OCE-PRF Track 1: Biological Mercury Hotspots: The Role of Phytoplankton Blooms in Nearshore Marine Mercury Bioaccumulation

浮游植物是汞在海洋食物网中的入口点，随后汞在鱼类中的积累是人类暴露的主要途径。然而，尽管浮游植物形成了这一关键环节，但它们在海洋汞动态中的作用尚不清楚，特别是在季节和地理变异性方面。这项研究旨在评估高生产力沿海海洋环境中汞循环的趋势，重点是一系列沿海泻湖系统浮游植物水华的季节性影响。泻湖提供了一个可进入的自然实验室，是汞在动物体内积累的潜在热点。由于沿海泻湖中的作用过程普遍存在于近岸海洋生境中(例如，藻类水华的发生、淡水-海水相互作用的动力学)，这项研究的结果将适用于整个沿海海洋系统，并将填补我们对近岸汞-食物网动态理解的主要空白。这一主题与环境监管机构有关，他们的任务是选择可行的补救办法并评估减少污染物的战略。此外，由于这个项目是实验室和现场密集型项目，它将为20-30名本科生志愿者提供动手培训，其中许多人将从代表性不足的群体中招募。海岸线支持一系列具有生产力的海洋生态系统，这些生态系统支撑着复杂的食物网。这类环境特别容易受到汞等生物持久性污染物的影响，这些污染物沿营养水平呈指数级积累。浮游植物是这一过程的第一步，也是最大的一步，它将汞集中在细胞中，最高可达周围水平的100,000倍。然而，人们对浮游植物汞吸收机制或浮游植物生长速度和/或生物量如何影响不同生态系统的吸收速度知之甚少。为了评估水华期间汞如何有效地进入食物链，以及评估水华对近岸系统季节性汞循环的长期影响，将对三个沿海泻湖系统进行研究。泻湖提供了一个半封闭的水体和一个圈养的食物网，因此是在整个水华周期中采样浮游植物的理想地点。为了限制汞积累的驱动因素，将通过实验室实验增加现场采样，以(1)量化不同种类的浮游植物吸收汞的速度，(2)评估浮游植物吸收汞的机制(内部同化与外部吸收)，以及(3)评估地下水-地表水相互作用是否提高沿海边缘汞的生物有效性。这项调查将确定导致汞在沿海海洋系统中的毒性、积累和迁移的基本生物地球化学过程，并能够更准确地说明沿海汞的来源和汇。这些问题是研究和环境资源组织都感兴趣的。

Phytoplankton are the entry point for mercury in marine food webs, and subsequent mercury accumulation in fish is the primary route of human exposure. Yet despite the fact that phytoplankton form this critical link, their role in marine mercury dynamics is not clear, especially with respect to seasonal and geographic variability. This study is designed to evaluate trends in mercury cycling in highly productive coastal marine environments, with a focus on the seasonal effects of phytoplankton blooms in a range of coastal lagoon systems. Lagoons provide an accessible natural laboratory and are potential hotspots for mercury accumulation in animals. Because the processes at play in coastal lagoons are prevalent in nearshore marine habitats (e.g., the occurrence of algal blooms, the dynamics of freshwater-seawater interaction), results from this study will be applicable to coastal marine systems in general and will close major gaps in our understanding of nearshore mercury-food web dynamics. This topic is relevant to environmental regulators who are tasked with selecting viable remediation alternatives and evaluating strategies for contaminant reduction. Furthermore, because this project is lab and field intensive, it will provide hands on training for 20-30 undergraduate volunteers, many of whom will be recruited from underrepresented groups.Coastlines support a range of productive marine ecosystems that sustain complex food webs. Such environments are particularly susceptible to biologically persistent contaminants, such as mercury, that accumulate exponentially along trophic levels. Phytoplankton represent the first and largest step in this process by concentrating mercury in their cells up to 100,000x above ambient levels. Yet little is known about phytoplankton mercury uptake mechanisms or how phytoplankton growth rate and/or biomass affects uptake rates in diverse ecosystems. To evaluate how effectively mercury enters the food web during algal blooms, and to assess the long-term effects of blooms on seasonal mercury cycling in nearshore systems, three coastal lagoon systems will be studied. Lagoons provide a semi-enclosed water body with a captive food web, and are therefore ideal locations to sample phytoplankton over the entire duration of a bloom cycle. To constrain the drivers of mercury accumulation, field sampling will be augmented with lab-based experiments to (1) quantify how rapidly different species of phytoplankton assimilate mercury, (2) assess the mechanism by which phytoplankton take up mercury (internal assimilation vs. external sorbtion) and (3) evaluate whether groundwater-surface water interaction enhances mercury bioavailability at the coastal margin. This investigation will identify fundamental biogeochemical processes that lead to the toxicity, accumulation, and transport of mercury in coastal marine systems and enable a more accurate account of coastal mercury sources and sinks. These issues are of interest to both research and environmental resource organizations.