Salinization triggers a trophic cascade in experimental freshwater communities with varying food-chain length

The application of road deicing salts in northern regions worldwide is changing the chemical environment of freshwater ecosystems. Chloride levels in many lakes, streams, and wetlands exceed the chronic and acute thresholds established by the United States and Canada for the protection of freshwater biota. Few studies have identified the impacts of deicing salts in stream and wetland communities and none have examined impacts in lake communities. We tested how relevant concentrations of road salt (15, 100, 250, 500, and 1000 mg Cl− L−1) interacted with experimental communities containing two or three trophic levels (i.e. no fish vs. predatory fish). We hypothesized that road salt and fish would have a negative synergistic effect on zooplankton, which would then induce a trophic cascade. We tested this hypothesis in outdoor mesocosms containing filamentous algae, periphyton, phytoplankton, zooplankton, several macroinvertebrate species, and fish. We found that the presence of fish and hi...全球北部地区道路除冰盐的应用，正在改变淡水生态系统的化学环境。诸多湖泊、溪流与湿地中的氯化物浓度，已超出美国与加拿大为保护淡水生物群落(freshwater biota)所设定的慢性与急性阈值。目前鲜有研究明确道路除冰盐对溪流与湿地生物群落的影响，且尚无研究探讨其对湖泊生物群落的作用。我们测试了不同浓度道路除冰盐（15、100、250、500及1000 mg Cl⁻ L⁻¹）与包含2至3个营养级(trophic levels)的实验生物群落（即无鱼组与掠食性鱼类组）的交互作用。我们提出假说：道路除冰盐与鱼类会对浮游动物(zooplankton)产生负面协同效应，进而引发营养级联效应(trophic cascade)。我们在包含丝状藻类、周丛生物(periphyton)、浮游植物(phytoplankton)、浮游动物(zooplankton)、多种大型无脊椎动物(macroinvertebrate)及鱼类的室外中型实验生态系统(mesocosms)中验证了该假说。我们发现，鱼类的存在与高……