ABSTRACT
Environmental effects monitoring at the La Grande hydroelectric complex (Québec, Canada) revealed important increases in mercury levels in fish caught downstream from reservoirs. A study was carried out in 1997 immediately below the Caniapiscau Reservoir to identify by which components mercury is transported downstream from reservoirs and to assess the amount of mercury being exported. Stomach contents of lake whitefish (Coregonus clupeaformis) captured immediately below the Caniapiscau Reservoir were examined to determine which components transfer mercury from lower trophic levels to fish. The analyses of water samples and drifting organisms collected below the reservoir indicate that the dissolved fraction (< 0.45 microm) and the suspended particulate matter (0.45-50 microm) are the major components by which methylmercury is transferred downstream of reservoirs, accounting for 64 and 33%, respectively, of the total amounts exported. Drifting organisms such as plant debris, benthic invertebrates, fish, phytoplankton and zooplankton are much less important pathways for mercury export because of their very low biomass per water volume coming out of the generating station, as opposed to the high biomass of suspended particulate matter. However, zooplankton is the major component by which methylmercury is directly transferred to non-piscivorous fish downstream.
Subject(s)
Mercury/analysis , Water Pollutants, Chemical/analysis , Water Supply/analysis , Animals , Biomass , Environmental Monitoring , Mercury/pharmacokinetics , Methylmercury Compounds/analysis , Methylmercury Compounds/pharmacokinetics , Plankton/metabolism , Plants/metabolism , Quebec , Salmonidae/metabolism , Shellfish/analysisABSTRACT
Osteoporosis is a common complication of Cushing's disease/syndrome. Fractures can be the presenting manifestation. We report two cases and review 28 others from the literature. Clinical, laboratory, and absorptiometry data are reviewed; the vertebrae and ribs were the most common fracture sites, and osteoporosis reversal after treatment varied with age, gender, and symptom duration. The pathophysiology, which remains controversial, is discussed. A search for Cushing's disease/syndrome should be part of the routine evaluation of osteoporosis in children and adults, particularly men.