Geography
Document Type
Article
Abstract
The expected reduction of ice algae with declining sea ice may prove to be detrimental to the Pacific Arctic ecosystem. Benthic organisms that rely on sea ice organic carbon (iPOC) sustain benthic predators such as the Pacific walrus (Odobenus rosmarus divergens). The ability to track the trophic transfer of iPOC is critical to understanding its value in the food web, but prior methods have lacked the required source specificity. We analyzed the H-Print index, based on biomarkers of ice algae versus phytoplankton contributions to organic carbon in marine predators, in Pacific walrus livers collected in 2012, 2014 and 2016 from the Northern Bering Sea (NBS) and Chukchi Sea. We paired these measurements with stable nitrogen isotopes (δ15N) to estimate trophic position. We observed differences in the contribution of iPOC in Pacific walrus diet between regions, sexes, and age classes. Specifically, the contribution of iPOC to the diet of Pacific walruses was higher in the Chukchi Sea (52%) compared to the NBS (30%). This regional difference is consistent with longer annual sea ice persistence in the Chukchi Sea. Within the NBS, the contribution of iPOC to walrus spring diet was higher in females (~45%) compared to males (~30%) for each year (p < 0.001), likely due to specific foraging behavior of females to support energetic demands associated with pregnancy and lactation. Within the Chukchi Sea, the iPOC contribution was similar between males and females, yet higher in juveniles than in adults. Despite differences in the origin of organic carbon fueling the system (sea ice versus pelagic derived carbon), the trophic position of adult female Pacific walruses was similar between the NBS and Chukchi Sea (3.2 and 3.5, respectively), supporting similar diets (i.e. clams). Given the higher quality of organic carbon from ice algae, the retreat of seasonal sea ice in recent decades may create an additional vulnerability for female and juvenile Pacific walruses and should be considered in management of the species.
Two files of Supporting Information are also available for download.
Publication Title
PLoS ONE
Publication Date
2021
Volume
16
Issue
8
ISSN
1932-6203
DOI
10.1371/journal.pone.0255686
Keywords
animals, arctic regions, biomarkers, carbon, climate change, diet, ecosystem, feeding behavior, female, food chain, ice cover, lactation, male, nutritional status, oceans and seas, phytoplankton, pregnancy, seasons, walruses
Repository Citation
Koch, Chelsea W.; Cooper, Lee W.; Woodland, Ryan J.; Grebmeier, Jacqueline M.; Frey, Karen E.; Stimmelmayr, Raphaela; Magen, Cédric; and Brown, Thomas A., "Female Pacific walruses (Odobenus rosmarus divergens) show greater partitioning of sea ice organic carbon than males: Evidence from ice algae trophic markers" (2021). Geography. 190.
https://commons.clarku.edu/faculty_geography/190
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Copyright
© 2021 Koch et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.