G9 (I) Mercury exposure in wildlife

Seasonal woodland pools are at tremendous risk due to habitat degradation and loss. Current conservation measures for this habitat type focus on protection from loss, however, non-point source pollution (such as mercury (Hg)) and disease are emerging concerns. This interdisciplinary research characterized the chemical environment of pool water, litter, and sediment to 2 cm depth in four short-hydroperiod (inundated three to nine weeks) seasonal woodland pools in Acadia National Park (ANP), Maine, USA, during April-June 2008 and upon October refill to determine (1) the rate of Hg bioaccumulation by developing wood frogs (Lithobates sylvaticus), (2) influences of surrounding landscape, seasonal hydrology, and pool water chemistry on Hg burdens in wood frog embryos and tadpoles, and (3) potential for transport into the terrestrial food chain through metamorph emigration from pools. We chose pools in regions of ANP with different landscape features and contrasting burn histories. There were no strong temporal patterns in upland and wetland litter total Hg (THg), however, THg in sediment was greatest at pool dry down in June. Upon October refill, THg in pool water in the unburned region equaled or exceeded June concentrations, whereas, THg in pool water in the burned region was at concentrations measured at April ice-out. Total Hg concentrations measured in wood frog embryos collected within 1-2 weeks of egg deposition (mid-April) were near or below detection limits (<0.2 ng; 0-0.49 ppb, wet weight(ww)). Concentrations increased to 17.1-54.2 ppb ww in tadpoles at final collection in early to mid-June when pools were nearly dry. At that time methyl Hg (MeHg) comprised 7.2-42.0% of THg in wood frog tadpoles, comparable to the proportion of THg that was MeHg in 2-3 year old green frog (L. clamitans) and bullfrog (L. catesbeiana) tadpoles collected in permanent water bodies in nearby watersheds (Bank et al. 2007), indicating rapid Hg uptake in wood frogs. Water collected from pools surrounded by softwoods had lower pH and greater THg and dissolved organic carbon than water from pools in hardwood settings. Total Hg concentrations in tadpoles, however, did not clearly reflect pool conditions or landscape setting. The relatively rapid bioaccumulation of THg in the developing larvae indicates that wood frog metamorphs could be potential vectors of Hg from wetlands to terrestrial food webs.

Birds can be efficient biovector transport agents between ecosystems (e.g., through feather molting), but to date little is known on the contribution of each ecosystem in explaining variations in mercury (Hg) concentrations within and among species. The objective of this study was to test whether migration explains variations in Hg concentrations observed in migratory fish-eating birds. Two migratory piscivorous bird species, the double-crested cormorant (Phalacrocorax auritus; short migrant) and the Caspian tern (Hydroprogne caspia; long migrant) were caught during the breeding season in Lake Ontario (Laurentian Great Lakes) and feathers grown during the winter were collected to analyze for total Hg and stable carbon (d¹³C), nitrogen (d¹⁵N) and hydrogen (dD) isotopes. Results indicate that a proportion of individuals had higher total Hg concentrations than the adverse effect threshold for adult piscivorous birds with concentrations ranging from 1.6 to 165 µg · g^-1 fresh weight. Isotopic values were highly variable with dD ranging from -83 to 105‰, d¹³C ranging from -29.4 to -8.7‰, and d¹⁵N ranging from 8.8 to 21.1‰ which indicates high intra- and inter-specific migration patterns and Hg exposure. Stable hydrogen isotope was the best predictor of total Hg and strong positive relationships were found for both species and this suggests that i)- Hg is readily bioavailable in southern locations or ii)- that Hg affects vital processes which can alter isotopic fractionation of hydrogen. High total Hg values were associated with high d¹³C values (marine habitats) and dD values (southern habitats) suggesting elevated Hg accumulation in those habitats. No clear relationship was observed between total Hg and d¹⁵N suggesting that input of anthropogenic nitrogen or trophic level are not significant factors affecting Hg accumulation in this context. Location where breeding occurred partly explained Hg levels in wintering grounds and this suggests a carry-over effect from breeding grounds. Alternatively, it suggests that migratory connectivity between breeding and wintering habitats is strong. This research project allowed understanding the effect of migration on Hg concentration in aquatic birds and the importance of biovector transport of Hg through birds.

