New research shows that sea ice disappearing is an important element of the food chain supporting female walruses in the Arctics Chukchi Sea. Researchers were able trace biomarkers specific to algae that grows within sea ice, which allowed them to link marine mammals to a food source that is rapidly decreasing in the face climate change. Credit: University of Maryland Center for Environmental Science/Lee Cooper
New research shows that sea ice disappearing is an important element of the food chain supporting female walruses in the Arctic's Chukchi Sea. Researchers were able trace biomarkers specific to algae that grows within sea ice, which allowed them to link marine mammals to a food source that is rapidly decreasing in the face climate change.
Chelsea Koch, lead author of the study and University of Maryland Center for Environmental Science said that the study builds upon work done in the Bering Seas and Chukchi Seas to demonstrate that these tracer of ice algae/phytoplankton can help monitor the ecosystem's response to the disappearing sea ice. "We can identify the response of the system to climate change by monitoring the sea ice biomarkers found in walruses, and other tissues of organisms in the region. This will allow us to continue to monitor the biomarkers of sea ice in walruses."
The Pacific Arctic marine ecosystem near Alaska has been adapted to fat-rich foods that are derived from biological production of sea ice. The sea floor is supplied with high-quality food thanks to the ice algae blooms. This supports high numbers of clams, and other benthic organisms in the Bering and Chukchi Seas. Walruses also have plenty of food to eat.
The loss of seasonal sea-ice poses a threat for Pacific walruses. This is because they depend on sea ice to rest, access, and forage in dense offshore clambeds. In recent years, sea ice has been disappearing in Alaska. This is why thousands of walruses have begun to arrive on the coast at the end of summer. They are not far from the best clam beds. These massive gatherings are likely to cause stampedes, which can lead to more deaths.
Koch and his research team anticipated higher levels of ice alga in the Chukchi Sea walruses based on their migration patterns. The northern Bering Sea results revealed a nuanced finding that was consistent with the traditional knowledge of St. Lawrence Island subsistence hunters.
Due to the Arctic's decline in seasonal sea ice, Walruses were considered for Endangered Species Act listing. Some Alaska Indigenous communities consider them to be a subsistence food source.
"One of our most interesting discoveries was that the sea ice biomarkers in female walruses from the northern Bering Sea were consistently higher than those in the males. These markers last for a few days to weeks in the livers of walruses. Koch stated that the elevated sea ice signature seen in females does not indicate an accumulation of their previous year's journey to the Chukchi Sea. Researchers were able trace biomarkers with liver tissue from subsistence hunters.
This supports the idea that the foraging behavior of females differs from males during the winter and spring months in the Bering Sea.
This work was done in collaboration with several partners in Alaska, including scientists from Clark University as well as the Scottish Association for Marine Science. The University of Alaska's Museum of the North provided samples from the Bering Sea. Subsistence hunters were also given the samples. The North Slope Borough Department of Wildlife Management (NSB DWM), collected samples from the Chukchi Sea as part of its harvest and walrus harvest monitoring program. Dr. Raphaela Stimmelmayr, co-author of the NSB DWM, stated that important studies such as this one would not have been possible without the support of hunters from regional community-based harvest monitoring programmes.
Continue exploring: Explore more Thousands of Pacific Walruses are again found along the Alaska coast
Chelsea W. Koch et. al., Female Pacific walruses, (Odobenus rosmarus diversus) show greater sea ice organic CO2 partitioning than males. Evidence comes from ice algae trophic marker, PLOS ONE (2021). Information from PLoS ONE: Chelsea W. Koch et. al., Female Pacific walruses, (Odobenus rosmarus diversgens), show greater sea ice organic matter partitioning than males. Evidence from ice trophic markers. DOI: 10.1371/journal.pone.0255686
