The chronic toxicity of mineral oil-wet and synthetic liquid-wet cuttings on an estuarine fish, Fundulus grandis

One of the major factors concerning oil-wet cuttings discharges in the long-term effect on the aquatic environment. This paper investigates the survival and growth of the mud minnow, Fundulus grandis, when exposed to different concentrations of mineral oil-wet and synthetic liquid-wet cuttings in flow-through bioassay chambers. The test fluids were a low aromatic mineral oil-based mud (MOBM) and a synthetic liquid-based mud (SBM). Each test fluid was added to a container of dried water-based cuttings which contained minimum hydrocarbons. The fluid and cuttings were mixed to obtain the desired test concentrations. The study tested three concentrations (1%, 5%, and 8.4% by dry weight) of each fluid on the cuttings. Growth rates during the 3-day period were modest with fish in 1% MOBM losing weight. The highest percent growth rates were obtained with fish cultured in 5% SBM and the controls. However, overall growth was not significantly different between treatments. Mean growth did show a significant difference between controls and 5% SBM, and other treatments. The cuttings of the 5% and 8.4% concentrations of both treatments looked like paste. These pastes may have slowed the movement of organics off of the cuttings beds and affected biodegradability and growth rates. Cuttings in the controls and 1% concentrations stayed suspended in the water column longer when disturbed and looked more like loose gravel. Uptake of the MOBM occurred in the internal organs and tissue of fish. No such uptake was observed in the fish tissue with the SBM; a very low level of synthetic liquid was detected in one gut sample only. This may be the major reason for the variations noted in growth rates. Fish mortality during the study was related to the buildup of anaerobic conditions and insufficient aeration. Fish survival for the entire study was 94%