Penguins as bioindicators of mercury contamination in the Southern Ocean: birds from the Kerguelen Islands as a case study

Influence of migration range and foraging ecology on mercury accumulation in Southern Ocean penguins

In order to evaluate mercury (Hg) accumulation patterns in Southern Ocean penguins, we measured Hg concentrations and carbon (δ13C) and nitrogen (δ15N) stable isotope ratios in body feathers of adult Adélie (Pygoscelis adeliae), gentoo (Pygoscelis papua), and chinstrap (Pygoscelis antarctica) penguins living near Anvers Island, West Antarctic Peninsula (WAP) collected in the 2010/2011 austral summer. With these and data from Pygoscelis and other penguin genera (Eudyptes and Aptenodytes) throughout the Southern Ocean, we modelled Hg variation using δ13C and δ15N values. Mean concentrations of Hg in feathers of Adélie (0.09 ± 0.05 μg g-1) and gentoo (0.16 ± 0.08 μg g-1) penguins from Anvers Island were among the lowest ever reported for the Southern Ocean. However, Hg concentrations in chinstrap penguins (0.80 ± 0.20 μg g-1), which undertake relatively broad longitudinal winter migrations north of expanding sea ice, were significantly higher (P < 0.001) than those in gentoo or Adélie penguins. δ13C and δ15N values for feathers from all three Anvers Island populations were also the lowest among those previously reported for Southern Ocean penguins foraging within Antarctic and subantarctic waters. These observations, along with size distributions of WAP krill, suggest foraging during non-breeding seasons as a primary contributor to higher Hg accumulation in chinstraps relative to other sympatric Pygoscelis along the WAP. δ13C values for all Southern Ocean penguin populations, alone best explained feather Hg concentrations among possible generalized linear models (GLMs) for populations grouped by either breeding site (AICc = 36.9, wi = 0.0590) or Antarctic Frontal Zone (AICc = 36.9, wi = 0.0537). Although Hg feather concentrations can vary locally by species, there was an insignificant species-level effect (wi < 0.001) across the full latitudinal range examined. Therefore, feeding ecology at breeding locations, as tracked by δ13C, control Hg accumulation in penguin populations across the Southern Ocean.

Interspecific Variations in the Internal Mercury Isotope Dynamics of Antarctic Penguins: Implications for Biomonitoring

Mercury (Hg) biomonitoring requires a precise understanding of the internal processes contributing to disparities between the Hg sources in the environment and the Hg measured in the biota. In this study, we investigated the use of Hg stable isotopes to trace Hg accumulation in Adélie and emperor penguin chicks from four breeding colonies in Antarctica. Interspecific variation of Δ199Hg in penguin chicks reflects the distinct foraging habitats and Hg exposures in adults. Chicks at breeding sites where adult penguins predominantly consumed mesopelagic prey showed relatively lower Δ199Hg values than chicks that were primarily fed epipelagic krill. Substantial δ202Hg variations in chick tissues were observed in both species (Adélie: -0.11 to 1.13‰, emperor: -0.27 to 1.15‰), whereas only emperor penguins exhibited the lowest δ202Hg in the liver and the highest in the feathers. Our results indicate that tissue-specific δ202Hg variations and their positive correlations with % MeHg resulted from MeHg demethylation in the liver and kidneys of emperor penguin chicks, whereas Adélie penguin chicks showed different internal responses depending on their exposure to dietary MeHg. This study highlights the importance of considering intra- and interspecific variations in adult foraging ecology and MeHg demethylation when selecting penguin chicks for Hg biomonitoring.

Evaluation of Metal Partitioning across Humboldt Penguin (Spheniscus humboldti) Egg Components

Humboldt Penguin (Spheniscus humboldti) population declines are attributable to several multifaceted anthropogenic impacts. At present, the exposure of Humboldt Penguins to high concentrations of heavy metals in the marine environment is a preeminent concern, due to mining along the Peruvian coast near key rookery sites. Metal and selenium concentrations were determined in eggs collected from September 2020 to April 2021 from a managed-care penguin population at the Brookfield Zoo to establish reference values for health indices conducted on wild populations. Concentrations of 16 elements, with emphasis on those found in mine efflux-arsenic, cadmium, copper, lead, mercury, selenium, and zinc-were assessed via inductively coupled plasma mass spectrometry in yolk, albumen, and eggshell. Data analyses indicate a clear delineation between egg constituents, with lipid-rich yolk displaying notably higher concentrations (μg/g) of arsenic (0.20 ± 0.064), chromium (0.086 ± 0.03), cobalt (0.01 ± 0.003), iron (238.65 ± 54.72), lead (0.32 ± 0.97), manganese (2.71 ± 0.66), molybdenum (0.57 ± 0.14), tin (3.29 ± 0.99), and zinc (64.03 ± 13.01) than other components (albumen and eggshell). These data confirm that heavy metals are partitioned differently across Humboldt Penguin egg components, which provides insight into the potential connection between embryonic nutrient source contamination and subsequent chick viability.

Assessing mercury contamination in Southern Hemisphere marine ecosystems: The role of penguins as effective bioindicators

Mercury (Hg) is a global pollutant known for its significant bioaccumulation and biomagnification capabilities, posing a particular threat to marine environments. Seabirds have been recognized as effective bioindicators of marine pollution, and, among them, penguins present a unique opportunity to serve as a single taxonomic group (Sphenisciformes) for monitoring Hg across distinct marine ecosystems in the Southern Hemisphere. In this study, we conducted a comprehensive systematic review of Hg concentrations, and performed a meta-analysis that took into account the various sources of uncertainty associated with Hg contamination in penguins. Beyond intrinsic species-specific factors shaping Hg levels, our results showed that the penguin community effectively reflects spatial patterns of Hg bioavailability. We identified geographic Hg hotspots in Australia, the Indian Ocean, and Tierra del Fuego, as well as coldspots in Perú and the South Atlantic. Furthermore, specific penguin species, namely the Southern Rockhopper (Eudyptes chrysocome) and Macaroni penguin (Eudyptes chrysolophus), are highlighted as particularly vulnerable to the toxic effects of Hg. Additionally, we identified knowledge gaps in geographic areas such as the Galápagos Islands, South Africa, and the coast of Chile, as well as in species including Fiordland (Eudyptes pachyrhynchus), Snares (Eudyptes robustus), Erect-crested (Eudyptes sclateri), Royal (Eudyptes schlegeli), Yellow-eyed (Megadyptes antipodes), and Galápagos (Spheniscus mendiculus) penguins. Overall, our study contributes to the growing body of literature emphasizing the role of penguins as bioindicators of Hg pollution, but it also highlights areas where further research and data collection are needed for a more comprehensive understanding of Hg contamination in marine ecosystems in the Southern Hemisphere.

Circumpolar assessment of mercury contamination: the Adélie penguin as a bioindicator of Antarctic marine ecosystems

Due to its persistence and potential ecological and health impacts, mercury (Hg) is a global pollutant of major concern that may reach high concentrations even in remote polar oceans. In contrast to the Arctic Ocean, studies documenting Hg contamination in the Southern Ocean are spatially restricted and large-scale monitoring is needed. Here, we present the first circumpolar assessment of Hg contamination in Antarctic marine ecosystems. Specifically, the Adélie penguin (Pygoscelis adeliae) was used as a bioindicator species, to examine regional variation across 24 colonies distributed across the entire Antarctic continent. Mercury was measured on body feathers collected from both adults (n = 485) and chicks (n = 48) between 2005 and 2021. Because penguins' diet represents the dominant source of Hg, feather δ13C and δ15N values were measured as proxies of feeding habitat and trophic position. As expected, chicks had lower Hg concentrations (mean ± SD: 0.22 ± 0.08 μg·g‒1) than adults (0.49 ± 0.23 μg·g‒1), likely because of their shorter bioaccumulation period. In adults, spatial variation in feather Hg concentrations was driven by both trophic ecology and colony location. The highest Hg concentrations were observed in the Ross Sea, possibly because of a higher consumption of fish in the diet compared to other sites (krill-dominated diet). Such large-scale assessments are critical to assess the effectiveness of the Minamata Convention on Mercury. Owing to their circumpolar distribution and their ecological role in Antarctic marine ecosystems, Adélie penguins could be valuable bioindicators for tracking spatial and temporal trends of Hg across Antarctic waters in the future.

