Diet shifts during egg laying: Implications for measuring contaminants in bird eggs

Winter Tracking Data Suggest that Migratory Seabirds Transport Per- and Polyfluoroalkyl Substances to Their Arctic Nesting Site

Seabirds are often considered sentinel species of marine ecosystems, and their blood and eggs utilized to monitor local environmental contaminations. Most seabirds breeding in the Arctic are migratory and thus are exposed to geographically distinct sources of contamination throughout the year, including per- and polyfluoroalkyl substances (PFAS). Despite the abundance and high toxicity of PFAS, little is known about whether blood concentrations at breeding sites reliably reflect local contamination or exposure in distant wintering areas. We tested this by combining movement tracking data and PFAS analysis (nine compounds) from the blood of prelaying black-legged kittiwakes (Rissa tridactyla) nesting in Arctic Norway (Svalbard). PFAS burden before egg laying varied with the latitude of the wintering area and was negatively associated with time upon return of individuals at the Arctic nesting site. Kittiwakes (n = 64) wintering farther south carried lighter burdens of shorter-chain perfluoroalkyl carboxylates (PFCAs, C9-C12) and heavier burdens of longer chain PFCAs (C13-C14) and perfluorooctanesulfonic acid compared to those wintering farther north. Thus, blood concentrations prior to egg laying still reflected the uptake during the previous wintering stage, suggesting that migratory seabirds can act as biovectors of PFAS to Arctic nesting sites.

Advancing exposure assessment approaches to improve wildlife risk assessment

The exposure assessment component of a Wildlife Ecological Risk Assessment aims to estimate the magnitude, frequency, and duration of exposure to a chemical or environmental contaminant, along with characteristics of the exposed population. This can be challenging in wildlife as there is often high uncertainty and error caused by broad-based, interspecific extrapolation and assumptions often because of a lack of data. Both the US Environmental Protection Agency (USEPA) and European Food Safety Authority (EFSA) have broadly directed exposure assessments to include estimates of the quantity (dose or concentration), frequency, and duration of exposure to a contaminant of interest while considering "all relevant factors." This ambiguity in the inclusion or exclusion of specific factors (e.g., individual and species-specific biology, diet, or proportion time in treated or contaminated area) can significantly influence the overall risk characterization. In this review, we identify four discrete categories of complexity that should be considered in an exposure assessment-chemical, environmental, organismal, and ecological. These may require more data, but a degree of inclusion at all stages of the risk assessment is critical to moving beyond screening-level methods that have a high degree of uncertainty and suffer from conservatism and a lack of realism. We demonstrate that there are many existing and emerging scientific tools and cross-cutting solutions for tackling exposure complexity. To foster greater application of these methods in wildlife exposure assessments, we present a new framework for risk assessors to construct an "exposure matrix." Using three case studies, we illustrate how the matrix can better inform, integrate, and more transparently communicate the important elements of complexity and realism in exposure assessments for wildlife. Modernizing wildlife exposure assessments is long overdue and will require improved collaboration, data sharing, application of standardized exposure scenarios, better communication of assumptions and uncertainty, and postregulatory tracking. Integr Environ Assess Manag 2024;20:674-698. © 2023 SETAC.

Mercury and methylmercury in birds and marine mammals inhabiting the coastal zone of the two King George Island's bays: Admiralty and King George Bay (maritime Antarctic)

The Antarctic is particularly sensitive to mercury (Hg) pollution and even low levels of Hg may cause significant damage in this fragile environment. The aim of this study was to investigate routes of mercury and methylmercury (MeHg) elimination by animals inhabiting the maritime Antarctic. The results showed that organisms at the highest trophic level (elephant seal) have the highest concentrations of THg and MeHg in both excrement and fur samples. Interspecies differences in mercury levels were observed in materials sourced from penguins of the genus Pysgocelis.¹³C and ¹⁵N values confirmed differences in the diets and foraging areas, which may affect Hg concentration in the tissues we analyzed. Time variations in THg and MeHg concentrations were observed in the excrement of the penguin species, which may be due to periods of fasting and intense feeding closely related to egg laying and moulting stages.

Long-term monitoring of exposure to toxic and essential metals and metalloids in the tawny owl (Strix aluco): Temporal trends and influence of spatial patterns

As a result of regulatory decisions, atmospheric deposition of most toxic metals and metalloids (MEs) has decreased in Europe over the past few decades. However, little is known about how this reduction translates into exposure at higher trophic levels in the terrestrial environment where temporal trends may be spatially heterogeneous due to local current or legacy sources of emissions (e.g., industry) or long-range transport of elements (e.g., marine transport). The aim of this study was to characterize temporal and spatial trends of exposure to MEs in terrestrial food webs using a predatory bird, the tawny owl Strix aluco, as a biomonitor. Toxic (Al, As, Cd, Hg, Pb) and essential/beneficial (B, Co, Cu, Mn, Se) elemental concentrations were measured in feathers of nest-captured females from 1986 to 2016, extending a previous study published over the time-series 1986-2005 (n = 1051), in a breeding population in Norway. A drastic decline over time was shown for the toxic MEs (-97 % for Pb, -89 % for Cd, -48 % for Al, and -43 % for As) except Hg. The beneficial elements B, Mn, and Se showed oscillations but an overall decline (-86 %, -34 %, and -12 %, respectively) whereas the essentials Co and Cu did not exhibit significant trends. The distance to potential sources of contamination influenced both the spatial patterns of concentrations in owl feathers and their temporal trends. The accumulation of As, Cd, Co, Mn and Pb was overall higher in the vicinity of sites recorded as polluted, and a greater temporal decrease of As, B, and Cd concentrations was found in the areas of further distance to polluted sites. The decrease of Pb concentrations was sharper further from the coast during the 1980s than in coastal areas, while the opposite was observed for Mn. The levels of Hg and Se were higher in coastal areas, and Hg temporal trends differed according to the distance to the coast. This study highlights the valuable insights provided by long-term survey of wildlife exposure to pollutants and landscape indicators to reveal regional or local patterns and detect unexpected events, data that are crucial for regulation and conservation of ecosystem health.

Advanced throughput analytical strategies for the comprehensive HRMS screening of organic micropollutants in eggs of different bird species

Raptors are ideal indicators for biomonitoring studies using wildlife in order to assess the environmental pollution in the terrestrial ecosystem, since they are placed in the highest trophic position in the food webs and their life expectancy is relatively long. In this study, 26 eggs of 4 bird species (Peregrine falcon, Eurasian curlew, Little owl and Eagle owl) collected in Germany, were investigated for the presence of persistent organic pollutants (POPs) and thousands of contaminants of emerging concern (CECs). Generic sample preparation protocols were followed for the extraction of the analytes and the purification of the extracts, and the samples were analyzed both by liquid (LC) and gas chromatography (GC) coupled to high resolution mass spectrometry (HRMS), for capturing a wide range of organic micropollutants with different physicochemical properties. State-of-the-art screening methodologies were applied in the acquired HRMS data, including wide-scope target analysis of 2448 known pollutants and suspect screening of over 65,000 environmentally relevant compounds. Overall, 58 pollutants from different chemical classes, such as plant protection products, per- and polyfluoroalkyl substances and medicinal products, as well as their transformation products, were determined through target analysis. Most of the detected compounds were lipophilic (logP>2), although the presence of (semi)polar contaminants should not be overlooked, underlying the need for holistic analytical approaches in environmental monitoring studies. p,p'-DDE, PCB 153 and PCB138, PFOS and methylparaben were the most frequently detected compounds. 50 additional substances were identified and semi-quantified through suspect screening workflows, including mainly compounds of industrial use with high production volume.

