Cell Pathology and Developmental Effects of Mine Waste Contamination on Invertebrates and Fish in the Methow River, Okanogan County, Washington (USA)

Abstract

A study of the effects of mine waste on Methow River habitat in the north Cascade Mountains in the state of Washington, U.S.A. revealed impacts of sediment metal contamination on invertebrates and fish. The objectives were to determine: (1) effects of metal contamination on the growth and development of caddisfly larvae (Ecclesomyia spp.) and trout (Oncorhynchus mykiss), (2) whether in vivo exposure of caddisfly larvae in microcosms to metal contaminants induces nuclear apoptosis and the formation of electron-dense granules in gut epithelial cell mitochondria, (3) whether in situ exposure of trout and caddisfly larvae to sediment metal contamination induces nuclear apoptosis and the formation of electron-dense granules in mitochondria of gut epithelial cells and hepatocytes, and (4) whether the composition of the mitochondrial granules reflects sediment metal contamination. Electron microscopy was used to detect the cytotoxic effects of metal contamination. An above-and-below-mine approach was used to compare exposed and reference populations. Copper contamination in sediments was associated with effects on trout and caddisfly larvae at the cellular level and with secondary effects related to reduced body weights and delayed development occurring at higher levels of biological organization. Electron dense granules in the mitochondria of exposed caddisfly and trout mitochondria were detected. Elemental analysis of mitochondrial granules by X-ray analysis suggested Cu was being sequestered by mechanisms that normally regulate transient cell Ca concentrations. Chromatin compaction, margination, and the observation that large vesicles with bi-layer membranes were being expelled from the nuclei of affected cells suggest that apoptosis was also occurring.