Photoinduced toxicity of anthracene to juvenile bluegill sunfish (Lepomis Macrochirus Rafinesque): Photoperiod effects and predictive hazard evaluation

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Abstract
The effect of daily light‐cycle duration (photoperiod) on the solar ultraviolet radiation (SUVR) ‐induced toxicity of anthracene to juvenile bluegill sunfish (Lepomis macrochirus R.) in a laboratory system under simulated sunlight was examined. Rates of acute mortality were dependent on both anthracene concentration and photoperiod. Median lethal time values calculated on the basis of accumulated SUVR exposure time (UV‐LT50) were compared with LT50 values calculated from real time of exposure (R‐LT50) to determine relative rates of phototoxic damage versus physiologic repair during periods of darkness. The comparison of these LT50 values indicated that the photoinduced toxicity of anthracene to fish was slowly repaired during periods of darkness but that enough damage accumulated over several SUVR cycles to cause acute mortality.The results from these experiments were incorporated into a relationship to predict no‐effect anthracene concentrations from the daily light‐cycle duration at one SUVR intensity. Information from acute toxicity tests was used to extrapolate to chronic no‐effect values. No‐effect anthracene concentrations in water were predicted to range from 1.2 μg/L for 24 h light:0 h dark photoperiod to 13.5 μg/L for a 6 h light: 18 h dark photoperiod. A no‐effect anthracene body burden of 131 μg/kg has been calculated for juvenile bluegill sunfish for a 16 h light:8 h dark photoperiod at an equivalent depth of 3.0 m in a typical eutrophic system. Thus, considering current natural polycyclic aromatic hydrocarbon concentrations in water and in fish tissue, there exists natural waters in which photoinduced PAH toxicity may occur.