COS 22-1 - Investigating changes over 120+ years in North-west Atlantic marine food webs using seabird feathers

Background/Question/Methods

Studying marine food web structures proves logistically challenging due to the sheer size of the world’s oceans. Seabirds have emerged as excellent indicators of marine food webs because of their nearly exclusive marine diets and their proximity to humans during the breeding season. Stable isotope technology is frequently employed for long-term diet studies. Stable isotope values within tissues of a consumer are direct indicators of foods eaten while those tissue develop, with nitrogen-15 being particularly useful in diet studies because it indicates an organisms’ trophic position. Here, we investigate long-term (120+ years) marine food web changes in the North-west Atlantic waters near Newfoundland by conducting stable isotope analyses of feathers of Newfoundland breeders Atlantic puffin (Fratercula arctica, n = 37) and Leach’s storm-petrel (Oceanodroma leucorhoa, n = 34). Seabird feathers were collected from Canadian museums and from independent collections of fellow researchers. Birds were restricted to adults collected during the breeding season. Feathers grown during the breeding season represent non-breeding (winter) diets. We utilize both bulk and amino-acid specific stable isotope analyses to investigate changes in δ¹⁵N over time in seabird feathers.

Results/Conclusions

Preliminary results show bulk stable δ¹⁵N values for Leach’s storm-petrels from 1904 to 2019 and increasing δ¹⁵N values for Atlantic puffins from 1899-2021. The results indicate Leach’s storm-petrels have had a relatively stable diet over the last century, whereas puffins have been feeding at higher trophic levels. Leach’s storm-petrels have a diverse diet consisting of small fishes, crustaceans, jellyfish and amphipods; this diversity of food sources may act as a protective measure against changes in food web structure due to commercial fishing pressures and climate change. The non-breeding diet of adult Atlantic puffins is poorly studied, however existing research indicates it consists mostly of small fish. There is evidence of diversity of preferred fish prey species among geographically distinct puffin colonies. Atlantic puffins breeding in Newfoundland are documented to prefer capelin (Mallotus villosus), a species in sharp decline. Future analysis will relate puffin δ¹⁵N values to δ¹⁵N values of potential prey populations, creating a timeline of changes in dominant puffin prey. Furthermore, amino-acid specific stable isotopes will elicit whether changes in bulk δ¹⁵N in puffins is related to a change in puffin diet or a change in δ¹⁵N values at the base of the food web, or both.