Climate change alters the trophic niche of a declining apex marine predator

Abstract

Changes in the world's oceans have altered nutrient flow, and affected the viability of predator populations when prey species become unavailable. These changes are integrated into the tissues of apex predators over space and time and can be quantified using stable isotopes in the inert feathers of historical and contemporary avian specimens. We measured δ(13) C and δ(15) N values in Flesh-footed Shearwaters (Puffinus carneipes) from Western and South Australia from 1936-2011. The Flesh-footed Shearwaters more than doubled their trophic niche (from 3.91 ± 1.37 ‰(2) to 10.00 ± 1.79 ‰(2) ), and dropped an entire trophic level in 75 years (predicted δ(15) N decreased from +16.9 ‰ to + 13.5 ‰, and δ(13) C from -16.9 ‰ to -17.9 ‰) - the largest change in δ(15) N yet reported in any marine bird, suggesting a relatively rapid shift in the composition of the Indian Ocean food web, or changes in baseline δ(13) C and δ(15) N values. A stronger El Niño-Southern Oscillation results in a weaker Leeuwin Current in Western Australia, and decreased Flesh-footed Shearwater δ(13) C and δ(15) N. Current climate forecasts predict this trend to continue, leading to increased oceanic 'tropicalization' and potentially competition between Flesh-footed Shearwaters and more tropical sympatric species with expanding ranges. Flesh-footed Shearwater populations are declining, and current conservation measures aimed primarily at bycatch mitigation are not restoring populations. Widespread shifts in foraging, as shown here, may explain some of the reported decline. An improved understanding and ability to mitigate the impacts of global climactic changes is therefore critical to the long-term sustainability of this declining species.

Rapidly increasing methyl mercury in endangered ivory gull ( Pagophila eburnea ) feathers over a 130 year record

“…This contrasts with other seabirds over similar time frames in the North Atlantic [38,51], North Pacific [18,52], and Indian and southern Oceans [53][54][55]. While we found that ivory gull stable-isotope values remained constant, their diet could have changed to different prey with similar isotopic values.…”

El Niño Southern Oscillation influences the abundance and movements of a marine top predator in coastal waters

“…), noddies ( Anous spp.) and terns ( Sterna fuscata ; Bond & Lavers, ; Surman & Nicholson, ). During our 6‐year study, there was one El Niño event spanning from May 2009 to March 2010, with the initial phase having the largest negative impact across Australia, when the SOI signal was weak (Bureau of Meteorology, ).…”

Responses of Marine Organisms to Climate Change across Oceans

“…Isotope analysis of the feathers of flesh-footed shearwaters from western and south Australia, where reproductive success has decreased and populations are in decline, shows that these seabirds have doubled their trophic niche and dropped a trophic level in 75 years (Bond and Lavers, 2014). By contrast, a recent Thermal affiliation is assigned in relation to the sampled region.…”

“…Other examples of differing mechanisms by which climate change can influence foraging and diets of seabirds include fleshfooted shearwaters, Puffinus carneipes, in the eastern Indian Ocean and wandering albatross, Diomedea exulans, in the Southern Ocean (Weimerskirch et al, 2012;Bond and Lavers, 2014). Isotope analysis of the feathers of flesh-footed shearwaters from western and south Australia, where reproductive success has decreased and populations are in decline, shows that these seabirds have doubled their trophic niche and dropped a trophic level in 75 years (Bond and Lavers, 2014).…”