Effects of food ration on survival and sublethal responses of lake chubsuckers (Erimyzon sucetta) exposed to coal combustion wastes.

Study organisms in chronic toxicological bioassays are often provided with excessive resources to remove food limitations as a confounding experimental variable. Under more ecologically realistic situations, resources are often less abundant and such restrictions may alter the responses of organisms to environmental contaminants. Here, we investigated the interaction between resource level and sediment toxicity in the lake chubsucker, Erimyzon sucetta. For 78 days we fed fish one of three ration levels (1X, 2X, 4X; uncontaminated food) that was grazed directly from either clean sand or coal ash-contaminated sediments. Despite provision of uncontaminated food, fish exposed to the contaminated sediments accumulated significant whole body concentrations of As, Se, Sr, and V. Food ration affected the pattern of Se accumulation, with lowest concentrations accumulated by fish supplied with the lowest rations (1X). Paradoxically, fish in the 1X-ash treatment were most adversely effected by ash-exposure, despite having Se burdens much lower than fish in the 2X- and 4X-ash treatments. Fish in the 1X-ash treatment exhibited higher mortality, lower proportional growth, and increased incidence of fin erosion compared to fish provided with higher rations. Such results may, in part, be explained by the apparent inability of fish with reduced rations to maintain positive energy balance, as evidenced by their higher standard metabolic rates compared to control fish fed similar rations. Our results underscore the importance of considering resource quantity and nutritional factors in chronic bioassays in order to draw more ecologically realistic conclusions about contaminant effects.