Amphibians mercury

AMPHIBIANS AND REPTILES Alligator, Alligator mississippiensis, from mercury-contaminated areas total mercury, 1994-95, Florida Everglades vs. Savannah River SC Blood No data vs. 2.2 FW 55... 

Birge, W.J., J.A. Black, A.G. Westerman, and J.E. Hudson. 1979. The effect of mercury on reproduction of fish and amphibians. Pages 629-655 in J. 0. Nriagu (ed.). The Biogeochemistry of Mercury in the Environment. Elsevier/North-Holland Biomedical Press, NY. 

The fly ash formed in coal combustion also represents a disposal problem (see also Chap. 14). Although there are some uses such as in concrete and bricks, soil stabilization, soil conditioner, and landfill cover, more need to be found.24 Additional uses in wallboard, concrete blocks, and other construction materials should be possible. Other ashes include bottom ash and boiler slag. Experiments have been run on the recovery of iron, aluminum, and other metals from the ashes, but the processes may not be economical at this time. This could reduce the need to mine for these other materials. Coal-fired power plants produce over 100 million tons of ash annually in the United States. Coal fly ash is routinely mixed with water and put into settling basins. This process extracts some arsenic, cadmium, mercury, selenium, and strontium into water, which can then cause abnormalities in amphibians.25... 

The toxicokinetics and toxicity of inorganic and organically bound mercury in reptiles and amphibians is largely unknown (Wolfe et al. 1998). 

Mercury concentrations as high as -lOOmgkg liver and 130mgkg hair were detected in this animal. The panthers most at risk appear to be those which consume mercury-contaminated raccoons, which in turn consume mercury-contaminated aquatic life, including invertebrates, fish and amphibians. In addition to mortality, adverse effects of mercury on the reproductive success of this endangered animal are most likely (Roelke et al. 1993). 

Elevated concentrations of mercury in amphibian tissues were also found in frogs and toads collected near a mining area in Yugoslavia. Maximum concentrations, in mg/kg fresh weight, were 2.3 in egg, 2.9 in lung, 24.0 in kidney, and 25.5 in liver conspecifics from a reference site contained <0.08 mg Hg/kg fresh weight in all tissues. 

Exposure pathways for adult amphibians include soils (dermal contact, liquid water uptake), water (dermal contact with surface water), air (cutaneous and lung absorption), and diet (adults are carnivores). All routes of exposure are affected by various physical, chemical, and other factors. Dietary exposure in adults, for example, is related to season of year, activity rates, food availability, consumption rate, and assimilation rates. Knowledge of these modifiers is necessary for adequate risk assessment of mercury as a possible factor in declining amphibian populations worldwide. 

Significant sublethal effects of mercury include an increased frequency of cancers, birth defects, and chromosomal aberrations in laboratory animals and wildlife. Adverse sublethal effects of mercurials also include growth inhibition, abnormal reproduction, histopathology, high mercury accumulations and persistence, and disrupted biochemistry, metabolism, and behavior. These - and other aspects of exposure to various mercurials by living organisms - are documented and discussed for representative species of bacteria and other microorganisms, aquatic and terrestrial plants and invertebrates, fishes, amphibians, birds, and mammals. 

Dietary exposure of amphibians in sites receiving mercury mainly via atmospheric deposition - estimated to range from 1.5 to 3.0 mg Hg/kg FW ration - may be sufficient to adversely affect survival, growth, and development. Studies with tadpoles of the southern leopard frog (Rana sphenocephala) fed mercury-containing diets for 254 days showed that about 28% died at the highest concentrations fed of 0.5 and 1.0 mg Hg +/kg FW ration malformation rates were dose-related, with 5.0% in controls, 5.6% in the 0.1 mg Hg/kg FW diet, 11.1% in the 0.5mg/kg and 27.8% in the l.Omg/kg diet. Malformations included dose-related scoliosis. Arrested growth and development, and tail resorption were also positively dose-related. Total mercury body burdens were also dose-related with about... 

The significance of mercury concentrations in amphibian tissues is not Imown with certainty and requires additional research for satisfactory risk assessment. The following areas are recommended for study acclimatization and adaptation to mercury mercury remobilization during periods of metamorphosis, hibernation, estivation, and reproduction critical organ concentrations and biomarkers of adverse mercury effects. These studies should also consider the influence of exposure duration and dose, mercury speciation, and mercury interaction with other metals. 

---