Using Crocodylians for monitoring mercury in the tropics

Mercury contamination is a widespread phenomenon that impacts ecosystems worldwide. Artisanal Small Scale Gold Mining (ASGM) activities are responsible for more than a third of atmospheric Hg emission. Due to Hg toxicity and its broad and elevated prevalence in the environment resulting from ASGM activities in the tropics, its biomonitoring is essential to better understand the availability of its methylmercury (MeHg) form in the environment. The Minamata Convention was ratified with the objective to "protect human health and the environment from anthropogenic emissions and releases of mercury compounds". Biomagnification of MeHg occurs through the trophic food web, where it biomagnifies and bioaccumulates in top predators. To monitor environmental MeHg contamination, studies have evaluated the use of living organisms; however, reptiles are among the least documented vertebrates regarding MeHg exposure. In this review we evaluate the use of crocodylians for Hg biomonitoring in tropical ecosystems. We found that out of the 28 crocodiles species, only 10 have been evaluated regarding Hg contamination. The remaining challenges when using this taxon for Hg biomonitoring are inconsistencies in the applied methodology (e.g., wet versus dry weight, tissues used, quantification method). However, due to their life history traits, crocodylians are particularly relevant for monitoring MeHg contamination in regions where ASGM activities occur. In conclusion and given their ecological and socio-economic importance, crocodylians are at great risk of MeHg contamination and are excellent bioindicators for tropical ecosystems.

Pelagic and estuarine birds as sentinels of metal(loid)s in the South Atlantic Ocean: Ecological niches as main factors acting on bioaccumulation

Activities related to the offshore exploration and production of oil and natural gas provide economic development and an essential energy source. However, besides the risk of petroleum hydrocarbon contamination, these activities can also be sources of metals and metalloids for marine organism contamination. In this research, we evaluated the potential use of two pelagic (black-browed albatross Thalassarche melanophris and yellow-nosed albatross T. chlororhynchos) and one estuarine bird species (neotropical cormorant Nannopterum brasilianus) as sentinels of contamination of As, Cd, Cr, Cu, Pb, Mn, Mo, Zn, Ni, Ba, V, and Hg in an area under influence of oil and gas activities. The analyses were carried out in samples collected from 2015 to 2022 from 97 individuals. A factor alert; an adaptation from the contamination factor is proposed to identify individuals with high concentrations that possibly suffered contamination by anthropogenic origin. Grouping all species, the metal(loid)s with the highest concentrations were in decreasing order: Zn > Cu > Mn > Hg > As > Cd > Mo > V > Cr > Ba > Ni > Pb. Similar concentrations were observed for V, Mn, Cr and Pb among the three species. Pelagic birds showed higher levels of concentrations for Hg, As and Cd. Based on the correlations and multivariate analysis performed, the results indicate that the ecological niche factor has greater relevance in the bioaccumulation of these elements compared to the habitat. Although some individuals showed high concentrations in part of the trace elements, suggesting exposure to anthropic sources, the direct influence of oil production and exploration activities was not observed, suggesting that activities on the continent are the primary contamination source. The results of this work highlight the role of seabirds as sentinels for metal(loid)s, contributing to the knowledge of the occurrence of contaminants in the South Atlantic Ocean.

Comparison of Plasma Trace Elements Between 2 Captive Humboldt Penguin (Spheniscus humboldti) Populations

Environmental pollutants and their effect on wildlife health play an important role in the conservation of endangered species and can be clinically relevant in captive animals too. Data on relevant concentrations of trace elements in captive birds with no known exposures are rare. For this study, silver, arsenic, gold, barium, cadmium, cobalt, chromium, copper, iron, mercury, magnesium, manganese, molybdenum, thallium, selenium, and zinc were measured by inductively coupled plasma mass spectrometry in lithium heparinized plasma samples from 18 Humboldt penguins at 2 zoological collections in Germany. The results showed that the plasma concentrations of silver, arsenic, gold, cadmium, cobalt, chromium, mercury, and selenium differed significantly (P ≤ 0.05) between the 2 penguin collections. The results indicate that the location of the birds has a strong influence on the plasma trace element concentrations. Well water used in the enclosures was suspected to be associated with these significant differences. Trace elemental concentrations in feed (eg, marine fish) and contamination from enclosure construction materials may also play a role. This study could provide a basis for further comparative, biomonitoring, toxicity, and reference interval studies.

Carryover effects of winter mercury contamination on summer concentrations and reproductive performance in little auks

Many animals migrate after reproduction to respond to seasonal environmental changes. Environmental conditions experienced on non-breeding sites can have carryover effects on fitness. Exposure to harmful chemicals can vary widely between breeding and non-breeding grounds, but its carryover effects are poorly studied. Mercury (Hg) contamination is a major concern in the Arctic. Here, we quantified winter Hg contamination and its carryover effects in the most abundant Arctic seabird, the little auk Alle alle. Winter Hg contamination of birds from an East Greenland population was inferred from head feather concentrations. Birds tracked with Global Location Sensors (GLS, N = 28 of the total 92) spent the winter in western and central North Atlantic waters and had increasing head feather Hg concentrations with increasing longitude (i.e., eastward). This spatial pattern was not predicted by environmental variables such as bathymetry, sea-surface temperature or productivity, and needs further investigation. Hg concentrations in head feathers and blood were strongly correlated, suggesting a carryover effect of adult winter contamination on the consequent summer concentrations. Head feather Hg concentrations had no clear association with telomere length, a robust fitness indicator. In contrast, carryover negative effects were detected on chick health, as parental Hg contamination in winter was associated with decreasing growth rate of chicks in summer. Head feather Hg concentrations of females were not associated with egg membrane Hg concentrations, or with egg volume. In addition, parental winter Hg contamination was not related to Hg burdens in chicks' body feathers. Therefore, we hypothesise that the association between parental winter Hg exposure and the growth of their chick results from an Hg-related decrease in parental care, and needs further empirical evidence. Our results stress the need of considering parental contamination on non-breeding sites to understand Hg trans-generational effects in migrating seabirds, even at low concentrations.

Trace elements in relation to trophic ecology of long-distance migratory shorebirds and seabirds in West Africa

Shorebirds and seabirds are abundant predators in coastal habitats worldwide, relying upon a high diversity of benthic invertebrates and fish, respectively. While occupying different trophic guilds, they are differently exposed to element contamination entering the coastal food web. Therefore, these birds have been used as bioindicators of environmental contamination in marine ecosystems. We analysed the concentration of trace elements in blood samples of 16 shorebird and seabird migratory species in a major non-breeding site, the Bijagós Archipelago, in regard to their trophic ecology. Overall, our study shows low exposure of this bird community to toxic elements, except for Hg. Most species presented Hg burdens within the moderate toxicity threshold, but one species (Dunlin) presented values at a potential high Hg toxicity risk. We found a positive relationship between Se and Ni concentrations and δ¹⁵N values (a proxy for trophic level). In addition, a positive relationship was found between δ¹³C (a proxy for habitat characteristics) and Hg, Fe, Cu and Mn, while the opposite pattern was recorded for As. Differences were also shown for several trace elements between the two studied trophic guilds: concentrations of As, Pb and Se were higher in pelagic fish consumers (seabirds), whereas Cr, Fe and Sr burdens were higher in benthic invertebrate consumers (shorebirds). Although previous studies in the same site revealed very high concentrations of Cd and Pb in some of the prey species of shorebirds and seabirds (bivalves and fishes), values found in birds for these two elements suggest no toxicological risk. Thus, exposure to toxic elements is not currently a threat to coastal bird populations, namely those facing apparent local declines in Guinea-Bissau, one of the most important non-breeding quarters for of West Africa. Still, Hg burdens were high in some species, deserving further monitoring.

