Physiology of Salinity-Dependent Naphthalene Toxicity in Fundulus heteroclitus

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Abstract
The influence of salinity on mortality in mummichogs, F. heteroclitus, subjected to naphthalene and the physiological bases for the salinity-dependent mortalities were determined. Fish were acclimated to 5 salinities, 2, 8, 15, 23 and 33.permill., and exposed to 6 and 4 mg naphthalene/l. At 4 mg/l, fish survival was greater at hypo- and near isoosmotic (15.permill.) salinities than at hyperosmotic salinities. At 6 mg/l, survival was generally greatest at 8 and 15.permill. and decreased at the salinity extremes. In fish exposed to 4 mg naphthalene/l, uptake was more rapid at the iso- and hyperosmotic salinities than at hypoosmotic salinities and osmotic imbalance occurred only at hyperosmotic salinities. Serum cortisol levels and O2 consumption rates increased at all salinities upon exposure to 4 mg naphthalene/l. The most significant increases in O2 consumption rates occurred at hyperosmotic salinities. The greater naphthalene uptake, osmotic imbalance and metabolic stress occurring at hyperosmotic salinities may contribute to the increased mortality of naphthalene-exposed fish acclimated to hyperosmotic salinities.