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Naphthalene makes up a substantial fraction of polycyclic aromatic hydrocarbons (PAHs) in crude oil and is an important by-product of industry; however, few studies have investigated the toxicity of naphthalene to aquatic organisms. We examined the toxicity of increasing concentrations (0, carrier control, 130, 200 and 400microg/l) of naphthalene to adult rainbowfish (Melanotaenia fluviatilis) for 3 and 14 days to determine its potential to act as an endocrine disruptor. After exposure for 3 days, no changes in sex steroids were measured. After 14 days, a decrease of serum estradiol in females and an increase in serum testosterone in males was observed. These results suggest that naphthalene has the potential to act as an endocrine disruptor, although since no changes in plasma vitellogenin concentrations were observed in either sex, it is unlikely that naphthalene is acting as a xenoestrogen. There was a positive correlation between the incidences of deformities in larval offspring with increasing naphthalene concentrations, suggesting parental transfer of the toxicant. Egg production, hatchability and larval lengths remained unaltered, whilst few changes were measured in gamma-glutamyltranspeptidase (GTP), an enzymatic indicator of spermatogenesis. Contrary to other PAHs, hepatic ethoxyresorufin-O-deethylase (EROD) activities declined with increasing exposure concentration, suggesting that naphthalene was either having a cytotoxic effect or disrupting enzyme synthesis.

The effect of exposure to petroleum hydrocarbons via the water column and through contaminated sediment upon changes in respiratory enzymes in the common mussel (Mytilus edulis planulatus) was investigated. Mussels were exposed to three concentrations of the water-accommodated fraction (WAF) of Bass Strait crude oil, for 24, 48, and 96 h. In a second study mussels were exposed to three concentrations of crude oil-contaminated sediment for 2 weeks and 1, 2, 4 and 6 months. Activities of citrate synthase (CS) and lactate dehydrogenase (LDH) were measured in the gills. In mussels exposed to WAF, a significant decrease in CS activity was observed over time (P<0.05), whereas treatment did not cause a significant change in CS activity (P>0.05); neither treatment nor time had an effect on LDH activity. Exposure to contaminated sediment did not have a significant effect on CS activity, however, time had a significant effect on CS activity (P<0.05). Both time and treatment had an effect on LDH activity (P<0.05). Results demonstrated that changes in gill CS and LDH are not sensitive biomarkers of petroleum hydrocarbon exposure in M. edulis planulatus.

The toxicity of petroleum hydrocarbons to marine aquatic organisms has been widely investigated; however, the effects on freshwater environments have largely been ignored. In the Australian freshwater environment, the potential impacts of petroleum hydrocarbons are virtually unknown. The toxicity of crude oil and related compounds were measured in the sensitive early life stages of the crimson-spotted rainbowfish (Melanotaenia fluviatilis). Waterborne petroleum hydrocarbons crossed the chorion of embryonic rainbowfish, reducing survival and hatchability. Acute exposures resulted in developmental abnormalities at and above 0.5 mg/L total petroleum hydrocarbons (TPH). Deformities included pericardial edema, disturbed axis formation, and abnormal jaw development. When assessing the acute toxicities of the water-accommodated fraction (WAF) of crude oil, dispersants, dispersant-oil mixtures, and naphthalene to larval rainbowfish, the lowest to highest 96-h median lethal concentrations for day of hatch larvae were naphthalene (0.51 mg/L), dispersed crude oil WAF (DCWAF)-9527 (0.74 mg/L TPH), WAF (1.28 mg/L TPH), DCWAF-9500 (1.37 mg/L TPH), Corexit 9500 (14.5 mg/L TPH), and Corexit 9527 (20.1 mg/L). Using naphthalene as a reference toxicant, no differences were found between the sensitivities of larval rainbowfish collected from adults exposed to petroleum hydrocarbons during embryonic development and those collected from unexposed adults.