Mercury (Hg), because of its deleterious effects on wildlife and its high concentrations in polar regions, has been widely studied in the Arctic. This provided important information regarding food ...web contamination, spatial and temporal trends of Hg in ecosystems or risk assessments for wildlife and Humans. Among the Arctic biota, seabirds have been among the most studied species due to their sensitivity to this toxicant, their role as bioindicators of the contamination status of their environment, and their consumption by Arctic communities. However, most studies that investigated Hg in Arctic seabirds focused on measurements in internal organs or in eggs, while few investigations have been performed on blood and feathers, despite the relevant and complementary information they provide. Here, we first provide a detailed overview of the specific information blood and feathers can bring when investigating Hg contamination of Arctic seabirds, including new knowledge on the poorly studied non-breeding period. Second, we perform a comprehensive review of the use of blood and feathers as non-lethal tissues to study Hg in Arctic seabirds. This review demonstrates important interspecific variations in Hg blood concentrations according to seabird trophic status, with seaducks generally presenting the lowest Hg concentrations while auks have the highest ones. However, all the observed Hg concentrations are below the admitted toxicity thresholds. Hg concentrations in feathers follow similar trends and gulls appear to be the most contaminated species, likely as a consequence of contrasting migratory and overwintering strategies. This review also confirms strong spatial variations with higher concentrations found in the Canadian Arctic and Pacific waters than in Greenland and the European Arctic. It also identifies some major understudied areas such as West Greenland, Aleutian Islands and Russia. Finally, we provide a thorough review of the current knowledge regarding molting patterns in Arctic seabirds, which is an essential information to interpret Hg concentrations measured in feathers. Overall, our results point out the importance of blood and feathers in seabird ecotoxicological assessments and highlight the need for large scale international collaborations and research programs.
•Feathers and blood were neglected in Arctic seabird Hg assessments.•Feathers are valuable to investigate seasonal variations of Hg contamination.•Highest Hg concentrations are found in Canadian and Pacific Arctic seabirds.•Species trophic status influences their Hg contamination.•Linking seabird movements to their contamination is an important research gap to fill.
Arctic organisms are exposed to various levels of pollutants, among which mercury (Hg) has raised important environmental concerns. Previous studies examining Hg levels, trends, and effects on Arctic ...marine top predators have focused on the Arctic region. However, many of these top predators, such as seabirds, migrate to spend a large part of their life cycle far from the Arctic in areas where their exposure to contaminants is largely unknown. By combining biotelemetry and Hg and stable isotope analyses, we studied the seasonal Hg contamination of little auks (Alle alle, the most abundant Arctic seabird) in relation to their distribution and marine foraging habitat, as well as its potential impacts on bird reproduction. We show that little auks were ∼3.5 times more contaminated when outside the breeding season, and that Hg that accumulated during this nonbreeding non-Arctic period was related to egg size the following season, with females having more Hg laying smaller eggs. Our results highlight that ecotoxicological studies should be expanded to yield a comprehensive understanding of contamination risks and associated threats to top predators over their entire annual cycle. Furthermore, we show that an important nonbreeding area located in the northwest Atlantic was associated with greater Hg contamination and demonstrate the utility of bird-borne miniaturized technology for evaluating the contamination of marine systems on large spatial scales.
•We assembled all cancer occurrences in aquatic and semi-aquatic animal species.•In 30 studies, cancer was linked to habitat pollution.•Based on this overview, we describe cancer vulnerability of ...different animal groups.•We point out biases, research gaps, and future directions in this field.
