Long-term residual contamination from oil spills and other sources of organic contaminants may exert sublethal baseline toxicity (narcosis) on fish populations. Low level, chronic exposures to narcotic chemicals such as polycyclic aromatic hydrocarbons (PAHs) may impose a metabolic cost on a fish, changing its allocation of energy available for growing, reproducing, foraging for food, and escaping predation. To examine this hypothesis, naïve Fundulus heteroclitus, a ubiquitous estuarine fish species with a short home range, were exposed to a gradient of PAH concentrations in their diets over 120 days. On days 0, 35, 62, 90, and 120, we measured individual fish growth parameters and standard metabolic rates. Standard metabolic rates increased with increasing PAH load (p = 0.087).

Long-term exposure to dietary PAHs altered fish maintenance respiration on individuals. We are developing a bioenergetic model to evaluate whether long-term exposure to PAHs sufficiently impacts individual parameters to the extent that the Fundulus population will be affected. Multiple life stages (e.g., eggs, larvae, juveniles, and adults) and generations will be represented with bioenergetic and bioaccumulative processes altered to mimic impacts measured in the experiment. The narcosis induction submodel subjects cohorts to metabolic alterations by imposing a narcotic gradient from no effect to a level where time to critical body residue shifts, thus changing population mortality probabilities. Each model scenario will be compared and contrasted to quantify PAH effects, and to discuss the importance of cumulative chemical stress to fish. Results from the study and model application will be used to evaluate long-term, population-level consequences of sublethal exposures to narcotic contaminants to improve the basis for risk assessment analyses.

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Author notes

1 The information in this paper reflects the views of the author, and does not necessarily reflect the official positions or policies of NOAA or the Department of Commerce.