Effects of ultraviolet-B light and polyaromatic hydrocarbon exposure on sea urchin development and bacterial bioluminescence

Polycyclic aromatic hydrocarbons (PAHs) are relatively common contaminants of the Gulf of Mexico and may be activated to more toxic metabolites by ultraviolet-B (UV-B) light. A marine bacterial bioassay system (Vibrio fischeri) which focused on the reduction of luciferase-mediated bioluminescence was utilized as a measure of toxicity to concurrent exposure to anthracene, benzo[a]pyrene, naphthalene, and phenanthrene and UV-B light (λ=280–320 nm). Inhibition of bacterial bioluminescence was observed following exposure to naphthalene (5 and 10 ppm) and phenanthrene (5 and 10 ppm) for 5 and 15 min. UV-B significantly (p<0.05) decreased the average bacterial bioluminescence in all treatments by 23.8%, as compared to control. No significant decrease in bioluminescence was observed with anthracene and benzo[a]pyrene at concentrations up to 24 and 1.6 ppm, respectively. Anthracene and benzo[a]pyrene are relatively insoluble in water (<45 ppb); therefore, the bioavailability of the two PAHs may significantly influence the exposure and effects of anthracene and benzo[a]pyrene to V. fischeri. Results of bacterial bioluminescence experiments were compared to a sea urchin (Lytechinus variegatus) development assay. Development of sea urchin embryos to the four- and 32-cell stage was utilized as a measure of toxicity to the combined effects of UV-B light and the PAHs, benzo[a]pyrene and phenanthrene. Developing sea urchins demonstrated a significant (p<0.05) dose-dependent decrease in growth rate following exposure to benzo[a]pyrene (1, 5, 50, and 100 ppb) and phenanthrene (1, 5, 50, and 100 ppb), with UV-B light (5.8 μW/cm2). Interaction analysis demonstrates that concurrent exposure to UV-B and PAHs results in additive toxicological effects in both marine organisms tested. Results of the present study suggest that environmental conditions present in the Gulf of Mexico, including both UV-B light and PAH exposure, have the potential to cause adverse toxicological effects to marine organisms.