Combined effects of pyrene and UV-light on algae and bacteria in an arctic sediment

The phototoxicity potential of pyrene on natural algae and bacteria in an arctic sediment was evaluated and compared to that of pyrene treatment alone based on some functional and structural endpoints. Microcosms with arctic sediment from a shallow-water marine bay were incubated with pyrene under three different light regimes, natural sunlight with UV-light (Light(UV)), natural sunlight without UV-light (Light) and dark. Presence of pyrene directly affected the algal community measured as decreased C-14-incorporation and decreased ammonium, nitrate and silicate uptake. These direct toxic effects from pyrene on the algae eventually led to indirect effects on the bacterial community observed as increased oxygen consumption. Besides the direct toxicity of pyrene to the benthic microbial community, indications of phototoxicity were found on the bacterial community detected as decreased oxygen consumption and increased bacterial diversity under Light(UV) compared to Light. No indication of phototoxicity of pyrene was found on the algae, which might be due to the high direct toxicity of pyrene. Our results indicate that shallow arctic marine areas might be affected by phototoxicity if concentrations of oil components in the sediments increase.