Bioaccumulation of Mercury and Radiocesium in Waterfowl Introduced to a Site with Legacy Contamination

Despite the propensity of waterfowl species to readily accumulate anthropogenic contaminants within polluted environments, few studies have examined bioaccumulation rates over time when entering such a contaminated site. We examined mercury (Hg) and radiocesium (¹³⁷ Cs) bioaccumulation over time in two waterfowl species released into a wetland system containing legacy contamination on the US Department of Energy's Savannah River Site in South Carolina. Released birds were collected at select time intervals over an exposure period of 94 days. We quantified total Hg concentrations in blood, muscle, and liver tissues, and ¹³⁷ Cs activity in whole-body and muscle tissues. The relationship between the contaminant burdens of different body tissue types was examined over time. Likely a result of microhabitat selection, mallards in our study readily accumulated both Hg and ¹³⁷ Cs at consistent rates over time within our study system, while ring-neck ducks did not. The findings demonstrated that whole blood can be used as a robust, nondestructive sampling alternative to estimate Hg burdens within muscle and liver, and whole-body ¹³⁷ Cs activity is a good predictor of muscle burdens. Understanding such bioaccumulation information in waterfowl is useful for the assessment of the potential health risk in wildlife, as well as being important for human risk assessment toward the consumption of popular game species. Environ Toxicol Chem 2022;41:2479-2487. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Continuing Persistence and Biomagnification of DDT and Metabolites in Northern Temperate Fruit Orchard Avian Food Chains

Dichlorodiphenyldichlorethane (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) (DDT) is an organochlorine insecticide that was widely used from the late 1940s to the 1970s in fruit orchards in the Okanagan valley, British Columbia, Canada, and in the process, contaminated American robin (Turdus migratorius) food chains with the parent compound and metabolite dichlorodiphenyldichloroethylene (1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene) (p,p'-DDE). In the present study, we examined the biological fate of these DDT-related (DDT-r) compounds at the same sites/region 26 years after a previous study by: (1) collecting soil, earthworms, and American robin eggs from apple, cherry, and pear orchards; (2) characterizing the diet and trophic positions of our biota using stable isotope analyses of δ¹³ C and δ¹⁵ N; and (3) estimating fugacity, biota-soil-accumulation factors (BSAFs), and biomagnification factors (BMFs). Mean p,p'-DDE concentrations (soil: 16.1 µg/g organic carbon-lipid equivalent; earthworms: 96.5 µg/g lipid equivalent; eggs: 568 µg/g lipid equivalent) revealed that contamination is present at elevated levels similar to the 1990s and our average soil DDE:DDT ratio of 1.42 confirmed that DDT is slowly degrading. American robins appeared to feed at similar trophic levels, but on different earthworms as indicated by egg stable isotope values (mean δ¹⁵ N = 8.51‰ ± 0.25; δ¹³ C = -26.32‰ ± 0.12). Lumbricidae and Aporrectodea worms shared a roughly similar δ¹⁵ N value; however, Lumbricus terrestris showed a markedly enriched δ¹³ C isotope, suggesting differences in organic matter consumption and physiological bioavailability. Biota-soil-accumulation factors and BMFs ranged over several orders of magnitude and were generally >1 and our fugacity analyses suggested that p,p'-DDE is still thermodynamically biomagnifying in American robin food chains. Our results demonstrate that DDT-r in fruit orchards remains bioavailable to free-living terrestrial passerines and may pose a potential toxicological risk. Environ Toxicol Chem 2021;40:3379-3391. © 2021 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Environment and Climate Change Canada.

Maternal transfer and occurrence of siloxanes, chlorinated paraffins, metals, PFAS and legacy POPs in herring gulls (Larus argentatus) of different urban influence

Urban herring gulls (Larus argentatus) are exposed to contaminants from aquatic, terrestrial and anthropogenic sources. We aim to assess if differences in urbanisation affect ecological niche and contaminant concentrations in female herring gulls. Furthermore, we investigated maternal transfer from mothers to eggs for all the target compounds, including chlorinated paraffins (CPs) and cyclic volatile methyl siloxane (cVMSs), which to our knowledge have not been assessed in herring gulls previously. We compare concentrations of legacy and emerging contaminants and metals in blood and eggs between two herring gull colonies located 51 km apart, in the urban influenced Norwegian Oslofjord. While both colonies are within an urbanised area, the inner fjord is more so, as it is surrounded by Oslo, the capital and largest city in Norway Stable isotopes of carbon and nitrogen indicated a more marine ecological niche in the outer than the inner fjord colony, although with overlap. Persistent organic pollutant (POP) concentrations were similar in the inner and outer fjord colonies, while the short-chained chlorinated paraffins (SCCP), which are recently added to the Stockholm convention and contaminants of emerging concern (CECs) varied, with higher concentrations of SCCP and the cVMS decamethylcyclopentasiloxane (D5) in females and eggs of the inner fjord colony. Per- and polyfluorinated substances (PFAS) concentrations were higher in the outer fjord colony, likely linked to releases from a point-source (airport and waste management facility with open access to food waste). In blood, chlorinated paraffins contributed most the total lipophilic contaminants (inner: 78%, outer: 56%), while polychlorinated biphenyls (PCBs) were the most abundant lipophilic contaminants in eggs (inner: 62%, outer: 46%). Dechloranes and brominated flame retardants (BFRs) were detected in few samples. Maternal transfer, assessed by egg to blood ratios, of cVMSs were similar to the POPs with mean log ratio 0.39 (D5), while it was lower for SCCPs, with log ratios-0.77. Our results indicate comparable POP exposure of the herring gulls in the inner and outer Oslofjord, likely due to overlap in ecological niches between the colonies and wide distribution of POPs. The differences between the colonies in concentrations of PFAS, cVMS and CPs shows that point source exposures and urban influence may be more important than ecological niche for these compounds.

Common Eider and Herring Gull as Contaminant Indicators of Different Ecological Niches of an Urban Fjord System

Seabirds like gulls are common indicators in contaminant monitoring. The herring gull (Larus argentatus) is a generalist with a broad range of dietary sources, possibly introducing a weakness in its representativeness of aquatic contamination. To investigate the herring gull as an indicator of contamination in an urban-influenced fjord, the Norwegian Oslofjord, we compared concentrations of a range of lipophilic and protein-associated organohalogen contaminants (OHCs), Hg, and dietary markers in blood (n = 15), and eggs (n = 15) between the herring gull and the strict marine-feeding common eider (Somateria mollissima) in the breeding period of May 2017. Dietary markers showed that the herring gull was less representative of the marine food web than the common eider. We found higher concentrations of lipophilic OHCs (wet weight and lipid weight) and Hg (dry weight) in the blood of common eider (mean ± SE ∑PCB = 210 ± 126 ng/g ww, 60 600 ± 28 300 ng/g lw; mean Hg = 4.94 ± 0.438 ng/g dw) than of the herring gull (mean ± SE ∑PCB = 19.0 ± 15.6 ng/g ww, 1210 ± 1510 ng/g lw; mean Hg = 4.26 ± 0.438 ng/g dw). Eggs gave opposite results; higher wet weight and lipid weight OHC concentrations in the herring gull (mean ± SE ∑PCB = 257 ± 203 ng/g ww, 3240 ± 2610 ng/g lw) than the common eider (mean ± SE ∑PCB = 18.2 ± 20.8 ng/g ww, 101 ± 121 ng/g lw), resulting in higher OHC maternal transfer ratios in gulls than eiders. We suggest that the matrix differences are due to fasting during incubation in the common eider. We suggest that in urban areas, herring gull might not be representative as an indicator of marine contamination but rather urban contaminant exposure. The common eider is a better indicator of marine pollution in the Oslofjord. The results are influenced by the matrix choice, as breeding strategy affects lipid dynamics regarding the transfer of lipids and contaminants to eggs and remobilization of contaminants from lipids to blood during incubation, when blood is drawn from the mother. Our results illustrate the benefit of a multispecies approach for a thorough picture of contaminant status in urban marine ecosystems. Integr Environ Assess Manag 2021;17:422-433. © 2020 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Yellow-legged gull eggs (Larus michahellis) as persistent organic pollutants and trace metal bioindicator for two nearby areas with different human impact

