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

河流排放对底栖生物向大陆边缘的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使海洋的pH值随时间降低的过程。本项目研究暴露于高河流沉积物负荷的海洋沉积物中的化学反应如何影响沿海沃茨的海洋酸化。虽然我们知道海洋酸化会影响沿海沃茨的海洋生物和商业渔业，但对海底沉积物中发生的反应如何影响水柱中的酸化过程知之甚少。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。本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输送了很高的沉积物负荷，在美国南部海岸的经济中发挥着重要作用。这项研究的结果将有助于海洋学界加深对三角洲和大陆架环境中海洋酸化过程的了解。它也将有利于决策者有兴趣预测沉积物的作用，对营养丰富的路易斯安那州大陆架排放控制的目的。该项目也有一个重要的教育组成部分，培训本科生、研究生和博士后学生，为本科生提供海上经验，并与K-12学生开展外联活动。将在密西西比河口附近和沿着附近大陆坡描述负责海底沉积颗粒转化的地球化学和微生物过程。将使用部署在海底的自主仪器对沉积物释放的酸（CO2）和碱（碱度）进行量化，以确定沉积物是否有助于周围水柱的酸度，还是提供碱来缓冲大气CO2输入对水柱的影响。由于密西西比河在冬末和春末的流量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，以确定河流流量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酸或碱释放到水柱的影响。因此，这项研究将从数量上了解海底大量沉积物对沉积物地球化学和微生物过程的作用及其对上覆沃茨的反馈。同时，将生成一个大型数据集，用于校准数学模型，更好地描述底栖-中上层相互作用的特征。这种努力是需要预测大陆边缘如何应对不断增加的压力，从人为活动。这一奖项反映了NSF的法定使命，并已被认为是值得支持的评价使用基金会的智力价值和更广泛的影响审查标准。

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.