Metabolic responses of some estuarine organisms to an industrial effluent



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Brett (1958) suggested the use of physiological criteria for assessing the presence of an indiscriminate or population stress such as chronic and/or sub-lethal toxicity. Because metabolism is an integrative characteristic, almost every stress condition placed upon an organism should be reflected by changes in metabolic rates. When critically evaluated, a metabolic indicator such as oxygen consumption may be useful in assessing the physiological state of an organism. In the case of fishes, much data on oxygen consumption are available to facilitate ecological interpretation. Studies involving the investigation of respiration of fishes exposed to pollutants have been primarily concerned with the effect of reduced oxygen tension. Because most industrial wastes have a high content of readily oxidizable materials, waters receiving them are rapidly depleted of oxygen. It is quite commonly known that this stress condition is reflected by the respiratory rate of fish (Fry, 1957). The literature reveals few investigations of changes in oxygen consumption rates as a direct result of the presence of a toxic pollutant. Jones (1962) reports changes in opercular movement rates as a result of exposure to metallic ions interfering with oxygen removal by the gills. Smith et al (1965) reported increased hematocrits in fish subjected to concentrations of papermill fiber. This suggests respiratory difficulty, as the same response is noted when fish are under decreased oxygen levels. MacLeod and Smith (1966) found that active metabolism of Pimphales promelas is reduced in water containing suspensions of wood fiber. Similar work was done by Smith et al (1966) using walleye fingerlings. It was found that after 190 days exposure to suspended groundwood fiber, routine metabolic rates were 18 per cent higher, but active metabolic rates were 15 per cent lower. Respiratory distress in some marine organisms subjected to polluting substances has been noted. Hood (1960) detected metabolic changes in Artemia salina, the brine shrimp, following exposure to various wastes and to phenol. Copeland and Wohlschlag (1966) examined routine metabolic changes in pinfish exposed to polluted water. Other criteria which have been used to assess the physiological state of fish in polluted systems include swimming speed, opercular movement rate, time for exhaustion to occur at a given swimming speed, and the per cent of fish able to swim at a given speed for a specified length of time. These methods are merely tests for endurance and do not allow for ecological interpretation as do changes in oxygen consumption rates. It was the purpose of this study, using oxygen consumption rate as an indicator, to learn of changes in the physiological state of certain estuarine organisms when subjected to sub-lethal concentrations and chronic exposure by an industrial waste