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

浮游植物是汞进入海洋食物网的入口，随后汞在鱼类体内的积累是人类接触汞的主要途径。然而，尽管浮游植物构成了这一关键环节，但它们在海洋汞动力学中的作用尚不明确，特别是在季节和地理变异性方面。本研究旨在评估高生产力沿海海洋环境中汞循环的趋势，重点关注一系列沿海泻湖系统中浮游植物大量繁殖的季节性影响。泻湖提供了一个可访问的天然实验室，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在近岸海洋栖息地（例如，藻类大量繁殖的发生、淡水-海水相互作用的动力学），这项研究的结果将适用于一般的沿海海洋系统，并将填补我们在理解近岸汞-食物网动力学方面的主要空白。本主题与负责选择可行的补救替代方案和评估污染物减少战略的环境监管机构有关。此外，由于该项目是实验室和实地密集型的，它将为20-30名本科志愿者提供实践培训，其中许多人将从代表性不足的群体中招募。这种环境特别容易受到生物持久性污染物的影响，如汞，这些污染物沿营养水平呈指数沿着积累。浮游植物是这一过程中的第一步，也是最大的一步，它们将汞集中在细胞中，比环境水平高出100，000倍。然而，人们对浮游植物的汞吸收机制以及浮游植物的生长速度和/或生物量如何影响不同生态系统中的吸收率知之甚少。为了评估藻类大量繁殖期间汞如何有效地进入食物网，并评估藻类大量繁殖对近岸系统中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与圈养的食物网，因此是理想的位置，采样浮游植物在整个持续时间的水华周期。为了限制汞积累的驱动因素，将通过实验室实验扩大实地采样，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（内部吸收与外部吸收），以及（3）评估地下水-地表水的相互作用是否增强了沿海边缘的汞生物利用度。这项调查将确定导致沿海海洋系统中汞的毒性、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.