Factors influencing EROD activity in feral winter flounder (Pleuronectes americanus) exposed to effluent from a pulp and paper mill in Newfoundland

摘要

Aquatic organisms can biotransform organic chemicals by producing a series of enzymes which include the mixed function oxygenase (MFO) system (Payne el al. 1987; Jimenez and Stegeman 1990; Collier et al. 1998). The liver is the major site that metabolizes these xenobiotics in fish. Although several bioindicators of stress are used to assess exposure to contaminants, the MFO system is used more often because of its short induction period (Jimenez and Stegeman 1990). However, a number of variables such as species offish, sex, age, temperature, nutritional status, heavy metals, pathological changes in the liver, etc., can have a profound influence oil the rate and extent of biotransformation (Eggens el al. 1995; Andersson and Forlin 1992; Kohler andPluta 1995; Karels and Oikari 2000; Mathieu et al. 1991; Lindstrom-Seppa and Stegeman 1995; Viarengo et al., 1997; Williams et al., 1998). Enzyme activity is usually reduced in nutritionally-deficient fish, after exposure to low temperatures and also shortly before spawning in females (Jimenez and Stegeman 1990). Effluent discharged by pulp and paper mills have been reported to induce MFO activity in a number of fish species (Andersson and Forlin 1992). Previous studies on winter flounder (Pleuronectesamericanus), a sediment-inhabiting, non-migratory species inhabiting a fjord receiving effluent from a sulphite-bleaching pulp and paper mill, revealed that it was sensitive to pollutants and exhibited MFO activity (Payne el al. 1987; Khan and Payne 1997). The fish in the north temperate region lives in shallow water (<15m), remains in the substrate when not foraging, has a limited home range and consequently is useful as a sentinel monitoring species. Spawning occurs in late spring. In view of these observations, a field study was conducted to ascertain the influence of gender, sexual maturity, water temperature and proximity to the pulp and paper mill on MFO activity in flounder living in the inlet. Additionally, it also compared condition (K) factorand hepatosomatic index (HSI) as indicators of nutritional status and gonadosomatic index (GSI) as a measure of gonadal maturity in pre-spawning, post-spawned and mature, non-spawning fish.