Carbon sources and trophic relationships of ice seals during recent environmental shifts in the Bering Sea

• Published in: Ecological Applications
• Main Authors: Wang, Shiway W., Springer, Alan M., Budge, Suzanne M., Horstmann, Lara, Quakenbush, Lori T., Wooller, Matthew J.
• Other Authors: Jensen, O., National Science Foundation, Alaska Department of Fish and Game
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2016
• Subjects: Arctic; Bering Sea; Chukchi; Erignathus barbatus; ice algae; Phytoplankton; Pusa hispida; Sea ice
• Online Access: http://dx.doi.org/10.1890/14-2421; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1890%2F14-2421; https://onlinelibrary.wiley.com/doi/pdf/10.1890/14-2421; https://onlinelibrary.wiley.com/doi/full-xml/10.1890/14-2421; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/14-2421

Abstract Dramatic multiyear fluctuations in water temperature and seasonal sea ice extent and duration across the Bering–Chukchi continental shelf have occurred in this century, raising a pressing ecological question: Do such environmental changes alter marine production processes linking primary producers to upper trophic‐level predators? We examined this question by comparing the blubber fatty acid (FA) composition and stable carbon isotope ratios of individual FA (δ 13 C FA ) of adult ringed seals ( Pusa hispida ), bearded seals ( Erignathus barbatus ), spotted seals ( Phoca largha ), and ribbon seals ( Histriophoca fasciata ), collectively known as “ice seals,” sampled during an anomalously warm, low sea ice period in 2002–2005 in the Bering Sea and a subsequent cold, high sea ice period in 2007–2010. δ 13 C FA values, used to estimate the contribution to seals of carbon derived from sea ice algae (sympagic production) relative to that derived from water column phytoplankton (pelagic production), indicated that during the cold period, sympagic production accounted for 62–80% of the FA in the blubber of bearded seals, 51–62% in spotted seals, and 21–60% in ringed seals. Moreover, the δ 13 C FA values of bearded seals indicated a greater incorporation of sympagic FAs during the cold period than the warm period. This result provides the first empirical evidence of an ecosystem‐scale effect of a putative change in sympagic production in the Western Arctic. The FA composition of ice seals showed clear evidence of resource partitioning among ringed, bearded, and spotted seals, and little niche separation between spotted and ribbon seals, which is consistent with previous studies. Despite interannual variability, the FA composition of ringed and bearded seals showed little evidence of differences in diet between the warm and cold periods. The findings that sympagic production contributes significantly to food webs supporting ice seals, and that the contribution apparently is less in warm years with low sea ice, ...