机碳（DIC）通量驱动。泻湖水中的甲烷始终处于过饱和状态 (250–49,000%)，导致大量可变排放量为 0.04–26 mg CH4 m−2 d−1。将我们的新数据集与之前的估计相结合，显示全球沿海泻湖排放量为 7.9 (1.4–34.7) Tg CH4 yr−1，中值为 5.4 mg CH4 m−2 d−1。集水区人口稠密的泻湖释放出更多的甲烷（223 mg CH4 m−2 d−1）。总体而言，预计富营养化、有机负荷和人口密度的增加将增加全球泻湖的甲烷通量。