TOXICITY OF BILE FROM FISH EXPOSED TO PENTACHLOROPHENOL-SPIKED SEDIMENT

Many pollutants are concentrated in sediments as well as in the bile o f fish. In order to evaluate if toxicity of fish bile can be used to d etermine lethal and sublethal exposure to pollutants, rainbow trout (O ncorhynchus mykiss) were exposed to pentachlorophenol- (PCP) spiked se diment. PCP was added to a natural fresh water sediment at concentrati ons of 4, 8, 16, 32 and 64 mg PCP/kg wet weight (w/w) and equilibrated with water at 10% sediment in water. Trout were exposed for 1 or 2 cl ays, sacrificed and their bile was tested for toxicity to Daphnia magn a. Exposure was monitored daily by toxicity tests of sediment and wate r using D. magna. Twenty-four hour EC50s, expressed as mg PCP/kg sedim ent w/w (mean +/- SD, N = 5), were 20 +/- 6.4 for sediment and 9.6 +/- 5.1 for water phase tests, respectively. The corresponding sediment 2 4-h LC50 for rainbow trout was ca 16 mg/kg w/w. Toxicity of bile was t ested directly and after extraction with acetone-hexane (1:3, v/v). Pr ior to extraction, subsamples of bile were hydrolyzed by acid (pH 3.5 at 70 degrees C for 3 h) and beta-glucuronidase (pH 5.0 at 40 degrees C for 3 h). Bile and bile extract toxicity in surviving trouts exposed to the median lethal sediment concentration (16 mg PCP/kg w/w) was > 10 x more toxic than bile from control fish, and hydrolyzed bile extra ct from fish exposed to 4 mg PCP/kg sediment was 10-50 x more toxic th an from control fish. Thus, toxicity tests with extracts of hydrolyzed bile were more sensitive than toxicity tests with water and sediment. Therefore, at least for chemicals readily excreted through the bile, toxicity tests may be used to quantify sublethal exposure in fish.