Municipal wastewater treatment plants (WWTPs) are a significant source of anthropogenic pollutants and are a serious environmental stressor in Laurentian Great Lakes ecosystems. In this study, we examined whether three freshwater fish species (bluegill sunfish Lepomis macrochirus, green sunfish Lepomis cyanellus, and round goby Neogobius melanostomus) collected near two wastewater effluent outflows in Lake Ontario showed altered measures of somatic investment and thermal tolerance. Fish of all three species collected near the WWTPs were larger with 50–60% heavier body masses compared to those collected at reference sites. Green sunfish had higher body condition and increased haematocrit at wastewater-contaminated sites, and both round goby and bluegill sunfish had larger livers (controlling for body mass) at wastewater-contaminated sites. Thermal tolerance (critical thermal maximum, CT_max) differed between species (green sunfish > bluegill sunfish > round goby), but was similar in fish collected at wastewater-contaminated sites compared to cleaner reference sites. Wastewater-contaminated sites had poorer water quality, higher nutrient loadings, and higher concentrations of anthropogenic contaminants (measured via polar organic chemical integrative samplers, POCIS) than reference sites. Our results suggest that fish in the wild may have some capacity to cope with WWTP effluent and avoid any potential impairments in thermal tolerance. Our findings also suggest that treated wastewater is changing water quality locally in Great Lakes watersheds, and that many fish species may be able to access extra nutrients provided by such effluent outflows. However, if outflow areas become preferred foraging areas this will inadvertently increase exposure to anthropogenic stressors and pollutants.

市政废水处理厂（WWTP）是人为污染物的重要来源，并且在Laurentian大湖生态系统中是严重的环境压力源。在这项研究中，我们检查了三种淡水鱼种类（大blue翻车鱼Lepomis macrochirus，绿翻车鱼Lepomis cyanellus和圆形虾虎鱼Neogobius melanostomus））在安大略湖的两个废水流出处附近收集，表明测量的体能投资和热耐受性发生了变化。与在参考点采集的鱼相比，在污水处理厂附近采集的所有三种鱼的体重更大，重达50-60％。绿色的翻车鱼的身体状况更高，且在污水污染的地点的血细胞比容增加，圆角虾虎鱼和蓝g的翻车鱼在受污水污染的地点的肝脏都更大（控制体重）。热容差（临界热最大值，CT_最大值）在物种之间有所不同（绿色翻车鱼>蓝g翻车鱼>圆形虾虎鱼），但与较干净的参考地点相比，在废水污染地点收集的鱼中相似。与参考地点相比，受污水污染的地点的水质较差，养分含量较高，人为污染物的浓度较高（通过极性有机化学综合采样器POCIS测量）。我们的结果表明，野外鱼类可能具有一定的能力应对污水处理厂的废水，并避免了对热耐受性的任何潜在损害。我们的发现还表明，经过处理的废水正在改变大湖流域的局部水质，许多鱼类可能能够获得由此类流出物提供的额外养分。然而，