Due to the interconnectedness of aquatic ecosystems through the highly effective marine and atmospheric transport routes, all aquatic ecosystems are potentially vulnerable to pollution. Whilst links between pollution and increased mortality of wild animals have now been firmly established, the next steps should be to focus on specific physiological pathways and pathologies that link pollution to wildlife health deterioration. One of the pollution-induced pathologies that should be at the centre of attention in ecological and evolutionary research is cancer, as anthropogenic contamination has resulted in a rapid increase of oncogenic substances in natural habitats. Whilst wildlife cancer research is an emerging research topic, systematic reviews of the many case studies published over the recent decades are scarce. This research direction would (1) provide a better understanding of the physiological mechanisms connecting anthropogenic pollution to oncogenic processes in non-model organisms (reducing the current bias towards human and lab-animal studies in cancer research), and (2) allow us to better predict the vulnerability of different wild populations to oncogenic contamination. This article combines the information available within the scientific literature about cancer occurrences in aquatic and semi-aquatic species. For the first aim, we use available knowledge from aquatic species to suggest physiological mechanisms that link pollution and cancer, including main metabolic detoxification pathways, oxidative damage effects, infections, and changes to the microbiome. For the second aim, we determine which types of aquatic animals are more vulnerable to pollution-induced cancer, which types of pollution are mainly associated with cancer in aquatic ecosystems, and which types of cancer pollution causes. We also discuss the role of migration in exposing aquatic and semi-aquatic animals to different oncogenic pollutants. Finally, we suggest novel research avenues, including experimental approaches, analysis of the effects of pollutant cocktails and long-term chronic exposure to lower levels of pollutants, and the use of already published databases of gene expression levels in animals from differently polluted habitats.
Combined effects of multiple, climate change-associated stressors are of mounting concern, especially in Arctic ecosystems. Elevated mercury (Hg) exposure in Arctic animals could affect behavioral ...responses to changes in foraging landscapes caused by climate change, generating interactive effects on behavior and population resilience. We investigated this hypothesis in little auks (Alle alle), a keystone Arctic seabird. We compiled behavioral data for 44 birds across 5 years using accelerometers while also quantifying blood Hg and environmental conditions. Warm sea surface temperature (SST) and low sea ice coverage reshaped time activity budgets (TABs) and diving patterns, causing decreased resting, increased flight, and longer dives. Mercury contamination was not associated with TABs. However, highly contaminated birds lengthened interdive breaks when making long dives, suggesting Hg-induced physiological limitations. As dive durations increased with warm SST, subtle toxicological effects threaten to increasingly constrain diving and foraging efficiency as climate change progresses, with ecosystem-wide repercussions.
Studying long-term trends of contaminants in Arctic biota is essential to better understand impacts of anthropogenic activities and climate change on the exposure of sensitive species and marine ...ecosystems. We concurrently measured temporal changes (2006–2014) in mercury (Hg) contamination of little auks (Alle alle; the most abundant Arctic seabird) and in their major zooplankton prey species (Calanoid copepods, Themisto libellula, Gammarus spp.). We found an increasing contamination of the food-chain in East Greenland during summer over the last decade. More specifically, bird contamination (determined by body feather analyses) has increased at a rate of 3.4% per year. Conversely, bird exposure to Hg during winter in the northwest Atlantic (determined by head feather analyses) decreased over the study period (at a rate of 1.5% per year), although winter concentrations remained consistently higher than during summer. By combining mercury levels measured in birds and zooplankton to isotopic analyses, our results demonstrate that inter-annual variations of Hg levels in little auks reflect changes in food-chain contamination, rather than a reorganization of the food web and a modification of seabird trophic ecology. They therefore underline the value of little auks, and Arctic seabirds in general, as bio-indicators of long-term changes in environmental contamination.
•We examined temporal trends of Hg in Arctic seabirds and major zooplankton species.•We investigated the role of underlying ecological drivers in seabird contamination.•Hg contamination of the East Greenland marine food web increased over the last decade.•Hg levels in Arctic seabirds reflect changes in the food-chain contamination.•Little auks are bio-indicators of long-term changes in environmental contamination.
Temporal increase of seabird exposure to Hg reflects changes in Arctic environmental contamination.
