Abstract
Sea‐ice coverage is a key abiotic driver of annual environmental conditions in Arctic marine ecosystems and could be a major factor affecting seabird trophic dynamics. Using stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) in eggs of thick‐billed murres (Uria lomvia), northern fulmars (Fulmarus glacialis), glaucous gulls (Larus hyperboreus), and black‐legged kittiwakes (Rissa tridactyla), we investigated the trophic ecology of prebreeding seabirds nesting at Prince Leopold Island, Nunavut, and its relationship with sea‐ice conditions. The seabird community of Prince Leopold Island had a broader isotopic niche during lower sea‐ice conditions, thus having a more divergent diet, while the opposite was observed during years with more extensive sea‐ice conditions. Species' trophic position was influenced by sea ice; in years of lower sea‐ice concentration, gulls and kittiwakes foraged at higher trophic levels while the opposite was observed for murres and fulmars. For murres and fulmars over a longer time series, there was no evidence of the effect of sea‐ice concentration on species' isotopic niche. Results suggest a high degree of adaptation in populations of high Arctic species that cope with harsh and unpredictable conditions. Such different responses of the community isotopic niche also show that the effect of variable sea‐ice conditions, despite being subtle at the species level, might have larger implications when considering the trophic ecology of the larger seabird community. Species‐specific responses in foraging patterns, in particular trophic position in relation to sea ice, are critical to understanding effects of ecosystem change predicted for a changing climate.
Highlights
Sea ice and its extensive presence throughout the spring and summer characterize polar seas of both hemispheres
Sea ice is fundamental to the cycle of biomass abundance in Arctic marine ecosystems, and its annual phenology of development and breakup plays a dominant role in ecosystem structure and function (Michel, Ingram, & Harris, 2006; Piepenburg, 2005; Post et al, 2013)
We investigated the trophic and isotopic ecology of prebreeding female northern fulmar (Fulmarus glacialis), thick‐billed murre (Uria lomvia), black‐legged kittiwake (Rissa tridactyla), and glaucous gull (Larus hyperboreus) at Prince Leopold Island (PLI), Nunavut, a colony of major importance for both diversity and abundance of seabirds in the Canadian high Arctic
Summary
Sea ice and its extensive presence throughout the spring and summer characterize polar seas of both hemispheres. The reductions in or absence of sea ice induced by earlier breakup of the pack could decouple trophic linkages between primary and sec‐ ondary producers in the food web (Michel et al, 2006; Piepenburg, 2005; Post et al, 2013) and change the structure of the planktonic community in the Arctic (Eisner, Napp, Mier, Pinchuk, & Andrews, 2014; Fujiwara, Hirawake, Suzuki, Imai, & Saitoh, 2014) Such changes potentially alter the abundance and access to preferred prey for seabirds (Divoky, Lukacs, & Drucknmiller, 2015; Gaston, Gilchrist, Mallory, & Smith, 2009; Provencher, Gaston, O'Hara, & Gilchrist, 2012). Loss of sea ice could induce seabirds to forage on suboptimal prey of lower energy content, which could have ad‐ verse effects on breeding success and fitness (Divoky et al, 2015; Gaston, Gilchrist, & Hipfner, 2005)
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