Combined effects of natural and anthropogenic factors on the physiology of aquatic animals

加拿大的淡水资源异常丰富，但人类活动对这些脆弱的生态系统的健康造成了严重威胁。特别是，采矿和冶炼作业大大增加了水、土壤和生物群中的金属浓度。鱼类特别容易受到环境污染的影响，因为除了直接的毒性影响外，它们还对食物网的其他层面产生综合影响。此外，来自污染环境的生物很少暴露于单一污染物，但除了高温、缺氧或饮食限制等其他自然压力源外，通常还暴露于复杂的混合物中。该项目的长期目标是阐明在环境现实条件下，自然应激源（热、缺氧和饮食限制）和金属污染物单独或联合对鱼类和水生无脊椎动物的代谢后果。具体来说，我们将研究鱼类和无脊椎动物金属毒性的种间差异，以及自然应激源和金属污染物对水生生物生理性能的协同和拮抗作用。为此，鱼类和无脊椎动物将在实验室中单独或联合暴露于金属和自然压力源。对这些应激源的代谢反应将通过测量有氧和合成代谢途径的关键酶的活性、线粒体代谢、氧化应激、基因转录水平和更一般的反应（如生长速度和能量储备的积累）来检查。还将进行实地研究，以确定水生动物代谢能力的自然变化特征。最终，这项研究将提高我们对淡水生物中金属毒性机制和自然压力源的额外影响的理解。这些信息对于提高我们制定保护淡水生态系统的合理办法的能力是至关重要的。

Canada is exceptionally rich in freshwater resources but human activities impose serious threats to the health of these fragile ecosystems. In particular, mining and smelting operations have significantly contributed to the increase in metal concentrations in water, soils and biota. Fish are particularly vulnerable to environmental contamination since, in addition to direct toxic effects, they integrate effects on other levels of the food web. Further, organisms from contaminated environments are rarely exposed to single contaminants but are typically exposed to complex mixtures in addition to other, natural, sources of stress like high temperatures, hypoxia or dietary restrictions. The long-term objective of this program is to elucidate the metabolic consequences of natural stressors (heat, hypoxia and dietary restriction) and metal contaminants individually and combined in fish and aquatic invertebrates under environmentally realistic conditions. Specifically, we will examine interspecific differences in metal toxicity in fish and invertebrates and the synergistic and antagonistic effects of natural stressors and metal contaminants on the physiological performance of aquatic organisms. To this end, fish and invertebrates will be exposed in the laboratory to metals and natural stressors alone and in combination. The metabolic response to these stressors will be examined by measuring the activity of key enzymes of aerobic and anabolic pathways, mitochondrial metabolism, oxidative stress, gene transcription levels and more general responses like growth rate and accumulation of energy reserves. Field studies will also be carried out to characterize natural variations in metabolic capacities of aquatic animals. Ultimately, this research will improve our understanding of the mechanisms of metal toxicity in freshwater organisms and of the additional impacts of natural stressors. This information is essential to improve our ability to develop sound approaches for the protection of our freshwater ecosystems.