The concentration of different persistent organic pollutants (POPs including chlorinated and brominated compounds) and trace metals and metalloids (As, Cd, Cu, Cr, Pb, Hg, Ni, and Zn) was examined in eggs from two colonies of yellow-legged gulls. The two colonies are established in Ría de Vigo, Northwest Spain, with a distance between them of only 10 km, one in Vigo town (industrial and harbour activities) and the other in the Cíes Islands in a Natural Park and Marine Protected Area -MPA- (with no known anthropogenic inputs). Statistically significant differences for the two colonies were observed for Hg, the sum of 7 CBs, the sum of DDTs y and the sum of 9 PBDEs, with values that could be causing some toxic effects in the area of the most anthropogenically influenced colony. The estimated isotopic niche was also calculated, based on δ¹⁵N and δ¹³C, for the two colonies, pointing to a wider diet in the Cíes colony when compared to the diet in the Vigo colony. The study supports the use of the yellow-legged seagull eggs as a bioindicator of pollution capable of differentiating pollution level even in geographically close areas.

Spatio-temporal variation of metals and organic contaminants in bank voles (Myodes glareolus)

Environmental contamination with metals and organic compounds is of increasing concern for ecosystem and human health. Still, our knowledge about spatial distribution, temporal changes and ecotoxicological fate of metals and organic contaminants in wildlife is limited. We studied concentrations of 69 elements and 50 organic compounds in 300 bank voles (Myodes glareolus), Europe's most common mammal, sampled in spring and autumn 2017-2018 in five monitoring areas, representing three biogeographic regions. In addition, we compared measured concentrations with previous results from bank voles sampled within the same areas in 1995-1997 and 2001. In general, our results show regional differences, but no consistent patterns among contaminants and study areas. The exception was for the lowest concentrations of organic contaminants (e.g. perfluorooctane sulfonate, PFOS), which were generally found in the northern Swedish mountain area. Concentrations of metals and organic contaminants in adults varied seasonally with most organic contaminants being higher in spring; likely induced by diet shifts but potentially also related to age differences. In addition, metal concentrations varied between organs (liver vs. kidney), age classes (juveniles vs. adults; generally higher in adults) as well as between males and females. Concentrations of chromium and nickel in kidney and liver in the northernmost mountain area were lower in 2017-2018 than in 1995-1997 and in three of four areas, lead concentrations were lower in 2017-2018 than in 2001. Current metal concentrations (except mercury) are not expected to negatively affect the voles. Concentrations of hexachlorobenzene displayed highest concentrations in 2001 in the mountains, while it was close to detection limit in 2017-2018. Likewise, PFOS concentrations decreased in the mountains and in south-central lowland forests between 2001 and 2017-2018. Our results suggest that season, age class and sex need to be considered when designing and interpreting results from monitoring programs targeting inorganic and organic contaminants in wildlife.

Influence of overwinter distribution on exposure to persistent organic pollutants (POPs) in seabirds, ancient murrelets (Synthliboramphus antiquus), breeding on the Pacific coast of Canada

Assessing the fate of both legacy and newer persistent organic pollutants (POPs) is an ongoing challenge. Top predators, including seabirds, are effective monitors of POPs because they forage over a range of marine habitats, integrating signals over space and time. However, migration patterns can make unravelling contaminant sources, and potentially assessments of the effectiveness of regulations, challenging if chemicals are acquired at distant sites. In 2014, we fitted geolocators on ancient murrelets (Synthliboramphus antiqueus) at four colonies on the Pacific Coast of Canada to obtain movement data throughout an annual cycle. All birds underwent a post-breeding moult in the Bering Sea. Around one-third then returned to overwinter on the British Columbia (BC) coast while the rest migrated to overwinter in waters along the north Asian coast. Such a stark difference in migration destination provided an opportunity to examine the influence of wintering location on contaminant signals. In summer 2015, we collected blood samples from returned geo-tagged birds and analyzed them for a suite of contaminants, including polybrominated diphenyl ethers (PBDEs), non-PBDE halogenated flame retardants, perfluoroalkyl substances (PFASs), organochlorines, and mercury. Feathers were also collected and analyzed for stable isotopes (δ¹³C, δ¹⁵N, and δ³⁴S). We found no significant differences in blood concentrations of any contaminant between murrelets from the two different overwinter areas, a result that indicates relatively rapid clearance of POPs accumulated during winter. Spatial variation in diet (i.e., δ¹³C) was associated with both BDE-47 and -99 concentrations. However, individual variation in trophic level had little influence on concentrations of any other examined contaminants. Thus, blood from these murrelets is a good indicator of recent, local contaminants, as most signals appear independent of overwintering location.

Predation risk is a function of alternative prey availability rather than predator abundance in a tropical savanna woodland ecosystem

Typically, factors influencing predation risk are viewed only from the perspective of predators or prey populations but few studies have examined predation risk in the context of a food web. We tested two competing hypotheses regarding predation: (1) predation risk is dependent on predator density; and (2) predation risk is dependent on the availability of alternative prey sources. We use an empirical, multi-level, tropical food web (birds-lizards-invertebrates) and a mensurative experiment (seasonal fluctuations in abundance and artificial lizards to estimate predation risk) to test these hypotheses. Birds were responsible for the majority of attacks on artificial lizards and were more abundant in the wet season. Artificial lizards were attacked more frequently in the dry than the wet season despite a greater abundance of birds in the wet season. Lizard and invertebrate (alternative prey) abundances showed opposing trends; lizards were more abundant in the dry while invertebrates were more abundant in the wet season. Predatory birds attacked fewer lizards when invertebrate prey abundance was highest, and switched to lizard prey when invertebrate abundance reduced, and lizard abundance was greatest. Our study suggests predation risk is not predator density-dependent, but rather dependent on the abundance of invertebrate prey, supporting the alternative prey hypothesis.

Impact of flow diversion by run-of-river dams on American dipper diet and mercury exposure

Run-of-river dams produce lower greenhouse gas emissions than large hydropower projects, but there is a paucity of research on their potential ecotoxicological impacts through disruption of natural flow regimes. We used stable isotopes (δ¹³ C, δ¹⁵ N, δ³⁴ S) to reconstruct diet and trace methylmercury in a predatory river-resident passerine, the American dipper (Cinclus mexicanus), at 7 regulated and 6 free-flowing mountain streams in coastal British Columbia, Canada. Assimilated diets were comparable among regulated and unregulated streams, dominated by benthic macroinvertebrates and resident freshwater fish, with negligible contributions from anadromous Pacific salmon. Although invertebrates at unregulated streams were isotopically similar along their gradient, dippers and invertebrates sampled below dams on regulated streams had ³⁴ S-depleted tissues, suggesting increased activity of sulfate-reducing bacteria and more Hg methylation below the dams. Mercury concentrations in dipper blood (417.6 ± 74.1 standard error [SE] ng/g wet wt at regulated streams, 340.7 ± 42.7 SE ng/g wet wt at unregulated streams) and feathers (1564 .6 ± 367.2 SE ng/g dry wt regulated, 1149.0 ± 152.1 SE ng/g dry wt unregulated), however, were not significantly different between stream types. Relative to other passerines across western North America, dippers in these densely forested mountain streams experienced high mercury exposure; and one recently regulated stream supported dippers with mercury concentrations of potential toxicity concern (up to 8459.5 ng/g dry wt in feathers and 1824.6 ng/g wet wt in whole blood). Elevated mercury in dippers is likely attributable to the birds' relatively high trophic position and high regional inorganic mercury deposition; however, biogeochemical conditions in reservoirs of some regulated streams may be contributing to methylmercury production. Environ Toxicol Chem 2018;37:411-426. © 2017 SETAC.

