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: 1559279
• 负责人: Wei-Jun Cai
• 金额: $ 73.66万
• 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: 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=1559279&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）是指由于吸收大气二氧化碳（CO2）而导致海洋 pH 值降低（或酸度增加）。 为了了解开放海洋如何受到 OA 的影响，人们进行了大量的研究，但沿海系统却很少受到关注。 在墨西哥湾北部 (nGOM) 陆架区域，底层水域的 pH 值比工业化前表层海洋的 pH 值低 0.45 个单位，而整个海洋的整体 pH 值下降了 0.1 个单位。即使 pH 值的微小变化也会对海洋中的碳酸盐化学产生很大影响，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，该地区受到密西西比河养分的大量输入。 这些人为氮的输入主要来自化肥，导致呼吸速率增加，从而降低水体中的氧气浓度，直至夏季缺氧。 这项研究将告诉我们，遭受富营养化和缺氧的沿海水域的OA将如何影响该地区的化学和生物学。 研究人员致力于海湾和东海岸地区的外展项目，与 K-12 学生和教师互动、本科生/研究生培训以及各种外展工作（OA 家庭研讨会、为公众和联邦、州和政府举办的讲座）当地代表）。 此外，还将创建一个项目网站，以向更广泛的受众传播研究成果。海洋对大气二氧化碳（CO2）的吸收增加，导致海水pH值和碳酸盐矿物饱和状态下降0.1个单位，这一过程被称为海洋酸化（OA），它威胁海洋生物的健康，改变海洋生态系统，和生物地球化学过程。人们相当多的注意力集中在了解OA对公海的影响上，但对沿海地区的关注较少。 最近的研究表明，墨西哥湾北部 (nGOM) 陆架底部水域的 pH 值相对于工业化前的值可降低 0.45 个单位。发生这种情况是因为二氧化碳输入（大气输入和原位呼吸）增加导致的酸化降低了海水的缓冲能力。 这种相互作用效应将随着时间的推移而增强，预计夏季 nGOM 底水 pH 值会降低 0.85 个单位，并导致碳酸盐矿物在本世纪末达到欠饱和状态。 特拉华大学和路易斯安那大学海洋联盟的研究人员将开展实地、实验室和建模相结合的项目来解决以下问题。 (1) 对受营养丰富的密西西比河影响的沿海水域酸化采取哪些物理、化学和生物控制措施？ (2) 沿海水域酸化、富营养化和缺氧之间有何联系； (3) 底层水的低 pH 值和高 CO2 浓度如何影响秋季、冬季和暴风雨期间水柱混合时的 CO2 释放？ (4) 人为强迫下河流输入的变化对沿海水体酸化有何影响？ 这项研究的结果旨在进一步了解影响全球GOM和河流主导的陆架生态系统中遭受富营养化和缺氧的沿海水域海洋酸化的过程。