Wintering in the Western Subarctic Pacific Increases Mercury Contamination of Red-Legged Kittiwakes

Abstract

Marine methylmercury concentrations vary geographically and with depth, exposing organisms to different mercury levels in different habitats. Red-legged kittiwakes (Rissa brevirostris), a specialist predator, forage on fish and invertebrates from the mesopelagic zone, a part of the ocean with elevated methylmercury concentrations. We used kittiwakes as bioindicators of MeHg concentrations in remote mesopelagic systems by examining how wintering distribution and habitat affected kittiwakes’ mercury exposure. In 2011–2017, we sampled winter-grown feathers on St. George Island, Alaska, from birds equipped with geolocation loggers. We measured total mercury (THg) and nitrogen stable isotopes in nape and head feathers grown during winter, respectively. THg concentration of kittiwake nape feathers averaged 4.61 ± 0.97 μg/g dry weight. Hierarchical cluster analysis was used to classify winter habitats with remotely sensed environmental variables along each bird’s track. Five habitat clusters were identified. Birds that spent more time in the Western Subarctic Gyre and those that wintered further south had elevated THg concentrations. In contrast to THg, trophic level varied annually but did not show strong spatial patterns. Our results documented spatial variability in THg exposure based on the oceanic wintering locations of red-legged kittiwakes and highlight their use as a bioindicator of MeHg across ocean basins.

Seasonal variation of mercury contamination in Arctic seabirds: A pan-Arctic assessment

“…New foundland murres: McFarlane Tranquilla et al, 2014). Further investigations combining migratory movements and Hg contamination in Pacific seabirds are needed to understand seabird vulnerability to Hg in this region (see Fleishman et al, 2019). Northwest Greenland little auk population had higher Hg concentrations compared to other Arctic regions, a pattern also found in some other seabirds and marine top predators (Albert et al, 2019;AMAP, 2011) and might be explained by similar elevated concentrations at both their breeding areas and their non-breeding areas off Newfoundland (Fort et al, 2013a).…”

“…However, current knowledge about Hg concentrations in Arctic seabirds is restricted mostly to the breeding period (but see Fleishman et al, 2019;Fort et al, 2014), and little is known about the non-breeding period, which is mostly spent in areas outside the Arctic.…”

Contrasting Spatial and Seasonal Trends of Methylmercury Exposure Pathways of Arctic Seabirds: Combination of Large-Scale Tracking and Stable Isotopic Approaches

“…Medium to high predators such as seabirds are exposed to significant environmental MeHg concentrations through their diet 15,16 and have been extensively studied as bioindicators of Hg exposure in marine food webs (e.g 17,18 ), including the Arctic [19][20][21] . Specific foraging habitats and migratory movements of Arctic seabirds strongly determine their exposure to distinct environmental MeHg sources in marine ecosystems 22,23 . However, studies on Hg exposure in Arctic seabirds have commonly put the focus towards the breeding season (summer) when seabirds are more accessible for researchers.…”

Relationships between mercury burden, sex, and sexually selected feather ornaments in crested auklet (Aethia cristatella)

“…Based on archival geolocation tracking data of birds from Buldir and Gareloi Island, Aleutian Islands between 2013 and 2015, significantly more females than males overwintered in the Kuroshio Current Large Marine Ecosystem (K. Robbins unpublished data). The Kuroshio Current Large Marine Ecosystem lies off the east cost of Japan (Di Lorenzo et al 2013); Red-legged Kittiwakes (Rissa brevirostris) wintering in the Kuroshio Current had the highest feather total Hg concentrations (Fleishman et al 2019).…”