Department of Oceanography and Coastal Sciences, College of the Coast and Environment, Louisiana State University, Baton Rouge, LA 70808, USA.
Department of Oceanography and Coastal Sciences, College of the Coast and Environment, Louisiana State University, Baton Rouge, LA 70808, USA.
Sci Total Environ. 2023 Jun 1;875:162685. doi: 10.1016/j.scitotenv.2023.162685. Epub 2023 Mar 7.
Methane (CH) is steadily increasing in the atmosphere from different sources including wetlands. However, there is limited landscape level CH flux data in deltaic coastal systems where the availability of freshwater is impacted by the combined effect of climate change and anthropogenic impacts. Here we determine potential CH fluxes in oligohaline wetlands and benthic sediments in the Mississippi River Delta Plain (MRDP), which is undergoing the highest rate of wetland loss and most extensive hydrological wetland restoration in North America. We evaluate potential CH fluxes in two contrasting deltaic systems, one undergoing sediment accretion as result of a freshwater and sediment diversions (Wax Lake Delta, WLD), and one experiencing net land loss (Barataria-Lake Cataouatche, BLC). Short- (<4 days) and long-term (36 days) incubations using soil and sediment intact cores and slurries were performed at different temperatures representing seasonal differences (10, 20, 30 °C). Our study revealed that all habitats were net sources of atmospheric CH in all seasons, and CH fluxes were generally the highest for the 20 °C incubation. The CH flux was higher in the marsh habitat of the recently formed delta system (WLD) with total carbon content of 5-24 mg C cm compared to the marsh habitat in BLC, which had high soil carbon content of 67-213 mg C cm. This suggests that the quantity of soil organic matter might not be a determining factor in CH flux. Overall, benthic habitats were found to have the lowest CH fluxes indicating that projected future conversions of marshes to open water in this region will impact the total wetland CH emission, although the overall contribution of such conversions to the regional and global carbon budgets is still unknown. Further research is needed to expand the CH flux studies by simultaneously using several methods across different wetland habitats.
甲烷（CH）正从湿地等不同来源在大气中稳定增加。然而，在受气候变化和人为影响综合作用影响淡水供应的三角洲沿海系统中，有关景观尺度 CH 通量的数据有限。在这里，我们确定了密西西比河三角洲平原（MRDP）寡盐水湿地和底栖沉积物中的潜在 CH 通量，该平原正在经历北美最高的湿地丧失率和最广泛的水文湿地恢复。我们评估了两个具有对比性的三角洲系统中的潜在 CH 通量，一个是由于淡水和沉积物改道而导致的泥沙淤积（Wax Lake Delta，WLD），另一个是正在经历净土地损失的系统（Barataria-Lake Cataouatche，BLC）。使用土壤和沉积物完整岩芯和泥浆在不同温度下进行了短期（<4 天）和长期（36 天）孵育，以代表季节性差异（10、20、30°C）。我们的研究表明，所有生境在所有季节均为大气 CH 的净源，并且在 20°C 孵育时 CH 通量通常最高。新形成的三角洲系统（WLD）中的沼泽生境的 CH 通量高于 BLC 中的沼泽生境，其总碳含量为 5-24mg C cm，而后者的土壤碳含量较高，为 67-213mg C cm。这表明土壤有机物质的数量可能不是 CH 通量的决定因素。总体而言，底栖生境的 CH 通量最低，这表明该地区未来将沼泽转化为开阔水域将影响湿地 CH 排放总量，尽管这种转化对区域和全球碳预算的总体贡献仍不清楚。需要进一步研究，通过同时在不同湿地生境中使用几种方法来扩展 CH 通量研究。