The double-crested cormorant (Phalacrocorax auritus) is a piscivorous waterbird with a broad distribution throughout North America. Each spring, large populations from the Gulf of Mexico and Lower Mississippi Valley return to Lake Winnipeg and the Laurentian Great Lakes to breed. Eggs and moulted feathers often serve as mercury sinks; therefore adult cormorants may serve as long-distance mercury vectors, depending on differential accumulation from marine, freshwater, or aquaculture-based diets on the wintering grounds. By combining isotopic and contaminant data on individuals, sources and consequences of contaminant loads can be interpreted. Multiple stable isotope ratios (d³⁴S, d¹⁵N, d¹³C and dD) and total mercury (THg) concentrations were measured in winter- and summer-grown primary feathers collected from cormorants breeding on Lake Winnipeg, Manitoba, in 2009 and 2010. Sulphur (d³⁴S), nitrogen (d¹⁵N) and carbon (d¹³C) stable isotopes were used to characterize diet and sources of THg exposure. Correlations between feather isotopes and long-term weighted average precipitation dD were used to assign feathers to Lake Winnipeg, the Gulf Coast region, or stopover sites. Mercury concentrations in feathers were then compared according to diet type and growth location. Population-level d³⁴S, d¹⁵N, and d¹³C results indicate an increased propensity to feed on freshwater rather than marine or aquaculture foods, with no significant difference in feather THg concentrations between the three diet types. However, feathers assigned to northern breeding sites (dD) have significantly higher THg concentrations than those grown in the Gulf Coast region. This suggests adult cormorants nesting on Lake Winnipeg are accumulating higher levels of THg from their summer, rather than winter, diets.

Seabirds have been used as biomonitors of environmental contamination, they are the top of the marine food chain, accumulating highest levels of pollutants, such as heavy metals. The feathers are archives of heavy metal exposures in birds - during the feathers´ growth the organism excrete contaminants accumulated in tissues. The feathers allow non-destructive sampling and permit retrospective study then they are particularly convenient for monitoring contamination in marine environment.. Mercury are heavy metal suffer smaller exogenous influence in their levels when feathers are analyzed; then the results indicate primarily due to endogenous deposition. This study compares mercury concentrations in feathers of adults Skuas (Catharacta maccormicki and C. lonnbergi) from Keller Peninsula (62^o05’S-58⁰24’W), Potter Cove (62^o16’S-58^o37’W) and Cierva Point (64^o09’S-60^o57’W) in Antarctic Peninsula with the objective to verify the influence of species and location in the contamination levels. All mercury levels in breast feathers were analyzed in the “Radioisotopes Laboratory Eduardo Penna Franca” at UFRJ. Mean mercury concentrations ranged from 1.85 to 3.95ppm. Concentration in C. maccormicki was significantly higher than in C. lonnbergi (U´=306.00; p=0.0012), but the concentration in different places not differ significantly (KW=0.6547, p=0.7208 for C. maccormicki; U´=16.00, p=0.1905 for C. lonnbergi). Since these birds are migratory, the contamination observed doesn’t represent only local exposures. Although these birds had similar feeding habits during summer, a detailed winter feeding habits is unknown. This might be the key to understand the differences in mercury levels observed. Mercury levels recorded in adult feathers are representative of the total exposure of the individual during the year (migratory and breeding periods). To differentiate between local and global contamination it’s necessary to analyze and to compare mercury levels in chicks and young birds with the levels recorded in adults. The young bird feathers probably will represent local contamination, while adults feathers may represent the total exposure that the birds are subjected during the whole year. Future work is necessary in order to investigate the influence of other factors in heavy metal accumulation; with the inclusion of the young birds in this study.

Acknowledgements:
National Council for Scientific and Technological Development (CNPq/MCT: 557049/2009-1), Brazilian Antarctic Program (PROANTAR), Rio de Janeiro State Foundation of Support for Research (FAPERJ) and Mount Sinai School of Medicine (Fogarty - NIH ITREOH). Instituto Antartico Argentino for their financial and logistical support.