No evidence of microplastic ingestion in emperor penguin chicks (Aptenodytes forsteri) from the Atka Bay colony (Dronning Maud Land, Antarctica)

Microplastic (<5 mm; MP) pollution has been an emerging threat for marine ecosystems around the globe with increasing evidence that even the world's most remote areas, including Antarctica, are no longer unaffected. Few studies however, have examined MP in Antarctic biota, and especially those from Antarctic regions with low human activity, meaning little is known about the extent to which biota are affected. The aim of this study was to investigate, for the first time, the occurrence of MP in the emperor penguin (Aptenodytes forsteri), the only penguin species breeding around Antarctica during the austral winter, and an endemic apex predator in the Southern Ocean. To assess MP ingestion, the gizzards of 41 emperor penguin chicks from Atka Bay colony (Dronning Maud Land, Antarctica), were dissected and analyzed for MP >500 μm using Attenuated Total Reflection Fourier-transform Infrared (ATR-FTIR) spectroscopy. A total of 85 putative particles, mostly in the shape of fibers (65.9 %), were sorted. However, none of the particles were identified as MP applying state-of-the-art methodology. Sorted fibers were further evidenced to originate from contamination during sample processing and analyses. We find that MP concentrations in the local food web of the Weddell Sea and Dronning Maud Land coastal and marginal sea-ice regions; the feeding grounds to chick-rearing emperor penguin adults, are currently at such low levels that no detectable biomagnification is occurring via trophic transfer. Being in contrast to MP studies on other Antarctic and sub-Antarctic penguin species, our comparative discussion including these studies, highlights the importance for standardized procedures for sampling, sample processing and analyses to obtain comparable results. We further discuss other stomach contents and their potential role for MP detection, as well as providing a baseline for the long-term monitoring of MP in apex predator species from this region.

Mercury and stable isotopes portray colony-specific foraging grounds in southern rockhopper penguins over the Patagonian Shelf

Mercury pollution is a serious global environmental issue and the characterization of its distribution and its driving forces should be urgently included in research agendas. We report unusually high mercury (Hg) concentrations (>5 μg/g) along with stable isotopes values in feathers of southern rockhopper penguins (Eudyptes chrysocome) from colonies in the Southwest Atlantic Ocean. We found a highly heterogenous prevalence of Hg throughout the study area and over a three-fold higher mean Hg concentration in southernmost colonies. Variation in Hg concentrations among colonies is primarily explained by site, rather than by trophic position. We provide further support to the existence of a Hg hotspot in the food web of the Patagonian Shelf and spatially restrict it to the southern tip of South America. Our findings highlight the need for regional and colony-based seabird conservation management when high local variability and plasticity in foraging habits is evident.

Mercury biomagnification in an Antarctic food web of the Antarctic Peninsula

Under the climate change context, warming Southern Ocean waters may allow mercury (Hg) to become more bioavailable to the Antarctic marine food web (i.e., ice-stored Hg release and higher methylation rates by microorganisms), whose biomagnification processes are poorly documented. Biomagnification of Hg in the food web of the Antarctic Peninsula, one of the world's fastest-warming regions, was examined using carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope ratios for estimating feeding habitat and trophic levels, respectively. The stable isotope signatures and total Hg (T-Hg) concentrations were measured in Antarctic krill Euphausia superba and several Antarctic predator species, including seabirds (gentoo penguins Pygoscelis papua, chinstrap penguins Pygoscelis antarcticus, brown skuas Stercorarius antarcticus, kelp gulls Larus dominicanus, southern giant petrels Macronectes giganteus) and marine mammals (southern elephant seals Mirounga leonina). Significant differences in δ¹³C values among species were noted with a great overlap between seabird species and M. leonina. As expected, significant differences in δ¹⁵N values among species were found due to interspecific variations in diet-related to their trophic position within the marine food web. The lowest Hg concentrations were registered in E. superba (0.007 ± 0.008 μg g^-1) and the highest values in M. giganteus (12.090 ± 14.177 μg g^-1). Additionally, a significant positive relationship was found between Hg concentrations and trophic levels (reflected by δ¹⁵N values), biomagnifying nearly 2 times its concentrations at each level. Our results support that trophic interaction is the major pathway for Hg biomagnification in Southern Ocean ecosystems and warn about an increase in the effects of Hg on long-lived (and high trophic level) Antarctic predators under climate change in the future.

Variation Among Species and Populations, and Carry-Over Effects of Winter Exposure on Mercury Accumulation in Small Petrels

Even in areas as remote as the Southern Ocean, marine organisms are exposed to contaminants that arrive through long-range atmospheric transport, such as mercury (Hg), a highly toxic metal. In previous studies in the Southern Ocean, inter-specific differences in Hg contamination in seabirds was generally related to their distribution and trophic position. However, the Blue Petrel (Halobaena caerulea) was a notable exception among small seabirds, with higher Hg levels than expected. In this study, we compared the Hg contamination of Blue Petrels and Thin-billed Prions (Pachyptila belcheri), which both spend the non-breeding season in polar waters, with that of Antarctic Prions (Pachyptila desolata), which spend the winter in subtropical waters. We collected body feathers and blood samples, representing exposure during different time-frames. Hg concentrations in feathers, which reflect contamination throughout the annual cycle, were related to δ13C values, and varied with ocean basin and species. Blue Petrels from breeding colonies in the southeast Pacific Ocean had much higher feather Hg concentrations than expected after accounting for latitude and their low trophic positions. Both Hg concentrations and δ15N in blood samples of Blue Petrels were much lower at the end than at the start of the breeding period, indicating a marked decline in Hg contamination and trophic positions, and the carry-over of Hg burdens between the wintering and breeding periods. Elevated Hg levels may reflect greater reliance on myctophids or foraging in sea-ice environments. Our study underlines that carry-over of Hg concentrations in prey consumed in winter may determine body Hg burdens well into the breeding season.

Mercury exposure driven by geographic and trophic factors in Magellanic penguins from Tierra del Fuego

Penguins accumulate mercury due to their long-life span together with their high trophic position. We sampled adult and juveniles' feathers from three colonies of Spheniscus magellanicus from Tierra del Fuego along an inshore-offshore corridor. We integrated toxicological information (mercury concentrations) and foraging biomarkers (δ¹³C, δ¹⁵N) into a common data analysis framework (isotopic niche analysis) to evaluate the influence of age, location, and foraging behaviors on mercury concentrations. Adults had higher feather mercury concentrations, δ¹³C, and δ¹⁵N values compared to juveniles. Also, adult and juvenile feather mercury concentrations differed between colonies, with lower mercury concentrations at the nearest inshore colony relative to the farther offshore colonies. Trophic position and the isotopic niche analyses suggest that this geographic gradient in mercury concentrations is due to differences in colonies' foraging areas. Understanding penguins' exposure to mercury derived from local food webs is a crucial first step in evaluating the impacts of this heavy metal on their conservation status.

Trace elements in Antarctic penguins and the potential role of guano as source of recycled metals in the Southern Ocean

Penguins dominate the Antarctic avifauna. As key animals in the Antarctic ecosystem, they are monitored to evaluate the ecological status of this pristine and remote region and specifically, they have been used as effective bioindicators suitable for long-term monitoring of metals in the Antarctic environment. However, studies about the role of this emblematic organism could play in the recycling of trace metals (TMs) in the Antarctic ecosystem are very limited. In this study we evaluate, using the peer review research articles already published and our own findings, the distribution of metals (i.e., Ca, Fe, Al, Na, Zn, Mg, Cu, K, Cd, Mn, Sr, Cr, Ni, Pb, Hg, V, Ba, Co, La, Ag, Rb, Hf, Sc, Au and Cs) and metalloids (As and Sb), measured in different biotic matrices, with emphasis on guano, of the Chinstrap (Pygoscelis antarcticus), Adélie (Pygoscelis adeliae) and Gentoo (Pygoscelis papua) penguins. Regarding bioactive metals, the high concentrations (μg g^-1 dry weight) of Cu (2.0 ± 1.4) x 10², Fe (4.1 ± 2.9) x 10², Mn (30 ± 34) and Zn (210 ± 90) reported in the guano from all the penguin species studied including our data, are of the same order of magnitude as those reported for whale feces (μg g^-1 dry weight): Cu (2.9 ± 2.4) x 10², Fe (1.5 ± 1.4) x 10², Mn (28 ± 17) and Zn (6.2 ± 4.3) x 10², and one order of magnitude higher than the metal contents in krill (μg g^-1 dry weight) of Cu (10.2 ± 5.5), Fe (24 ± 29) and Zn (13.5 ± 1.7). This suggest that penguin's excretion products could be an important source of these essential elements in the surface water, with an estimated annual release on a breeding season for Cu, Fe, Mn, Zn respectively of 28, 56, 4 and 29 tons, for the Chinstrap, Adélie and Gentoo penguins. The results provide evidence on the potential influence of penguins recycling TMs in the surface layer of the water column.

