Combined effects of natural and anthropogenic stressors in fish

鱼在环境中会受到各种各样的压力。像其他变温动物一样，它们的体内温度反映环境温度，因此会随季节波动。鱼类也暴露在工业、城市和农业排放的污染物中。金属是一种特殊的污染物，因为它们也自然存在于环境中，其中有几种，如铁或铜，是生命所必需的。然而，镉等其他金属是非必需的，所有金属，无论是否必需，浓度高时都会有毒。这项研究计划旨在研究温度变化和金属接触对鱼类状况和健康的综合影响。我们将研究高温引起的应力是否会增加它们对金属污染的敏感性，反之亦然。该计划还调查了几种加拿大淡水鱼对这些压力源的耐受极限。***这项研究的大部分将使用受控的实验室暴露于黄鲈的热应力和金属，黄鲈是一种广泛分布在加拿大的北美鱼类，在矿区大量存在，还有黑头鲦鱼和三棘棘鱼。为了使实验室实验具有环境相关性，必须在实地验证实验室结果。为此，我们还将研究来自魁省北部Rouyn-Noranda矿区的三种野生鱼类对温度变化和金属暴露的反应。在春、夏、冬3个季节分别对1个干净湖泊和1个金属污染湖泊的黄鲈进行取样，并与实验室观测结果进行对比。我们还将对来自同一湖泊的大型食肉动物北梭鱼和大型底栖鱼类白吸盘进行取样，以便对这两种压力源在不同营养水平上的后果提供全球概述。***低温鱼类细胞膜中多不饱和脂肪酸的比例增加，这些脂质更容易受到金属和热应激引起的氧化应激的影响。因此，我们将研究膜组成在金属和温度引起的有害影响中的作用。我们还将研究线粒体的功能，线粒体是负责细胞能量生产的细胞器，对金属和温度高度敏感。最后，我们将测量细胞性能的指标，包括参与能量生产和抗氧化能力的酶，氧化应激和能量积累的指标，使用生化和分子工具。***除了更好地了解金属污染对水生生物的毒性作用机制外，这项研究还将提高我们评估全球变暖背景下人为活动对加拿大鱼类风险的能力。

Fish are exposed to a variety of stressors in their environment. Like other ectotherms, their internal temperature reflects environmental temperature and hence fluctuates seasonally. Fish are also exposed to contaminants released by industry, cities and agriculture. Metals are a peculiar type of contaminants, because they are also naturally present in the environment and several of them, like iron or copper, are essential for life. However, other metals like cadmium are non-essential, and all metals, essential or not, become toxic at high concentrations. This research program aims at examining the combined effects of variations in temperature and metal exposure on fish condition and health. We will investigate whether the stress induced by elevated temperatures increases their sensitivity to metal contamination, and vice-versa. The program also investigates the limits of tolerance to these stressors for several species of Canadian freshwater fish. ***Most of this research will use controlled laboratory exposures to thermal stress and metals in yellow perch, a North American fish that is widely distributed in Canada and that is abundant in mining areas, as well as fathead minnow and three-spined sticklebacks. In order for laboratory experiments to have an environmental relevance, it is essential to validate laboratory findings in the field. To this end, we will also examine the response of fish to temperature variations and metal exposure in three species of wild fish from the mining area of Rouyn-Noranda, northern Québec. Yellow perch will be sampled in spring, summer and winter in one clean and one metal-contaminated lake and their condition indicators compared with laboratory observations. We will also sample Northern pike, a large predator, and white sucker, a large benthic fish, from the same lakes, in order to provide a global overview of the consequences of these two stressors at different trophic levels. ***The proportion of polyunsaturated fatty acids increases in the cell membranes of cold-acclimated fish and these lipids are more vulnerable to oxidative stress, induced both by metals and heat stress. We will therefore examine the role of membrane composition in the deleterious effects induced by metals and temperature. We will also investigate the functioning of mitochondria, organelles responsible for cellular energy production and highly sensitive to metals and temperature. Finally we will measure indicators of cell performance, including enzymes involved in energy production and antioxidant capacities, indicators of oxidative stress and of energy accumulation, using biochemical and molecular tools. ***Beyond a better understanding of the mechanisms of toxic action of metal contamination in aquatic organisms, this research will enhance our capacity to evaluate the risk for Canadian fish of anthropogenic activities in the context of global warming.