Freshwater pollution is a major global concern. Common methods for determining the effects of contaminants on freshwater organisms involve short-term laboratory experiments with otherwise healthy organisms. However, in natural systems, organisms are commonly exposed to parasites, which could alter their ability to survive exposure to aquatic contamination. We used a freshwater crustacean (Daphnia dentifera) to quantify the effects of parasite exposure on mortality from two common freshwater contaminants (elevated salinity [NaCl] and carbaryl). In our salinity trial, both parasite exposure and elevated salinity reduced survival in an additive manner. In our carbaryl trial, exposure to carbaryl reduced survival and we found a less-than-additive (i.e. antagonistic) interaction between carbaryl and the parasite; the parasite only reduced survival in the control (no carbaryl) treatments. Our results demonstrate that parasites and contaminants can jointly affect mortality in aquatic organisms in an additive or less-than-additive manner.

中文翻译：

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在淡水甲壳动物中，寄生虫暴露对水生污染物，西维因和盐度升高的死亡率的影响

淡水污染是全球主要关注的问题。确定污染物对淡水生物的影响的常用方法包括使用其他健康生物进行短期实验室实验。但是，在自然系统中，生物通常会接触到寄生虫，这可能会改变其抵御水生污染物生存的能力。我们使用了淡水甲壳动物（Daphnia dentifera）以量化寄生虫暴露对两种常见淡水污染物（盐度[NaCl]和西维因）升高的死亡率的影响。在我们的盐度试验中，寄生虫暴露和盐度升高均以累加方式降低了生存率。在我们的西维因试验中，西维因暴露降低了存活率，并且我们发现西维因与寄生虫之间的相互作用小于加性（即拮抗）相互作用。该寄生虫仅降低了对照（无西维因）治疗的存活率。我们的研究结果表明，寄生虫和污染物可以加性或加性方式共同影响水生生物的死亡率。