Investigating metal bioavailability to aquatic organisms: Biogeochemical perspectives

过去一个世纪的采矿活动给水生生态系统带来了巨大的环境风险，特别是在拥有大量矿物和水生资源（占世界表面淡水的20%和世界最长海岸线）的加拿大。现在人们普遍认识到，金属对水生生物的生物利用度（即生物积累和毒性）取决于水的物理化学特性（例如pH值、温度、盐度、溶解有机物（DOM））。然而，一些关键环境因素对金属生物利用度的影响仍未得到充分评价，影响了我们准确评估金属生态风险的能力。尽管有大量证据表明，盐度会影响暴露于天然水体全盐度梯度（即0 - 35ppt）的河口物种的金属生物利用度，但这种调节机制的特征仍然很差。这种知识差距部分是由于难以理解水化学和生物生理学相互交织的作用，这两者都随着盐度的变化而变化。同样，虽然温带地区天然水体的温度通常在4至25°C之间，但金属的环境风险主要取决于在实验室环境温度（即约15至20°C）下进行的毒理学研究。然而，温度可以影响金属水的地球化学和生物生理，这两者都可以对金属的生物利用度产生强烈的影响。然而，很少有研究调查这些温度对水生生物毒理学结果的影响，特别是在冬季与夏季的情况下。利用分析地球化学、生物化学、生理学和生态毒理学的元素，我的实验室将探索金属对水生生物的生物利用度在(1)盐度和(2)温度下的调节机制。值得注意的是，我们将开发一种新的离子交换技术来表征盐度对金属水化学的影响，然后利用广盐浮游植物研究盐度如何影响金属的生物利用度。此外，在淡水中，我们将表征温度对金属水相地球化学的影响（特别是对金属- dom结合的影响），然后表征金属对冬季适应和夏季适应鱼类的生物利用度。目前的研究计划满足了世界范围内对控制金属与水生生物相互作用过程的更好理解的需要。值得注意的是，我们将解决关于盐度和温度控制对水生生物金属生物利用度的机制和相关性的基本知识空白。最终，这项研究将提供迫切需要的信息，以准确预测金属的空间和季节环境风险。最后，这个项目构成了一个独特的HQP培训机会，学生将使用跨学科的科学来解决公共和私营部门感兴趣的重大社会问题。

Mining activities over the past century have created a significant environmental risk for aquatic ecosystems, particularly in Canada, which holds both large mineral and aquatic resources (20% of the world's surface fresh water and the world's longest coastline). It is now well-recognized that metal bioavailability (i.e. bioaccumulation and toxicity) to aquatic organisms depends on the water's physico-chemical characteristics (e.g. pH, temperature, salinity, dissolved organic matter (DOM)). Yet, the effects of some critical environmental factors on metal bioavailability remain poorly evaluated, impairing our ability to accurately assess metal's ecological risk. Despite considerable evidence that salinity affects metal bioavailability to estuarine species exposed to the full salinity gradient of natural waters (i.e. 0 - 35 ppt), the mechanisms of this modulation remain poorly characterized. This knowledge gap is partially due to the difficulties in deciphering the intertwined roles of water chemistry and organism physiology, which both vary with salinity. Similarly, while temperatures of natural waters typically range from 4 to 25°C in temperate regions, the environmental risk of metals mostly relies on toxicological studies performed at lab ambient temperatures, i.e. around 15 - 20°C. Yet, temperature can affect metal aqueous geochemistry and organism physiology, which can both have strong impacts on metal bioavailability. However, there have been few studies that have investigated these temperature effects on toxicological outcomes in aquatic organisms, especially in winter vs. summer scenarios. Using elements of analytical geochemistry, biochemistry, physiology and ecotoxicology, my lab will explore the mechanisms underlying the modulation of metal bioavailability to aquatic organisms with (1) salinity and (2) temperature. Notably, we will develop a new ion-exchange technique to characterize the effects of salinity on metal aqueous geochemistry, then investigate how salinity affects metal bioavailability using euryhaline phytoplankton. Furthermore, in fresh water, we will characterize the effects of temperature on metal aqueous geochemistry (notably on metal-DOM binding), then characterize metal bioavailability to winter-acclimatized vs. summer-acclimatized fish. The present research program meets a worldwide need for an improved understanding of the processes controlling the interactions of metals with aquatic organisms. Notably, we will address fundamental knowledge gaps about the mechanisms and relevance of salinity and temperature controls on metal bioavailability to aquatic organisms. Ultimately, this research will provide critically needed information to accurately predict the environmnental risk of metals, spatially and seasonally. Finally, this program constitutes a unique HQP training opportunity, where students will use interdisciplinary science to address major societal issues of interest to both the public and the private sector.