title: Spatial and temporal variation of an ice-adapted predator's feeding ecology in a changing Arctic marine ecosystem.
abstract: Spatial and temporal variation can confound interpretations of relationships within and between species in terms of diet composition, niche size, and trophic position (TP). The cause of dietary variation within species is commonly an ontogenetic niche shift, which is a key dynamic influencing community structure. We quantified spatial and temporal variations in ringed seal (Pusa hispida) diet, niche size, and TP during ontogeny across the Arctic-a rapidly changing ecosystem. Stable carbon and nitrogen isotope analysis was performed on 558 liver and 630 muscle samples from ringed seals and on likely prey species from five locations ranging from the High to the Low Arctic. A modest ontogenetic diet shift occurred, with adult ringed seals consuming more forage fish (approximately 80 versus 60 %) and having a higher TP than subadults, which generally decreased with latitude. However, the degree of shift varied spatially, with adults in the High Arctic presenting a more restricted niche size and consuming more Arctic cod (Boreogadus saida) than subadults (87 versus 44 %) and adults at the lowest latitude (29 %). The TPs of adult and subadult ringed seals generally decreased with latitude (4.7-3.3), which was mainly driven by greater complexity in trophic structure within the zooplankton communities. Adult isotopic niche size increased over time, likely due to the recent circumpolar increases in subarctic forage fish distribution and abundance. Given the spatial and temporal variability in ringed seal foraging ecology, ringed seals exhibit dietary plasticity as a species, suggesting adaptability in terms of their diet to climate change.
authors.affiliation: Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, N9B 3P4, Canada. dyurkow@uwindsor.ca.
authors.forename: David J
authors.initials: DJ
authors.lastname: Yurkowski
authors.affiliation: Freshwater Institute, Fisheries and Oceans Canada, Winnipeg, MB, R3T 2N6, Canada. steve.ferguson@dfo-mpo.gc.ca.
authors.forename: Steven H
authors.initials: SH
authors.lastname: Ferguson
authors.affiliation: Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, N9B 3P4, Canada. semeniuk@uwindsor.ca.
authors.forename: Christina A D
authors.initials: CA
authors.lastname: Semeniuk
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, V8W 3P6, Canada. Tanya.Brown@mun.ca.
authors.forename: Tanya M
authors.initials: TM
authors.lastname: Brown
authors.affiliation: Aquatic Ecosystem Protection Research Division, Environment Canada, Burlington, ON, L7R 4A6, Canada. Derek.Muir@ec.gc.ca.
authors.forename: Derek C G
authors.initials: DC
authors.lastname: Muir
authors.affiliation: Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, N9B 3P4, Canada. afisk@uwindsor.ca.
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Fisk
mesh_terms: D000818:Animals; D001110:Arctic Regions; D002247:Carbon Isotopes / Q000032:analysis; D057231:Climate Change; D004032:Diet; D017753:Ecosystem; D005399:Fishes; D020387:Food Chain; D007053:Ice; D009587:Nitrogen Isotopes / Q000032:analysis; D046048:Seals, Earless / Q000502:physiology*; D013995:Time; D015048:Zooplankton
chemical_list: D002247:Carbon Isotopes; D007053:Ice; D009587:Nitrogen Isotopes
keywords: Arctic; Ontogenetic niche shift; Ringed seal; Stable isotopes; Trophic position