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S11 Ecotoxicology of mercury

Monday, 25 July, 2011

MS11-P1 — 11:00-12:00 and 17:30-18:30
EXTRACORPOREAL EXCRETION OF MERCURY FROM MICE AND GOLDFISH BY MOLYBDENUM COMPLEX
Authors: AIKOH, Hiromi1, FUKUYAMA, Yuki2, MIYAI, Yuuki2, SHIBAHARA, Takashi2
(1) Department of Zoology, Okayama University of Science,, aikoh@zool.ous.ac.jp; (2) Department of Chemistry, Okayama University of Science, Ridai-cho, Okayama 700-0005, Japan;

We reported that incomplete cubane-type sulfur-bridged nitrilotriacetato molybdenum(IV) complex [Mo3S4(Hnta)3]2-, referred to as NTA complex, reacted quickly with mercury to give intensively colored product, which was used for spectrophotometric determination of mercury1). Also, we reported that NTA complex helped to excrete mercury abundantly in urine of mice which had been exposed to metallic mercury vapor.2) We have examined whether NTA complex is effective for the excretion of mercuric ion, Hg(II). Mercuric ion was injected intraperitonealy to mice, the effect of NTA complex is not so effective. Then we used sulfur-bridged cysteinato molybdenum(V) complex [Mo2O2S2(cys)2]2-, referred to as CYS complex. After intraperitoneal injection of mercuric ion to mice, the amounts of the urinary mercury excretion were measured. The cumulative amounts of mercury for 5 days were compared: the group of mice that received the CYS complex solution excreted about 3.5 times more than the group that received water only. These results suggest that mercury in vivo was transferred by CYS complex to the kidney and accumulated there, and discharged in the urine.

Mercury in tuna fish is one of the big health problems, and we have also examined whether CYS complex is effective for the excretion of mercuric ion from fishes. We used goldfish as experimental material. Mercuric ion was injected intraperitonealy, and then CYS complex solution was injected alike. The amount of mercury remaining in the goldfish injected with CYS complex is clearly lower than that in the goldfish without CYS complex injection. This result suggests that CYS complex highly promotes extracorporeal excretion of mercury of goldfish.

1) H. Aikoh, M. Yamate, M. Takahashi, T. Shibahara, Physiol. Chem. Phys. & Med. NMR, 29, 109-122(1997).
2) H. Aikoh, C. Tagawa, T. Shibahara, J. Occup. Health, 44, 334-336(2002).

MS11-P2 — 11:00-12:00 and 17:30-18:30
UPTAKE OF METHYLMERCURY IN FARM-RAISED RAINBOW TROUT (ONCORHYNCHUSS MYKISS) AND YELLOW PERCH (PERCA FLAVESCENS)
Authors: BABIARZ, Christopher1, BINKOWSKI, Fred2, CRESWELL, Joel3, BABBINAT, Abbey4
(1) University of Wisconsin --Madison, cbabiarz@wisc.edu; (2) Great Lakes WATER Institute; (3) Brooks-Rand ; (4) University of Wisconsin -- Madison.

Aquaculture in the United States is a rapidly growing industry that provides stocker, bait, and food fish. Recent reports of contaminant level differences between wild and farm-raised fish have elevated interest in best management practices for aquaculture. Reported mercury levels in farm-raised fish are well below the 1000 ng/g US Food and Drug Administration tolerance limit for commercially sold fish, but occasionally exceed the 49 ng/g consumption advisory trigger set by the US Environmental Protection Agency. Wisconsin fish have markedly higher concentrations, ranging from 60 and 530 ng/g HgT. We used a field and laboratory approach to evaluate the critical components that govern MeHg concentrations in two contrasting species of fish that are commonly farmed in the Great Lakes region of the USA. The critical components include the food source, fish species, growth stage, health, and water quality. The information gathered was used to calibrate a contaminant accumulation model that is based on a bioenergetics approach. Concentrations in fishmeal available in Wisconsin ranged from 9 to 108 ng/g total mercury (HgT) and are typically 75% to 90% MeHg. Higher concentrations are generally associated with fine grain feed, and coupled with their higher feeding rates, this suggests that farm-raised juvenile fish receive a higher burden of mercury than their older counterparts. We also explored methylation rate potentials in the detrital material and the pond sediments. Although these sources have little direct contribution to mercury levels in fish, they may influence the concentrations in sediment and waste byproducts. Recovery and beneficial reuse of aquaculture effluents and byproducts is a growing area of development, and information on MeHg levels in these compartments is lacking. To our knowledge these are the first data available on MeHg concentrations in these compartments. Finally, best-management practices to improve aquaculture techniques will be presented.

