Importance of Riverine Discharge on the Benthic Flux of Alkalinity to Continental Margins

河流排放对大陆边缘底栖生物碱度通量的重要性海洋酸化是由于吸收大气中的二氧化碳而随着时间的推移降低海洋pH值的过程。本项目研究暴露在高河流沉积物负荷下的海洋沉积物中的化学反应如何影响沿海水域的海洋酸化。虽然我们知道海洋酸化影响沿海水域的海洋生物和商业渔业，但对于海底沉积物中发生的反应如何影响水柱中的酸化过程，我们知之甚少。来自河流的大量沉积物在这些过程中的作用也从未被研究过。这项研究将在密西西比河和墨西哥湾进行。密西西比河向墨西哥湾的大陆架运送了大量的沉积物，在美国南部沿海的经济中起着重要的作用。这项研究的结果将有助于海洋学界增加对三角洲和陆架环境中海洋酸化过程的理解。它也将有利于决策者对预测富营养化的路易斯安那大陆架沉积物的作用以控制排放感兴趣。该项目还具有重要的教育组成部分，包括培训本科生、研究生和博士后，为本科生提供海上体验，并与K-12学生开展外展活动。对沉积在海底的颗粒的转化负责的地球化学和微生物过程将在密西西比河河口附近和附近的大陆斜坡上进行表征。将使用部署在海底的自动仪器对沉积物中酸（CO2）和碱（碱度）的释放进行量化，以确定沉积物是否会导致周围水柱的酸性，还是提供缓冲水柱免受大气CO2输入的碱。由于密西西比河在冬末和春末的排放比一年中其他时间向沿海地区提供了更多的沉积物，因此每年将进行两次研究巡航，以确定河流排放的季节性变化如何影响酸和碱释放到水柱中。然后将使用数学模型来预测季节变化对释放到水柱中的酸或碱的影响。因此，这项研究将提供大量沉积物沉积到海底对沉积物地球化学和微生物过程的作用以及它们对上覆水域的反馈的定量理解。同时，将产生一个大型数据集，用于校准数学模型和更好地描述底栖-远洋相互作用。需要这样的努力来预测大陆边缘如何对人类活动不断增加的压力作出反应。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Importance of Riverine Discharge on the Benthic Flux of Alkalinity to Continental MarginsOcean acidification is the process that lowers the pH of the ocean over time due to uptake of atmospheric carbon dioxide. This project investigates how chemical reactions in marine sediments exposed to high riverine sediment loads influence ocean acidification in coastal waters. Although we know that ocean acidification affects marine life and commercial fisheries in coastal waters, little is known about how acidification processes in the water column are influenced by reactions occurring in sediments on the sea floor. The role of large sediment deposits from rivers in these processes has also never been investigated. This study will be conducted in the Mississippi River and Gulf of Mexico. The Mississippi River transports a high sediment load to the continental shelf in the Gulf of Mexico and plays an important role in the economy of the southern coast of the United States. Results from this study will be useful to the oceanographic community for increasing understanding of ocean acidification processes in delta and shelf environments. It will also benefit decision makers interested in predicting the role of sediments on the nutrient -rich Louisiana shelf for discharge control purposes. This project also has an important educational component by training undergraduate, graduate, and postdoctoral students, providing experiences at sea for undergraduates, and conducting outreach activities with K-12 students.The geochemical and microbiological processes responsible for the transformation of particles deposited on the seafloor will be characterized near the Mississippi River mouth and along the nearby continental slope. The release of acids (CO2) and bases (alkalinity) from the sediment will be quantified using autonomous instruments deployed on the seafloor to determine whether sediments contribute to the acidity of the surrounding water column or instead provide bases to buffer the water column from atmospheric CO2 inputs. As the Mississippi River discharge during the later Winter and Spring provides much more sediment to the coastal zone compared to the rest of the year, research cruises will be taken twice a year to determine how seasonal variations in riverine discharge affect the release of acids and bases into the water column. Mathematical models will then be used to predict the effect of seasonal variations on acids or bases release to the water column. This study will therefore provide a quantitative understanding of the role of large sediment depositions to the seafloor on sediment geochemical and microbiological processes and their feedback to the overlying waters. Simultaneously, a large data set will be generated and used to calibrate mathematical models and better characterize benthic-pelagic interactions. Such efforts are needed to predict how continental margins respond to constantly increasing stress from anthropogenic activities.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.