Villanueva,Xitlalli; Berthelemy Nicole (Weber State University)
Faculty Advisor: Berthelemy, Nicole (Weber State University, Zoology)
Introduction: Mercury, originating from mining and industrial activity, has been accumulating in the Great Salt Lake water and has contaminated its food web. Some of the mercury chloride (HgCl) is transformed by benthic bacteria to the more toxic monomethyl mercury (MeHg). While the effect of HgCl on the brine shrimp Artemia franciscana has been described, little is known about the effects of MeHG on this shrimp, except that it is more toxic. We correlated the tissue mercury concentrations to the amount of mercury present in the sea-water (SW). We also tested the ability of the shrimp to depurate mercury accumulated in the tissues.
Results: - Adult Artemia survived at least one week when exposed to concentrations ranging from 10-9 to 10-5g/L HgCl or MeHg. Shrimp exposed to 10-4g/L HgCl or MeHg died within two days.
Fertility was influenced by mercury exposure. The number of offspring per brood produced by females exposed to 10-6g/L or less HgCl was around 150, significantly higher than the average 80 offspring per brood produced by females exposed to 10-6g/L MeHg. When exposed to 10-5g/l HgCl and MeHg, the females brood size was 47 and 24, respectively.
- Artemia is able to maintain low level of tissue mercury, up to exposure to 10-6g/L HgCl and 10-7 g/L for MeHg. Exposure to higher mercury concentrations leads to much higher mercury levels, about 35 ppm HgCl for SW reaching 10-5g/L and 300 ppm with exposure to 10-4 MeHg.
Discussion: While both HgCl and MeHg are lethal to the shrimp, after a few days exposure, at concentration higher than 10-6 g/L, MeHg has a stronger effect on fertility, with brood size near half the size. Also, MeHg, the organic form of mercury, is accumulated in much higher level than the inorganic form. The organic form has a better ability to cross cell membranes. Since the mercury levels in the Great Salt Lake reach 55 ng/L (= 0.055 10-6g/L) and 30 ng/L (0.03 10-6 g/L) for HgCl and MeHG, respectively, the brine shrimp population is likely not affected by this pollutant.
Conclusion: Mercury has a strong effect on Artemia metabolism. We will study, next, the shrimp response to the oxidative stress induced by the mercury exposure.