TA3 Metals in the Environment: Aquatic Biological Perspectives
254 Portland Ballroom
8:00 AM - 12:00 PM, Tuesday
() Physiological impact of acute molybdenum exposure in freshwater fish.
Reid, S.1, 1 Okanagan University College, Kelowna, British Columbia, Canada
ABSTRACT- As of 2002, the Canadian Environmental Quality Guidelines for aquatic life (freshwater) is 73 ug Mo.L-1. There are no Canadian drinking water guidelines for this metal, although British Columbia and the World Health Organization have drinking water guidelines of 250 and 70 ug Mo.L-1 respectively. Very little is known about the physiological impact of molybdenum on freshwater fish. It has been demonstrated that this metal is relatively non-toxic with toxic estimates based on 96 h LC50's ranging from 70 to >3000 mg.L-1 depending on species, size of fish and test conditions. I have shown that acute sublethal molybdenum exposure has little or no impact on a variety of physiological parameters of freshwater fish. Despite the apparent lack of direct acute toxicity, when combined with an additional stress such as exercise, exercise and air exposure or hypoxia, the detrimental effects of molybdenum become evident. Exposure to 25 or 250 mg Mo.L-1 prior to exercise results in post-exercise loss of equilibrium and exercise-induced delayed mortality in kokanee that were not observed in controls. In addition we have characterized molybdenum accumulation in gill, liver and plasma of kokanee (Oncorhynchus nerka Kennerlyi) and gill and plasma of rainbow trout (O. mykiss). Based on these data, I suggested that molybdenum acted as a non-specific gill irritant that lead to alterations in internal acid-base status and gill gas exchange. Most recently, I characterized significant adverse physiological effects in cannulated, exercised rainbow trout following 7 days exposure to only 2.5 mg Mo.L-1. These results support the hypothesis that the toxicity of molybdenum in exercised freshwater fish is the result of adverse alterations in the oxygen and carbon dioxide exchange likely due to gill epithelium swelling and increased mucus production; a mechanism in common with aluminum and nickel.
Key words: Oncorhynchus, molybdenum, exercise, toxicity