title: Salinization triggers a trophic cascade in experimental freshwater communities with varying food-chain length.
abstract: 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.
authors.affiliation: Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
authors.forename: William D
authors.initials: WD
authors.lastname: Hintz
authors.affiliation: Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
authors.forename: Brian M
authors.initials: BM
authors.lastname: Mattes
authors.affiliation: Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Schuler
authors.affiliation: Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
authors.forename: Devin K
authors.initials: DK
authors.lastname: Jones
authors.affiliation: Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
authors.forename: Aaron B
authors.initials: AB
authors.lastname: Stoler
authors.affiliation: Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
authors.forename: Lovisa
authors.initials: L
authors.lastname: Lind
authors.affiliation: Department of Biological Sciences, Darrin Fresh Water Institute, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York, 12180, USA.
authors.forename: Rick A
authors.initials: RA
authors.lastname: Relyea
mesh_terms: D000818:Animals; D058448:Biota / Q000187:drug effects; D002122:Calcium Chloride / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D005399:Fishes; D020387:Food Chain; D060106:Lakes / Q000737:chemistry*; D015636:Magnesium Chloride / Q000009:adverse effects*; D009518:New York; D000074284:Periphyton / Q000187:drug effects; D010839:Phytoplankton / Q000187:drug effects; D054712:Salinity; D012965:Sodium Chloride / Q000009:adverse effects*; D014874:Water Pollutants, Chemical / Q000009:adverse effects*; D015048:Zooplankton / Q000187:drug effects
chemical_list: D014874:Water Pollutants, Chemical; D015636:Magnesium Chloride; D012965:Sodium Chloride; D002122:Calcium Chloride
keywords: ecosystem services; freshwater contaminants; lake ecosystem; land use; macroinvertebrates; novel ecosystems; osmoregulation; predation; primary producers; salinity; sublethal effects