MS11-P3 — 11:00-12:00 and 17:30-18:30
LASER-ABLATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (LA-ICP-MS) IMAGING OF MERCURY DISTRIBUTION IN FISH LIVER MACROPHAGE CENTERS
Authors: ROBERTS, Aaron1, SMITH, JD1, BARST, BD2, CHUMCHAL, MM3, GEVERTZ, AK1, HUDELSON, K1, HART, A1, VERBECK, G1, DREVNICK, PE2
(1) University of North Texas, aproberts@unt.edu; (2) Université du Québec; (3) Texas Christian University;

Recent field and laboratory studies have shown positive correlations with mercury exposure and pathologies in fish organs. In this study we sampled spotted gar, from wetland and open water habitats of Caddo Lake (TX/LA), for total mercury and liver pathology. We identified darkly pigmented deposits in gar livers as melanomacrophage centers which were positively correlated with total mercury in the organ. Furthermore, we noted habitat-specific differences between wetland and open water gar. Wetland sampled fish had higher total mercury in muscle and liver and a higher abundance of melanomacrophage centers. Mercury speciation analysis of Caddo Lake gar livers has revealed inorganic mercury as the predominant form. The tissue-level distribution of heavy metals can give evidence of the cellular mechanisms for their fate, toxicity, and transport. LA-ICP-MS is a multi-element technique for determination and quantification of metal and metalloid elements in samples, and when coupled with laser ablation as a sample introduction method, can produce 3-D contour plot images of relative mercury concentration within tissues. We have used this technique to localize higher levels of mercury to melanomacrophage centers in the livers of environmentally exposed gar from Caddo Lake. Macrophages have been associated with methylmercury demethylation in mammalian tissues. High ratios of inorganic:organic mercury in fish liver tissues and total mercury association with melanomacrophage centers supports a role for these hematopoietic cells in mercury metabolism.

MS11-P4 — 11:00-12:00 and 17:30-18:30
SUBLETHAL EFFECTS OF MERCURY IN LIVERS OF FISH FROM U.S. NATIONAL PARKS OF THE WESTERN GREAT LAKES REGION
Authors: SANDHEINRICH, Mark B.1, BAILEY, Sean W.1, BUECHEL, Sondra C.1, HARO, Roger J.1, ROLFHUS, Kristofer R.1, WIENER, James G.1
(1) University of Wisconsin-La Crosse, sandhein.mark@uwlax.edu

Exposure to methylmercury causes oxidative stress in the tissues of fish through the formation of radical oxygen species and lipid peroxidation. Lipid peroxidation of membranous organelles produces lipofuscin, a pigment that accumulates in the liver of fish. A previous study demonstrated that liver pigmentation can be measured spectrophotometrically and was correlated with total mercury in the liver and axial muscle of northern pike. We evaluated the effects of methylmercury on fish health as part of a project assessing the bioaccumulation of methylmercury in biota from six national parks of the western Great Lakes region (USA). Our objectives were to determine (1) if fish could be easily categorized as having low or high concentrations of mercury based solely on visual inspection of liver color and (2) if the quantity of lipofuscin in liver was correlated with mercury in the axial muscle of northern pike, largemouth bass, and smallmouth bass. Without knowing the source of the fish or the concentration of mercury in the axial muscle, the color of individual livers was classified as light, intermediate, or dark. Pigment from livers was extracted with chloroform and measured spectrophotometrically. There was a significant difference in the mean concentration of mercury in the axial muscle of fish with livers that were classified as light, intermediate or dark. For example, concentrations of mercury in northern pike with dark livers were almost two-fold those of pike with light livers. There was a significant positive relationship between liver color and concentrations of mercury in the axial muscle of northern pike and smallmouth bass, but not largemouth bass. Results of this study suggest that liver color may potentially be used to estimate relative concentrations of mercury in fish. There is also evidence of deleterious effects of mercury on fish in several national parks of the Great Lakes region and that fish species differ in their sensitivity to mercury.