Variation in organochlorine and mercury levels in first and replacement eggs of a single-egg clutch breeder, the thick-billed murre, at a breeding colony in the Canadian Arctic

Contaminant concentrations may vary among sequentially-laid eggs in multi-egg clutches, and this variation has implications for the interpretation of contaminant concentrations in monitoring programs. The thick-billed murre (Uria lomvia) is a key species for monitoring contaminants in the Canadian Arctic and lays only a single egg per year. Therefore, the potential issue of intra-clutch variation in contaminant concentrations is avoided. However, if the egg is removed or lost early in the incubation stage, the adult female murre will relay. In this study, we examined contaminant concentrations and patterns in first-laid and replacement eggs of thick-billed murres breeding in northern Hudson Bay in order to determine whether or not these eggs could be sampled interchangeably. Concentrations of the major legacy organochlorines (e.g. PCBs, DDT, chlordanes) were generally higher, and total mercury concentrations lower, in the replacement eggs compared with the first-laid eggs. The organochlorine profile was comprised primarily of ΣDDT and Σ₇₀PCB, and Σ₇₀PCB was comprised primarily of hexa-hepta PCBs in both first-laid and replacement eggs. As both concentrations and organochlorine patterns showed differences between first-laid and replacement eggs, we recommend that randomly selected first-laid eggs of thick-billed murres be consistently sampled for contaminant monitoring in the Canadian Arctic.

Egg-laying sequence influences egg mercury concentrations and egg size in three bird species: Implications for contaminant monitoring programs

Bird eggs are commonly used in contaminant monitoring programs and toxicological risk assessments, but intraclutch variation and sampling methodology could influence interpretability. The authors examined the influence of egg-laying sequence on egg mercury concentrations and burdens in American avocets, black-necked stilts, and Forster's terns. The average decline in mercury concentrations between the first and last eggs laid was 33% for stilts, 22% for terns, and 11% for avocets, and most of this decline occurred between the first and second eggs laid (24% for stilts, 18% for terns, and 9% for avocets). Trends in egg size with egg-laying order were inconsistent among species, and overall differences in egg volume, mass, length, and width were <3%. The authors summarized the literature, and among 17 species studied, mercury concentrations generally declined by 16% between the first and second eggs laid. Despite the strong effect of egg-laying sequence, most of the variance in egg mercury concentrations still occurred among clutches (75-91%) rather than within clutches (9%-25%). Using simulations, the authors determined that accurate estimation of a population's mean egg mercury concentration using only a single random egg from a subset of nests would require sampling >60 nests to represent a large population (10% accuracy) or ≥14 nests to represent a small colony that contained <100 nests (20% accuracy). Environ Toxicol Chem 2016;35:1458-1469. Published 2015 Wiley Periodicals Inc. on behalf of SETAC. This article is a US Government work and, as such, is in the public domain in the United States of America.

Tracking pan-continental trends in environmental contamination using sentinel raptors-what types of samples should we use?

Biomonitoring using birds of prey as sentinel species has been mooted as a way to evaluate the success of European Union directives that are designed to protect people and the environment across Europe from industrial contaminants and pesticides. No such pan-European evaluation currently exists. Coordination of such large scale monitoring would require harmonisation across multiple countries of the types of samples collected and analysed-matrices vary in the ease with which they can be collected and the information they provide. We report the first ever pan-European assessment of which raptor samples are collected across Europe and review their suitability for biomonitoring. Currently, some 182 monitoring programmes across 33 European countries collect a variety of raptor samples, and we discuss the relative merits of each for monitoring current priority and emerging compounds. Of the matrices collected, blood and liver are used most extensively for quantifying trends in recent and longer-term contaminant exposure, respectively. These matrices are potentially the most effective for pan-European biomonitoring but are not so widely and frequently collected as others. We found that failed eggs and feathers are the most widely collected samples. Because of this ubiquity, they may provide the best opportunities for widescale biomonitoring, although neither is suitable for all compounds. We advocate piloting pan-European monitoring of selected priority compounds using these matrices and developing read-across approaches to accommodate any effects that trophic pathway and species differences in accumulation may have on our ability to track environmental trends in contaminants.

Effect of laying sequence on egg mercury in captive zebra finches: an interpretation considering individual variation

Bird eggs are used widely as noninvasive bioindicators for environmental mercury availability. Previous studies, however, have found varying relationships between laying sequence and egg mercury concentrations. Some studies have reported that the mercury concentration was higher in first-laid eggs or declined across the laying sequence, whereas in other studies mercury concentration was not related to egg order. Approximately 300 eggs (61 clutches) were collected from captive zebra finches dosed throughout their reproductive lives with methylmercury (0.3 μg/g, 0.6 μg/g, 1.2 μg/g, or 2.4 μg/g wet wt in diet); the total mercury concentration (mean ± standard deviation [SD] dry wt basis) of their eggs was 7.03 ± 1.38 μg/g, 14.15 ± 2.52 μg/g, 26.85 ± 5.85 μg/g, and 49.76 ± 10.37 μg/g, respectively (equivalent to fresh wt egg mercury concentrations of 1.24 μg/g, 2.50 μg/g, 4.74 μg/g, and 8.79 μg/g). The authors observed a significant decrease in the mercury concentration of successive eggs when compared with the first egg and notable variation between clutches within treatments. The mercury level of individual females within and among treatments did not alter this relationship. Based on the results, sampling of a single egg in each clutch from any position in the laying sequence is sufficient for purposes of population risk assessment, but it is not recommended as a proxy for individual female exposure or as an estimate of average mercury level within the clutch.

A review on exposure and effects of arsenic in passerine birds

Arsenic (As) is a metalloid of high concern because of its toxic effects for plants and animals. However, it is hard to find information on this metalloid in passerines. This review presents a comprehensive overview of As exposure and effects in birds, and more particularly in passerines, as a result of an extensive search of the literature available. Internal tissues are the most frequently analyzed matrices for As determination in passerines (37.5% of the reviewed studies used internal tissues), followed by feathers and eggs (32.5% each), feces (27.5%), and finally blood (15%). A clear tendency is found in recent years to the use of non-destructive samples. Most studies on As concentrations in passerines have been done in great tit (Parus major; 50%), followed by pied flycatcher (Ficedula hypoleuca; 22.5%). Some factors such as diet and migratory status are crucial on the interspecific differences in As exposure. More studies are needed to elucidate if intraspecific factors like age or gender affect As concentrations in different tissues. The literature review shows that studies on As concentrations in passerines have been done mainly in the United States (30%), followed by Belgium (22.5%), and Finland (20%), making evident the scarce or even lack of information in some countries, so we recommend further research in order to overcome the data gap, particularly in the southern hemisphere. Studies on humans, laboratory animals and birds have found a wide range of effects on different organ systems when they are exposed to different forms of As. This review shows that few field studies on As exposure and effects in passerines have been done, and all of them are correlative so far. Arsenic manipulation experiments on passerines are recommended to explore the adverse effects of As in free-living populations at similar levels to those occurring in the environment.

