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The small, sub-ice copepod Jaschnovia brevis is rich in triacylglycerols, suggesting a feeding behaviour not constrained to the seasonal phytoplankton bloom. The copepod's triacylglycerol reserves contain: the diatom biomarkers 16:1n-7 (23.9%), 20:5n-3 (8.5%) and C16 PUFA (1.3%), the flagellate biomarkers 18:4n-3 (3.7%) and 22:6n-3 (3.3%), and the Calanus copepod biomarkers 20:1n-9 (7.7%) and 22:1n-11 (6.2%). Total lipid from particulates in the water column contained polar lipid (45.0%), wax esters (24.9%) and triacylglycerols (11.2%) as major components. The total lipids in the particulates were rich in 18:1n-9 (31.5%) and 16:0 (21.2%), and relatively rich in 18:0 (7.8%) and 18:2n-6 (9.2%). The triacylglycerols in the particulates contained 16:1n-7 (20.7%), C16 PUFA (4.1%), 18:4n-3 (1.9%), 20:5n-3 (3.6%), 22:6n-3 (1.9%), 20:1n-9 (5.2%) and 22:1n-11 (3.9%). The polar lipids in the particulates contained 16:1n-7 (17.3%), C16 PUFA (7.8%), 18:4n-3 (3.3%), 20:5n-3 (14.5%) and 22:6n-3 (9.6%). The fatty alcohols in the wax esters of the particulates were mainly 16:0 (11.3%), 20:1n-9 (21.1%) and 22:1n-11 (30.6%). The nature of the particulates, their possible origin in living and non-living material, and their role in the nutrition of J. brevis are discussed.

The complete diet composition structure of the most numerous planktivorous sea bird, little auk (Alle alle), in the European Arctic, is still not fully recognized. Although regular constituents of little auk chick diets, the copepods, Calanus glacialis and C. finmarchicus have been previously relatively well described, more taxa were frequent ingredients of the bird’s meals. Therefore, the role of the little auks supplementary diet components (SDCs) at two colonies in the Svalbard Archipelago, Hornsund and Magdalenefjorden, in 2007–2009, is a main subject of this comparative study. Because the SDCs often consisted of scarce but large zooplankters, this investigation was focused on biomass as a proxy of the SDCs’ energy input. Although the total biomass of the food delivered to chicks in both colonies was similar, in Magdalenefjorden, the proportion of SDCs was twice that found in Hornsund. The main SDCs in Hornsund were Decapoda larvae (with predominating Pagurus pubescens) and Thysanoessa inermis, whereas the main SDCs in Magdalenefjorden were C. hyperboreus and Apherusa glacialis. Previous investigations, which indicated lipid richness of SDCs, together with our ecological results from the colonies, suggest that this category might play a compensatory role in little auk chick diets. The ability to forage on diverse taxa may help the birds to adapt to ongoing Arctic ecosystem changes.

Lipid class and fatty acid compositions were determined in Limacina helicina and Clione limacina from an Arctic fjord and the marginal ice zone around Svalbard. C. limacina had higher levels of neutral lipids, including both alkyldiacylglycerols (ADG) and triacylglycerols (TAG), than L. helicina, which contained mainly TAG. However, considerable heterogeneity in the lipid classes and their fatty acids/alcohols were observed in C. limacina in that only two out of the seven specimens analysed were lipid-rich and contained both ADG and TAG, the others having only low percentages of TAG. In specimens of C. limacina containing ADG, 15:0 and 17:1n-8 were prominent fatty acids in both ADG and TAG. The fatty acids of the TAG of L. helicina were variable but 15:0 and 17:1n-8 were absent. We consider the heterogeneity in the fatty acid compositions of L. helicina to reflect temporal and spatial variability in the animals' predominantly phytoplanktonic and particulate diet, which occasionally includes small copepods. We further consider L. helicina to be the prime food for C. limacina and the noticeable amounts of 22:1 found in one sample of C. limacina to reflect significant input of Calanus either directly or indirectly through their prime food, L. helicina. We view the heterogeneity in the fatty acid compositions of both L. helicina and C. limacina, as well as the ability of C. limacina to biosynthesise WE, ADG, 15:0, and 17:1n-8, as adaptations to a large variation of food availability that enables C. limacina to synthesise lipids rapidly and flexibly. Thus, the lipid biochemistry of C. limacina is important in enabling the species to thrive in strong pulses in polar systems.