Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
Ecol Appl. 2017 Apr;27(3):833-844. doi: 10.1002/eap.1487. Epub 2017 Mar 13.
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) 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 high salt had a negative synergistic effect on the zooplankton community, which in turn caused an increase in phytoplankton. Contributing to the magnitude of this trophic cascade was a direct positive effect of high salinity on phytoplankton abundance. Cascading effects were limited with respect to impacts on the benthic food web. Periphyton and snail grazers were unaffected by the salt-induced trophic cascade, but the biomass of filamentous algae decreased as a result of competition with phytoplankton for light or nutrients. We also found direct negative effects of high salinity on the biomass of filamentous algae and amphipods (Hyalella azteca) and the mortality of banded mystery snails (Viviparus georgianus) and fingernail clams (Sphaerium simile). Clam mortality was dependent on the presence of fish, suggesting a non-consumptive interactive effect with salt. Our results indicate that globally increasing concentrations of road salt can alter community structure via both direct and indirect effects.
全球北方地区道路融雪盐的应用正在改变淡水生态系统的化学环境。许多湖泊、溪流和湿地中的氯化物含量超过了美国和加拿大为保护淡水生物群制定的慢性和急性阈值。很少有研究确定融雪盐对溪流和湿地群落的影响，也没有研究调查其对湖泊群落的影响。我们测试了相关浓度的道路盐（15、100、250、500 和 1000 mg Cl/L）与包含两个或三个营养级的实验群落（即无鱼与有掠食性鱼类）之间如何相互作用。我们假设道路盐和鱼类对浮游动物会产生负协同作用，从而引发营养级联。我们在含有丝状藻类、周丛生物、浮游植物、浮游动物、几种大型无脊椎动物物种和鱼类的户外中试生态系统中测试了这一假设。我们发现，鱼类和高盐度对浮游动物群落有负协同作用，这反过来又导致浮游植物增加。造成这种营养级联幅度较大的原因是高盐度对浮游植物丰度的直接正向影响。盐度引起的营养级联效应对底栖食物网的影响是有限的。周丛生物和蜗牛食草动物不受盐度诱导的营养级联影响，但由于与浮游植物竞争光照或养分，丝状藻类的生物量减少。我们还发现，高盐度对丝状藻类和片脚类动物（Hyalella azteca）的生物量以及带纹神秘螺（Viviparus georgianus）和钉螺（Sphaerium simile）的死亡率有直接的负面影响。蛤类死亡率取决于鱼类的存在，这表明其与盐度存在非消耗性相互作用。我们的研究结果表明，全球范围内道路盐浓度的增加可以通过直接和间接效应改变群落结构。
