Mercury exposure and short-term consequences on physiology and reproduction in Antarctic petrels

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\u27s 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. Blood Hg concentrations in Antarctic petrels were driven by trophic position and were not related to short-term breeding output

Mercury exposure and short-term consequences on physiology and reproduction in Antarctic petrels

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\u27s 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

Seabirds reveal mercury distribution across the North Atlantic

Author contributionsC.A. and J.F. designed research; C.A., B. Moe, A.T., S.D., V.S.B., B. Merkel, J.Å., and J.F. performed research; C.A., B. Moe, M.B.-F., A.T., S.D., V.S.B., B. Merkel, J.Å., J.L., C.P.-P., and J.F. analyzed data; C.A., B.M., V.S.B., and J.F. sample and data collection, data coordination and management, statistical methodology; H.S. sample and data contribution and Data coordination and management; D.G., M.B.-F., F. Amélineau, F. Angelier, T.A.-N., O.C., S.C.-D., J.D., K.E., K.E.E., A.E., G.W.G., M.G., S.A.H., H.H.H., M.K.J., Y. Kolbeinsson, Y. Krasnov, M.L., J.L., S.-H.L., B.O., A.P., C.P.-P., T.K.R., G.H.S., P.M.T., T.L.T., and P.B. sample and data contribution; A.T., P.F. and S.D. sample and data contribution and statistical methodology; J.Å. statistical methodology; J.F. supervision; and C.A., B. Moe, H.S., D.G., A.T., S.D., V.S.B., B. Merkel, J.Å., F. Amélineau, F. Angelier, T.A.-N., O.C., S.C.-D., J.D., K.E., K.E.E., A.E., P.F., G.W.G., M.G., S.A.H., H.H.H., Y. Kolbeinsson, Y. Krasnov, S.-H.L., B.O., A.P., T.K.R., G.H.S., P.M.T., T.L.L., P.B., and J.F. wrote the paper.Peer reviewe

Mercury exposure in a large subantarctic avian community

International audienceMercury (Hg) contamination poses potential threats to ecosystems worldwide. In order to study Hg bioavailability in the poorly documented southern Indian Ocean, Hg exposure was investigated in the large avian community of Kerguelen Islands. Adults of 27 species (480 individuals) showed a wide range of feather Hg concentrations, from 0.4 ± 0.1 to 16.6 ± 3.8 µg g-1 dry weight in Wilson's storm petrels and wandering albatrosses, respectively. Hg concentrations increased roughly in the order crustacean- < fish- ≤ squid- ≤ carrion-consumers, confirming that diet, rather than taxonomy, is an important driver of avian Hg exposure. Adults presented higher Hg concentrations than chicks, due to a longer duration of exposure, with the only exception being the subantarctic skua, likely because of feeding habits' differences of the two age-classes in this species. High Hg concentrations were reported for three species of the poorly known gadfly petrels, which merit further investigation

Essential element (micro-nutrient) concentrations in 78 coastal to oceanic forage species sampled in the Bay of Biscay, Northeast Atlantic, between 2002 and 2008

The dataset contains the concentrations of 11 essential elements (micro-nutrients) analysed in whole bodies of 78 forage species sampled on the continental shelf or in the canyons of the Bay of Biscay, North-East Atlantic. The species encompass jellyfish, crustaceans, cephalopods, cartilaginous and bony fish from coastal to oceanic and deep-sea waters. The elements include two macro-minerals (nitrogen and phosphorous) and nine trace elements (arsenic, cobalt, chromium, copper, iron, manganese, nickel, selenium, and zinc). Most of the specimens were collected during the annual EVHOE fishery campaigns (“Evaluation Halieutique de l'Ouest de l'Europe”; https://doi.org/10.18142/8) conducted each autumn by the “Institut Français de Recherche pour l'Exploitation de la Mer” (Ifremer) on R/V Thalassa, between 2002 and 2008, by benthic trawling with marge vertical opening or by pelagic trawling. Some species were additionally sampled during the same period from opportunistic fishing boats. As far as possible, the size range of these forage species was selected to match published prey sizes for cetacean predators in the Bay of Biscay. All the material was frozen immediately after collection and kept at –20°C until being processed. In the laboratory, whole organisms were briefly thawed. To reduce inter-individual variability, few to hundreds of individuals (depending on the size of species) were grouped for each species (i.e. constitution of pools) and homogenized using a stainless-steel knife mill, carefully rinsed with ultrapure water between each sample. These pools of whole specimens (corresponding to analytical samples) were frozen again –20°C, freeze-dried and reduced into fine powder until further analyses. A total of 115 samples was finally analysed. The process of organisms and samples (brief thawing, homogenization, freeze-dried and reduction into powder) was done within a maximum of two years after at-sea collection, and the samples (powders) were stored in a clean and dry place until analyses. Total element analyses on samples were then all conducted at the same date (in 2016). Total nitrogen (N) concentrations were determined following the Kjeldahl method (AOAC, 1990). Briefly, this method consists in digesting the samples with sulfuric acid to transform all N present into ammonium sulfate. The solution is then alkalized and the resulting ammonia is determined by distillation into a known volume of boric acid, the excess of which (corresponding to the amount of nitrogen in samples) is finally determined by titration. For all other elements, aliquots of samples (~200 mg dry weight of homogenised powder) were digested using a 6:2 (v/v) mixture with nitric acid (HNO3 69%, Trace Metal Grade®, FisherScientific) and hydrochloric acid (HCl, 34%, Trace Metal Grade®, FisherScientific). Acidic digestion of the samples was performed overnight at room temperature and then in a microwave oven (START-D, Milestone). Total concentrations of the micro-mineral phosphorus (P) and of the essential trace elements arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), selenium (Se) and zinc (Zn) were determined by inductively coupled plasma atomic emission spectrometry (ICP-OES, Vista-Pro Varian) and/or mass spectrometry (ICP-MS, X Series 2 Thermofisher Scientific). The quality assurance of these elemental analyses relied on blank and internal standard controls, and on the accuracy and reproducibility of data relative to the certified reference materials (CRMs) used in each analytical run. The CRMs used were TORT-3 (lobster hepatopancreas, National Research Council of Canada/NRCC) and DOLT-4 (dogfish liver, NRCC). Blank values were systematically below the detection limits and CRM values concurred with certified concentrations, with recovery rates ranging between 83% and 116% depending on the elements and on the CRM. Limits of quantification (LOQ) were calculated for each sample, depending on the mass of the aliquot analysed. The few concentrations below LOQ were replaced by half of the LOQ for each sample of concern. Specifically, this concerned 19 and 2 samples out of the 115 analysed for Cr and Ni respectively, corresponding to about 15% of values (for Cr) or much less than 15% (for Ni), in which cases this method of replacing non-detects by half the LOQ may be applied for data analysis (U.S. Environmental Protection Agency, 2000). All elemental concentrations given on a dry weight basis can be converted on a wet weight basis according to the average percentages of moisture given for each species