Mercury levels in humpback whales, and other Southern Ocean marine megafauna

Mercury is a known potent neurotoxin. The biogeochemical cycle of mercury in the remote Antarctic region is still poorly understood, with Polar climate change contributing added complexity. Longitudinal biomonitoring of mercury accumulation in Antarctic marine megafauna can contribute top-down insight into the bio-physical drivers of wildlife exposure. The bioaccumulative nature of organic mercury renders high trophic predators at the greatest risk of elevated exposure. Humpback whales represent secondary consumers of the Antarctic sea-ice ecosystem and an ideal biomonitoring species for persistent and bioaccumulative compounds due to their extended life-spans. This study provides the first results of mercury accumulation in humpback whales, and places findings within the context of mercury accumulation in both prey, as well as six other species of Antarctic marine megafauna. Combined, these findings contribute new baseline information regarding mercury exposure to Antarctic wildlife, and highlights methodological prerequisites for routine mercury biomonitoring in wildlife via non-lethally biopsied superficial tissues.

Trace elements and stable isotopes in penguin chicks and eggs: A baseline for monitoring the Ross Sea MPA and trophic transfer studies

Multi-tissue trace elements (TEs), C, N concentrations and stable isotopes (δ¹³C, δ¹⁵N) of chick carcasses and eggs of Adélie and Emperor penguins were studied to i) provide reference data before the recent institution of the Ross Sea Marine Protected Area (Antarctica), and ii) provide conversion factors that allow estimating C, N, δ¹³C and δ¹⁵N in edible tissues from non-edible ones, thus improving the use of stable isotopes in contamination and trophic transfer studies. Higher concentrations of As, Cd, Cr, Cu, Hg, Mn and Pb were found in chick carcasses than in eggs, suggesting increasing contamination in recent decades and high toxicity risks for penguin consumers. Isotopic conversion factors highlighted small differences among body tissues and conspecifics. These values suggest that chick carcasses are reliable indicators of the energy pathways underlying the two penguin species, their trophic position in the food web and their exposure to TEs.

Molecular response of a sub-antarctic population of the blue mussel (Mytilus edulis platensis) to a moderate thermal stress

The Kerguelen Islands (49°26'S, 69°50'E) represent a unique environment due to their geographical isolation, which protects them from anthropogenic pollution. The ability of the endemic mussel, part of the Mytilus complex, to cope with moderate heat stress was explored using omic tools. Transcripts involved in six major metabolic functions were selected and the qRT-PCR data indicated mainly changes in aerobic and anaerobic energy metabolism and stress response. Proteomic comparisons revealed a typical stress response pattern with cytoskeleton modifications and elements suggesting increased energy metabolism. Results also suggest conservation of protein homeostasis by the long-lasting presence of HSP while a general decrease in transcription is observed. The overall findings are consistent with an adaptive response to moderate stresses in mussels in good physiological condition, i.e. living in a low-impact site, and with the literature concerning this model species. Therefore, local blue mussels could be advantageously integrated into biomonitoring strategies, especially in the context of Global Change.

Trophic ecology drives trace element concentrations in the Antarctic octopod community

Despite the Antarctic Ocean being considered a pristine environment, elevated trace element concentrations have been reported in many marine organisms. The Antarctic Ocean is particularly vulnerable to climate change, which can also affect the bioaccumulation of trace element concentrations in biota. While Antarctic octopods are key components of the regional food webs as prey for a variety of predators (e.g., seals, fish, and seabirds), their contamination state by trace elements remains largely unknown. This study investigated the trace element concentrations in relation to the trophic ecology in Antarctic octopods. Stable isotope values (δ¹³C and δ¹⁵N) and trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were measured in eight different species (Adelieledone polymorpha, Pareledone aequipapillae, P. albimaculata, P. aurata, P. charcoti, P. cornuta, P. felix, and P. turqueti) sampled near Elephant Island, close to the Antarctic Peninsula. Stable isotopes of δ¹⁵N varied among species, with significant differences between A. polymorpha and P. aurata suggesting potential niche segregation. Trace element concentrations also differed among species and with sampling depth, which likely reflects their trophic ecology. The data presented in this study provides the first insight into the trace element concentrations for these endemic octopods in this vulnerable habitat and their stable isotope values.

Foraging ecology drives mercury contamination in chick gulls from the English Channel

Although mercury (Hg) occurs naturally, human activity is currently the greatest source of release and the ocean receives Hg inputs by rivers and atmospheric deposition. Seabirds including chicks serve as valuable bioindicators of Hg contamination, reflecting local contamination around the colony. This study investigates the ecological drivers (trophic position and foraging habitat) influencing Hg concentrations in blood and feathers of chicks of three sympatric marine gull species. Chicks were sampled between 2015 and 2017 in the Seine Estuary, one of the most Hg contaminated rivers in Europe, and in the Normand-Breton Gulf (the Chausey Islands), 200 km west, as a reference site with limited contaminant inputs. The trophic status of the chicks was evaluated based on the relative abundance of stable isotopes (δ¹³C, δ¹⁵N and δ³⁴S). There was a tight correlation between Hg concentrations, as well as the abundance of stable isotopes, in blood and feathers. Great black-backed gull had the highest blood Hg concentrations of the species (1.80 ± 0.92 μg⋅g^-1 dry weight (dw)); the Lesser black-backed gull had intermediate concentrations (0.61 ± 0.18 μg⋅g^-1 dw); and the European herring gull had the lowest (0.37 ± 0.26 μg⋅g^-1 dw). Individuals with the highest trophic position showed consistently the highest Hg concentrations. The positive relationship between Hg concentrations and the feeding habitat (marine vs terrestrial) indicated that the main source of Hg for gulls in the English Channel is marine prey. This exposure led to relatively high Hg concentrations in Great black-backed gull, which may produce toxic effects to individuals with potential consequences for their populations.

Influence of Species-Specific Feeding Ecology on Mercury Concentrations in Seabirds Breeding on the Chatham Islands, New Zealand

Mercury (Hg) is a toxic metal that accumulates in organisms and biomagnifies along food webs; hence, long-lived predators such as seabirds are at risk as a result of high Hg bioaccumulation. Seabirds have been widely used to monitor the contamination of marine ecosystems. In the present study, we investigated Hg concentrations in blood, muscle, and feathers of 7 procellariform seabirds breeding on the Chatham Islands, New Zealand. Using bulk and compound-specific stable isotope ratios of carbon and nitrogen as a proxy of trophic position and distribution, we also tested whether Hg contamination is related to the species-specific feeding ecology. Mercury exposure varied widely within the seabird community. The highest contaminated species, the Magenta petrel, had approximately 29 times more Hg in its blood than the broad-billed prion, and approximately 35 times more Hg in its feathers than the grey-backed storm petrel. Variations of Hg concentrations in blood and feathers were significantly and positively linked to feeding habitats and trophic position, highlighting the occurrence of efficient Hg biomagnification processes along the food web. Species and feeding habitats were the 2 main drivers of Hg exposure within the seabird community. The Pterodroma species had high blood and feather Hg concentrations, which can be caused by their specific physiology and/or because of their foraging behavior during the interbreeding period (i.e., from the Tasman Sea to the Humboldt Current system). These 2 threatened species are at risk of suffering detrimental effects from Hg contamination and further studies are required to investigate potential negative impacts, especially on their reproduction capability. Environ Toxicol Chem 2021;40:454-472. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Seabird droppings: Effects on a global and local level

Seabirds, with approximately 1 billion specimens, are the main exchangers of nutrients between Terrestial and Marine Systems and they have become an emerging interest group because of their effects on the planet's ecosystem. This review paper aims to highlight the impact of seabird droppings at different trophic levels, their occurrence, ecological risks and effects on soil, water, atmosphere and biota at global and local level to try to understand the ecological and climatic changes associated with the activities of these birds. Seabirds they have a very marked influence on the ecosystems where they form their colonies since, in addition to their function as predators, alongside with their depositions, they condition the primary producers and, consequently, the rest of the food chain. Their excrements contain large amounts of N, P and trace elements, most of which are bioavailable. In this study, besides bringing together the different works on nutrients and trace elements in excrements and differentiating some terms referring to these excrements, a brief historical overview of their importance for agriculture is made. In addition, the impacts produced by these birds on the ecosystem are also analysed according to two levels, at a global and local level. At each of these levels, a current state of the effects on the different compartments of the ecosystems is made, from the biota to the soils, the water or the atmosphere. This review supports the idea that more studies are needed both at the atmospheric level and in the terrestrial or marine environment for a better understanding of the changes these birds generate.