Despite the limited direct anthropogenic mercury (Hg) inputs in the circumpolar Arctic, elevated concentrations of methylmercury (MeHg) are accumulated in Arctic marine biota. However, the MeHg ...production and bioaccumulation pathways in these ecosystems have not been completely unraveled. We measured Hg concentrations and stable isotope ratios of Hg, carbon, and nitrogen in the feathers and blood of geolocator-tracked little auk Alle alle from five Arctic breeding colonies. The wide-range spatial mobility and tissue-specific Hg integration times of this planktivorous seabird allowed the exploration of their spatial (wintering quarters/breeding grounds) and seasonal (nonbreeding/breeding periods) MeHg exposures. An east-to-west increase of head feather Hg concentrations (1.74–3.48 μg·g–1) was accompanied by significant spatial trends of Hg isotope (particularly Δ199Hg: 0.96–1.13‰) and carbon isotope (δ13C: −20.6 to −19.4‰) ratios. These trends suggest a distinct mixing/proportion of MeHg sources between western North Atlantic and eastern Arctic regions. Higher Δ199Hg values (+0.4‰) in northern colonies indicate an accumulation of more photochemically impacted MeHg, supporting shallow MeHg production and bioaccumulation in high Arctic waters. The combination of seabird tissue isotopic analysis and spatial tracking helps in tracing the MeHg sources at various spatio-temporal scales.
Mercury (Hg) is a pervasive contaminant reaching Antarctic environments through atmospheric transport and deposition. Seabirds as meso to top predators can accumulate high quantities of Hg through ...diet. Reproduction is one of the most sensitive endpoints of Hg toxicity in marine birds. Yet, few studies have explored Hg exposure and effects in Antarctic seabirds, where increasing environmental perturbations challenge animal populations. This study focuses on the Antarctic petrel Thalassoica antarctica from Svarthamaren, Antarctica, where the world's largest breeding population is thought to be in decline. Hg and the stable isotopes of carbon (δ13C, proxy of feeding habitat) and nitrogen (δ15N, trophic position/diet) were measured in red blood cells from 266 individuals over two breeding years (2012–13, 2013–14). Our aims were to 1) quantify the influence of individual traits (size and sex) and feeding ecology (foraging location, δ13C and δ15N values) on Hg exposure, and 2) test the relationship between Hg concentrations with body condition and breeding output (hatching success and chick survival). Hg concentrations in Antarctic petrels (mean ± SD, 0.84 ± 0.25, min-max, 0.42–2.71 μg g−1 dw) were relatively low when compared to other Antarctic seabirds. Hg concentrations increased significantly with δ15N values, indicating that individuals with a higher trophic level (i.e. feeding more on fish) had higher Hg exposure. By contrast, Hg exposure was not driven by feeding habitat (inferred from both foraging location and δ13C values), suggesting that Hg transfer to predators in Antarctic waters is relatively homogeneous over a large geographical scale. Hg concentrations were not related to body condition, hatching date and short-term breeding output. At present, Hg exposure is likely not of concern for this population. Nevertheless, further studies on other fitness parameters and long-term breeding output are warranted because Hg can have long-term population-level effects without consequences on current breeding success.
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•Blood Hg concentrations were measured in a large sample of adult Antarctic petrels.•We assessed the influence of individual traits and feeding ecology on Hg exposure.•Hg exposure was low and dependent on trophic position.•Hatching date, success, and chick survival were not related to Hg burdens in parents.•Assessment of Hg correlates with other fitness traits and over the long-term is warranted.
Blood Hg concentrations in Antarctic petrels were driven by trophic position and were not related to short-term breeding output.
