The effects of an invasive species on the environment can be altered by anthropogenic activities such as nutrient pollution or the presence of additional invasive species with similar or unique traits. Using experimental mesocosms, we tested the separate and combined effects of three invasive mollusks (zebra mussels, Asian clams, and banded mystery snails) on freshwater environments in nutrient‐poor and nutrient‐enriched conditions. We predicted that in nutrient‐poor conditions, single mollusk species would reduce the abundance of algae and zooplankton, but nutrient enrichment would mitigate these effects. Regardless of nutrient additions, paired bivalve species would reduce phytoplankton and zooplankton abundance, increasing periphyton biomass. Bivalves and snails paired together would reduce periphyton, phytoplankton, and zooplankton compared to communities with paired bivalve species. Finally, nutrient enrichment would increase the survival or biomass of paired bivalves and snails. Single, paired, and three co‐occurring invasive mollusks did not affect algae or zooplankton abundance. Banded mystery snails reduced nutrient concentrations in high‐nutrient conditions more than other invasive species, but the reduced nutrients did not affect algal abundance. Paired invasive species did not affect the survival or biomass of other invasive species. Nutrient enrichment increased the biomass of zebra mussels and mystery snails, but not Asian clams. Additionally, zebra mussel reproduction increased in the high‐nutrient treatment when banded mystery snails were present, but not when all three species were together. We conclude that human‐induced trophic states might determine the effects that single and multiple invasive species have in freshwater environments.

中文翻译：

---

营养物质富集和侵入性软体动物对淡水环境的影响

入侵物种对环境的影响可以通过人为活动（例如营养物污染）或存在其他具有相似或独特特征的入侵物种来改变。我们使用实验性的宇宙观，在营养缺乏和营养丰富的条件下，测试了三种侵入性软体动物（斑马贻贝，亚洲蛤和带状神秘蜗牛）在淡水环境中的单独和联合作用。我们预测在营养不足的情况下，单一的软体动物物种会减少藻类和浮游动物的丰度，但是营养物质的丰富会减轻这些影响。无论添加何种营养素，配对的双壳类物种都会减少浮游植物和浮游动物的数量，从而增加浮游植物的生物量。双壳类和蜗牛配对会减少浮游植物，浮游植物，和浮游动物相比，双壳类动物成对存在。最后，养分富集将增加成对的双壳类和蜗牛的存活率或生物量。单个，成对和三个同时出现的侵入性软体动物不会影响藻类或浮游动物的丰度。带状神秘蜗牛在高养分条件下比其他入侵物种减少的养分含量更高，但减少的养分不会影响藻类的丰度。配对的入侵物种不会影响其他入侵物种的生存或生物量。营养物质的增加增加了斑马贻贝和神秘蜗牛的生物量，但没有增加亚洲蛤的生物量。此外，当出现带状神秘蜗牛时，在高营养处理中斑马贻贝繁殖增加，但当所有三个物种在一起时则不然。