MCA: Developing a Paleorecord of Hg in Long-Lived Mollusks from the Gulf of Maine

汞污染是影响生态系统和人类健康的严重环境问题，人类接触汞的大部分来自食用海鱼。气候变化和自然气候变率对海洋生态系统中汞的移动和生物积累的影响尚不完全清楚。这种理解对于制定目标和评估限制海洋生态系统汞污染和人类接触的政策努力的进展至关重要。这项研究旨在建立一个保存在缅因湾蛤壳中大约1000年的汞记录，缅因湾是世界上海洋变暖最快的地区之一。就像树木的年轮一样，蛤壳具有可以精确确定年代的层，并且有可能保存生物群过去汞浓度和积累变化的高度分辨率信号。重要的是，这种汞记录可以与保存在蛤壳中的其他类型的气候代理信息配对，提供有关这种生物中海洋汞如何随着气候变化而变化的详细信息。这一记录将提供一个特别有用的数据集，用于校准和改进预测政策和气候变化对海洋生态系统从几个世纪的汞污染中恢复的影响的模型。其他更广泛的影响包括在以本科生为主的机构（格林内尔学院）和大型公立研究型大学（爱荷华州立大学）的研究人员之间建立新的区域科学伙伴关系，以及为本科生研究提供新的机会。将从缅因湾沿海地区收集北极岛屿软体动物的样本，并将贝壳汞浓度与水、沉积物和生物群中总汞和甲基汞（MeHg）的浓度进行比较。这些比较将使研究人员能够评估贝壳汞是否是环境汞和甲基汞生物积累的可靠代理，并评估同期贝壳样品的可重复性。缅因湾汞的主要年代学将建立在高分辨率测量贝壳汞的基础上，该测量基于现有的跨年代的A. islandica贝壳档案，跨越了过去一千年，这一时期跨越了重大的气候和海洋环流变化，以及当地和全球来源的汞排放大幅增加。该记录可直接与现有的和新的古气候代用记录进行比较，包括现有的氧稳定同位素记录和新测量的微量元素记录（Ba和Mn）。这项工作的结果将允许确定汞生物积累对自然气候变率的敏感性，并评估生物地球化学-气候耦合模型，用于预测各种气候变化情景下海洋生物群中未来汞的轨迹。该项目由地球科学部地球生物学和低温地球化学计划、海洋科学部海洋地质学和地球物理计划以及促进竞争性研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

Mercury (Hg) contamination is a serious environmental problem that affects ecosystems and human health, with most of human exposure coming from marine fish consumption. The impact of climate change and natural climate variability on the movement and bioaccumulation of Hg in marine ecosystems is not fully understood. Such understanding is vital to setting targets and assessing the progress of policy efforts to limit Hg contamination of marine ecosystems and human exposure. This research seeks to develop an approximately 1000-year record of Hg preserved in clam shells collected from the Gulf of Maine, one of the most rapidly warming regions of the world’s oceans. Like tree rings, clam shells possess layers that can be precisely dated and have potential to preserve highly resolved signals of past variation in Hg concentrations and accumulation by biota. Importantly, this Hg record can be paired with other kinds of climate proxy information preserved in the clam shells, giving detailed information about how marine Hg in this organism changes in response to a changing climate. This record will provide an especially useful dataset for calibrating and improving models for predicting the effects of policy and climate change on the recovery of marine ecosystems from centuries of Hg pollution. Other broader impacts include development of a new regional scientific partnership between researchers at a predominantly undergraduate institution (Grinnell College) and a large public research university (Iowa State University) and new opportunities for undergraduate research.Samples of the mollusk Arctica islandica will be collected from coastal locations in the Gulf of Maine and shell Hg concentrations compared to water, sediment, and biota concentrations of total Hg and methylmercury (MeHg). These comparisons will permit the researchers to evaluate whether shell Hg is a robust proxy of environmental Hg and MeHg bioaccumulation and to assess reproducibility of coeval shell samples. A master chronology of Hg in Gulf of Maine will then be constructed based on measuring shell Hg at high-resolution for an existing cross-dated A. islandica shell archive spanning the last millennium, a period which spans significant climatic and ocean circulation changes and large increases in Hg emissions from local and global sources. This record can be directly compared to existing and novel paleoclimate proxy records, including existing oxygen stable isotope records and newly measured trace-element records (Ba and Mn). Results of this work should permit determination of the sensitivity of Hg bioaccumulation to natural climate variability and evaluation of coupled biogeochemical-climate models used for predicting trajectory of future Hg in marine biota under various climate change scenarios. This project is jointly funded by the Division of Earth Sciences Geobiology and Low-Temperature Geochemistry Program, the Division of Ocean Sciences Marine Geology and Geophysics Program and the Established Program to Stimulate Competitive Research (EPSCoR).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.