Collaborative Research: The effects of terrestrial organic matter inputs on coastal mercury cycling, methylmercury production and bioaccumulation

合作研究：陆地有机物输入对沿海汞循环、甲基汞生产和生物累积的影响气候变化将影响污染物、有机物和营养物质从陆地向沿海海洋的输送。这是因为更高的降雨量和气候变暖增加了从陆地到沿海沃茨的径流。径流也会影响沿海藻类的大量繁殖。这些变化预计将改变水中汞的分布，并影响其生物吸收的可用性。水银是一种剧毒。它被吸收进入食物网，污染鱼类和海产品，影响人类健康。该项目将研究从陆地输送到沿海沃茨的有机物如何影响海水和缅因州湾食物网中的汞浓度。缅因州湾是美国最大和最重要的沿海渔场之一。该项目将测量在不同藻华条件和河流流量下从研究航行中收集的样本中汞的浓度和同位素。实验室实验将用于研究陆源有机物如何影响浮游生物中的汞积累。该项目将为STEM领域的四名本科生提供研究经验。将向一名博士生和一名博士后研究员提供培训。该项目的调查结果将提供关于气候变化对海洋沃茨和食物网中汞含量影响的重要信息。为实现《水俣公约》（一项旨在减少汞向环境排放的全球性条约）的目标，需要这些信息。本项目将研究气候变化对陆地有机物和缅因州沃茨汞浓度的影响。具体来说，科学家们将研究影响以下因素的复杂且经常相互竞争的过程：1）汞循环和分布; 2）甲基汞的形成; 3）微型浮游生物对甲基汞的吸收。陆地有机物在将汞从流域转移到沿海和近海沃茨方面发挥着重要作用。它还通过提供促进微生物对汞的甲基化的微环境来控制水中甲基汞的形成，这是海产品吸收甲基汞的第一步。然而，一些浮游生物可以直接利用有机物作为食物来源（所谓的“混合营养生物”），并在进食过程中生物积累甲基汞。在一年中的某些时候，混养生物可以在沿海沃茨的微型浮游生物组合中占主导地位，以前的研究尚未探讨这种摄食模式对食物网底部甲基汞吸收的影响。该项目将通过以下方式研究有机物质动态对汞和甲基汞循环和生物累积的影响：1）在陆地有机物质输送量不断增加的缅因州海湾进行实地调查和船上实验; 2）在对比碳获取模式和有机物质特性及浓度的情况下，利用自养和兼养微型浮游生物类群进行实验室微观实验。这项工作还将应用新的汞和甲基汞特定同位素分析和有机物质量测量，以增加对沿海环境中汞循环的了解。该研究将填补预测环境变化对海洋甲基汞水平影响的重要空白，为减少汞排放和甲基汞暴露提供关键信息，并预测未来海产品中汞水平的变化。该奖项反映了NSF的法定使命，并被认为值得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来支持。

Collaborative Research: The effects of terrestrial organic matter inputs on coastal mercury cycling, methylmercury production and bioaccumulationClimate change will influence the delivery of contaminants, organic matter, and nutrients from land to the coastal ocean. This is because higher rainfall and warming increase runoff from land to coastal waters. Runoff also influences coastal algal blooms. These changes are expected to alter the distribution of mercury in the water and impact its availability for biological uptake. Mercury is a potent toxin. Its uptake into the food web contaminates fish and seafood and affects human health. This project will study how organic matter delivered from land to coastal waters affects mercury concentrations in seawater and in the food webs of the Gulf of Maine. The Gulf of Maine is one of the largest and most important coastal fishing grounds in the United States. This project will measure the concentration and isotopes of mercury on samples collected from research cruises under different algal bloom conditions and river flows. Lab experiments will be used to study how land-derived organic matter affects mercury accumulation in plankton. The project will provide research experiences for four undergraduate students in a STEM field. Training will be provided to a PhD student and a postdoctoral fellow. Findings from the project will provide critical information about the effect of climate change on mercury levels in marine waters and food webs. This information is needed for achieving the goals of the Minamata Convention, a global treaty for reducing mercury emissions to the environment.This project will examine the effects of climate change on terrestrial organic matter and mercury concentrations in Gulf of Maine waters. Specifically, the scientists will study the complex and often competing processes that influence: 1) mercury cycling and distribution; 2) the formation of methylmercury; and 3) methylmercury uptake to microplankton. Terrestrial organic matter plays an important role in transferring mercury from watersheds to coastal and offshore waters. It also controls the formation of methylmercury in water by providing a microenvironment that promotes the methylation of mercury by microbes, which represents the first step for uptake of methylmercury into seafood. However, some plankton can directly use organic matter as a food source (so-called “mixotrophs”) and can bioaccumulate methylmercury during feeding. Mixotrophs can dominate microplankton assemblages in coastal waters at some times of the year, and previous studies have not explored the impact of this feeding mode on methylmercury uptake at the base of the food web. This project will study the effects of organic matter dynamics on mercury and methylmercury cycling and bioaccumulation through 1) field surveys and shipboard experiments in the Gulf of Maine, where delivery of terrestrial organic matter is increasing, and 2) through laboratory microcosm experiments using autotrophic and mixotrophic microplankton taxa under contrasting carbon acquisition modes and organic matter characteristics and concentrations. This work will also apply novel mercury and methylmercury-specific isotope analyses and measures of organic matter quality to increase understanding of mercury cycling in coastal environments. This research will fill important gaps in predicting the effects of environmental changes on marine methylmercury levels, providing critical information to mitigating mercury emissions and methylmercury exposures, and for predicting changes in mercury levels in seafood in the future.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.