Temporal trends of essential omega-3 fatty acids in Atlantic and Pacific food webs as measured in eggs of Leach's storm-petrel Oceanodroma leucorhoa

Abstract

Leach's storm-petrel Oceanodroma leucorhoa populations in the North Atlantic have declined in recent decades. The cause of those declines is not clear but one potential contributing factor could be reductions in the availability of essential nutrients due to changing marine ecology resulting from global warming. One group of particular concern is the omega-3 highly unsaturated fatty acids (n-3 HUFAs), in particular, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Dietary sources of EPA and DHA are required for normal growth and development in higher consumers, including birds. However, previous work has predicted increases in sea surface temperatures may cause declines in their availability. Here, we investigate this possibility by examining temporal trends (1992-2015) in EPA and DHA concentrations in Leach's storm-petrel eggs from 5 Canadian colonies: 2 on the Atlantic coast (Gull, Kent Islands) and 3 on the Pacific coast (Hippa, Storm, Cleland Islands). Neither EPA nor DHA concentrations in eggs decreased with time on either coast; rather, on the Atlantic coast, both EPA and DHA increased over the period of study. Carbon stable isotopes in the same eggs indicated that storm-petrels foraging in offshore, pelagic waters may have had increased access to n-3 HUFA. The data generated here provide a baseline for future comparisons. Ongoing regular monitoring of fatty acids in seabird eggs would be prudent given the likelihood of further increases in ocean temperatures.