When species competing for the same resources coexist, some segregation in the way they utilize those resources is expected. However, little is known about how closely related sympatric breeding ...species segregate outside the breeding season. We investigated the annual segregation of three closely related seabirds (razorbill Alcatorda, common guillemot Uriaaalge and Brünnich's guillemot U. lomvia) breeding at the same colony in Southwest Greenland. By combining GPS and geolocation (GLS) tracking with dive depth and stable isotope analyses, we compared spatial and dietary resource partitioning. During the breeding season, we found the three species to segregate in diet and/or dive depth, but less in foraging area. During both the post-breeding and pre-breeding periods, the three species had an increased overlap in diet, but were dispersed over a larger spatial scale. Dive depths were similar across the annual cycle, suggesting morphological adaptations fixed by evolution. Prey choice, on the other hand, seemed much more flexible and therefore more likely to be affected by the immediate presence of potential competitors.
Abstract
Climate change affects the Arctic more than any other region, resulting in evolving weather, vanishing sea ice and altered biochemical cycling, which may increase biotic exposure to chemical ...pollution. We tested thermoregulatory impacts of these changes on the most abundant Arctic seabird, the little auk (
Alle alle
). This small diving species uses sea ice-habitats for foraging on zooplankton and resting. We equipped eight little auks with 3D accelerometers to monitor behavior, and ingested temperature recorders to measure body temperature (T
b
). We also recorded weather conditions, and collected blood to assess mercury (Hg) contamination. There were nonlinear relationships between time engaged in different behaviors and T
b
. T
b
increased on sea ice, following declines while foraging in polar waters, but changed little when birds were resting on water. T
b
also increased when birds were flying, and decreased at the colony after being elevated during flight. Weather conditions, but not Hg contamination, also affected T
b
. However, given our small sample size, further research regarding thermoregulatory effects of Hg is warranted. Results suggest that little auk T
b
varies with behavior and weather conditions, and that loss of sea ice due to global warming may cause thermoregulatory and energic challenges during foraging trips at sea.
Mercury (Hg), one of the elements most toxic to biota, accumulates within organisms throughout their lifespan and biomagnifies along trophic chain. Due to their key role in marine systems, ...cephalopods constitute a major vector of Hg in predators. Further, they grow rapidly and display complex behaviours, which can be altered by neurotoxic Hg. This study investigated Hg concentrations within 81 cephalopod specimens sampled in the Bay of Biscay, which belonged to five species: Eledone cirrhosa, Sepia officinalis, Loligo vulgaris, Todaropsis eblanae and Illex coindetii. Hg concentrations were measured in the digestive gland, the mantle muscle and the optic lobes of the brain. The digestive gland and the mantle were tissues with the most concentrated Hg among all species considered (up to 1.50 μg.g−1 dw), except E. cirrhosa. This benthic cephalopod had 1.3-fold higher Hg concentrations in the brain (up to 1.89 μg.g−1 dw) than in the mantle, while other species had 2-fold lower concentrations of Hg in the brain than in the mantle. Brain-Hg concentrations can be predicted from muscle-Hg concentrations for a given species, which facilitates the assessment of Hg toxicokinetics in cephalopods. In the most contaminated E. cirrhosa individual, the chemical form of Hg in its digestive gland, mantle muscle and optic lobes, was determined using High energy-Resolution X-ray Absorption Near Edge Structure (HR XANES) spectroscopy. In the digestive gland, 33 ± 11% of total Hg was inorganic Hg speciated as a dicysteinate complex (Hg(Cys)2), which suggested that the demethylation of dietary MeHg occurs in this organ. All Hg found in the mantle muscle and the optic lobes is methylated and bound to one cysteinyl group (MeHgCys complex), which implies that dietary MeHg is distributed to these tissues via the bloodstream. These results raised the questions regarding interspecific differences observed regarding Hg brain concentrations and the possible effect of Hg on cephalopod functional brain plasticity and behaviour.
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•Hg levels were measured in digestive gland, muscle and brain in 5 cephalopod species.•Hg concentrations in the optic lobes can be predicted from muscle ones.•Highest Hg concentrations were found in the optic lobes of the octopus E. cirrhosa.•XANES showed 33% of iHg in octopus digestive gland suggesting demethylation.•100% of MeHg in brain and muscle implies dietary MeHg storage in these tissues.
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