Photo-induced toxicity of PAHs to Hyalella azteca and Chironomus tentans: effects of mixtures and behavior

In the aquatic environment, polycyclic aromatic hydrocarbon (PAH) contamination can result from several anthropogenic sources such as petroleum runoff, industrial processes, and petroleum spills. When ultraviolet light (UV) is present at sufficient intensity, the acute toxicity of some PAHs to aquatic biota is greatly enhanced. This photo-induced toxicity of PAHs is directly influenced by the amount of PAH and by the level of UV intensity present in the aquatic environment. Thus, behavioral responses and habits that affect an aquatic organismʹs exposure to UV as well as exposure to PAHs can influence the extent to which damage due to photo-induced toxicity occurs. Experiments demonstrated the effects of photo-induced toxicity of anthracene and fluoranthene on the survival of two benthic macroinvertebrates, the midge Chironomus tentans and the freshwater amphipod Hyalella azteca. This study further investigated the survival and behavior of the test organisms in different substrates (no substrate, a sand monolayer, leaf discs, and sediment) with and without UV. The free-swimming, epibenthic H. azteca avoided the effects of photo-induced toxicity of PAHs to some extent by hiding in leaves when this substrate was available. Results emphasize the importance of organismsʹ behavior in affecting the photo-induced toxicity of PAHs in the aquatic environment.