CAPSULE

This review summarizes the most interesting published studies on As exposure and effects in passerines.

Tracking the sources of polybrominated diphenyl ethers in birds: foraging in waste management facilities results in higher DecaBDE exposure in males

Differences in feeding ecology are now recognized as major determinants of inter-individual variations in contaminant profiles of free-ranging animals, but exceedingly little attention has been devoted to the role of habitat use. Marked inter-individual variations and high levels of polybrominated diphenyl ethers (PBDEs) (e.g., DecaBDE) have previously been documented in ring-billed gulls (Larus delawarensis) breeding in a colony near Montreal (QC, Canada). However, the environmental sources of these compounds, and thus the reasons causing these large inter-individual variations remain unidentified. In the present study, we used GPS-based telemetry (±5 to 10m precision) to track ring-billed gulls from this colony to reconstruct their movements at the landscape level. We related habitat use of individual gulls (n=76) to plasma concentrations (ng/g ww) and relative contributions (percentages) to Σ38PBDEs of major congeners in the internationally restricted PentaBDE and current-use DecaBDE mixtures. Male gulls that visited waste management facilities (WMFs; i.e., landfills, wastewater treatment plants and related facilities; 25% of all GPS-tracked males) exhibited greater DecaBDE (concentrations and percentages) and lower PentaBDE (percentages) relative to those that did not. In contrast, no such relationships were found in females. Moreover, in males, DecaBDE (concentrations and percentages) increased with percentages of time spent in WMFs (i.e., ~5% of total foraging time), while PentaBDE (percentages) decreased. No relationships between percentages of time spent in other habitats (i.e., urban areas, agriculture fields, and St. Lawrence River) were found in either sex. These findings suggest that animals breeding in the vicinity of WMFs as well as mobile species that only use these sites for short stopovers to forage, could be at risk of enhanced DecaBDE exposure.

Brominated flame retardant trends in aquatic birds from the Salish Sea region of the west coast of North America, including a mini-review of recent trends in marine and estuarine birds

Polybrominated diphenyl ethers (PBDEs) increased in many matrices during the 1990s and early 2000s. Since voluntary restrictions and regulations on PBDEs were implemented in North America circa early 2000s, decreases in PBDEs have occurred in many of these same matrices. To examine temporal trends in the North Pacific, we retrospectively analysed PBDEs and eight non-PBDE flame retardants (FR) in eggs of two aquatic bird species, great blue herons, Ardea herodias, and double-crested cormorants, Phalacrocorax auritus, collected along the British Columbia coast, Canada from 1979 to 2012. Increasing PBDE concentrations were observed in both species followed by significant decreases post-2000 for all dominant congeners and ΣPBDE. Non-PBDE FRs were generally undetected in cormorant eggs, or detected at very low levels in heron eggs, except for hexabromocyclododecane (HBCDD). HBCDD, currently unregulated in North America, was not detected in early sampling years; however low concentrations were observed in both species in recent sampling years (2003-2012). Dietary tracers (δ(13)C and δ(15)N) did not change significantly over time, indicating that temporal changes in PBDEs are likely caused by implemented regulations. A comparison with recently published temporal trends of ΣPBDE in marine birds from North America and Europe is given.

Spatial and temporal trends in brominated flame retardants in seabirds from the Pacific coast of Canada

Polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD) are bioaccumulative flame retardants. PBDEs increased in many ecosystems during the late 20th century, but recently have declined in some environments. To examine trends in the northern Pacific, we analysed PBDEs, HBCDD and carbon and nitrogen stable isotopes (δ13C and δ15N) to account for dietary effects in archived eggs of three seabird species from British Columbia, Canada, 1990-2011 (rhinoceros auklets, Cerorhinca monocerata; Leach's storm-petrels, Oceanodroma leucorhoa; ancient murrelets, Synthliboramphus antiquus, 2009 only). PBDEs increased until approximately 2000 and then decreased, while HBCDD increased exponentially throughout the examined period. No significant changes in dietary tracers were observed. HBCDD and ΣPBDE levels varied among species; ΣPBDE also varied among sites. Temporal changes in contaminant concentrations are unlikely to have been caused by dietary changes, and likely reflect the build-up followed by decreases associated with voluntary phase-outs and regulations implemented in North America to control PBDEs.

Variation in riparian consumer diet composition and differential bioaccumulation by prey influence the risk of exposure to elements from a recently remediated fly ash spill

Emerging aquatic insects play a key role in transporting aquatic nutrients and contaminants to riparian consumers. However, little is known about how within- and between-year variation in the diet or patterns of element bioaccumulation in emerging insect taxa may influence the risk of exposure to wildlife. During 2 breeding seasons, the composition of the diet of tree swallows (Tachycineta bicolor) was examined at several colonies that were exposed to element contamination from a remediated coal fly ash spill to determine how variation in the diet influenced the risk of exposure to elements. The proportion of the diet that consisted of insects with an aquatic larval stage was positively related to concentrations of As, Fe, Se, and Tl in the samples. The proportion of the diet that consisted of Chironomidae (midges) was positively related to exposure to these elements at most colonies within and between years. Ephemeroptera (mayflies) contained higher concentrations of Se than midges, including 17 samples with concentrations of Se above 5 µg/g dry mass, the threshold of toxicological concern for birds. This was even the case at colonies several kilometers downstream from the spill. The results indicate that greater consideration should be given to the pattern of element bioaccumulation among different prey taxa and their relative importance in the diet to better assess the risk of contaminant exposure.

Comparing temporal trends of organochlorines in guillemot eggs and Baltic herring: advantages and disadvantage for selecting sentinel species for environmental monitoring

Within Europe, the Marine Strategy Framework Directive (MSFD) is aimed at addressing the chemical status and quality of the marine environment. One of the main goals is to achieve Good Environmental Status (GES) in the marine environment. Environmental monitoring of biota e.g., Baltic herring and guillemot eggs, is conducted annually in Sweden to follow temporal changes in environmental contaminants. To determine the suitability of guillemot eggs as a sentinel species for investigating GES, we compared temporal trends of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in these two species from single sampling sites within Sweden. Lipid content from guillemot eggs was consistently high and stable (yearly mean for >40 years, ∼12%) compared to that of herring (yearly mean for >20 years, ∼3%). A significant decreasing trend of ΣPCDD/F in TEQ WHO1998 was observed in guillemot eggs, but no trend was seen in herring. CB118 significantly decreased in both species, but in the last 10 years this decrease was not significant in herring. A number of advantages, such as high lipid content in the egg and a low coefficient of variation make guillemot suitable as a sentinel species. The advantages and disadvantages of using either guillemot eggs or Baltic herring are compared.

Residues of chromium, nickel, cadmium and lead in Rook Corvus frugilegus eggshells from urban and rural areas of Poland

We examined the concentrations of chromium (Cr), nickel (Ni), cadmium (Cd) and lead (Pb) in Rook Corvus frugilegus eggshells from 43 rookeries situated in rural and urban areas of western (=intensive agriculture) and eastern (=extensive agriculture) Poland. We found small ranges in the overall level of Cr (the difference between the extreme values was 1.8-fold; range of concentrations=5.21-9.40 Cr ppm), Ni (3.5-fold; 1.15-4.07 Ni ppm), and Cd (2.6-fold; 0.34-0.91 Cd ppm), whereas concentrations of Pb varied markedly, i.e. 6.7-fold between extreme values (1.71-11.53 Pb ppm). Eggshell levels of these four elements did not differ between rural rookeries from western and eastern Poland, but eggshells from rookeries in large/industrial cities had significantly higher concentrations of Cr, Ni and Pb than those from small towns and villages. Our study suggests that female Rooks exhibited an apparent variation in the intensity of trace metal bioaccumulation in their eggshells, that rapid site-dependent bioaccumulation of Cu, Cr, Ni and Pb occurs as a result of the pollution gradient (rural<urban), and that Cd levels are probably regulated physiologically, even though these were relatively high, which could be treated as an overall proxy of a heavy Cd load in the soil environment.

