Toxicity and sublethal effects of No. 2 fuel oil on the supralittoral isopod Lygia exotica

1. No. 2 fuel oil was of relatively low toxicity to the intertidal isopod Lygia exotica as indicated by the TLm values of over 100% for the WSF and 73 ppm at 24 and 48 hours and 36.5 ppm at 96 hours for the OWD. 2. Respiration was not significantly affected by short term exposure to several concentrations of No. 2 fuel oil prepared as either a WSF or OWD. 3. Lygia contamined by a spill of No. 2 fuel oil and Bunker C residual oil contained high concentrations of dibenzothiophenes. It is not known whether the dibenzothiophenes were accumulated by the Lygia tissues or absorbed to the exoskeleton. Therefore, the high mortality of Lygia following the spill cannot yet be attributed to the dibenzothiophenes.