It is evident that heavy metals released in the environment affect the reproductive processes and fertility of animals. Toxic metals affect the male and female reproductive system directly or indirectly. Mercury is used in agriculture as fungicide, in medicine as topical antiseptic and disinfectant and in chemistry as an intermediate in the production of other mercury compounds. The present study was planned to investigate the effect of mercuric chloride on enzymatic and non-enzymatic antioxidants in the testis and epididymis of adult albino rats. Adult male albino rats were administered mercuric chloride at two different doses, 1mg and 2 mg/kg body weight, orally, daily for 45 days. At the end of the experimental period the animals were sacrificed, testis and the epididymis were removed. Antioxidant enzymes like catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase and glutathione-s-transferase were estimated in the testis and epididymis extract. Lipid peroxidation, hydrogen peroxide, vitamin C and vitamin E were also estimated. Mercuric chloride administration had no effect on the body weight of the animals but the weight of the testis and epididymis was decreased. Almost all the antioxidant enzymes studied were markedly diminished in the testis and epididymis of mercuric chloride treated animals. The non-enzymatic antioxidants vitamin C and vitamin E were also decreased. The lipid peroxidation and hydrogen peroxide were significantly increased. However, the influence was found to be more in 2mg treated when compared to 1mg mercuric chloride treated rats. The present study suggests the reproductive toxicity of mercury by inducing the oxidative stress in the testis and epididymis and possible interference in sperm production and further maturational processes.

Antarctica is one of the most remote regions on our planet and has no known point sources of mercury contamination. These characteristics make it an excellent location for investigating long-range mercury transport and atmospheric deposition. At present, the bioavailability of mercury in coastal and pelagic marine food webs surrounding the Antarctic Peninsula (AP) is not well understood and research is often limited to a few seabird breeding colonies throughout this large region. The purpose of the present study was to evaluate spatial trends in mercury availability in the Southern Ocean surrounding the Antarctic Peninsula using Pygoscelis penguins as biomonitors. In the Antarctic, penguins can serve as excellent biomonitors as they forage at a moderate trophic level, have a long lifespan and permanent ecological niche, breed in large colonies of hundreds to thousands of nesting pairs, and have previously been shown to accumulate biologically relevant concentrations of mercury. Eggshells from three species of Pygoscelis penguins (P. adeliae, P.papua, and P. antarctica) have been collected annually over the past six years across the AP as part of on-going investigations into penguin diets and foraging habits. Stable isotope analysis of eggshells collected in 2006 has provided evidence of geographic and interspecific differences in dietary composition and foraging habits among species; this study found that Adélie penguin (P. adeliae) eggshells from the eastern AP, South Shetlands, and South Orkneys shared similar isotopic signatures while those in the western AP had significantly lower d¹⁵N and d¹³C values. To investigate whether this geographic disparity in dietary composition and foraging habits has led to regional differences in the risk of exposure to mercury, we analyzed mercury in egg membranes collected from Pygoscelis penguins from 23 breeding colonies along the eastern and western AP, South Shetland Islands, and South Orkneys in 2006. Preliminary analyses suggest that dietary exposure to mercury in the Southern Ocean surrounding the Antarctic Peninsula may be uniform as no differences in mercury were detected in Adélie penguin egg membrane among breeding colonies. Analyses into interspecific differences and annual trends of mercury availability in this region are ongoing as a means to better characterize the deposition of this pollutant in an ostensibly remote ecosystem.

Common terns (Sterna hirundo, COTE) are a species of concern in the St. Lawrence River system. Given that the River also has many Areas of Concern (AOC) with elevated contaminants, our goal was to survey contaminant burdens in COTE adults and juveniles and assess exposure. We investigated the relationship between diet (stable carbon (d13C) and nitrogen (d15N) isotopes) and mercury (Hg) bioaccumulation in three COTE colonies along a 150-km transect of the St. Lawrence River. The foraging range of the colony furthest downstream includes two Areas of Concern (AOC), while the two upstream colonies are more removed from known point sources of Hg. We also sampled winter- and summer- grown breast feathers to compare diet and Hg exposure on the terns’ breeding ground vs. the terns’ wintering grounds. Terns were sampled twice: upon arrival to the breeding grounds to collect ‘winter’ breast feathers, and just prior to hatching the same individuals were re-trapped to sample regrown ‘summer’ breast feathers. The results of this study will assist regional managers in evaluating the effectiveness of the AOC recovery plan in relation to key migratory piscivorous bird species.