Mercury bioaccumulation in Southern Appalachian birds, assessed through feather concentrations

Mercury contamination in wildlife has rarely been studied in the Southern Appalachians despite high deposition rates in the region. From 2006 to 2008 we sampled feathers from 458 birds representing 32 species in the Southern Appalachians for total mercury and stable isotope δ (15)N. Mercury concentrations (mean ± SE) averaged 0.46 ± 0.02 μg g(-1) (range 0.01-3.74 μg g(-1)). Twelve of 32 species had individuals (7 % of all birds sampled) with mercury concentrations higher than 1 μg g(-1). Mercury concentrations were 17 % higher in juveniles compared to adults (n = 454). In adults, invertivores has higher mercury levels compared to omnivores. Mercury was highest at low-elevation sites near water, however mercury was detected in all birds, including those in the high elevations (1,000-2,000 m). Relative trophic position, calculated from δ (15)N, ranged from 2.13 to 4.87 across all birds. We fitted linear mixed-effects models to the data separately for juveniles and year-round resident adults. In adults, mercury concentrations were 2.4 times higher in invertivores compared to omnivores. Trophic position was the main effect explaining mercury levels in juveniles, with an estimated 0.18 ± 0.08 μg g(-1) increase in feather mercury for each one unit rise in trophic position. Our research demonstrates that mercury is biomagnifying in birds within this terrestrial mountainous system, and further research is warranted for animals foraging at higher trophic levels, particularly those associated with aquatic environments downslope from montane areas receiving high mercury deposition.

Equations for lipid normalization of carbon stable isotope ratios in aquatic bird eggs

Stable isotope ratios are biogeochemical tracers that can be used to determine the source of nutrients and contaminants in avian eggs. However, the interpretation of stable carbon ratios in lipid-rich eggs is complicated because (13)C is depleted in lipids. Variation in (13)C abundance can therefore be obscured by variation in percent lipids. Past attempts to establish an algebraic equation to correct carbon isotope ratios for lipid content in eggs have been unsuccessful, possibly because they relied partly on data from coastal or migratory species that may obtain egg lipids from different habitats than egg protein. We measured carbon, nitrogen and sulphur stable isotope ratios in 175 eggs from eight species of aquatic birds. Carbon, nitrogen and sulphur isotopes were enriched in lipid-extracted egg samples compared with non extracted egg samples. A logarithmic equation using the C∶N ratio and carbon isotope ratio from the non extracted egg tissue calculated 90% of the lipid-extracted carbon isotope ratios within ±0.5‰. Calculating separate equations for eggs laid by species in different habitats (pelagic, offshore and terrestrial-influenced) improved the fit. A logarithmic equation, rather than a linear equation as often used for muscle, was necessary to accurately correct for lipid content because the relatively high lipid content of eggs compared with muscle meant that a linear relationship did not accurately approximate the relationship between percent lipids and the C∶N ratio. Because lipid extraction alters sulphur and nitrogen isotope ratios (and cannot be corrected algebraically), we suggest that isotopic measurement on bulk tissue followed by algebraic lipid normalization of carbon stable isotope ratio is often a good solution for homogenated eggs, at least when it is not possible to complete separate chemical analyses for each isotope.

Persistent organic pollutant concentrations in fledglings of two arctic seabird species

Persistent organic pollutants (POPs) and stable isotopes were measured in muscle from fledglings of two arctic seabird species, Northern fulmar (Fulmarus glacialis) and Black-legged kittiwakes (Rissa tridactyla). The purpose was to compare POP concentrations between species, in an age class that is highly vulnerable to POPs but little studied, relate to diet using stable isotopes, and quantify differences across life stages (egg to adult). Northern fulmar fledglings had significantly higher POP concentrations than kittiwake, consistent with results reported for adults of these species. Surprisingly, carbon and nitrogen stable isotopes did not differ between species, which does not match data for, or the known feeding ecology, of the adults. Fulmar/kittiwake POP concentration ratios varied across life stages indicating variable POP exposure and accumulation with age in seabirds, indicating that of the use of avian species-specific thresholds should only be done with caution in ecosystem-based POP risk management.

Interspecific differences in egg production affect egg trace element concentrations after a coal fly ash spill

In oviparous vertebrates, trace elements transfer from mother to offspring during egg production. For animals that produce eggs slowly, like turtles, the trace element concentration of each egg reflects an integration of dietary and stored accumulation over the duration of vitellogenesis. Because turtles also produce eggs synchronously, all eggs within a clutch should exhibit uniform trace element concentrations. In contrast, for animals that produce eggs in sequence and primarily from current dietary resources, like many birds, the trace element concentrations of eggs should be less uniform within a clutch, and likely reflect short-term changes in dietary exposure. We tested the hypothesis that stinkpot turtle (Sternotherus odoratus) clutches exhibit lower variability and higher repeatability in barium, selenium, strontium, and thallium concentrations than those of tree swallows (Tachycineta bicolor) from a site impacted by a recent coal ash spill. All four trace elements exhibited significantly lower variability and significantly higher repeatability in stinkpot clutches than in swallow clutches. Mean trace element concentrations of stinkpot eggs were also significantly higher than those of swallow eggs although both species feed primarily on aquatic invertebrates. Variability in swallow egg trace element concentrations was partially due to significant laying order effects. Our results support the hypothesis that interspecific variation in the source of resources and in the synchronicity and rate of egg production can lead to interspecific differences in the variability of egg trace element concentrations.

Migration and opportunistic feeding increase PCB accumulation in Arctic seabirds

It is widely accepted that body concentrations of persistent organic pollutants (POPs) tend to increase with trophic level (TL). Yet, little attention has been paid to the causes in the underlying differences in POP body concentrations between species occupying similar TLs. In this paper we use two modeling approaches to quantify the importance of migration and opportunistic feeding, relative to that of trophic level, in explaining interspecific differences in polychlorinated biphenyl (PCB) body concentrations between 6 Arctic seabird species breeding in the Barents Sea: Little Auk (Alle alle), Black Guillemot (Cepphus grylle), Brünnich's Guillemot (Uria lomvia), Common Eider (Somateria mollissima), Black-legged Kittiwake (Rissa tridactyla), and Glaucous Gull (Larus hyperboreus). As a first approach, we use additive models to analyze two independent data sets (n = 470 and n = 726). We demonstrate that migration, opportunistic feeding, and TL significantly (p < 0.001) increase PCB body concentrations by a factor 3.61-4.10, 2.66-20.95, and 2.38-2.41, respectively. Our second approach, using a mechanistic bioaccumulation model, confirmed these positive effects on the body burdens but suggested lower effects of migration, opportunistic feeding, and TL (1.55, 2.39, and 2.38) than did our statistical analysis. These two independent approaches demonstrate that the effects of migration and opportunistic feeding on seabird body burdens can be similar to that of an increase of one TL and should therefore be accounted for in future analyses.

