As climate change reshapes the Arctic, 91亚色 researchers are shedding new light on how declining sea ice affects the health of the ringed seals and polar bears that depend on them.
Understanding how climate change affects Arctic wildlife is becoming urgent as the North warms faster than the rest of the planet.
鈥淐limate warming is a global problem but it鈥檚 most severe in the North, where the climate is warming about four times faster than the global average,鈥 says Gregory W. Thiemann, a professor in the Faculty of Environmental & Urban Change.
Rising temperatures are driving declines in sea ice and reshaping Arctic marine ecosystems. Species such as ringed seals and polar bears depend on sea ice for habitat, but scientists are working to understand exactly how climate-driven changes affect these species and the food webs that support them.
Ringed seals, in particular, play a vital role in the Arctic food web as consumers of smaller, fat-rich food sources such as fish and plankton. Their fat-rich diet makes them a primary food source for polar bears.
Despite the importance of ringed seals in the Artcic habitat, how they respond to climate-driven changes in ice and prey availability, and the ripple effects of those changes through the ecosystem, was not fully understood.
Katie Florko, a 91亚色 biology alum, was inspired to find a way to change that.
鈥淏y tracking shifts in their diet and body condition over nearly two decades, we can better understand how environmental change is affecting a species that is central to both the food web and subsistence,鈥 she says.
The project began while Florko was completing her master's degree in biology at 91亚色 under Thiemann's supervision. Although Florko graduated in 2018 and continued her research through a PhD at the University of British Columbia and a postdoctoral fellowship, she and her collaborators continued developing the study.
In published in Environmental and Sustainability Indicators, Florko and Thiemann drew on a long-standing collaboration between 91亚色 and Fisheries and Oceans Canada that has worked with local Inuvialuit hunters in the Northwest Territories to monitor ringed seal populations in the Amundsen Gulf.
For the study, local hunters collected measurements and samples from 236 ringed seals harvested between 1996 and 2015. Small pieces of blubber were sent to the researchers, who analyzed the fatty acids they contained. Because those compounds provide clues about what an animal has been eating, the team was able to reconstruct the seals' diets. They then combined those dietary indicators with environmental data and measures of seal and polar bear body condition to understand how climate, habitat and food availability influence Arctic predators.
The analysis revealed that ringed seals were generally in better shape when they were feeding on prey associated with sea ice, particularly Arctic cod, an important source of energy in the area. Seals also tended to be healthier during years when ice dynamics made productive feeding areas easier to access.
The findings suggest that sea ice influences more than just where ringed seals live; it can also affect their access to food and ability to build the energy reserves needed to survive, reproduce and raise their young.
Because ringed seals are the primary prey of polar bears, researchers also wanted to know whether environmental conditions affecting seals could influence the predators that depend on them.
鈥淪tudying both predator and prey offered a rare opportunity to link changes at multiple levels of the Arctic food web and better understand how climate-driven changes in sea ice can ripple through the food web,鈥 says Florko.
The research also examined body-condition data from 108 polar bears collected in the same region between 1999 and 2015. By comparing those records with the ringed seal data, they hoped to determine whether environmental factors affecting seals could also be affecting the bears that depend on them.
While the relationships between habitat, diet and seal health proved complex, one result stood out. Among female polar bears, which tend to feed on a less varied diet than males, their body health closely tracked that of ringed seals.
"Female polar bear body condition tended to be high when ringed seal condition was also high," says Thiemann. 鈥淚n other words, healthier prey were associated with healthier polar bears.鈥
The findings offer a clearer picture of how climate change can affect Arctic ecosystems. Rather than influencing individual species in isolation, changes in sea ice can alter prey availability, affect the health of ringed seals and ultimately influence the predators that depend on them.
The team says continued monitoring will be essential for understanding how a rapidly changing Arctic affects wildlife in the years ahead.
"I think this area is important to continue studying because understanding climate impacts requires looking beyond individual species. Changes in sea ice, prey availability and predator body condition are all interconnected, and we need to understand those relationships to predict how Arctic ecosystems may change in the future," says Florko.