Collaborative Research: Sediment Geochemical Control on Ocean Acidification and Carbon Budget in a River Dominated Shelf System

合作研究：沉积物地球化学对河流主导陆架系统海洋酸化和碳收支的控制

• 批准号: 1756815
• 负责人: Wei-Jun Cai
• 金额: $ 14.37万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-03-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1756815&HistoricalAwards=false
• 关键词: Collaborative; Research; Sediment; Geochemical; Control

In many coastal regions fertilizer washed down rivers leads to high production of algae. Consumption of organic material produced by the algae in deeper waters or in sediments consumes oxygen, leading to low-oxygen "dead zones" in many places like the northern Gulf of Mexico. This process of nutrient input, algal growth, and loss of oxygen is called eutrophication. Consumption of the organic matter also releases dissolved carbon dioxide into the water, and contributes directly and indirectly to ocean acidification. In order to understand and predict this impact on acidification, it is important to understand how much of the organic matter degradation occurs in the water column versus in the sediments, how variable it is between seasons and years, and how it is affected by processes such as storms that disturb the bottom sediments. In this project, investigators from three institutions along with their graduate and undergraduate students will conduct a combination of field observations and computer modeling to address these questions in the northern Gulf of Mexico. They will share their results with the public through local outreach activities, and with secondary school students in Louisiana through partnerships and curriculum development with local teachers.The proposed research will use a combined observational and numerical modeling approach to better understand the role of shelf sediment in driving bottom water dissolved inorganic carbon (DIC) and pH dynamics and acidification at seasonal scales. Past and current studies have not addressed this mechanism. This current lack of knowledge makes it difficult to construct a comprehensive carbon budget for this region. The proposed research will (i) quantify the role of benthic fluxes in DIC production leading to acidification in the bottom water; (ii) determine the importance of the seasonally changing benthic DIC flux in acidifying the bottom water; and (iii) explore the importance of episodic resuspension events in modulating benthic fluxes of DIC. Seasonal sampling will be carried out in Louisiana shelf using state of the art benthic lander platform to record in situ sediment and bottom water oxygen consumption rates, organic matter remineralization rates, sediment oxygen penetration depths, benthic fluxes of DIC and accompanying pH drop. Bottom current velocities and turbidity will also be recorded in conjunction with sediment porewater and water column sampling. Complementing these detailed near-bed and seabed observations, we will utilize a recently developed coupled hydrodynamics, sediment transport and biogeochemistry model (HydroBioSed) to scale up observed estimates of benthic fluxes to an annual scale.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.

在许多沿海地区，化肥被冲入河流导致藻类大量繁殖。更深水域或沉积物中藻类产生的有机物质的消耗会消耗氧气，导致墨西哥湾北部等许多地方出现低氧“死亡区”。这种养分输入、藻类生长和氧气流失的过程称为富营养化。有机物的消耗也会将溶解的二氧化碳释放到水中，并直接和间接地导致海洋酸化。为了理解和预测对酸化的影响，重要的是要了解水体中与沉积物中发生的有机物降解有多少，季节和年份之间的变化有多大，以及它如何受到诸如此类的过程的影响。就像扰乱底部沉积物的风暴一样。在该项目中，来自三个机构的研究人员及其研究生和本科生将结合实地观察和计算机建模来解决墨西哥湾北部的这些问题。他们将通过当地的外展活动与公众分享他们的成果，并通过与当地教师的合作和课程开发与路易斯安那州的中学生分享他们的成果。拟议的研究将采用结合观测和数值建模的方法来更好地了解陆架沉积物在驱动底层水溶解无机碳 (DIC) 和 pH 动态以及季节性尺度的酸化。过去和当前的研究尚未解决这一机制。由于目前缺乏知识，因此很难为该地区构建全面的碳预算。拟议的研究将 (i) 量化底栖通量在 DIC 生产中导致底层水酸化的作用； (ii) 确定季节性变化的底栖 DIC 通量对酸化底层水的重要性； (iii) 探讨间歇性再悬浮事件在调节 DIC 底栖通量中的重要性。将使用最先进的底栖登陆器平台在路易斯安那陆架进行季节性采样，以记录原位沉积物和底层水耗氧率、有机物再矿化率、沉积物氧渗透深度、底栖 DIC 通量和伴随的 pH 值下降。底部水流速度和浊度也将与沉积物孔隙水和水柱采样一起记录。为了补充这些详细的近海床和海底观测，我们将利用最近开发的耦合流体动力学、沉积物迁移和生物地球化学模型 (HydroBioSed)，将海底通量的观测估计扩大到年度规模。该奖项反映了 NSF 的法定使命，并被视为值得通过使用基金会的智力优点和更广泛的影响审查标准进行评估来支持。

项目成果

Benthic Respiration in Hypoxic Waters Enhances Bottom Water Acidification in the Northern Gulf of Mexico

缺氧水域的底栖呼吸增强了墨西哥湾北部底层水的酸化

• DOI: 10.1029/2020jc016152
• 发表时间: 2020-09-22
• 期刊: Journal of Geophysical Research
• 作者: Hongjie Wang;J. Lehrter;K. Maiti;K. Fennel;A. Laurent;N. Rabalais;N. Hussain;Qian Li;Baoshan Chen;K. M. Scaboo;W. Cai
• 通讯作者: W. Cai