Spatial and temporal variation in the diet of tree swallows: implications for trace-element exposure after habitat remediation

Emerging aquatic insects play a key role in transporting aquatic contaminants into terrestrial ecosystems. Tree swallows are frequently the focus of studies examining this movement because they are thought to forage heavily on emerging aquatic insects when breeding in riparian areas. We examined the tree swallow diet to determine if trace elements from a recently remediated coal fly ash spill were moving into the terrestrial ecosystem. We collected bolus samples from adult tree swallows as they entered the nest box to feed their young. Despite strategically locating boxes in riparian areas, we found that the consumption of insects with an aquatic larval stage ranged from 28 to 75% of insects among colonies. We also found significant differences among colonies in the taxa found in bolus samples. Chironomidae (midges) were the primary emerging aquatic insects consumed by tree swallows, whereas Ephemeroptera were brought to nestlings infrequently. The consumption of insects with an aquatic larval stage, Chironomidae in particular, was positively correlated with exposure to trace elements from the spill. Bolus samples from the spill site contained greater concentrations of many trace elements compared with reference locations, but concentrations of most elements were lower than levels thought to cause reproductive impairment. These results support the hypothesis that emerging aquatic insects transport trace elements to terrestrial consumers and that Chironomidae play an important role in this movement. Our results also indicate that it is important to assess the composition of the diet and to not infer exposure to trace elements based on nesting location.

Eurasian dipper eggs indicate elevated organohalogenated contaminants in urban rivers

Many urban European streams are recovering from industrial, mining, and sewage pollution during the 20th century. However, associated recolonization by clean water organisms can potentially result in exposure to legacy or novel toxic pollutants that persist in the environment. Between 2008 and 2010, we sampled eggs of a river passerine, the Eurasian dipper (Cinclus cinclus), from 33 rivers in South Wales and the English borders (UK) which varied in catchment land use from rural to highly urbanized. Dipper egg δ(15)N and δ(13)C stable isotopes were enriched from urban rivers while δ(34)S was strongly depleted, effectively discriminating their urban or rural origins at thresholds of 10% urban land cover or 1000 people/km(2). Concentrations of total polychlorinated biphenyls (PCBs) and polybrominated biphenyl ethers (PBDEs) were positively related to urban land cover and human population density while legacy organochlorine pesticides such as p,p'-DDE, lindane, and hexachlorobenzene were found in higher concentrations at rural sites. Levels of PBDEs in urban dipper eggs (range of 136-9299 ng/g lw) were among the highest ever reported in passerines, and some egg contaminants were at or approaching levels sufficient for adverse effects on avian development. With the exception of dieldrin, our data shows PCBs and other organochlorine pesticides have remained stable or increased in the past 20 years in dipper eggs, despite discontinued use.

First report of chlorinated and brominated hydrocarbon pollutants in marine bird eggs from an oceanic Indian Ocean island

We report for the first time levels of persistent organic pollutants in marine bird eggs from an oceanic island in the Indian Ocean, the world's third largest ocean. Ten eggs each of the Common Noddy, also known as the Brown Noddy (Anous stolidus), and Sooty Tern (Sterna fuscata) were collected from Ile Cocos off the coast of the island of Rodrigues, located 560 km east of the island of Mauritius. ΣPCBs had the highest levels (2.2 and 2.6n g/g wm, wet mass; 20 and 19 ng/g lm, lipid mass) for common Noddy and Sooty Tern, respectively (and following), then ΣDDT (1.9 and 3.1 ng/g wm; 17 and 23 ng/g lm), and mirex (0.96 and 0.69 ng/g wm; 8.7 and 5.0 ng/gl m). ΣChlordanes (0.094 and 0.15 ng/g wm; 0.48 and 0.73 ng/g lm) and Σtoxaphenes (0.26 and 0.61 ng/g wm; 2.4 and 5.9 ng/g lm) are rare data for these compounds from this ocean. Brominated flame retardants were low (0.08 and 0.07 ng/g wm; 0.7 and 0.7 ng/g lm). Multivariate analyses indicated different contamination patterns in the prey items as Sooty Terns had significantly higher levels of mean Σchlordanes and Σtoxaphenes, as well as CB105, -108 and -157. p,p'-DDE had an association with thinner eggshells in the Sooty Tern. Although the contaminant levels were in all respects low, industrialisation, development on the periphery, commercial exploitation of the marine environment, and pollutants transferred over long distances by marine debris is likely to add to chemical pressure in this region. Monitoring changes in background levels of pollutants in remote regions will indicate such trends, and marine bird eggs from Rodrigues would be an excellent site.

Factors influencing legacy pollutant accumulation in alpine osprey: biology, topography, or melting glaciers?

Persistent organic pollutants (POPs) can be transported long distances and deposited into alpine environments via cold trapping and snow scavenging processes. Here we examined biotic and abiotic factors determining contaminant variability of wildlife in alpine ecosystems. We measured POPs in eggs and plasma of an apex predator, the osprey (Pandion haliaetus) breeding in 15 mountainous watersheds across a broad latitudinal, longitudinal and altitudinal range in western Canada. After accounting for proximate biotic factors such as trophic level (δ(15)N) and carbon source (δ(13)C), variability in contaminant concentrations, including ΣDDT (sum of trichlorodiphenylethane-related compounds), toxaphene, hexachlorobenzene (HCB), total chlordane, and ΣPCBs (polychlorinated biphenyls) in osprey tissues was explained by interactions among relative size of watersheds, water bodies, elevation, and glacial input. ΣDDT in nestling plasma, for example, decreased with lake elevation, probably as a result of local past inputs from agricultural or public health usage at lower altitude sites. In contrast, toxaphene, never used as an insecticide in western Canada, increased with elevation and year-round snow and ice cover in both plasma and eggs, indicating long-range atmospheric sources as dominant for toxaphene. Lower chlorinated PCBs in plasma tended to decrease with elevation and ice cover consistent with published data and model outcomes. Temporal trends of POPs in osprey eggs are coincident with some modeled predictions of release from melting glaciers due to climate change. Currently we suggest that contaminants largely are released through annual snowpack melt and deposited in large lower elevation lakes, or some smaller lakes with poor drainage. Our study highlights the importance of understanding how biological processes integrate physical when studying the environmental chemistry of wildlife.

Influence of landscape composition and diversity on contaminant flux in terrestrial food webs: a case study of trace metal transfer to European blackbirds Turdus merula

Although understanding the influence of the spatial arrangement of habitats and interacting communities on the processes of pollutant flux and impacts is critical for exposure and risk assessment, to date few studies have been devoted to this emergent topic. We tested the hypothesis that landscape composition and diversity affect the transfer of trace metals to vertebrates. Bioaccumulation of Cd and Pb in blood and feathers of European blackbirds Turdus merula (n=138) was studied over a smelter-impacted area (Northern France). Landscape composition (type and occurrence of the different habitats) and diversity (number of different habitat types and the proportional area distribution among habitat types) were computed around bird capture locations. Diet composition and contamination were assessed. No sex-related differences were detected, while age-related patterns were found: yearlings showed a sharper increase of tissue residues along the pollution gradient than older birds. Factors determining bird exposure acted at nested spatial scale. On a broad scale, environmental contamination mainly influenced metal levels in blackbirds, tissue residues increasing with soil contamination. At a finer grain, landscape composition and soil properties (pH, organic matter, clay) influenced metal transfer, while no influence of landscape diversity was detected. Landscape composition better explained metal transfer than soil properties did. Diet composition varied according to landscape composition, but diet diversity was not influenced by landscape diversity. Surprisingly, metal accumulation in some insect taxa was as high as in earthworms (known as hyper-accumulators). Results strongly suggested that variations in diet composition were the drivers through which landscape composition influenced metal transfer to blackbirds. This study shows that landscape features can affect pollutant transfer in food webs, partly through ecological processes related to spatial and foraging behavior of birds, and brings evidences underpinning the need to better consider landscape in environmental risk assessment and management of contaminated lands.

