Photoinduced toxicity of fluoranthene to northern leopard frogs (Rana pipiens)

Rana pipiens larvae (96-118 h old) were exposed for 48 h in a flow-through system to clean water or five concentrations (0.89, 2.18, 6.99, 12.0, and 3 0.6 mu g/L) of the phototoxic polycyclic aromatic hydrocarbon (PAH) fluoran thene. Following this uptake period, the larvae were divided into four grou ps: one for immediate tissue residue analysis, a second for residue analysi s following 48 h of depuration in clean water, and two for a 48-h exposure in clean water to ultraviolet (UV) light at two different levels. At the hi ghest treatment, mean (+/-SD) UVA (310-390 nm)intensity was 8.12 +/- 0.19 x 10(2) mu W/cm(2), whereas at a lower treatment the UVA intensity was 4.45 +/- 0.05 x 10(2) mu W/cm(2). Larval frogs bioaccumulated fluoranthene in di rect proportion to the water exposure concentrations, with initial whole-bo dy PAH concentrations of 1.48, 3.53, 4.85, 11.3, and 18.7 mu g/g at the bye treatment levels. No mortality of the animals occurred during the 48-h upt ake phase. When the frogs were placed in clean water, the fluoranthene was rapidly depurated, with up to 80% lost in 48 h. Exposure to UV light follow ing fluoranthene exposure significantly enhanced toxicity of the PAH. Media n time to death decreased as the product of UVA light intensity and fluoran thene body residue increased. For larval R. pipiens, sufficient tissue resi dues of fluoranthene were bioaccumulated within 48 h, at water exposure con centrations in the range of 2 to 10 mu g/L, to be lethal when combined with a UVA exposure simulating a fraction of summertime, midday sunlight in nor thern latitudes.