MS11-P5 — 11:00-12:00 and 17:30-18:30
MERCURY EXPOSURE AND NEUROCHEMICAL IMPACTS IN ATLANTIC WHITE-SIDED DOLPHINS AND COMMON DOLPHINS FROM THE NORTHWEST ATLANTIC
Authors: NAM, DONG-HA1, MONTIE, Eric 2, BASU, Nil 2
(1) Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan 48109, USA, dongha@umich.edu; (2) Department of Science and Mathematics, University of South Carolina Beaufort, Bluffton, SC 29909, USA;

Higher tropic marine mammals including dolphins accumulate high mercury (Hg) levels in their tissues. Although Hg is a potent neurotoxicant, little is known about its neurotoxic risk to marine mammals. Here we determined total Hg levels in liver and in three brain regions (cerebellar grey matter, cerebellar white matter, occipital cortex) from common dolphins (CD; Delphinus delphis; n=8) and Atlantic white-sided dolphins (AWD; Lagenorhynchus acutus; n=8) that were collected from stranded individuals from the coastal beaches of Massachusetts, U.S.A. Some of these samples originated from fetuses. We also explored whether changes in neurochemical enzymes (monoamine oxidase (MAO), acetylcholinesterase (AChE)) and receptors (muscarinic acetylcholine (mAChR), N-methyl-D-aspartic acid (NMDAR)) were associated with brain Hg exposure. Mean levels of hepatic Hg in CD and AWD were 134ppm dry wt (n=7; range: 3.0-401ppm) and 28ppm (n=7; 1.6-58ppm), respectively, which exceed clinical thresholds in some mammalian wildlife. In the cerebellum, there was no difference in Hg values between white and gray matters from both dolphin species, and thus an average was taken for each individual. In the CD, mean brain Hg level in the cerebellum was 2.7ppm (n=14; range: 0.25-9.7ppm), and in the occipital cortex was 1.8ppm (n=4; 1.3-2.2 ppm). However, AWD had relatively low brain Hg levels (0.74ppm in cerebellum; 0.86ppm in occipital cortex). Mercury concentrations in fetal livers (1.8ppm in CD; 1.0ppm in AWD) were much lower than levels measured in corresponding maternal tissues (401ppm in CD; 41ppm in AWD). However, there was substantial enrichment of Hg in the fetal cerebellum compared to adults (5.5ppm versus 1.7ppm in CD; 0.67ppm versus 0.56ppm in AWD), thus suggesting that Hg is efficiently transferred and distributed into fetal brains, and that such maternal transfer may cause neurological effects in the fetus. When brain Hg was related to neurochemical biomarkers, Hg levels were negatively associated with MAO activity in cerebellar cortex in CD (n=7; r=-0.725; p<0.05). Despite limited sample size, apparent trends were observed between Hg and MAO activity (n=4; r=-0.945) and mAChR levels (n=4; r=0.945) in occipital cortex of CD. No correlations were found in AWD likely due to relatively low brain Hg levels. Our results suggest that dolphins (especially, common dolphins) accumulate substantial levels of Hg, capable of causing molecular changes in neuronal signaling. Further studies are warranted with greater samples sizes, and future studies should focus on the effects of Hg on brain function.

MS11-P6 — 11:00-12:00 and 17:30-18:30
INTERACTIONS BETWEEN SE AND HG IN AQUATIC ANIMALS
Author: BELZILE, Nelson1
(1) Laurentian University, nbelzile@laurentian.ca

Lakes around Sudbury, Canada contain Se at higher than background levels which decrease with distance away from the centre of the mining and smelting activities. This creates an ideal site for studies on the interactions between Se and Hg in aquatic organisms. It has been demonstrated in our field studies that the presence of Se in lake water decreases the mercury assimilation and methylation in fish and other aquatic organisms. A reverse relationship between total/methyl mercury and Se in fish and its different organs and in various species of aquatic invertebrates has been systematically observed. In a study with different fish organs, it was also observed that a drastic drop in the proportion of methylmercury over total Hg occurred when Se concentration in lake reached a certain level, suggesting the existence of threshold concentrations of Se in triggering a demethylation process within living organisms. Furthermore, our recent study with mute swan shows a clear positive correlation between Se and Hg. The capture birds from Lake Erie and Lake St. Clair did not demonstrate any obvious physical stress from accumulated Se.

MS11-P7 — 11:00-12:00 and 17:30-18:30
BI-PHASIC TRENDS IN WISCONSIN COMMON LOON BLOOD MERCURY CONCENTRATIONS - 1992-2010
Authors: MEYER, Michael W.1, RASMUSSEN, Paul W.1, WATRAS, Carl J.1, FEVOLD, Brick M.2, KENOW, Kevin P.3, EVERS, David4
(1) Wisconsin Department of Natural Resources, Michael.Meyer@Wisconsin.gov; (2) IGISES; (3) U.S.Geological Survey; (4) Biodiversity Research Institute.

Wisconsin Department of Natural Resources (WDNR) is assessing the ecological risk of mercury (Hg) in aquatic systems by monitoring common loon (Gavia immer) population dynamics and blood Hg concentrations. Loon adults and chicks were captured using a night-lighting technique during the summers of 1992-2010 and 1,661 blood samples were collected. In this paper we report temporal trends in blood Hg concentrations based on 334 samples collected from adults recaptured in subsequent years (resampled 2-9 times) and from 421 blood samples of chicks collected at lakes resampled 2-8 times. Temporal trends were assessed with generalized additive mixed effects models (GAMMs) and mixed effects models to account for the potential lack of independence among observations from the same loon or same lake. Trend analyses indicated that Hg concentrations in the blood of Wisconsin loons declined over the period 1992-2000, increased during 2002-2010, but not to the level observed in the early 1990s. The best fitting linear mixed effects model included separate trends for the two time periods. The estimated trend in Hg concentration among the adult loon population during 1992-2000 was -2.6% per year and the estimated trend during 2002-2010 was +1.8% per year; chick blood Hg concentrations decreased by -6.5% per year during 1992-2000, but increased 1.8% per year during 2002-2010. This bi-phasic pattern is similar to trends observed for waterborne methylmercury (meHg) and SO4 within our study area. The latter trends are strongly associated with changes in the regional water cycle, independent of changes in the atmospheric deposition of Hg or SO4. We tentatively conclude that drought-induced changes in the aquatic meHg cycle have rippled though the food chain to loons. But we caution that this effect may have lake-specific and/or region-specific attributes. We also caution that our findings do not discount the importance of anthropogenic emissions or atmospheric deposition. Instead, they illustrate how additional factors may exacerbate the bioaccumulation and trophic transfer of meHg ultimately derived from depositional loadings.

MS11-P8 — 11:00-12:00 and 17:30-18:30
METHYLMERCURY CAUSES REDUCED GPX ACTIVITY IN BRAIN OF ADULT ZEBRAFISH FEMALES, AND INTERRUPTS MOTORNEURON AXON GROWTH IN ZEBRAFISH EMBRYOS AFTER MATERNAL TRANSFER.
Authors: ELLINGSEN, Staale1, AMLUND, Heidi 1, BOYLE, David2, LUNDEBYE, Anne Katrine1
(1) NIFES, Bergen, Norway, sel@nifes.no; (2) University of Plymouth, Plymouth, UNITED KINGDOM;

Methylmercury (MeHg) is an environmental contaminant that accumulates in the seafood chain and represents a significant risk to human health. Maternal transfer of MeHg is frequently associated with neurobehavioral deficits like altered motoric and cognitive functions during early life stages, but MeHg also has neurotoxic effects in adults. MeHg exposure affects many basic cellular processes, and knowledge about the underlying molecular mechanisms is the key to improve MeHg neurotoxic risk assessment.

Quadruplicate groups of 25 female adult zebrafish were exposed to dietary MeHg for six weeks. MeHg was added to a commercial zebrafish diet as MeHg-cysteine at nominal concentrations of 0, 10 and 20 mg Hg/kg. The final concentration in the diets were 0.09 ± 0.004, 7.9 ± 0.5 and 17.8 ± 1.8 mg Hg/kg (control diet n = 5; enriched diets n = 10). At six weeks, eight females from each tank were individually paired with non-exposed males, and eggs were collected from successful crosses. Maternal transfer of MeHg was dose dependent, with approximately twice as much mercury found in eggs from females fed the 20 mg Hg/kg diet (6.7 ± 1.7 ng Hg/egg, n=3) compared to the 10 mg Hg/kg diet (2.6 ± 0.3 ng Hg/egg, n=3).

In pooled samples of brain and liver of adult female zebrafish exposed to dietary MeHg, we found total glutathione (GSH) concentrations and glutathione-S-transferase (GST) total specific activity to be unaltered. The specific activity of glutathione peroxidase (GPx) in liver was not affected by dietary treatment, while in brain the specific activity of GPx was significantly decreased.

In 1-day old embryos from exposed female zebrafish, spinal cord primary motorneurons were visualized by immunohistochemistry (Znp-1 antibody). Normally caudal primary (CaP) motorneurons project ventrally along the medial somatic muscle surface until they reach the turning point between the dorsal and medial muscles, where they project ventrally and innervate the ventral myotome. We observed a significant disturbance in CaP axon growth in embryos from females fed the 20 mg Hg/kg diet. Their axons projected beyond the turning point, but then growth ceased, leading to a shortened axon. Abnormal branching and misguided axon growth was also seen beyond the turning point. Whole mount in situ hybridization analyses indicate that the observed interruption of axons is caused by mis-regulation of genes involved in axon guidance and growth.

MS11-P9 — 11:00-12:00 and 17:30-18:30
EFFECTS OF ENVIRONMENTAL SELENIUM ON BIOACCUMULATION OF MERCURY IN RIVER AND STREAM FISH FROM THE WESTERN UNITED STATES
Authors: RALSTON, Nicholas1, PETERSON, Spencer 2, RALSTON, Carla1, RAYMOND, Laura1
(1) University of North Dakota, nralston@undeerc.org; (2) U.S. E.P.A. (retired);

The environmental availability of selenium (Se) must be considered when assessing mercury (Hg) bioaccumulation in aquatic ecosystems. High Hg–Se binding affinities result in the formation of insoluble mercury selenide (HgSe), potentially explaining the . inverse relationships between Se availability and Hg bioaccumulation that have been noted in previous studies of Hg-Se interactions in lake fish.

The purpose of this study was to examine the influence of environmental Se on Hg bioaccumulation in fish from rivers and streams in the western United States. Since tissue Se content reliably reflects dietary Se intake, fish Se was used to indicate environmental Se availability. We hypothesized that formation of HgSe in tissues of prey animals would limit uptake of Hg by predators. Therefore, we expected increased availability of Se in the food web to be accompanied by diminished Hg bioaccumulation in fish tissue. To test this hypothesis, 15 species of fish were collected from 130 sites across the western United States (total n = 659), and whole body Hg and Se contents were analyzed and evaluated in relation to fish weight and length.

We found significant inverse relationships between Hg and Se in three piscivorous species (northern pike, northern pikeminnow, and walleye) and four nonpiscivorous species (common carp, white sucker, shorthead redhorse, and black bullhead). Mercury occurred in molar excess of Se in only 13 of 659 fish, primarily northern pikeminnows. Only six of the fish in this study exceeded the methylmercury water quality criterion. As expected, molar Hg:Se ratios in the fish increased significantly with increasing weight and length in all piscivores studied (northern pike, northern pikeminnow, walleye, and smallmouth bass) as well as in five nonpiscivores (common carp, white sucker, shorthead redhorse, largescale sucker, and brown trout). However, Hg:Se molar ratios in excess of equimolar stoichiometries appear unlikely to occur except in locales directly influenced by point source emissions.

In summary, our findings support the hypothesis that Se availability is inversely related to Hg bioaccumulation in freshwater fish from rivers and streams. In certain fish species such as walleye, the influence of Se availability on total body Hg in fish was greater than the influence of size. It appears likely that poor Se availability may be a major influence on Hg “hot spots” that are often observed in low-Se regions.

MS11-P10 — 11:00-12:00 and 17:30-18:30
MERCURY INHIBITS NEUROCHEMICAL MARKERS IN THE BRAIN OF POLAR BEARS (URSUS MARITIMUS) IN VITRO
Authors: MICHAEL, Kwan1, CHAN, Laurie HM2
(1) Nunavik Research Centre, m_kwan@makivik.org; (2) UNBC.

Mercury (Hg) is a neurotoxicant that is found at elevated concentrations in the Arctic ecosystem. Little is known about its effect on the brain of wildlife such as polar bears. Neurochemical biomarkers, changes in brain chemistry, have been suggested as preclinical indicators associated with contaminant exposure. The purpose of this study was to study the effects of Hg on the activity of monoamine oxidase (MAO) and acetylcholinesterase (ChE) and binding to the muscarinic acetylcholine receptor (mAChR) extracted from two brain regions of wild polar bears (Ursus maritimus). Membrane respectively enzyme fractions of brain homogenate of both cerebellum and occipital lobe were exposed to mercuric chloride (HgCl2) or methylmercurychloride (MeHgCl), ranging from 0 to 320 µM for mAChR binding, 0 to 500 µM for MAO activity, 0 to 100 µM (HgCl2) respectively 0 to 1000 µM (MeHgCl) for ChE activity, for 15 min at room temperature. Both HgCl2 and MeHgCl decreased MAO and ChE activity in a dose-response manner and also inhibited the binding to the mAChR. HgCl2 was a more potent inhibitor of the three markers than MeHgCl in both brain region. The half maximal inhibitory concentrations (IC50) for the different markers and brain regions will be presented. These data show that Hg is a more potent inhibitor of neurochemical components than MeHg in the brain of polar bears. Identifying the effects of exposure to neurotoxic substances in representative species offers a perspective relevant to both human and ecological risk assessment

MS11-P11 — 11:00-12:00 and 17:30-18:30
MERCURY LEVELS IN MAGELLANIC PENGUIN WRECKED AT THE BRAZILIAN COAST: PROPOSAL OF A POTENTIAL MONITORING TOOL FOR MARINE POLLUTION AT THE SOUTH ATLANTIC COAST
Authors: VEGA, C.1, VILAS BOAS, V.2, SICILIANO, S.2, CAMPOS, R.3, GONCALVES, R.A. 3, BARROCAS, P.G.2, HACON, S.2
(1) Fundação OsWaldo Cruz, Departamento de Endemias, Rio de Janeiro; Pontifícia Universidade Católica do Rio de Janeiro , claudveg@yahoo.com; (2) Fundação OsWaldo Cruz, Departamento de Endemias, Rio de Janeiro; (3) Pontifícia Universidade Católica do Rio de Janeiro;

Seabirds have been identified as good indicators of marine pollution, as they occupy different levels of the trophic chain, they are distributed worldwide, and their ecology is well known. There are some surveys of heavy metal levels in marine bird species from different areas around the world. However, in penguins there are just a few studies of heavy metal levels. S. magellanicus is the most abundant species of penguin in South America, with breeding colonies along the Pacific and Atlantic coasts (in Chile and Argentina), including the Falkland Islands. In the present work, we propose the Magellanic Penguin (Spheniscus magellanicus) as a tool for monitoring Hg levels at the Brazilian coast. For this purpose, muscle and liver from specimens of wrecked Magellanic penguins were analyzed for Hg levels by Cold vapor atomic absorption spectrometry (CVAAS), these were collected from two different areas of the Brazilian coast: Rio de Janeiro and from Rio Grande do Sul during winter 2006 and 2008. The average concentration of the 2006 samples from RS (muscle: 0.1 µg/g and liver 0.8 µg/g) were statistically different from the ones of 2008 (muscle: 0.5 µg/g; liver:3.3 µg/g). In RJ´s samples the average value for 2006 presented non-statistical differences (muscle: 0.4 µg/g and liver: 1.3 µg/g) compared with 2008 (0.6 µg/g and 1.4 µg/g). However In 2006 the average of the total of individuals collected was statistically different (muscle: 0.3 µg/g and liver: 1.4 µg/g) of the ones of 2008 (muscle: 0.6 µg/g and 2.7 µg/g). The southeast coast of Brazil is an area with strong industrial and urban activities that drain waste into the near shore sea water as no data of Hg in Magellanic penguins in the Brazilian coast was found in the literature, it is important to continue this assessment along the years for a better understanding of this process and verify if their Hg levels represent anthropogenic contamination or natural levels in the species.

Monday, 25 July, 2011