title: Broad shifts in the resource use of a commercially harvested fish following the invasion of dreissenid mussels.
abstract: Dreissenid mussels, including the zebra (Dreissena polymorpha) and quagga (Dreissena rostiformus bugensis) mussel, are invasive species known for their capacity to act as ecosystem engineers. They have caused significant changes in the many freshwater systems they have invaded by increasing water clarity, reducing primary productivity, and altering zooplankton and benthic invertebrate assemblages. What is less clear is how their ecosystem engineering effects manifest up the food web to impact higher trophic levels, including fish. Here, we use a biological tracer (stable isotopes of carbon and nitrogen) to analyze long-term and broad-scale trends in the resource use of benthivorous lake whitefish (Coregonus clupeaformis) in the Laurentian Great Lakes, where dreissenid mussels have become established in each lake except Lake Superior. We measured stable isotope ratios from archived material (fish scale samples) collected over several decades by multiple agencies and from 14 locations around the Great Lakes. In the majority of locations, the δ13C of lake whitefish increased following the establishment of dreissenid mussels. Trends in δ15N were less clear, but significant breakpoints in the time series occurred within 5 yr of dreissenid establishment in several locations, followed by declines in δ15N. In contrast, isotopic signatures in Lake Superior locations did not show these trends. Our results provide evidence that lake whitefish shifted toward greater reliance on nearshore benthic production, supporting the theory that fundamental energy pathways are changed when dreissenid mussels become established. Importantly, these effects were noted across multiple, large, and complex ecosystems spanning a broad geographic area. Our study underscores the potential for aquatic invasive species to alter key ecosystem services as demonstrated here through their impacts on energy pathways supporting a commercially harvested fish species.
authors.affiliation: Department of Environmental and Life Sciences, Trent University, 1600 West Bank Drive, Peterborough, Ontario, K9J 7B8, Canada.|Aquatic Research and Monitoring Section, Ontario Ministry of Natural Resources and Forestry, 2140 East Bank Drive, Peterborough, Ontario, K9L 0G2, Canada.
authors.forename: Shannon A
authors.initials: SA
authors.lastname: Fera
authors.affiliation: IISD Experimental Lakes Area Inc., 111 Lombard Avenue, Suite 325, Winnipeg, Manitoba, R3B 0T4, Canada.|Department of Biology, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario, P7B 5E1, Canada.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Rennie
authors.affiliation: Department of Environmental and Life Sciences, Trent University, 1600 West Bank Drive, Peterborough, Ontario, K9J 7B8, Canada.|Aquatic Research and Monitoring Section, Ontario Ministry of Natural Resources and Forestry, 2140 East Bank Drive, Peterborough, Ontario, K9L 0G2, Canada.
authors.forename: Erin S
authors.initials: ES
authors.lastname: Dunlop
mesh_terms: D000818:Animals; D049872:Bivalvia; D049875:Dreissena / Q000502:physiology*; D017753:Ecosystem; D005398:Fisheries / Q000706:statistics & numerical data; D005399:Fishes / Q000502:physiology*; D020387:Food Chain; D058865:Introduced Species; D060106:Lakes
keywords: Coregonidae; aquatic invasive species; benthic-pelagic coupling; benthification; mid-depth sink; nearshore phosphorus shunt; regime shift