HISTOPATHOLOGIC BIOMARKERS IN FERAL FRESH-WATER FISH POPULATIONS EXPOSED TO DIFFERENT TYPES OF CONTAMINANT STRESS

Histopathologic alterations of gill, liver, and spleen were studied in feral fish from three freshwater ecosystems that experience different types of contaminant stress. East Fork Poplar Creek (EFPC), a third-o rder stream in East Tennessee, receives point source discharges of mix ed contaminants from a nuclear weapons facility located near its headw ater. The Pigeon River (PR), a high-gradient fifth order stream, is im pacted by bleached kraft mill effluent (BKME). Hartwell Reservoir (HR) , a US Army Corp of Engineers impoundment of the Savannah River, conta ins high levels of PCBs in sediment and biota. Brushy Fork Creek (BFC) , the Little River (LR), and the Tugaloo River (TR) are relatively fre e of contaminants, and served as reference sites for the three respect ive ecosystems of this study. Certain organ and tissue lesions, detect ed microscopically, were common to fish from both reference and contam inated sites. These included parasites, inflammation, glycogen deficie ncy, macrophage aggregates (MA), and diffuse fatty change in the liver ; parasites and MA in the spleen; and parasites, secondary lamellar fu sion, and variable epithelial cell hyperplasia in the gills. Lesions f ound only in fish from contaminated sites were: (1) cholangiomas in li ver of redbreast sunfish (Lepomis auratus) collected from EFPC; (2) am phophilic and eosinophilic foci of cellular alteration, diffuse biliar y preductular and ductular hyperplasia with islands of hyperplastic ba sophilic hepatocytes, and two metastatic thyroidal carcinomas in splee n of redbreast sun fish from PR; (3) severe lipidosis, vacuolated and basophilic foci in largemouth bass (Micropterus salmoides) from HR; (4 ) splenic lymphoid cell depletion and vascular congestion, with necros is of reticuloendothelial cells in fish collected from EFPC and HR; (5 ) hyperplasia of mucous and chloride cells, deformed branchial cartila ge, severe and diffuse aneurysms of lamellae, and edema at the base of the secondary lamellae were in gill of fish from all three sites. The finding of specific lesions only in fish from contaminated sites sugg ests a contaminant etiology. Histopathology biomarker lesions identifi ed in this study are similar to those observed in laboratory exposures of fishes to specific pollutants. Further refinement of these biomark er approaches will be discussed in light of multiple stressors and the ir effects.