Trophic and fitness correlates of mercury and organochlorine compound residues in egg-laying Antarctic petrels

Understanding the drivers and effects of exposure to contaminants such as mercury (Hg) and organochlorine compounds (OCs) in Antarctic wildlife is still limited. Yet, Hg and OCs have known physiological and fitness effects in animals, with consequences on their populations. Here we measured total Hg (a proxy of methyl-Hg) in blood cells and feathers, and 12 OCs (seven polychlorinated biphenyls, PCBs, and five organochlorine pesticides, OCPs) in plasma of 30 breeding female Antarctic petrels Thalassoica antarctica from one of the largest colonies in Antarctica (Svarthamaren, Dronning Maud Land). This colony is declining and there is poor documentation on the potential role played by contaminants on individual physiology and fitness. Carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotope values measured in the females' blood cells and feathers served as proxies of their feeding ecology during the pre-laying (austral spring) and moulting (winter) periods, respectively. We document feather Hg concentrations (mean ± SD, 2.41 ± 0.83 μg g^-1 dry weight, dw) for the first time in this species. Blood cell Hg concentrations (1.38 ± 0.43 μg g^-1 dw) were almost twice as high as those reported in a recent study, and increased with pre-laying trophic position (blood cell δ¹⁵N). Moulting trophic ecology did not predict blood Hg concentrations. PCB concentrations were very low (Σ₇PCBs, 0.35 ± 0.31 ng g^-1 wet weight, ww). Among OCPs, HCB (1.02 ± 0.36 ng g^-1 ww) and p, p'-DDE (1.02 ± 1.49 ng g^-1 ww) residues were comparable to those of ecologically-similar polar seabirds, while Mirex residues (0.72 ± 0.35 ng g^-1 ww) were higher. PCB and OCP concentrations showed no clear relationship with pre-laying or moulting feeding ecology, indicating that other factors overcome dietary drivers. OC residues were inversely related to body condition, suggesting stronger release of OCs into the circulation of egg-laying females upon depletion of their lipid reserves. Egg volume, hatching success, chick body condition and survival were not related to maternal Hg or OC concentrations. Legacy contaminant exposure does not seem to represent a threat for the breeding fraction of this population over the short term. Yet, exposure to contaminants, especially Mirex, and other concurring environmental stressors should be monitored over the long-term in this declining population.

Mercury isotopes of key tissues document mercury metabolic processes in seabirds

Seabirds accumulate significant amounts of mercury (Hg) due to their long-life span together with their medium to high trophic position in marine food webs. Hg speciation and Hg isotopic analyses of total Hg in different tissues (pectoral muscles, liver, brain, kidneys, blood and feathers) were assessed to investigate their detoxification mechanisms. Three species with contrasted ecological characteristics were studied: the Antarctic prion (zooplankton feeder), the white-chinned petrel (pelagic generalist consumer) and the southern giant petrel (scavenger on seabirds and marine mammals). The difference of mass-dependent fractionation (MDF, δ²⁰²Hg) values between liver and muscles (up to 0.94 ‰) in all three seabirds strongly suggests hepatic demethylation of the isotopically lighter methylmercury (MeHg) and subsequent redistribution of the isotopically heavier fraction of MeHg towards the muscles. Similarly, higher δ²⁰²Hg values in feathers (up to 1.88 ‰) relative to muscles and higher proportion of MeHg in feathers (94-97%) than muscles (30-70%) likely indicate potential MeHg demethylation in muscle and preferential excretion of MeHg (isotopically heavier) in the growing feathers during moult. The extents of these key detoxification processes were strongly dependent on the species-specific detoxification strategies and levels of dietary MeHg exposure. We also found higher mass-independent fractionation (MIF, Δ¹⁹⁹Hg) values in feathers relative to internal tissues, possibly due to different integration times of Hg exposure between permanently active organs and inert tissues as feathers. Hg isotope variations reported in this study show evidence of detoxification processes in seabirds and propose a powerful approach for deep investigation of the Hg metabolic processes in seabirds.

Mercury exposure in an endangered seabird: long-term changes and relationships with trophic ecology and breeding success

Mercury (Hg) is an environmental contaminant which, at high concentrations, can negatively influence avian physiology and demography. Albatrosses (Diomedeidae) have higher Hg burdens than all other avian families. Here, we measure total Hg (THg) concentrations of body feathers from adult grey-headed albatrosses (Thalassarche chrysostoma) at South Georgia. Specifically, we (i) analyse temporal trends at South Georgia (1989-2013) and make comparisons with other breeding populations; (ii) identify factors driving variation in THg concentrations and (iii) examine relationships with breeding success. Mean ± s.d. feather THg concentrations were 13.0 ± 8.0 µg g^-1 dw, which represents a threefold increase over the past 25 years at South Georgia and is the highest recorded in the Thalassarche genus. Foraging habitat, inferred from stable isotope ratios of carbon (δ¹³C), significantly influenced THg concentrations-feathers moulted in Antarctic waters had far lower THg concentrations than those moulted in subantarctic or subtropical waters. THg concentrations also increased with trophic level (δ¹⁵N), reflecting the biomagnification process. There was limited support for the influence of sex, age and previous breeding outcome on feather THg concentrations. However, in males, Hg exposure was correlated with breeding outcome-failed birds had significantly higher feather THg concentrations than successful birds. These results provide key insights into the drivers and consequences of Hg exposure in this globally important albatross population.

Biological factors affecting total mercury and methylmercury levels in Antarctic penguins

Penguins in Antarctica occupy high trophic levels, thus accumulating high amounts of mercury (Hg) through bioaccumulation and biomagnification. Blood reflects the current levels of contaminants circulating in the body, while feathers are known as the main route of Hg elimination in birds. Studies sampling chicks and adults can provide a comprehensive picture of bioaccumulation and local contamination. Three pygoscelid species (Pygoscelis adeliae, Pygoscelis antarcticus and Pygoscelis papua) have circumpolar distributions being the ideal sentinels of Antarctic environmental pollution. This study aimed to assess Hg contamination of the pristine Antarctic region using non-destructive penguin samples. Fieldwork was carried out during the austral summer of 2013/2014 in the South Shetland Islands, off the north-west Antarctic Peninsula. Concentrations of total Hg (ng.g^-1 dw) in blood ranged from 39 to 182 in chicks and 45 to 581 in adults, while concentrations in feathers ranged from 73 to 598 in chicks and 156 to 1648 in adults. Most Hg in feathers (about 70%) is accumulated in the form of methylmercury. Differences were demonstrated in mercury bioaccumulation were related to species and age, but not to sex. To our knowledge this is the first study to report MeHg levels in both juvenile and adult pygoscelid penguins.

A "seabird-eye" on mercury stable isotopes and cycling in the Southern Ocean

Since mercury (Hg) biogeochemistry in the Southern Ocean is minimally documented, we investigated Hg stable isotopes in the blood of seabirds breeding at different latitudes in the Antarctic, Subantarctic and Subtropical zones. Hg isotopic composition was determined in adult penguins (5 species) and skua chicks (2 species) from Adélie Land (66°39'S, Antarctic) to Crozet (46°25'S, Subantarctic) and Amsterdam Island (37°47'S, Subtropical). Mass-dependent (MDF, δ²⁰²Hg) and mass-independent (MIF, Δ¹⁹⁹Hg) Hg isotopic values separated populations geographically. Antarctic seabirds exhibited lower δ²⁰²Hg values (-0.02 to 0.79 ‰, min-max) than Subantarctic (0.88 to 2.12 ‰) and Subtropical (1.44 to 2.37 ‰) seabirds. In contrast, Δ¹⁹⁹Hg values varied slightly from Antarctic (1.31 to 1.73 ‰) to Subtropical (1.69 to 2.04 ‰) waters. The extent of methylmercury (MeHg) photodemethylation extrapolated from Δ¹⁹⁹Hg values was not significantly different between locations, implying that most of the bioaccumulated MeHg was of mesopelagic origin. The larger increase of MDF between the three latitudes co-varies with MeHg concentrations. This supports an increasing effect of specific biogenic Hg pathways from Antarctic to Subtropical waters, such as Hg biological transformations and accumulations. This "biogenic effect" among different productive southern oceanic regions can also be related to different mixed layer depth dynamics and biological productivity turnover that specifically influence the vertical transport between the mesopelagic and the photic zones. This study shows the first Hg isotopic data of the Southern Ocean at large scale and reveals how regional Southern Ocean dynamics and productivity control marine MeHg biogeochemistry and the exposure of seabirds to Hg contamination.

