title: Stable sulfur isotopes identify habitat-specific foraging and mercury exposure in a highly mobile fish community.
abstract: Tracking the uptake and transfer of toxic chemicals, such as mercury (Hg), in aquatic systems is challenging when many top predators are highly mobile and may therefore be exposed to chemicals in areas other than their location of capture, confounding interpretation of bioaccumulation trends. Here we show how the application of a less commonly used ecological tracer, stable sulfur isotope ratios (34S/32S, or δ34S), in a large river-delta-lake complex in northern Canada allows differentiation of resident from migrant fishes, beyond what was possible with more conventional13C/12C and15N/14N measurements. Though all large fishes (n=105) were captured in the river, the majority (76%) had δ34S values that were indicative of the fish having been reared in the lake. These migrant fishes were connected to a food chain with greater Hg trophic magnification relative to the resident fish of the river and delta. Yet, despite a shallower overall trophic magnification slope, large river-resident fish had higher Hg concentrations owing to a greater biomagnification of Hg between small and large fishes. These findings reveal how S isotopes can trace fish feeding habitats in large freshwater systems and better account for fish movement in complex landscapes with differential exposure pathways and conditions.
authors.affiliation: University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Global Institute for Water Security, Saskatoon, SK S7N5B3, Canada. Electronic address: meghan.carr@usask.ca.
authors.forename: Meghan K
authors.initials: MK
authors.lastname: Carr
authors.affiliation: University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Global Institute for Water Security, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Toxicology Centre, Saskatoon, SK S7N5B3, Canada.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Jardine
authors.affiliation: University of Saskatchewan, Global Institute for Water Security, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Toxicology Centre, Saskatoon, SK S7N5B3, Canada.
authors.forename: Lorne E
authors.initials: LE
authors.lastname: Doig
authors.affiliation: University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Global Institute for Water Security, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Toxicology Centre, Saskatoon, SK S7N5B3, Canada.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Jones
authors.affiliation: University of Saskatchewan, Global Institute for Water Security, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Toxicology Centre, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, School of Public Health, Saskatoon, SK S7N5B3, Canada.
authors.forename: Lalita
authors.initials: L
authors.lastname: Bharadwaj
authors.affiliation: University of Saskatchewan, Toxicology Centre, Saskatoon, SK S7N5B3, Canada.
authors.forename: Brett
authors.initials: B
authors.lastname: Tendler
authors.affiliation: Environment and Climate Change Canada, National Wildlife Research Centre, Ottawa, ON K1A0H3, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Chételat
authors.affiliation: University of Alberta, Department of Renewable Resources, Edmonton, AB T6G2R3, Canada.
authors.forename: Pete
authors.initials: P
authors.lastname: Cott
authors.affiliation: University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK S7N5B3, Canada; University of Saskatchewan, Global Institute for Water Security, Saskatoon, SK S7N5B3, Canada.
authors.forename: Karl-Erich
authors.initials: KE
authors.lastname: Lindenschmidt
mesh_terms: D000818:Animals; D002170:Canada; D002247:Carbon Isotopes; D000074062:Environmental Biomarkers; D004784:Environmental Monitoring; D005399:Fishes; D020387:Food Chain; D060106:Lakes; D008628:Mercury / Q000032:analysis*; D009587:Nitrogen Isotopes; D013460:Sulfur Isotopes; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D002247:Carbon Isotopes; D000074062:Environmental Biomarkers; D009587:Nitrogen Isotopes; D013460:Sulfur Isotopes; D014874:Water Pollutants, Chemical; D008628:Mercury
keywords: Bioaccumulation; Delta; Food web; SIA; Trophic position