Challenges in assessing the toxic effects of polycyclic aromatic hydrocarbons to marine organisms: A case study on the acute toxicity of pyrene to the European seabass (Dicentrarchus labrax L.) Joana R. Almeida a,b,⇑ , Carlos Gravato b , Lúcia Guilhermino a,b a ICBAS – Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Departamento de Estudos de Populações, Laboratório de Ecotoxicologia, Largo do Prof. Abel Salazar 2, 4099-003 Porto, Portugal b CIIMAR – Centro Interdisciplinar de Investigação Marinha e Ambiental, Laboratório de Ecotoxicologia e Ecologia, Universidade do Porto, Rua do Bragas 289, 4050-123 Porto, Portugal article info Article history: Received 1 September 2011 Received in revised form 26 October 2011 Accepted 31 October 2011 Available online 9 December 2011 Keywords: Marine ecological risk assessment Marine fish PAHs Acute toxicity and biotransformation Human risk assessment abstract The acute toxicity (96 h) of pyrene (PY) to European seabass (Dicentrachus labrax) juveniles assessed in a semi-static bioassay (SSB) with medium renewal at each 12 h, and in a static bioassay (SB) without med- ium renewal was compared in laboratorial conditions (water PY concentrations: 0.07–10 mg L À1 ). Main findings in the SSB that assessed mainly the toxicity of PY and its metabolites were: increased levels of bile PY metabolites in good agreement with the profile of lipid peroxidation levels (LPO) in exposed fish relating PY exposure and oxidative damage; increased levels of PY-type compounds in the brain indi- cating their ability to cross the blood–brain barrier; increased levels of these substances in liver and mus- cle which are edible tissues for humans thus raising concern on potential adverse effects on consumers of fish from PY contaminated areas; a significant inhibition of glutathione S-transferase activity suggesting its involvement in PY detoxication as toxicant scavenger; finally, an almost complete impairment of the swimming velocity at all the PY concentrations linking sub-individual to higher population level effects. In the SB, where the overall toxicity of PY, its metabolites and environmental degradation products was evaluated, 19% and 79% of PY decay in test media was found at 12 and 96 h, respectively. In general, the effects were similar to those of SSB but with significant effects being induced at higher PY concentrations indicating that the parental compound is more toxic than its environmental degradation products. The other main differences relatively to the SSB were: increased levels of PY-type substances in the liver sug- gesting more accumulation in this organ. Therefore, these findings highlight the need of carefully consid- ering experimental design options when assessing the toxicity of readily degradable substances to marine fish, and stress the importance of taking into consideration the toxicity of environmental degra- dation products in addition to toxic effects of the parental substance and its metabolites for marine eco- logical risk assessment. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The assessment of ecotoxicological effects of readily degradable polycyclic aromatic hydrocarbons (PAHs) on marine organisms using laboratorial bioassays is challenging. In addition to their ra- pid degradation in water (increased by photochemical oxidation), resulting in several degradation products, they also undergo a complex biotransformation resulting in several reactive metabo- lites, some of them being more toxic than the parental compound, and all these substances may interact with saltwater test media (Haritash and Kaushik, 2009). When considering laboratory bioassays for assessing ecotoxico- logical acute effects of these substances on pelagic fish, three options regarding exposure conditions are available: (i) flow- through conditions; (ii) semi-static conditions; and (iii) static conditions. Using a flow-through bioassay has the advantage of maintain the desired concentrations of the toxicant as recom- mended by standard guidelines, simultaneously removing any ex- creted metabolites and degradation products that may have been produced in the test media. However, such conditions require a high amount of the test substance, a considerable human effort in pre- paring test media, and a high amount of toxic waste is produced, thus increasing the overall costs of the assessment. Using semi-sta- tic bioassay conditions with medium renewal at intervals short 0045-6535/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2011.10.059 ⇑ Corresponding author at: CIIMAR – Centro Interdisciplinar de Investigação Marinha e Ambiental, Laboratório de Ecotoxicologia e Ecologia, Universidade do Porto, Rua do Bragas 289, 4050-123 Porto, Portugal. Tel.: +351 223401828; fax: +351 223390608. E-mail address: jalmeida@ciimar.up.pt (J.R. Almeida). Chemosphere 86 (2012) 926–937 Contents lists available at SciVerse ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere