This study evaluates the toxicity, accumulation, chronic effects and mode of action of methylmercury on the reproduction of the teleost fish, Oryzias latipes. The median lethal concentration, 96h-LC50, for adult Oryzias was + 88+9.8 μg CH₃Hg⁺/1 as determined in a static system. Residue analysis by gas chromatography showed that fish exposed to 43 to 1000 μg CH₃Hg⁺/1 had tissue levels below 40 μg CH₃Hg⁺/g while fish exposed to more than 1000 μg CH₃Hg⁺/1 accumulated methylmercury steadily and reached levels as high as 408.1 μg CH₃Hg⁺/g. Death seems to occur when tissue level reaches 25 μg CH₃Hg⁺/g. Studies on long-term exposure to 0.0, 4,3, 10.7 and 21.5 μg of methylmercury in a flow-through system confirmed this observation. Four-hour exposure of 8.5 and 42.9 μg/1 of methylmercury on alternate days during the fish's normal oviposition period resulted in inhibition of oviposition. This observation occurred only oh days when fish were exposed to methylmercury but not on days when fish were returned to clean water. However, at a concentration of 85 μg CH₃Hg⁺/1, complete inhibition was observed even on days when fish were returned to clean water. High rates of accumulation with low rates of excretion of methylmercury were suggested explanations for these observations. Six-week exposure to 4.3, 10.7 and 21.5 μg/1 of methylmercury resulted in inhibition of spawning. This inhibition was directly related to the log of exposure concentrations. At the end of six weeks, both male and female gonads showed reduction in size; the females were more sensitive. However, hatchability of the spawned eggs was not affected by the exposure. Juvenile fish were very sensitive to methylmercury. After two weeks of exposure, one-week old juvenile exposed to 0.0, 4.3, 10.7 and 21.5 μg CH₃Hg⁺/1 had mortality rate of 2.2%, 54.3%, 64.9% and 99.4% respectively. Synthetic LH-RH, at concentrations of 100 and 1000 ng/g body weight, was effective in stimulating ovarian development in Oryzias. This shows that the LH-RH (synthesis based on structure of porcine LH-RH) has biological activity in Oryzias. When exposed to methylmercury, spawning activities were inhibited. LH injections were able to restore the spawning activities inhibited by the methylmercury treatment, but not LH-RH. However, histology of the pituitary gland showed stimulation of gonadotropic cells by LH-RH injection with no restoration of spawning activities. This suggests that methylmercury- may be blocking the release of gonadotropin. In vitro ovulation was affected by previous exposure to methylmercury. Addition of methylmercury directly to the incubation medium further reduced the percentage of in vitro ovulation in the previously treated fish. Using oocytes from untreated donor fish, the percent inhibition of in vitro ovulation by methylmercury was directly related to the log of doses used. A possible bioassay with in vitro ovulation was suggested. Among the various steroids used (progesterone, cortisone, estradiol and testosterone), cortisone was the only steroid effective in restoring in vitro ovulation blocked by the presence of methylmercury in the incubation medium. Ecological implications of these findings are discussed. / Science, Faculty of / Zoology, Department of / Graduate

The effects of short term exposures to sublethal doses of mercuric chloride were studied using species of anadromous fish. Aspects of grou/th and behaviour u/ere used as indicators of physiological and psychological malfunctions due to mercurialism. The characteristic migration tendencies ( upstream or downstream ) of Lower Babine and Fulton River alevins were tested in experimental laboratory channels. The were conducted in a chamber in which a day, dawn through dusk, could be simulated. Each stock was divided into three groups and each group was assigned a level of treatment ( control, 0.5 ppm and 1.0 ppm HgCl₂ ). The performance of the fish in each group placed in the channels was scored. An analysis of data obtained from the migration experiments indicated that sublethal mercurialism had a disruptive influence on migration patterns of Sockeye salmon alevins. The lower level of intoxication produced a downstream drift in both stocks while the fish treated at the higher level of intoxication showed an upstream migrational tendency in both stocks. The effects of sublethal mercurialism on growth were studied using Sockeye, Chum, and Coho salmon fry. The fish received standard daily feedings. The fed fish for each of the species were divided into three treatment groups ( control, 0.5 ppm and 1.0 ppm mercuric chloride ) .Weight data were collected and analyzed using regression analysis and the analysis of covariance. The fed Sockeye and Chum salmon fry showed a significant weight loss (⍺= 0.05 ) in the 0.5 ppm and the 1.0 ppm treatments when compared to their respective controls. There was no significant difference in weight between treatments in the fed Coho salmon experiment. A six week starvation experiment was designed to test if there were any significant differences in weight loss between control fish and fish treated with 0.5 ppm and 1.0 ppm mercuric chloride. Regression analysis and the analysis of covariance did not reveal any statistically significant differences on the rates of weight loss. A flight responce experiment was conducted using Coho salmon prey and predators. Wild and hatchery Coho salmon prey were used with hatchery Coho predators. Three treatment levels of mercuric chloride were administered ( control, 0.5 ppm and 1.0 ppm ), Prey and predators were placed in an experimental laboratory performance channel and, after a timed exposure to each other, scores indicative of flight responce mere obtained. The data was analyzed using the Kolmogorov-Smirnov Large sample : one tailed test. No significant differences in the responces between treatments were noted for the hatchery Coho. The wild Coho prey treated with 0.5 ppm and 1.0 ppm mercuric chloride had a statistically significant differences when compared to their controls. It was noted that as the level of intoxication increased the the level of flight responce decreased. The results of the above experiments indicate that mercurialism has measurable effects on the physiology and psychology of fish at sublethal level. / Science, Faculty of / Zoology, Department of / Graduate

The effects of sublethal additions of mercuric chloride were studied in the marine diatom Skaletonema costatug (Grev.) Cleve grown in ammonium-limited chemostats and batch cultures. In the short-term Hg exposure (up to 5 hours), unexposed chemostat effluents were simultaneously perturbed with 5 μM NH₄Cl and Hg concentrations ranging from 0.04 to 5.53 nM HgCl₂. In the long-term Hg exposure (679. 5 hours), ammonium-starved effluents were only perturbed with 5 μM NH₄Cl. In the short-term Hg exposure, when the effluent from the chemostat culture was starved for 1.5 hours, Hg decreased the affinity for the substrate (increased Ks value) and the rate of ammonium assimilation or the internally controlled uptake rate, Vimax . When the effluent was starved for 30 hours, only Vimax was reduced. These effects occurred between 1.84 and 3,68, and at 0,18 nM HgCl₂ in effluents starved for 1.5 and 30 hours, respectively. The maximum rate of uptake, Vs, was not depressed. In the long-term Hg exposure, at least 0.37 nH HgCl₂ decreased the specific growth rate and the maximum cell density, while the chlorophyll a per cell increased. A period of population decline was followed by resumption of growth. Morphological alterations were observed before and after the recovery. In the long-term experiment, six days of continual exposure to 0.37 nM HgCl₂ gradually increased the Ks value without affecting Vs and Vimax. The results from exposure to 3.68 nM HgCl₂ were similar to the short-term Hg exposure, since both the substrate affinity (Ks value) and the assimilatory rate Vimax were impaired. In addition, the maximal uptake rate, Vs, was also reduced after exposure to 3.68 nM HgCl₂ for six days in the long-term experiment. After resumption of growth in the Hg-treated cultures, when a new steady-state was established, the affinity for the substrate and assimilatory rates increased in phase D (day 23) compared to phase A (day 6). The recovery of growth and nutrient uptake rates in phase D, may have been partially mediated by the acquisition of Hg tolerance and the appearance of cells of a different stage of the sexual life cycle, as suggested by differences in cell size and chemical composition. An attempt was made to determine whether a short-term physiological response (Hg induction of metallothionein synthesis) could be responsible for the recovery. The 250 nm absorbance profile, of nutrient-saturated cultures exposed for 90 to 116 hours to sublethal concentrations of mercury, showed no large absorbance peak in the medium molecular weight pool, corresponding to laetallothionein, as it occurs in animals exposed to heavy metals. The intracellular distribution and levels of Cu, Zn, and Hg in S. costatum, grown in nutrient-saturated batch cultures, were affected by 0.37 nM HgCl₂. A concentration equal to or greater than 1.84 nM HgCl₂ reduced the growth rate and cell density, possibly due to the accumulation of Hg in the high m.w. pool. Exposure to 1.84 nM HgCl₂ prior to a second addition of 5.53 nM reduced Hg levels in ths high m.w. pool. Upon Hg exposure, Zn levels decreased in the high and low m.w. fractions but gradually increased in the medium m.w. pool. Copper slightly increased in the high m.w. pool but remained constant in the medium and low m.w. pools, in relation to total intracellular levels. High levels of Cu and Zn in the low m.w. pool suggests that a substance of a lower m.w., than usually reported for metallothionein, may be involved in the storage and detoxification of heavy metals in S. costatum. / Science, Faculty of / Botany, Department of / Graduate

No description available.

No description available.

Indiana University-Purdue University Indianapolis (IUPUI) / Mercury (Hg) has proven to be a risk to the public, mainly through the consumption of fish. Because of this, many fish consumption advisories have been issued in Indiana. Although much is known about the global cycle of mercury, little is known about how local and regional emission sources of mercury impact local and regional mercury cycling. This study’s objective was to determine the scope of mercury concentration in central Indiana by using a broad grid of soil mercury measurements. Sampling was designed to capture the net retained mercury content in soils, and to determine whether spatial patterns in exist in soil mercury contents that could be related to emission sources of mercury and post-emission transport patterns from wind. Results from this study revealed significant differences in mercury concentrations for soils in central Indiana. The core of the study area, concentrated in the urban area of Indianapolis, exhibited soil mercury contents that were 20 times higher than values in the outskirts of the study area. The spatial pattern resembled a bulls-eye shape centered on Indianapolis, and with comparison to the reported Hg emission from local sources, including a coal-fired power plant, indicates a strong regional deposition signal linked to those emission sources but marked by wind-driven transport to the northeast. This effect of local emission sources resulting in local deposition indicates that limiting mercury emissions will have a net beneficial impact on local environmental quality and human health.

The threat of environmental mercury (Hg), particularly methylmercury (MeHg), exposure to the health of humans has been well documented. Thus, it is important to monitor exposure and body burden for public health protection. The first objective of this thesis was to characterize the risk of Hg exposure in two Canadian coastal communities: Grand Marian (n = 91) and St. Andrews/St. Stephen (n = 52), New Brunswick, Canada, using dietary questionnaires and hair analysis. Average Hg intakes and body burden were below the most conservative guidelines. We attributed these results to the low Hg concentrations found in the species commonly consumed: haddock, canned tuna, lobster and pollock (all below 0.2 mg/kg). The analytical method employed to determine Hg in hair, cold vapor atomic absorption (CV-AAS), required a bundle of 100-150 hair strands and involved lengthy chemical digestion procedures which reduce throughput. Direct solid introduction techniques minimize these weaknesses. Our second and third objectives were to evaluate two such methods: (1) combustion, gold amalgamation, atomic absorption spectrometry (C-GA-AAS) and (2) laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) for measuring total Hg in single hair strands. Hair samples with a wide range of Hg exposure were obtained from communities. A 1:1 relationship was observed between C-GA-AAS and the established CV-AAS for analysis of 1-cm hair segments. Additionally, the average relative standard deviation (RSD) of Hg between hair strands within an individual was 6.5 +/- 2.8%, thus justifying the use of a single hair strand for biomonitoring. With a limit of quantification of 0.10 ng of total Hg, a single hair strand with average weight of 0.5 mg and Hg concentrations of 0.2 mg/kg can be measured routinely. Using LA-ICP-MS, we showed that a single laser shot can sample hair material within 50 mum along a single hair strand which is equivalent to less than one day of

No description available.

In this thesis mercury concentrations in biota of the upper South Saskatchewan River Basin are assessed in three non-industrialized systems. Mercury levels in large sport fish (northern pike, walleye, lake trout) frequently exceeded the consumption limit of 0.5ppm. Goldeye and mooneye of the Oldman River and lake whitefish of Waterton Lakes were below 0.5ppm total mercury. Agricultural and urban effluents constituted no sources of significant mercury loadings to the Oldman River. A doubling of mercury biomagnification factors between longnose dace and their food suggests bioenergetic heterogeneity of these fish along the river gradient. Basin-specific mercury levels were detected for the upper and middle basins in Waterton Lakes, and are associated with food web characteristics, and fish bioenergetics. High mercury levels in a new reservoir were in part attributed to increased loadings from flooded soils, as is commonly observed, but also to bioenergetic constraints and growth inefficiency as a result of non-piscivory of this population. / xiii, 130 leaves : ill. ; 29 cm. --

Two Oregon reservoirs contaminated by different mercury sources were compared for mercury distribution in sediment and bioaccumulation by fish. The average mercury concentration in the sediment of Cottage Grove reservoir (0.67 �� 0.05 ��g/g dry wt) was higher than for Dorena Reservoir (0.12 �� 0.01 ��g/g dry wt). Sediment mercury in the main tributary of Cottage Grove Reservoir, which drains the tailing of past mercury mining activities, was ten fold higher than mercury in sediment from other reservoir tributaries with no evidence of mining. However, there were no significant differences between sediment mercury concentrations in the tributaries of the Dorena Reservoir, which has no mercury mining history within its watershed. Three fish species (largemouth bass, bluegill, crappie) from Cottage Grove Reservoir had significantly higher levels of mercury than the same species from Dorena Reservoir. These results indicated that a point source, Black Butte Mine, contributed amounts of mercury in excess of natural deposits based on differences in bioaccumulation among fish populations from these two systems. Cottage Grove Reservoir was examined for environmental evidence of point source mercury pollution. High mercury concentrations were found at various points around the suspected source, the Black Butte Mine area. The highest concentration occurred close to the kiln. The mercury concentration in the sediments of a creek below the mine dump was up to ten times higher than that of the sediments of a creek from a watershed adjacent to the watershed of the mine area. Two sediment cores from the deep area were collected to assess for pollution history profiles. These showed mercury loading in Cottage Grove Reservoir was consistent with the past mercury production in Black Butte Mine. Therefore most of mercury in Cottage Grove Reservoir was believed to be of Black Butte Mine origin. Mercury contents in pore water and food web indicated that continuing mercury transportation from the point source create a management problem in Cottage Grove Reservoir. / Graduation date: 1996