Latitudinal, sex and inter-specific differences in mercury and other trace metal concentrations in Adélie and Emperor penguins in the Ross Sea, Antarctica

We sought to determine mercury (Hg) and other trace metal concentrations in Adélie (Pygoscelis adeliae) and emperor penguin (Aptenodytes forsteri) breast feathers from the Ross Sea, Antarctica, and relate those concentrations to the trophic position and the habitats in which each of these species forage. Adélie penguin feathers from the southern Ross Sea colonies were higher in Hg than those sampled further north in the Ross Sea, potentially due to greater exposure to local sources, such as volcanism. Female Adélie penguins had lower feather total Hg concentrations than males. This may reflect female penguin's capacity to eliminate Hg through the egg development and laying process, or the larger and/or older prey items that male birds can consume, reflected by their higher trophic position. Emperor penguins have higher Hg concentrations than Adélie penguins which is also partially explained by Adélie penguins feeding at lower trophic levels than emperor penguins.

Trace elements and persistent organic pollutants in chicks of 13 seabird species from Antarctica to the subtropics

Seabirds from remote regions are mainly exposed to environmental contaminants from non-point contamination of their food webs. Pre-fledging seabird chicks are fed by their parents with marine prey captured in the vicinity of breeding colonies. Contaminant concentrations in tissues of pre-fledging chicks can thus be mostly related to local dietary sources, and have the potential to unravel spatial patterns of environmental contamination in marine ecosystems. Here, mercury (Hg), 13 other trace elements, and 18 persistent organic pollutants (POPs) were quantified in blood of chicks across four breeding locations that encompass a large latitudinal range in the southern Indian Ocean (from Antarctica, through subantarctic areas, to the subtropics), over a single breeding season. Thirteen species of penguins, albatrosses and petrels were studied, including endangered and near-threatened species, such as Amsterdam albatrosses and emperor penguins. Blood Hg burdens varied widely between species, with a factor of ~50 between the lowest and highest concentrations (mean ± SD, 0.05 ± 0.01 and 2.66 ± 0.81 µg g^-1 dry weight, in thin-billed prions and Amsterdam albatrosses, respectively). Species relying on Antarctic waters for feeding had low Hg exposure. Concentrations of POPs were low in chicks, with the exception of hexachlorobenzene. Contaminant concentrations were mainly explained by species differences, but feeding habitat (inferred from δ¹³C values) and chicks' body mass also contributed to explain variation. Collectively, our findings call for further toxicological investigations in Amsterdam albatrosses and small petrel species, because they were exposed to high and diverse sources of contaminants, and in macaroni penguins, which specifically showed very high selenium concentrations. CAPSULE: Seabird chicks from four distant sites in the southern Indian Ocean had contrasted blood metallic and organic contaminant patterns depending on species, feeding habitat and body mass.

Body feather mercury and arsenic concentrations in five species of seabirds from the Falkland Islands

Several pollutants, including heavy metals, magnify along the food chain, and top predators such as seabirds can be used to monitor their trends in the marine environment. We studied mercury and arsenic contamination in body feathers in penguins, petrels and cormorants in three islands of the Falklands Islands. There were significant differences among species and sites in the concentration of trace elements in feathers. Black-browed albatrosses and gentoo penguins had consistently high mercury concentrations on New Island, while Rockhopper penguins and imperial shags presented considerably higher concentrations at Beauchene Island. Mercury levels in black-browed albatrosses increased since 1986 on one of the islands, probably reflecting world-wide emission trends. Rockhopper penguins exhibited high arsenic levels, but levels were less variable among species, and were not correlated with mercury levels, suggesting low biomagnification. These results provide a reference line for bioindication studies using feathers from species on the Falkland Islands.

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

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.

Using blood and feathers to investigate large-scale Hg contamination in Arctic seabirds: A review

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.

Temporal and interspecific variation in feather mercury in four penguin species from Macquarie Island, Australia

We measured mercury (Hg) concentrations in feathers from four penguin species collected on Macquarie Island, Southern Ocean, to 1) establish baseline Hg concentrations; and 2) compare Hg from samples collected in 2002 ("modern") and from museum specimens collected between 1937 and 1976 ("historic"). Inter-specific differences in feather Hg reflected known differences in habitats and diversity of diets: benthic-foraging Gentoo penguins and Rockhopper penguins that foraged both inshore and offshore had significantly higher feather mercury than the more pelagic, specialist foraging King and Royal penguins. Hg significantly decreased between historic and modern samples in King and Royal penguins. This decrease could be due to changes in either diet, foodwebs, or atmospheric Hg input and sources in the Southern Hemisphere. Because Macquarie Island is home to 2.8 million marine animals, these data may indicate that other species that forage and breed in this region are also exposed to low Hg concentrations in this environment.

Horizontal and vertical food web structure drives trace element trophic transfer in Terra Nova Bay, Antarctica

Despite a vast amount of literature has focused on trace element (TE) contamination in Antarctica during the last decades, the assessment of the main pathways driving TE transfer to the biota is still an overlooked issue. This limits the ability to predict how variations in sea-ice dynamics and productivity due to climate change will affect TE allocation in the food web. Here, food web structure of Tethys Bay (Terra Nova Bay, Ross Sea, Antarctica) was first characterised by analysing carbon and nitrogen stable isotopes (δ¹³C, δ¹⁵N) in organic matter sources (sediment and planktonic, benthic and sympagic primary producers) and consumers (zooplankton, benthic invertebrates, fish and birds). Diet and trophic position were also characterised using Bayesian mixing models. Then, relationships between stable isotopes, diet and TEs (Cd, Cr, Co, Cu, Hg, Ni, Pb and V) were assessed in order to evaluate if and how horizontal (organic matter pathways) and vertical (trophic position) food web features influence TE transfer to the biota. Regressions between log[TE] and δ¹³C revealed that the sympagic pathway drives accumulation of V in primary consumers and Cd and Hg in secondary consumers, and that a coupled benthic/pelagic pathway drives Pb transfer to all consumers. Regressions between log[TE] and δ¹⁵N showed that only Hg biomagnifies across trophic levels, while all the others TEs showed a biodilution pattern, consistent with patterns observed in temperate food webs. Although the Cd behavior needs further investigations, the present findings provide new insights about the role of basal sources in the transfer of TEs in polar systems. This is especially important nowadays in light of the forecasted trophic changes potentially resulting from climate change-induced modification of sea-ice dynamics.

The influence of global climate change on the environmental fate of anthropogenic pollution released from the permafrost: Part I. Case study of Antarctica

This article presents a review of information related to the influence of potential permafrost degradation on the environmental fate of chemical species which are released and stored, classified as potential influence in future Antarctic environment. Considering all data regarding climate change prediction, this topic may prove important issue for the future state of the Antarctic environment. A detailed survey on soil and permafrost data permitted the assumption that this medium may constitute a sink for organic and inorganic pollution (especially for persistent organic pollution, POPs, and heavy metals). The analysis of the environmental fate and potential consequences of the presence of pollutants for the existence of the Antarctic fauna leads to a conclusion that they may cause numerous negative effects (e.g. Endocrine disruptions, DNA damage, cancerogenicity). In the case of temperature increase and enhanced remobilisation processes, this effect may be even stronger, and may disturb natural balance in the environment. Therefore, regular research on the environmental fate of pollution is required, especially in terms of processes of remobilisation from the permafrost reserves.

