Lipids and stable isotopes in common eider, black-legged kittiwake and northern fulmar: a trophic study from an Arctic fjord

Lipid class and fatty acid compositions were determined in common eider (Somateria mollissima), black-legged kittiwake (Rissa tridactyla) and northern fulmar (Fulmarus glacialis) from Kongsfjorden, Spitsbergen. Muscle and liver were sampled in all species, while fat tissue was sampled in eiders and fulmars. Triacylglycerols (TAG) dominated the lipid class compositions of all tissues, and the major fatty acids found in TAG were: 18:1n9, 16:0, 18:0, 20:5n3 and 16:1n7 for eider; 16:0, 18:1n9, 18:0,20:1n9 and 16:1n7 for kittiwake; 18:1n9, 16:0,20:1n9,22:1n11, and 18:0 for fulmar. To attain information on prey composition, fatty acid signature analysis was performed on muscle fatty acid profiles of the bird species, together with fatty acid data from potential prey species. This study of lipids combined with stable isotopes supports the following findings: (1) Common eiders are strongly linked to the benthic food chain, through both fatty acid compositions (high levels of 20:4n6) and stable isotope values (high levels of delta(13)C). (2) Black-legged kittiwakes and northern fulmars are linked to the pelagic food chain, through both fatty acid compositions (high levels of 20:1n9 and 22:1n11) and stable isotope values (low levels of delta(13)C). The high level of 20:1 and 22:1 moieties also indicates the importance of Calanus in the Arctic pelagic food chain supporting fulmar and kittiwake. (3) The levels delta(15)N show that of the 3 species, the fulmar occupies the highest trophic level, followed by kittiwake and common eider.