Evaluation of the acute and chronic toxicity of fluoranthene-spiked sediments in the presence of UV light using the amphipod Hyalella azteca

Polycyclic aromatic hydrocarbons (PAHs) are a family of ubiquitous contaminants. Among them, fluoranthene is one of the most abundant and is therefore a good model for research. It has been shown that solar ultraviolet radiation (SUVR) enhances the toxicity of this contaminant. Accordingly, phototoxicity is taken into account when assessing the potential hazard of PAH contamination in the aquatic environment. However, little is known about PAHs potential hazard in benthic environments. In an effort to regulate sediment contamination by fluoranthene, the United States Environmental Protection Agency (U.S. EPA) has established a sediment quality criterion (SQC). Unfortunately, very little information on the phototoxicity of fluoranthene contaminated sediments existed and, therefore this factor was not included in the calculation of this criterion. As a result, the primary objective of this study was to evaluate the SQC for fluoranthene in the presence of SUVR using the amphipod Hyalella azteca. Because of the lack of standardization in this field, first it was necessary to find an experimental design which optimized space and time that would allow the assessment of acute toxicity. A protocol with 2 chambers of 40 organisms in each test condition was chosen. With this experimental design, toxicity data were obtained in the laboratory using simulated SUVR. Later these data were validated with an experiment under natural SUVR. In addition, a chronic toxicity assessment was performed using a concentration of about 1/3 the SQC for fluoranthene. In this assessment all of the parameters necessary to build a bioenergetic model for Hyalella azteca were estimated. Even at this low fluoranthene concentration deleterious effects were detected, affirming the conclusion that the present SQC needs to be recalculated. The use of a bioenergetic approach for the evaluation of the chronic phototoxicity of fluoranthene contaminated sediments was recommended since production, growth, molting, respiration and excretion provided a sensitive assessment. Furthermore, the bioenergetic model also pointed to possible sites of action (gill and body wall membranes) of fluoranthene + SUVR.