Humboldt penguins' feathers as bioindicators of metal exposure

Avian feathers have the potential to accumulate trace elements originating from contaminated food and polluted environments. In fact, in feathers, metals bind to keratin, a sulphur-containing protein for which several metals have a strong affinity. Here, the concentrations of 18 essential and non-essential elements were investigated in a Humboldt penguin (Spheniscus humboldti) colony housed at the Acquario di Cattolica (Italy). This species is listed as vulnerable in the Red List of the International Union for Conservation of Nature. According to the literature, there is usually a link between metal levels in the diet of birds and levels detected in their feathers. Thus, metals were also determined in the penguins' food (capelin, Mallotus villosus). We hypothesize that the controlled conditions in which birds are kept in captivity, and the homogeneous diet that they follow could allow a better understanding of metal bioaccumulation (such as mercury) or bio-dilution (such as arsenic) in the marine food chain, indicated by penguins' feathers. Moreover, comparisons with our previous investigations performed on an ex-situ African penguin (Spheniscus demersus) colony suggest that penguins living indoors have lower body burden of metals than those living outdoors. Indeed, environmental contaminants usually found in areas subjected to anthropogenic impact, where zoos and aquaria are often located, are not accumulated to levels of concern.

Assessment of heavy metal contamination from penguins and anthropogenic activities on Fildes Peninsula and Ardley Island, Antarctic

Fildes Peninsula, with a high density of scientific stations, has been significantly impacted by anthropogenic activities. However, the contamination from penguins, a biovector that transports pollutants from ocean to land, has seldom been assessed. In this study, 32 lacustrine surface sediment samples on Fildes Peninsula and 8 lacustrine surface sediment samples on Ardley Island were collected to determine Cu, Zn, Pb, Ni, Cr, Cd, Co, Sb, Hg and P levels. The results showed that the heavy metal contents of lacustrine sediments on Ardley Island are significantly higher than those on Fildes Peninsula. The contaminants on Fildes Peninsula are mainly derived from anthropogenic activities, while the contaminants on Ardley Island are transported to the lacustrine sediments in the form of penguin guanos after a series of biomagnification in the food chain. The results indicated that the impact of penguin-transported contamination on Antarctic environment outweighs human activities near scientific stations in some areas. Therefore, more attention should be paid to the impacts of Antarctic animals on the Antarctic environment.

Mercury Exposure in Humboldt (Spheniscus humboldti) and Chinstrap (Pygoscelis antarcticus) Penguins Throughout the Chilean Coast and Antarctica

Penguins are reliable sentinels for environmental assessments of mercury (Hg) due to their longevity, abundance, high trophic level, and relatively small foraging areas. We analyzed Hg concentrations from blood and feathers of adult Humboldt penguins (Spheniscus humboldti) and feathers of chinstrap penguins (Pygoscelis antarcticus) from different reproductive colonies with variable degrees of urbanization and industrialization along the Chilean and Antarctic coasts. We evaluated Hg concentration differences between species, sexes (Humboldt penguins), and localities. Our results showed significantly greater levels in Humboldt penguins than in chinstrap penguins and nonsignificant differences between sexes among Humboldts. Penguin Hg concentrations showed a latitudinal pattern, with greater values of the metal at lower latitudes, independent of the species. Both studied penguin species showed elevated Hg concentrations compared to their congeners, highlighting the necessity to investigate potential negative effects on their populations. Although differences between species are possibly due to variation in diet and trophic level, our results suggest an important effect of the degree of Hg pollution adjacent to foraging areas. Further research on Hg content in prey species and environmental samples, together with a larger overall sample size, and investigation on penguin's diet and trophic level are needed to elucidate Hg bioavailability in each location and the role of local Hg pollution levels. Likewise, it is important to monitor Hg and other heavy metals of ecotoxicological importance in penguin populations in vulnerable regions of Chile.

Chinstrap penguin population genetic structure: one or more populations along the Southern Ocean?

Background

Historical factors, demography, reproduction and dispersal are crucial in determining the genetic structure of seabirds. In the Antarctic marine environment, penguins are a major component of the avian biomass, dominant predators and important bioindicators of ecological change. Populations of chinstrap penguins have decreased in nearly all their breeding sites, and their range is expanding throughout the Antarctic Peninsula. Population genetic structure of this species has been studied in some colonies, but not between breeding colonies in the Antarctic Peninsula or at the species’ easternmost breeding colony (Bouvetøya).

Results

Connectivity, sex-biased dispersal, diversity, genetic structure and demographic history were studied using 12 microsatellite loci and a mitochondrial DNA region (HVRI) in 12 breeding colonies in the South Shetland Islands (SSI) and the Western Antarctic Peninsula (WAP), and one previously unstudied sub-Antarctic island, 3600 km away from the WAP (Bouvetøya). High genetic diversity, evidence of female bias-dispersal and a sign of population expansion after the last glacial maximum around 10,000 mya were detected. Limited population genetic structure and lack of isolation by distance throughout the region were found, along with no differentiation between the WAP and Bouvetøya (overall microsatellite F_ST = 0.002, p = 0.273; mtDNA F_ST = − 0.004, p = 0.766), indicating long distance dispersal. Therefore, genetic assignment tests could not assign individuals to their population(s) of origin. The most differentiated location was Georges Point, one of the southernmost breeding colonies of this species in the WAP.

Conclusions

The subtle differentiation found may be explained by some combination of low natal philopatric behavior, high rates of dispersal and/or generally high mobility among colonies of chinstrap penguins compared to other Pygoscelis species.

Electronic supplementary material

The online version of this article (10.1186/s12862-018-1207-0) contains supplementary material, which is available to authorized users.

Identification of sources and bioaccumulation pathways of MeHg in subantarctic penguins: a stable isotopic investigation

Seabirds are widely used as bioindicators of mercury (Hg) contamination in marine ecosystems and the investigation of their foraging strategies is of key importance to better understand methylmercury (MeHg) exposure pathways and environmental sources within the different ecosystems. Here we report stable isotopic composition for both Hg mass-dependent (e.g. δ²⁰²Hg) and mass-independent (e.g. Δ¹⁹⁹Hg) fractionation (proxies of Hg sources and transformations), carbon (δ¹³C, proxy of foraging habitat) and nitrogen (δ¹⁵N, proxy of trophic position) in blood of four species of sympatric penguins breeding at the subantarctic Crozet Islands (Southern Indian Ocean). Penguins have species-specific foraging strategies, from coastal to oceanic waters and from benthic to pelagic dives, and feed on different prey. A progressive increase to heavier Hg isotopic composition (δ²⁰²Hg and Δ¹⁹⁹Hg, respectively) was observed from benthic (1.45 ± 0.12 and 1.41 ± 0.06‰) to epipelagic (1.93 ± 0.18 and 1.77 ± 0.13‰) penguins, indicating a benthic-pelagic gradient of MeHg sources close to Crozet Islands. The relative variations of MeHg concentration, δ²⁰²Hg and Δ¹⁹⁹Hg with pelagic penguins feeding in Polar Front circumpolar waters (1.66 ± 0.11 and 1.54 ± 0.06‰) support that different MeHg sources occur at large scales in Southern Ocean deep waters.

Seabird Tissues As Efficient Biomonitoring Tools for Hg Isotopic Investigations: Implications of Using Blood and Feathers from Chicks and Adults

Blood and feathers are the two most targeted avian tissues for environmental biomonitoring studies, with mercury (Hg) concentration in blood and body feathers reflecting short and long-term Hg exposure, respectively. In this work, we investigated how Hg isotopic composition (e.g., δ²⁰²Hg and Δ¹⁹⁹Hg) of blood and feathers from either seabird chicks (skuas, n = 40) or adults (penguins, n = 62) can accurately provide information on exposure to Hg in marine ecosystems. Our results indicate a strong correlation between blood and feather Hg isotopic values for skua chicks, with similar δ²⁰²Hg and Δ¹⁹⁹Hg values in the two tissues (mean difference: -0.01 ± 0.25 ‰ and -0.05 ± 0.12 ‰, respectively). Since blood and body feathers of chicks integrate the same temporal window of Hg exposure, this suggests that δ²⁰²Hg and Δ¹⁹⁹Hg values can be directly compared without any correction factors within and between avian groups. Conversely, penguin adults show higher δ²⁰²Hg and Δ¹⁹⁹Hg values in feathers than in blood (mean differences: 0.28 ± 0.19‰ and 0.25 ± 0.13‰), most likely due to tissue-specific Hg temporal integration. Since feathers integrate long-term (i.e., the intermoult period) Hg accumulation, whereas blood reflects short-term (i.e., seasonal) Hg exposure in adult birds, the two tissues provide complementary information on trophic ecology at different time scales.

