Toxicity evaluation of PAHs in the sponge Hymeniacidon heliophila: field assessment and laboratory assays - a preliminary study

Polycyclic aromatic hydrocarbons (PAHs) have been extensively studied in the aquatic environment, although the mechanism of action and biological effects of this xenobiotic in several species, including sponges, are not yet well known. In this context, the aims of the present study were to apply the sponge Hymeniacidon heliophila as a biomonitor for PAH contamination, and to determine PAH depuration and chrysene accumulation patterns through bioassays, evaluating biomarkers in order to verify sublethal responses to exposure. The monitoring of two Southeastern Brazilian areas, Quadrado da Urca and Itaipu beach, indicated bioconcentration of PAHs in sponges. A predominantly petrogenic character was observed in the evaluated areas. Uptake of chrysene and elimination of PAHs were evaluated in H. heliophila, through the biomarkers neutral red and reduced glutathione (GSH), as well as histological evaluations. In the depuration assay, sponges from Quadrado da Urca, a contaminated site, were transferred to aquaria and collected at 24, 48, 72, 96, 168, 240 and 336 h. No significant depuration occurred during the first 96 h, and no changes were verified in the evaluated biomarkers. However, the sponges were able to depurate PAHs from 96 h to 336 h, indicating that this species may reach a healthy status if the environment is uncontaminated. An accumulation bioassay was carried up to 96 h, with sponges from Itaipu beach, in order to evaluate their ability to accumulate chrysene and show immediate effects. Accumulation was intense during 72 h, followed by a decline at 96 h. Neutral red retention time declined with chrysene accumulation, and the decrease of accumulation at 96 h seems related to GSH production. Histological structures were proven to be useful biomarkers of sponge health for experimental conditions. Thus, H. heliophila is confirmed to be an adequate bioindicator PAHs exposure.