Collaborative Research: pH Dynamics and Interactive Effects of Multiple Processes in a River-Dominated Eutrophic Coastal Ocean

合作研究：以河流为主的富营养化沿岸海洋中多个过程的 pH 动态和相互作用效应

• 批准号: 1559312
• 负责人: Nancy Rabalais
• 金额: $ 17.74万
• 依托单位: Louisiana Universities Marine Corsortium
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-15 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1559312&HistoricalAwards=false
• 关键词: Collaborative; Research; pH; Dynamics; Interactive

Ocean acidification (OA) refers to the lowering of ocean pH (or increasing acidity) due to uptake of atmospheric carbon dioxide (CO2). A great deal of research has been done to understand how the open ocean is influenced by OA, but coastal systems have received little attention. In the northern Gulf of Mexico (nGOM) shelf region, pH in bottom waters can measure up to 0.45 units less than the pH of the pre-industrial surface ocean, in comparison to the 0.1 overall pH decrease across the entire ocean. Carbonate chemistry in the ocean is greatly influenced by even small changes in pH, so these seemingly minor changes lead to much greater impacts on the biology and chemistry of the ocean. The researchers plan to study coastal OA in the nGOM, a region subject to high inputs of nutrients from the Mississippi River. These inputs of anthropogenic nitrogen mostly derived from fertilizers leads to increased respiration rates which decreases oxygen concentrations in the water column to the point of hypoxia in the summer. This study will inform us how OA in coastal waters subject to eutrophication and hypoxia will impact the chemistry and biology of the region. The researchers are dedicated to outreach programs in the Gulf and east coast regions, interacting with K-12 students and teachers, undergraduate/graduate student training, and various outreach efforts (family workshops on OA, lectures for the public and federal, state, and local representatives). Also, a project website will be created to disseminate the research results to a wider audience. Increased uptakes of atmospheric carbon dioxide (CO2) by the ocean has led to a 0.1 unit decrease in seawater pH and carbonate mineral saturation state, a process known as Ocean Acidification (OA), which threatens the heath of marine organisms, alters marine ecosystems, and biogeochemical processes. Considerable attention has been focused on understanding the impact of OA on the open ocean but less attention has been given to coastal regions. Recent studies indicate that pH in bottom waters of the northern Gulf of Mexico (nGOM) shelf can be as much as 0.45 units lower relative to pre-industrial values. This occurs because the acidification resulting from increased CO2 inputs (both atmospheric inputs and in-situ respiration) decreases the buffering capacity of seawater. This interactive effect will increase with time, decreasing summertime nGOM bottom-water pH by an estimated 0.85 units and driving carbonate minerals to undersaturation by the end of this century. Researchers from the University of Delaware and the Louisiana Universities Marine Consortium will carry out a combined field, laboratory, and modeling program to address the following questions. (1) What are the physical, chemical, and biological controls on acidification in coastal waters impacted by the large, nutrient-laden Mississippi River?; (2) What is the link between coastal-water acidification, eutrophication, and hypoxia; (3) How do low pH and high CO2 concentrations in bottom waters affect CO2 out-gassing during fall and winter and storm periods when the water column is mixed?; and (4) What are the influences of changing river inputs under anthropogenic forcing on coastal water acidification?Results from this research aim to further our understanding of the processes influencing ocean acidification in coastal waters subject to eutrophication and hypoxia both in the GOM and river-dominated shelf ecosystems globally.

海洋酸化（OA）是指由于吸收大气中的二氧化碳（CO2）而导致海洋pH值降低（或酸度增加）。 人们已经做了大量的研究来了解开放海洋是如何受到OA的影响的，但海岸系统却很少受到关注。 在墨西哥湾北方大陆架区域，底层沃茨的pH值比工业化前的表层海洋的pH值低0.45个单位，而整个海洋的pH值总体下降0.1个单位。海洋中的碳酸盐化学会受到pH值微小变化的极大影响，因此这些看似微小的变化会对海洋的生物学和化学产生更大的影响。研究人员计划研究nGOM的沿海OA，该地区受到来自密西西比河的高营养物质输入的影响。 这些主要来自肥料的人为氮输入导致呼吸速率增加，从而降低水柱中的氧浓度，使夏季缺氧。 这项研究将告诉我们如何在沿海沃茨的OA受到富营养化和缺氧将影响该地区的化学和生物。 研究人员致力于在海湾和东海岸地区的推广计划，与K-12学生和教师，本科生/研究生培训，以及各种推广工作（家庭研讨会OA，讲座为公众和联邦，州和地方代表）互动。 此外，还将建立一个项目网站，向更广泛的受众传播研究成果。海洋对大气中二氧化碳（CO2）的吸收增加导致海水pH值和碳酸盐矿物饱和度下降0.1个单位，这一过程被称为海洋酸化（OA），它威胁着海洋生物的健康，改变海洋生态系统和海洋地球化学过程。相当多的注意力集中在了解有机农业对公海的影响，但对沿海地区的关注较少。 最近的研究表明，墨西哥湾北方大陆架底层沃茨的pH值比工业化前的值低0.45个单位。出现这种情况是因为增加的CO2输入（大气输入和原地呼吸）导致的酸化降低了海水的缓冲能力。 这种相互作用将随着时间的推移而增加，使夏季nGOM底层水pH值降低约0.85个单位，并在本世纪末将碳酸盐矿物推向欠饱和状态。 来自特拉华州大学和路易斯安那大学海洋联合会的研究人员将开展一项综合实地、实验室和建模计划，以解决以下问题。(1)受富含营养物质的密西西比河影响的沿海沃茨酸化的物理、化学和生物控制措施是什么？(2)海岸水酸化、富营养化和缺氧之间的联系是什么？（3）当水柱混合时，底部沃茨的低pH值和高CO2浓度如何影响秋冬季节和风暴期间的CO2出气？以及（4）人为强迫下河流输入的变化对沿海水体酸化的影响是什么？从这项研究的结果，旨在进一步我们的理解的过程影响海洋酸化的沿海沃茨富营养化和缺氧的GOM和河流为主的全球大陆架生态系统。