Combined effects of natural and anthropogenic stressors in fish

鱼类在其环境中暴露于各种压力源。与其他外温动物一样，它们的内部温度反映了环境温度，因此季节性波动。鱼类也暴露在工业、城市和农业释放的污染物中。金属是一种特殊类型的污染物，因为它们也天然存在于环境中，其中一些金属，如铁或铜，是生命所必需的。然而，其他金属如镉是非必需的，所有金属，无论是不是必需的，在高浓度下都会变得有毒。这项研究计划的目的是研究温度和金属暴露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热应力和黄鲈鱼中的金属，黄鲈鱼是一种北美鱼类，广泛分布在加拿大，在矿区大量存在，以及黑头呆鱼和三棘鱼。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研究结果。为此，我们还将研究来自魁北克省北方鲁安-诺兰达矿区的三种野生鱼对温度变化和金属暴露的反应。在春、夏、冬3个季节分别对一个清洁湖泊和一个金属污染湖泊的黄鲈进行采样，并将其状况指标与实验室观测结果进行比较。我们还将采样北方梭子鱼，一个大型的捕食者，和白色吸盘，一个大型的底栖鱼类，从同一个湖泊，以提供一个全球性的概述，这两个压力在不同的营养水平的后果。 多不饱和脂肪酸的比例增加，在细胞膜的冷驯化的鱼，这些脂质更容易受到氧化应激，诱导金属和热应激。因此，我们将研究膜组合物的作用，在金属和温度引起的有害影响。我们还将研究线粒体的功能，线粒体是负责细胞能量产生的细胞器，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，使用生物化学和分子工具。 除了更好地了解水生生物中金属污染的毒性作用机制外，这项研究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.