Metals in Feathers of African Penguins (Spheniscus demersus): Considerations for the Welfare and Management of Seabirds Under Human Care

Bird feathers have been proven to be reliable indicators of metal exposure originating from contaminated food and polluted environments. The concentrations of 15 essential and non-essential metals were investigated in African penguins (Spheniscus demersus) feathers from a Northwestern Italian zoological facility. These birds are exclusively fed with herring from the northeast Atlantic Ocean. Certain elements, such as Hg and Cd, reflected the bioaccumulation phenomena that occur through the marine food chain. The levels of Cr, Mn, and Ni were comparable to those registered in feathers of birds living in polluted areas. These results are important for comparative studies regarding the health, nutrition and welfare of endangered seabirds kept under human care.

A Global Overview of Exposure Levels and Biological Effects of Trace Elements in Penguins

Trace elements are chemical contaminants that can be present almost anywhere on the planet. The study of trace elements in biotic matrices is a topic of great relevance for the implications that it can have on wildlife and human health. Penguins are very useful, since they live exclusively in the Southern Hemisphere and represent about 90% of the biomass of birds of the Southern Ocean. The levels of trace elements (dry weight) in different biotic matrices of penguins were reviewed here. Maps of trace element records in penguins were included. Data on exposure and effects of trace elements in penguins were collected from the literature. The most reported trace elements in penguins are aluminum, arsenic, cadmium, lead, mercury, copper, zinc, and manganese. Trace elements have been measured in 11 of the 18 species of penguins. The most studied biotic matrices are feathers and excreta. Most of the studies have been performed in Antarctica and subantarctic Islands. Little is known about the interaction among metals, which could provide better knowledge about certain mechanisms of detoxification in penguins. Future studies of trace elements in penguins must incorporate other metals such as vanadium, cobalt, nickel, and chromium. Data of metals in the species such as Eudyptes pachyrhynchus, Eudyptes moseleyi, Eudyptes sclateri, Eudyptes robustus, Eudyptes schlegeli, Spheniscus demersus, Spheniscus mendiculus, and Megadyptes antipodes are urged. It is important to correlate levels of metals in different biotic matrices with the effects on different species and in different geographic locations.

Pygoscelis antarcticus feathers as bioindicator of trace element risk in marine environments from Barton Peninsula, 25 de Mayo (King George) Island, Antarctica

We report the contents of elements in feathers of Chinstrap penguin (Pygoscelis antarcticus), which had not been informed up to now, such as silver and bromine and others listed as hazardous by the United States Environmental Protection Agency as arsenic, cobalt, chromium, and mercury. Analyses of the element concentrations in feathers, adult and chicken, from Barton Peninsulas at 25 de Mayo (King George) Island, South Shetlands, were made by Instrumental Neutron Activation Analysis. Samarium, lanthanum a, thorium, and uranium concentrations in Chinstrap penguin feathers were below 0.1 mg/kg. This suggests that the elements in feather do not come from atmospheric particles surface deposition. Arsenic (0.120 ± 0.050 mg/kg) and cobalt (0.030 ± 0.020 mg/kg) concentrations were lower than the reports for other colony of Chinstrap penguins, and essential elements as iron (26 ± 12 mg/kg), zinc (78.0 ± 5.3 mg/kg), and chromium (0.51 ± 0.27 mg/kg) were in the same range while Se (2.90 ± 0.65 mg/kg) content were the lowest reported. Mercury (0.43 ± 0.21 mg/kg), chromium (0.210 ± 0.060 mg/kg), and silver (0.083 ± 0.003 mg/kg) in chicks tended to be lower than in adults. Iron, cobalt, and arsenic concentrations in feathers found in this study were the lowest compared to measurements were in several penguin species in Antarctica. These results confirm to feathers like effective indicators for the trace elements incorporated in the penguins and it provide a data set which can adds to the baseline for bioindication studies using feathers.

Sexual and individual foraging segregation in Gentoo penguins Pygoscelis papua from the Southern Ocean during an abnormal winter

Knowledge about sexual segregation and gender-specific, or indeed individual specialization, in marine organisms has improved considerably in the past decade. In this context, we tested the "Intersexual Competition Hypothesis" for penguins by investigating the feeding ecology of Gentoo penguins during their austral winter non-breeding season. We considered this during unusual environmental conditions (i.e. the year 2009 had observations of high sea surface and air temperatures) in comparison with the long term average at Bird Island, South Georgia. Through conventional (i.e. stomach contents) and stable isotopic values from red blood cells, plasma and feathers of both male and female Gentoo penguins, we showed that there were significant differences between sexes, with males feeding mainly on fish (54% by mass) followed by crustaceans (38%) whereas females fed mainly on crustaceans (89% by mass) followed by fish (4%). Themisto gaudichaudii was the most important crustacean prey for males (64% by mass; 82% by number; 53% by frequency of occurrence) and females (63% by mass; 77% by number; 89% by frequency of occurrence), contrasting with all previous studies that found Antarctic krill Euphausia superba were generally the main prey. Stable isotopic data showed that, in terms of habitat use (based on δ 13C), there were significant differences in short-term carbon signatures between males and females (based on plasma and red blood cells), suggesting that both sexes explored different habitats, with females exploring more offshore pelagic waters and males feeding more in coastal benthic waters. Based on δ 15N, males fed on significantly higher trophic level than females (based on plasma and red blood cells), in agreement with our diet results., Thus, Gentoo penguins behave in a similar manner to other non-breeding penguins species (e.g. king, macaroni and rockhopper penguins), albeit at a smaller spatial scale (as they do not disperse as these other penguins do), in that they have a wider habitat and trophic niche during the Antarctic Winter (in comparison to Summer). We also detected individual specialization in feeding/trophic levels for each gender, with certain males feeding mainly on fish and certain females mainly on crustaceans, which may be driven the prevailing environmental conditions that lead individuals to search for alternative prey, and cause sexual diet segregation. Our results provide further information to help improve understanding about sexual segregation and individual specialization of marine organisms, while contributing valuable information on the winter diet for Antarctic monitoring programs and for modelling Antarctic marine food webs.

Mercury in the ecosystem of Admiralty Bay, King George Island, Antarctica: Occurrence and trophic distribution

Mercury (Hg) can reach the environment through natural and human-related sources, threatening ecosystems all over the planet due to its well known deleterious effects. Therefore, Antarctic trophic webs, despite being relatively isolated, are not exempt of its influence. To evaluate Hg concentrations in an Antarctic ecosystem, different tissues from 2 species of invertebrates, 2 of fish, 8 of birds, 4 of pinnipeds and at least 5 of vegetation were investigated (n=176). For animals, values ranged from 0.018 to 48.7μgg^-1 dw (whole Antarctic krill and Antarctic Fur Seal liver). They were generally correlated to trophic position (assessed by δ¹⁵N and δ¹³C) but also to cephalopods and myctophids consumption. For vegetation, values ranged from 0.014 to 0.227μgg^-1 dw (Colobanthus quitensis and an unidentified lichen), with lichens presenting significantly higher values than mosses, likely due to year-round exposure and absorption of animal derived organic matter, as hypothesized by literature.

Differing foraging strategies influence mercury (Hg) exposure in an Antarctic penguin community

Seabirds are ideal model organisms to track mercury (Hg) through marine food webs as they are long-lived, broadly distributed, and are susceptible to biomagnification due to foraging at relatively high trophic levels. However, using these species as biomonitors requires a solid understanding of the degree of species, sexual and age-specific variation in foraging behaviors which act to mediate their dietary exposure to Hg. We combined stomach content analysis along with Hg and stable isotope analyses of blood, feathers and common prey items to help explain inter and intra-specific patterns of dietary Hg exposure across three sympatric Pygoscelis penguin species commonly used as biomonitors of Hg availability in the Antarctic marine ecosystem. We found that penguin tissue Hg concentrations differed across species, between adults and juveniles, but not between sexes. While all three penguins species diets were dominated by Antarctic krill (Euphausia superba) and to a lesser extent fish, stable isotope based proxies of relative trophic level and krill consumption could not by itself sufficiently explain the observed patterns of inter and intra-specific variation in Hg. However, integrating isotopic approaches with stomach content analysis allowed us to identify the relatively higher risk of Hg exposure for penguins foraging on mesopelagic prey relative to congeners targeting epipelagic or benthic prey species. When possible, future seabird biomonitoring studies should seek to combine isotopic approaches with other, independent measures of foraging behavior to better account for the confounding effects of inter and intra-specific variation on dietary Hg exposure.