RAPID: Waiting to Exhale: Quantifying Tropical Storm-Induced Increased Flux of Coastal Wetland Carbon into the Atmosphere?

在2020年夏秋两季，路易斯安那州的沿海海湾经历了一系列热带风暴/飓风的影响。热带风暴马可、飓风劳拉、萨利和贝塔从马可81公里向巴拉塔里亚湾逼近，贝塔从81公里向贝塔逼近379公里。风暴侵蚀会导致沿海土壤中的碳以二氧化碳(CO2)的形式释放到大气中。科学家很少有机会评估热带风暴对湿地土壤碳转化为向大气释放二氧化碳的影响，因为他们没有风暴前的详细测量数据与风暴后的数据进行比较。这个项目有机会受益于现有的NSF拨款，并有四年的广泛测量。快速反应资金将支持在2020年风暴过后立即和一年后对巴拉塔里亚湾进行密集采样。尽管沿海盆地没有受到直接打击，但沼泽边缘的侵蚀率比四年来的长期平均水平高出60倍。这已经是一个重要的发现，因为大多数测量都集中在直接袭击的海岸线上，但显然，热带风暴在相当远的距离提供了驱动海浪能量的风场，导致了大量的湿地侵蚀。因此，特别活跃的热带风暴季节导致大量富含碳的湿地土壤在相对较短的时间内被倾倒到巴拉塔里亚湾浅水、好氧水域中。该项目要解决的主要问题是，2020年风暴季节的加速侵蚀是否以及如何导致从海湾向大气排放的二氧化碳大幅增加，以及这种影响将持续多久。研究小组将在明年继续测量沼泽边缘侵蚀，与每月两次海湾表层水域的水样相关，以确定溶解的无机和有机碳以及溶解的二氧化碳。采样工作将沿着距离开阔海湾湿地侵蚀站很近的横断面进行。将使用一个模型估计海-气二氧化碳通量，并将其与湿地侵蚀率相关联。研究小组将把风暴事件引起的“海湾呼吸”速率与明年的进行比较。这一快速项目将产生几个重要成果：1)确定一些重大风暴对大气的湿地碳损失的增加和时间影响，类似于气候变化下未来的预期；2)了解有机碳分解为二氧化碳是否会加剧沿海海湾的海岸酸化。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In the summer and fall of 2020, the coastal bays of Louisiana have experienced impacts from a number of tropical storms/hurricanes in close procession. Tropical storm Marco, Hurricanes Laura, Sally and Beta made their closest approaches to Barataria Bay from 81 km for Marco, up to 379 km for Beta. Storm erosion can lead to carbon from coastal soils being released to the atmosphere as carbon dioxide (CO2). Scientists rarely have the opportunity to assess the impact of tropical storms on the conversion of wetland soil carbon to CO2 release to the atmosphere, because they don’t have detailed measurements from before the storms to compare with post-storm data. This project has an opportunity to benefit from an existing NSF grant with four years of extensive measurements. RAPID-response funding will support intensive sampling of Barataria Bay in the immediate aftermath of the 2020 storms, and up to a year afterwards. Despite no direct strikes to the coastal basin, marsh edge erosion rates were up to 60 times higher than the 4-year long-term average. This is already an important finding since most measurements focus on coastlines with direct strikes but clearly, substantial wetland erosion occurs from tropical storms imparting wind fields driving wave energy at substantial distances. Consequently, a particularly active tropical storm season has led to significant carbon-rich wetland soil being dumped into the shallow, aerobic waters of the Barataria Bay in a relatively short period of time. The primary questions to be addressed by this project are whether and how accelerated erosion from the 2020 storm season will lead to a significant increase in CO2 outgassing from the bay to the atmosphere, and for how long the effects will persist. The team of investigators will continue to measure marsh edge erosion over the next year correlated to twice a month water sampling of bay surface waters for determination of dissolved inorganic and organic carbon, and dissolved CO2. Sampling will be conducted along transects running from close proximity to the wetland erosion stations out in the open bay. Air-sea CO2 flux will be estimated using a model and correlated to the wetland erosion rates. The team will compare the storm event-induced “bay respiration” rate with that of next year. This RAPID project will yield several important outcomes: 1) Determination of the increase and temporal impact of wetland carbon loss to the atmosphere from a number of significant storms, similar to what is expected for the future under a changing climate; 2) Understanding if the organic C breakdown to CO2 will increase coastal acidification within the coastal bay.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.