评估水生动物种群多代暴露于化学污染的影响对于生态风险评估至关重要。然而,除了罕见的例子报告在污染环境中持续存在的人群中零星出现毒理学耐受性,当涉及生活史特征的改变时,来自实地研究的结论性结果更加有限。这里,我们调查了长期暴露于镉(Cd)是否会影响与尺寸相关的生活史特征(即青春期的大小,成人中位大小,最大尺寸)在Gammarusfosarum,欧洲河流生态系统的基石物种。我们研究了生活在位于自然区域的源头河流中的13个G.fosarum(隐秘谱系B)的田间种群,这些源头河流散布在大的地理尺度上,并且由于当地地球化学背景的不同而暴露于生物可利用的Cd污染水平。我们对所调查的河段的物理和物理化学条件进行了详细描述。土地利用参数,水文特征(流量,斜坡,河流宽度,流动结构,基材的马赛克),和物理化学条件(温度,电导率,溶解氧)进行测量。使用标准化的主动生物监测程序(Gammaruscaging)评估金属生物可利用性污染。根据对13个人口的实地人口普查,我们的结果表明,慢性镉污染显着影响山沟草物种的生活史,随着种群所有大小特征的显著减少(青春期的大小,成人中位大小,最大尺寸)。此外,我们在实验室的暴露测试中证实了受污染人群的镉耐受性。然后可以提出各种假设来解释与尺寸相关的生活史特征的修饰:Cd的直接毒性作用,镉耐受性的成本,或者是暴露在毒性压力下的生活史的适应性进化。
Assessing the effects of multigenerational exposure of aquatic animal populations to chemical contamination is essential for ecological risk assessment. However, beyond rare examples reporting the sporadic emergence of a toxicological tolerance within populations that persist in contaminated environments, conclusive results are even more limited from field studies when it comes to the alteration of life-history traits. Here, we investigated whether long-term exposure to cadmium (Cd) influences size-related life-history traits (i.e., size at puberty, median adult size, maximum size) in Gammarus fossarum, a keystone species of European stream ecosystems. We studied 13 field populations of G. fossarum (cryptic lineage B) living in headwater rivers located in natural areas scattered at a large geographical scale and exposed to contrasted bioavailable Cd contamination levels due to different local geochemical backgrounds. We achieved a detailed description of the physical and physicochemical conditions of the river reaches investigated. Land-use parameters, hydrological characteristics (flow, slope, river width, flow structure, mosaic of substrates), and physicochemical conditions (temperature, conductivity, dissolved oxygen) were measured. Metallic bioavailable contamination was assessed using a standardized active biomonitoring procedure (Gammarus caging). Based on the field demographic census of the 13 populations, our results demonstrated that chronic Cd contamination significantly influences life-history in the G. fossarum species, with a significant reduction in all size traits of populations (size at puberty, median adult size, maximum size). In addition, we confirmed Cd-tolerance in contaminated populations during exposure tests in the laboratory. Various hypotheses can be then put forward to explain the modification of size-related life-history traits: a direct toxic effect of Cd, a cost of Cd-tolerance, or an adaptive evolution of life-history exposed to toxic pressure.