E A r c h i v e s o f n v i r o n m e n t a l c o n t a m i n a t i o naAbstract. The effects of paper mill effluents on histological, enzyme histochemical and ultrastructural parameters of the liver of male bullhead (Cottus gobio L.) were investigated in an alpine river at the end of the low-water period (in March). Histological examination revealed a marked depletion of glycogen, necrosis of single hepatocytes and a high degree of liver parasitization. The enzyme histochemical tests for acid phosphatase and nonspecific esterase signaled lysosomal alterations. Ultrastructural findings showed a loss of cellular compartmentalization, lysosomal alterations, proliferation of smooth endoplasmic reticulum and peroxisomes, proliferation of collagen fibers in the space of Disse, and hepatic cell necrosis. Histological examination revealed a marked improvement in the condition of the liver after the high-water period.The quantity and nature of its effluents render the pulp and paper industry one of the most serious sources of pollution in rivers. Therefore a great number of studies have been carried out on the effects of pulp and paper mill effluents on fish, but due to the different production processes employed by the industry the results of such studies are not easily comparable. Investigations made on fish exposed to bleached kraft mill effluents (BKME) have revealed effects on carbohydrate metabolism, strong induction of biotransformation enzymes and reduced gonadal growth (Andersson et al. 1987;Larsson et al. 1988) as well as an increased occurrence of diseases (Thulin et al. 1988). Bengtsson et al. (1988) demonstrated vertebral deformation in fish exposed to pulp mill effluents. Only a few studies have been carried out on histopathological effects: Fujiya (1961) demonstrated lesions in the liver, kidney, spleen, and digestive tract in fish exposed to kraft pulp mill wastes; Couillard et al. (1988) found a fusion of the gill lamellae, and Lethinen (1990) reported alterations in the hepatic cells as a result of BKME exposure. Because of the important rol e played by the liver in the detoxification and excretion of lipophilic organic compounds (xenobiotics) this organ has been subjected to more detailed investigation in connection with pulp and paper mill effluents. The present study was aimed at determining the effects of the effluents of two paper mills on the liver of the bullhead (Cottus gobio) in an Austrian river, using histological. histochemical and ultrastructural procedures. Since a large part of the investigation was carried out immediately before the spawning season of the fish, and the liver of females (as do other teleosts) normally exhibits marked morphological and functional changes during exogenous vitellogenesis (Bun Ng and Idler 1983), only male animals were used in order to avoid unnecessary variables.
MethodsAt the end of the low water period in March 1990, using an electric fishing device (4.5 kW impulse) male bullhead were caught in an alpine river upstream of (site 1 ) and downstream of (si...
Zinc is a potential toxicant to fish with water hardness and pH constituting the principal modifying factors of Zn toxicity (Alabaster and Lloyd 1980; Bradley and Sprague 1985; Everall et al. 1989). Major toxic effects of elevated concentrations of waterborne Zn are disturbances of acid-base and ionoregulation (e.g., impairment of the branchial uptake of Ca 2+ ), disruption of gill tissue and hypoxia (Alabaster and Lloyd 1980; Hogstrand et al. 1994), Even at sublethal concentrations, chronic effects such as decreased reproduction, reduced growth and histopathological alterations in various tissues may occur (Spear 1981; Holcombe et al. 1979). Zinc can be accumulated via the gills and/or the digestive tract, However, the relative roles of water and food as sources of Zn uptake are not yet fully elucidated (Dallinger et al. 1987; Spry et al. 1988).The aim of the experimental study presented in this paper was to find an explanation for the unexpected results of a field investigation of a Zn-polluted Austrian river, where despite very high total Zn concentrations in the water and in the sediment (water: mean value 1.6 mg•L -1 , extreme values up to 4.9 mg•L -1 ; sediment: 30 gžL -', dry weight), Zn levels in organs of rainbow trout were within the range of concentrations found in fish from a control site and similiar to those reported in the literature for fish from low-contaminated waters (Hofer et al. 1989). Furthermore, only minor histopathological changes in rainbow trout could be found. In consequence, we carried out a laboratory experiment to study Zn uptake from both Zn-contaminated water and diet at Zn concentrations found in the field study.
MATERIAL AND METHODSThe experiments were conducted with rainbow trout (Oncorhynchus mykiss) yearlings (40-60 g body weight) obtained from a local fish farm. Fish were maintained at 8°C in well aerated laboratory tap water with the following physiochemical characteristics: alkalinity 1700-1800 µeq•L -1 , hardness 140-180 mg•L -1 as CaCO 3 , pH 7.8-8.2, conductivity 215-230 µSžcm -1 , sodium 0.2-0.3 mg•L -1 , potassium 0.15-0.20 mgŽL -1 , chloride 0.25-0.35 mgŽL -1 . Water hardness, pH and temperature corresponded to those found in the Zn-polluted river investigated in the field study.One group (ZW) of 50 rainbow trouts was kept in each of two 200-L tanks (continous flow rate 1.5 LŽmin -1 ). After acclimation, Zn (as ZnSO 4 ) was dosed by a LKB-peristaltic pump from a stock solution. Due to high mortality (up to 14%) after one day of exposure to the Correspondence to: G. Köck
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