Combined effects of natural and anthropogenic stressors in fish

加拿大淡水资源特别丰富，但人类活动对这些脆弱生态系统的健康构成严重威胁。例如，采矿和冶炼作业大大提高了水、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，因为除了直接的有毒影响外，它们还会对食物链的其他层面产生影响。此外，来自受污染环境的生物体很少接触单一污染物，但通常除了暴露在高温、低氧或饮食限制等其他自然应激源之外，还暴露在复杂的混合物中。该计划的长期目标是阐明自然应激源(热、低氧和饮食限制)和金属污染物在环境现实条件下单独和组合在加拿大淡水鱼中的代谢后果。具体地说，我们将研究金属毒性的种间差异，以及自然应激源和金属污染物对鱼类生理性能的协同和拮抗效应。为此，鱼将在实验室中暴露于金属和自然应激源的组合中。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、细胞膜磷脂脂肪酸多不饱和以及更普遍的反应，如生长速度和能量储备的积累来检验。还将进行实地研究，以确定野生鱼类在金属积累和毒性方面的种间差异以及代谢能力的自然变化。最终，这项研究将提高我们对淡水生物中金属毒性的机制以及自然应激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健全办法的能力至关重要。

Canada is exceptionally rich in freshwater resources but human activities impose serious threats to the health of these fragile ecosystems. For instance, 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 Canadian freshwater fish under environmentally realistic conditions. Specifically, we will examine interspecific differences in metal toxicity and the synergistic and antagonistic effects of natural stressors and metal contaminants on the physiological performance of fish. To this end, fish will be exposed in the laboratory to metals and natural stressors combined. 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, cell membrane phospholipid fatty acid polyunsaturation and more general responses like growth rate and accumulation of energy reserves. Field studies will also be carried out to characterize interspecific differences in metal accumulation and toxicity and natural variations in metabolic capacities of wild fish. 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.