Environmental Controls on Aquatic Ecosystem Sensitivity to Metal Bioaccumulation

金属自然存在于环境中;然而，人类活动改变了这些元素的地球化学循环，增加了它们向空气，土壤和水中的释放。点源排放的金属污染可对生态系统和人类健康产生局部和长期影响（通过大气迁移）。关于环境条件如何控制加拿大北部沉积的金属的命运，目前没有足够的信息。我的研究项目的最新证据表明，与温带湖泊相比，北极湖泊对金属生物累积（特别是汞）更敏感。需要进行新的研究，以确定气候相关因素如何影响金属的生物积累及其在食物链中的转移，以评估和减轻金属污染对这些巨大水资源的影响。所涉及的环境过程是复杂的，发生在多个尺度上。在生态系统尺度上，高纬度地区的非生产性湖泊（即有机物产量较低）可能会在食物链的底部积累更多的金属，因为从水中吸收的污染物质量“集中”在较少的微生物生物量中。在生物体层面上，较低的温度和较低的食物供应改变了消费者的生理机能，这可能会提高他们的金属水平。特别是，较慢的生长速度可能导致北极水生生物体内金属含量较高。在今后五年中，该研究方案将侧重于两个关键的气候相关因素-温度和生产力-在控制北方水生生态系统对汞和砷的生物累积和食物链转移的敏感性方面的作用。由于汞在大气中的远距离迁移，汞是一种优先污染物，尽管北方资源开发释放了砷，但关于北极湖泊中砷积累的信息很少。实验室和现场实验将研究寒冷，非生产性环境如何增强生物体的金属积累及其通过食物链的转移。由于这些因素在环境中是相关的，因此需要在受控条件下采用实验方法来分离潜在的独立和相互作用效应。该研究计划将为未来气候变化对金属污染的影响提供基于过程的预测，提高我们确定金属沉积命运的能力，并支持北方人仍广泛用于生计渔业的大量水资源的管理和保护。

Metals occur naturally in the environment; however, human activities have altered the biogeochemical cycles of these elements and increased their release to air, soils, and water. Metal pollution from point source emissions can have both local and long-range impacts (through atmospheric transport) on ecosystem and human health. There is currently insufficient information on how environmental conditions control the fate of metals deposited in Canada's North. Recent evidence from my research program indicates that Arctic lakes are more sensitive to metal bioaccumulation (specifically mercury) compared with lakes at temperate latitudes. New research is needed to identify how climate related factors affect the bioaccumulation of metals and their transfer in food chains in order to evaluate and mitigate impacts of metal pollution on these vast water resources. The environmental processes involved are complex and occur at multiple scales. At the ecosystem scale, unproductive lakes (i.e. having lower organic matter production) at higher latitudes may accumulate more metals at the base of the food chain because the contaminant mass taken up from water is “concentrated” in less microbial biomass. At the organism scale, colder temperatures and low food availability alter the physiology of consumers that may enhance their metal levels. In particular, slower growth rates may lead to higher metal levels in Arctic aquatic organisms. Over the next five years, this research program will focus on the role of two key climate-related factors - temperature and productivity - in controlling the sensitivity of northern aquatic ecosystems to bioaccumulation and food chain transfer of mercury and arsenic. Mercury is a priority contaminant due to its long-range atmospheric transport, and little information is available on arsenic accumulation in Arctic lakes despite releases from northern resource developments. Laboratory and field experiments will investigate how cold, unproductive environments enhance organism accumulation of metals and their transfer through the food chain. Because these factors are correlated in the environment, experimental approaches under controlled conditions are needed to separate potential independent and interactive effects. This research program will provide process-based predictions for future climate-change impacts on metal pollution, improve our ability to determine the fate of metal deposition, and support the management and protection of vast water resources still widely used by northerners for subsistence fisheries.