Organohalogen exposure in a Eurasian Eagle owl (Bubo bubo) population from Southeastern Spain: temporal-spatial trends and risk assessment

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and organochlorine insecticides (OCs) were analysed in 58 Eurasian Eagle owl (Bubo bubo) unhatched eggs collected between 2004 and 2009 in Southeastern Spain. Levels of p,p'-DDE were found to be higher than in eggs laid by other European owls in the same decade, probably due to the greater agricultural activity in our study area. Compared to other European raptors, exposure to PCBs can be considered intermediate, but low to PBDEs. Land use differences and prey availability were the rationale to divide the study area in two subareas in further assessments. Temporal trends of HCB, p,p'-DDE, β-HCH, PCBs and PBDEs were significantly different in each subarea, generally increasing over time in the Southern but decreasing or remaining stable in the Northern. On the contrary, levels of cyclodienes tended to decrease in both subareas. Dietary shifts with a greater amount of birds are suggested as a cause for increasing organochlorine loads in raptors. This may explain the increasing trend in the Southern territories. However, due to the proximity of most of these nests to Cartagena, an important industrial city, increasing environmental pollution cannot be ruled out. Although average levels of the compounds analysed are below threshold levels, 17% of the samples exceeded 400 pg g(-1)ww (wet weight), the LOAEC for Total TEQs. Moreover, a negative correlation between TEQ concentrations and the metabolizable fraction of PCBs (F(prob)=0.0018) was found when TEQs values were above 10 pg g(-1)ww. This could be indicative of hepatic enzymes induction in the birds exposed at higher concentrations, which are mainly breeding in the Southern subarea. These females could be suffering from Ah-receptor-related toxic effects, some of which have been related to altered bird reproduction. Finally, a significant negative correlation between p,p'-DDE levels and eggshell thickness (r=-0.469, p<0.001) was observed, with about 17% of eggshell thinning for eggs with p,p'-DDE levels above 100 μg g(-1)lw. The persistence of this degree of thinning over a period of time has been related to population declines in other raptor species.

Pattern of mercury allocation into egg components is independent of dietary exposure in Gentoo penguins

Avian eggs have become one of the most common means of evaluating mercury contamination in aquatic and marine environments and can serve as reliable indicators of dietary mercury exposure. We investigated patterns of mercury deposition into the major components of penguin eggs (shell, membrane, albumen, and yolk) using the Gentoo penguin (Pygoscelis papua) as a model species. Eggs were collected from both wild and captive populations of Gentoo penguins to compare the allocation of mercury into individual egg components of birds feeding at disparate trophic positions as inferred by stable isotope analysis. Mercury concentrations in captive penguins were an order of magnitude higher than in wild birds, presumably because the former were fed only fish at a higher trophic position relative to wild penguins that fed on a diet of 72-93% krill (Euphausia spp.). Similar to previous studies, we found the majority of total egg mercury sequestered in the albumen (92%) followed by the yolk (6.7%) with the lowest amounts in the shell (0.9%) and membrane (0.4%). Regardless of dietary exposure, mercury concentrations in yolk and membrane, and to a lesser degree shell, increased with increasing albumen mercury (used as a proxy for whole-egg mercury), indicating that any component, in the absence of others, may be suitable for monitoring changes in dietary mercury. Because accessibility of egg tissues in the wild varies, the establishment of consistent relationships among egg components will facilitate comparisons with any other study using eggs to assess dietary exposure to mercury.

American dippers indicate contaminant biotransport by Pacific salmon

Migrating salmon can increase productivity in Pacific Northwestern streams and lakes through the deposition of nutrients from their decomposing carcasses after spawning. Several studies also report simultaneous biotransport of persistent organic pollutants that have contaminated lake food webs, although no similar effect has been shown conclusively in rivers. We tested the prediction that salmon enhance contaminants in river food webs using the American dipper (Cinclus mexicanus), an aquatic songbird and a recognized indicator of stream quality. Over 3 years, we analyzed 29 dipper eggs and aquatic invertebrate samples from 14 different rivers in 10 catchments in southern British Columbia, Canada to assess whether variations in autumn spawning density of Pacific salmon were reflected in dipper egg contamination or stable carbon and nitrogen isotopes. δ(13)C isotope signatures, but not δ(15)N, in aquatic invertebrates and dipper eggs increased among catchments in proportion to the average density of spawning salmon. Concentrations of brominated flame retardants (PBDEs), dichlorodiphenyltrichloroethane metabolites (DDTs), and chlordane compounds were related in part to the δ(13)C measure of salmon density, but mercury, chlorobenzenes, and polychlorinated biphenyls (PCBs) were explained better by dipper trophic level. We conclude that spawning Pacific salmon result in the increased availability of salmon fry as dipper prey and salmon are a significant source of PBDEs, DDTs, and chlordanes to river ecosystems. However, contrary to lake studies, postspawn concentrations of legacy PCBs in river birds, even in salmon-rich rivers, were not significantly higher than would be expected from atmospheric deposition alone. We recommend using δ(13)C isotopes to trace salmon-derived lipids which may persist over winter particularly in rivers, and are potentially a better reflection of lipophilic contaminant transfer.

Cadmium accumulation in small mammals: species traits, soil properties, and spatial habitat use

In this study, the impact of species-specific spatial habitat use, diet preferences, and soil concentrations and properties on the accumulation of cadmium in small mammals was investigated. The results show that for the wood mouse (Apodemus sylvaticus), a mobile species with a large range in diet composition, accumulation of cadmium was not related to local soil concentrations or soil properties, but to diet preferences. For the common vole (Microtus arvalis), a nonmobile, specific feeding species, accumulation of cadmium was related to local soil concentrations or properties. For the bank vole (Myodes glareolus), a species with a smaller home range than the wood mouse but a broader diet spectrum than the common vole, both local soil properties and diet appeared to affect the cadmium accumulation in the kidneys. The results of this field study show that species-specific traits of small mammals are important determinants of accumulation of cadmium on a local scale. For site-specific assessment of risks of contaminants, such information is essential in order to understand exposure dynamics.

Local to continental influences on nutrient and contaminant sources to river birds

Stable isotope and contaminant analyses revealed differences in nutrient sources and contaminant pathways in two species of dipper, Cinclus mexicanus and Cinclus cinclus in western Canada and western Britain. We collected dipper prey and eggs from relatively pristine British Columbian rivers contrasting in the presence of salmon-derived nutrients, and rural Welsh rivers with varying food-web complexity associated with stream acidity. Enriched delta(13)C and to a lesser extent delta(15)N in American dipper eggs and prey confirmed that streams with migrating Pacific salmon were enriched with marine-derived nutrients, but overall contaminant concentrations did not differ strongly in dipper eggs between rivers with and without salmon. However dipper contaminant profiles, particularly PBDEs, mercury and SigmaDDTs, were related to delta(13)C, reflecting the marine influence and greater fish consumption at salmon sites. Irrespective of catchment influences and despite feeding at a higher trophic level, American dipper eggs (n = 17) contained lower levels of organohalogens than Eurasian dippers (n = 37), but with similar PCB (153 and 138) and PBDE (47 and 99) congeners dominanating. Eurasian dipper eggs from circumneutral streams contained more dieldrin, SigmaDDT and Sigmahexachlorocyclohexanes while Sigmachlordanes, mirex, SigmaPBDEs and SigmaPCBs predominated at acid sites. Our data reveal how dippers indicate contaminant levels and sources under contrasting conditions at scales ranging from local to intercontinental, but local environmental conditions apparently alter feeding ecology and exposure pathways even in these closely related species.