Nutritional grouping of marine forage species reveals contrasted exposure of high trophic levels to essential micro‐nutrients

By transferring energy and nutrients from plankton to top predators, forage species play a major ecological role in marine food webs. While large differences in energy densities have been demonstrated among these species, other determinants of their quality remain poorly explored. We analysed 78 forage species from the Bay of Biscay, NE Atlantic, for their concentrations in various chemical elements with a documented biological role (i.e. micro-nutrients). Species encompassed jellyfish, crustaceans, cephalopods, cartilaginous and bony fish. Elements included two essential macro-minerals (nitrogen and phosphorous) and nine trace elements (arsenic (As), cobalt, copper (Cu), chromium, iron, manganese, nickel, selenium (Se), zinc). We showed a broad range of elemental composition values across forage species, partly driven by taxonomy (fish versus crustaceans/cephalopods) or their habitat (coastal versus oceanic, pelagic versus benthic). Some elements (As, Cu or Se) were more variable than others, especially in fish for Cu and Se. The 78 forage species were then classified by hierarchical clustering analysis (HCA) into different nutritional groups, based on their composition in eleven elements. Mean concentrations of each element in the diet of eight cetacean species was finally calculated, as well as the importance of each nutritional group (as defined by HCA including all elements) for each predator species. We revealed contrasting diets in terms of exposure to elements. Neritic common dolphins and harbour porpoises but also minke whales were thus mainly supplied by the Se-enriched nutritional group composed of small (pelagic) schooling fish (including sandeels, (horse) mackerel and also some Clupeids), while the diets of pilot whales or Risso's dolphins that mostly consume benthic cephalopods were clearly Cu-enriched. This study raises the issue of essential element composition as another determinant of food quality, and the risk associated with changes in forage species' availability for the proper functioning of marine food webs and ecosystems

Relationships between stable isotopes and trace element concentrations in the crocodilian community of French Guiana

International audienceTrace elements in the blood of crocodilians and the factors that influence their concentrations are overall poorly documented. However, determination of influencing factors is crucial to assess the relevance of caimans as bioindicators of environmental contamination, and potential toxicological impact of trace elements on these reptiles. In the present study, we determined the concentrations of 14 trace elements (Ag, As, Cd, Cr, Co, Cu, Fe, Hg, Pb, Mn, Ni, Se, V, and Zn) in the blood of four French Guiana caiman species (Spectacled Caiman Caiman crocodilus [n = 34], the Black Caiman Melanosuchus niger [n = 25], the Dwarf Caiman Paleosuchus palpebrosus [n = 5] and the Smooth-fronted Caiman Paleosuchus trigonatus [n = 20]) from 8 different sites, and further investigated the influence of individual body size and stable isotopes as proxies of foraging habitat and trophic position on trace element concentrations. Trophic position was identified to be an important factor influencing trace element concentrations in the four caiman species and explained interspecific variations. These findings highlight the need to consider trophic ecology when crocodilians are used as bioindicators of trace element contamination in environmental studies

Lead, mercury, and selenium alter physiological functions in wild caimans (Caiman crocodilus)

International audienceEnvironmental contaminants affect ecosystems worldwide and have deleterious effects on biota. Non-essentialmercury (Hg) and lead (Pb) concentrations are well documented in some taxa and are described to cause multipledetrimental effects on human and wildlife. Additionally, essential selenium (Se) is known to be toxic at highconcentrations but, at lower concentrations, Se can protect organisms against Hg toxicity. Crocodilians areknown to bioaccumulate contaminants. However, the effects of these contaminants on physiological processesremain poorly studied. In the present study, we quantified Hg, Pb and Se concentrations in spectacled caimans(Caiman crocodilus) and investigated the effects of these contaminants on several physiological processes linkedto osmoregulatory, hepatic, endocrine and renal functions measured through blood parameters in 23 individuals.Mercury was related to disruption of osmoregulation (sodium levels), hepatic function (alkaline phosphataselevels) and endocrine processes (corticosterone levels). Lead was related to disruption of hepatic functions(glucose and alanine aminotransferase levels). Selenium was not related to any parameters, but the Se:Hg molarratio was positively related to the Na+ and corticosterone concentrations, suggesting a potential protective effectagainst Hg toxicity. Overall, our results suggest that Hg and Pb alter physiological mechanisms in wild caimansand highlight the need to thoroughly investigate the consequences of trace element contamination incrocodilians