The influence of mine waste contamination on invertebrates and fish in the Methow River Valley, Okanogan County, Washington (U.S.A.)
A study of mine-waste contamination effects on Methow River habitat on the eastern slopes of the north Cascade Mountains in Washington state, U.S.A., revealed trace element impacts on invertebrates and fish. Ore deposits in the area were mined for gold, silver, copper and zinc until the early 1950's, but the mines are now inactive. The trace elements arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) were the focus of this study.The objectives of this study were to determine, (1) the concentrations of Cu, As and other trace elements in sediments and water in the Methow River above and below the Alder Mine, Red Shirt Mill and Alder Mill, (2) whether in vivo exposure of caddisfly larvae to Cu and As in microcosm chambers containing contaminated water and sediments induced nuclear apoptosis and the formation of electron-dense granules in the matrix of gut epithelial cell mitochondria, (3) whether in situ exposure of caddisfly larvae and triploid trout to Cu and As in water or sediments in the Methow River induces the formation of nuclear apoptosis and electron-dense submitochondrial granules in gut epithelial cells and hepatocytes, (4) whether the composition of the electron-dense granules relates to exposure, and (5) the effects of trace element contamination in the Methow River on the growth and developments of caddisfly larvae (Ecclesomyia spp.) and trout ( Oncorhynchus mykiss).Electron microscopy was used to observe the effect of trace element contamination from mine waste on invertebrates and fish in the Methow River. An above-and-below-mine approach was used to compare exposed and reference populations.In this study, I showed that it is likely that trace elements from the abandoned mines near the Methow River are affecting benthic invertebrates and fish at the cellular level with secondary effects related to reduced body weights and delayed development occurring at higher levels of biological organization. The trace elements Cu, As, Cd, Mn, and Pb were significantly higher in Methow River sediments below the mines compared to the reference area above the mines. No effects from mine waste contamination on dissolved metal concentrations in the Methow River were observed. Food chain effects resulting from mitochondrial collapse and the diversion of energy coincides with reduced growth and delayed development in caddisfly larvae and trout in the Methow River. Submitochondrial granules were induced in the mitochondria of live caddisfly larvae and trout exposed in vivo to abandoned mine waste contamination in stream water, sediments, and periphyton. The incidence of submitochondrial granules was significantly higher in caddisfly and trout exposed to abandoned mine waste in both controlled microcosms and to contaminants in situ in the Methow River below abandoned mines. Elemental analysis of submitochondrial granules by X-ray analysis suggest that bioavailable forms of Cu are present at high concentrations in the environment surrounding the organism, its cells and the mitochondria and in small intestine epithelial cells and hepatocytes of caddisfly and trout from the Methow River. Chromatin compaction, margination and the observation that large vesicles with bilayer membranes were being expelled from the nuclei of affected cells from caddisfly larvae and fish exposed to Cu suggest both apoptosis and mitochondrial failure are occurring.
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