Combined effects of natural and anthropogenic stressors in fish

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构成严重威胁。例如，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，来自受污染环境的生物体很少暴露于单一污染物，但通常暴露于复杂的混合物以及其他天然的应激源，如高温、缺氧或饮食限制。该计划的长期目标是阐明自然应激源（热，缺氧和饮食限制）和金属污染物单独和结合在加拿大淡水鱼在环境现实条件下的代谢后果。具体而言，我们将研究种间差异的金属毒性和自然应激和金属污染物对鱼类的生理表现的协同和拮抗作用。为此，鱼类将在实验室中暴露于金属和自然应激源的组合。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度和更一般的反应如生长速率和能量储备的积累来检查对这些应激源的代谢反应。还将进行实地研究，以确定野生鱼类金属积累和毒性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机制的理解，以及对自然压力的额外影响的理解。这一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.