Abstract
Stable carbon (δ13C) and nitrogen (δ15N) isotope analysis was conducted on modern and archaeological polar bear bone collagen from the Canadian Arctic Archipelago to investigate potential changes in polar bear foraging ecology over four-millennia. Polar bear δ13C values showed a significant decline in the modern samples relative to all archaeological time-bins, indicating a disruption in the sources of production that support the food web, occurring after the Industrial Revolution. The trophic structure, indicated through δ15N, remained unaltered throughout all time periods. The lower δ13C observed in the modern samples indicates a change in the relative importance of pelagic (supported by open-water phytoplankton) over sympagic (supported by sea ice-associated algae) primary production. The consistency in polar bear δ13C through the late Holocene includes climatic shifts such as the Medieval Warm Period (MWP, A.D. 950-1250) and the early stages of the Little Ice Age (LIA, A.D. 1300-1850). These findings suggest that polar bears inhabit a food web that is more pelagic and less sympagic today than it was through the Late Holocene. We suggest that modern, anthropogenic warming has already affected food web structure in the Canadian Arctic Archipelago when modern data are contextualized with a deep time perspective.
Research Highlights
Modern polar bear bone collagen δ13C suggests recent decline in ice associated prey.
Archaeological polar bear bone collagen suggests food web stability for millennia.
No change in sea-ice association through the Medieval Warm Period and Little Ice Age.
Recent isotopic shifts are unusual relative to the stability of ancient samples.
Modern Arctic warming has isotopically observable impacts that past events did not.
Research HighlightsOR
Significance Statement The lack of behavioral plasticity of both polar bears and their principal prey, ringed seals, make these species particularly vulnerable to declining sea ice. While the Lancaster Sound food web has demonstrated stability through past climate fluctuations, the speed and magnitude of ongoing changes in the Arctic has had an observable effect on the source of primary production. Given that past climate fluctuations are referenced as an argument to minimize the importance of modern anthropogenic warming, it is important to take opportunities to position contemporary climate change relative to the archaeological record. Here we present a unique illustration of the effects of past and present warming on polar bear diet and the marine food web in the Canadian Arctic Archipelago.
Competing Interest Statement
The authors have declared no competing interest.
