Publications by authors named "Halfdan H Helgason"

Mercury (Hg) is a heterogeneously distributed toxicant affecting wildlife and human health. Yet, the spatial distribution of Hg remains poorly documented, especially in food webs, even though this knowledge is essential to assess large-scale risk of toxicity for the biota and human populations. Here, we used seabirds to assess, at an unprecedented population and geographic magnitude and high resolution, the spatial distribution of Hg in North Atlantic marine food webs.

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Plastic pollution is distributed patchily around the world's oceans. Likewise, marine organisms that are vulnerable to plastic ingestion or entanglement have uneven distributions. Understanding where wildlife encounters plastic is crucial for targeting research and mitigation.

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Knowledge of the ecology and at-sea distribution of migratory species like seabirds has substantially increased over the last two decades. Furthermore, an increasing number of studies have recently focused on chemical contamination of birds over their annual cycle. However, the understanding of the combined effects of spatial movements and contamination on seabirds' life-history traits is still scarce.

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Each winter, the North Atlantic Ocean is the stage for numerous cyclones, the most severe ones leading to seabird mass-mortality events called "winter wrecks." During these, thousands of emaciated seabird carcasses are washed ashore along European and North American coasts. Winter cyclones can therefore shape seabird population dynamics by affecting survival rates as well as the body condition of surviving individuals and thus their future reproduction.

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Article Synopsis
  • Mercury (Hg) accumulation in Arctic seabirds is higher during the non-breeding period than in the breeding period, with concentrations being up to 3 times greater overall.
  • Research involving nine migratory alcid species revealed significant spatial differences in Hg levels, particularly between the Atlantic and Pacific regions, indicating varying exposure risks.
  • Most seabird colonies had Hg concentrations above the threshold for harmful effects during winter, highlighting potential vulnerabilities that require further study on spatial ecotoxicology and migration impact on Hg exposure.
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Article Synopsis
  • Despite low direct mercury inputs in the Arctic, marine life accumulates high levels of methylmercury (MeHg), with unclear pathways for its production and bioaccumulation.
  • Researchers studied Hg concentrations and stable isotope ratios in blood and feathers of little auks from different Arctic colonies to explore their MeHg exposure during various seasons and locations.
  • Findings show a geographic increase in Hg levels and specific trends in isotope ratios, suggesting different MeHg sources, particularly highlighting more contaminated MeHg in certain northern areas, which points to the role of environmental conditions in MeHg accumulation.
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Background: Foraging strategies of seabird species often vary considerably between and within individuals. This variability is influenced by a multitude of factors including age, sex, stage of annual life cycle, reproductive status, individual specialization and environmental conditions.

Results: Using GPS-loggers, we investigated factors affecting foraging flight characteristics (total duration, maximal range, total distance covered) of great skuas of known sex breeding on Bjørnøya, Svalbard, the largest colony in the Barents Sea region.

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