Ecotoxicology and Environmental Safety 62 (2005) 376–382 Rapid communication Effects of salinity on biomarker responses in Crassostrea rhizophorae (Mollusca, Bivalvia) exposed to diesel oil Angela Zaccaron da Silva a , Juliano Zanette a , Jaime Fernando Ferreira b , Joa˜ o Guzenski c , Maria Risoleta Freire Marques a , Afonso Celso Dias Bainy a,Ã a Laborato´rio de Biomarcadores de Contaminac - a˜o Aqua´tica e Imunoquı´mica, Departamento de Bioquı´mica, CCB, Universidade Federal de Santa Catarina, 88040-900, Floriano´polis, SC, Brazil b Laborato´rio de Moluscos Marinhos, Departamento de Aquicultura, CCA, Universidade Federal de Santa Catarina, 88040-900, Floriano´polis, SC, Brazil c Empresa de Pesquisa Agropecua´ria e Extensa˜o Rural de Santa Catarina, 88034-901, Floriano´polis, SC, Brazil Received 8 October 2004; received in revised form 10 December 2004; accepted 10 December 2004 Available online 25 January 2005 Abstract Crassostrea rhizophorae is a euryhaline oyster that inhabits mangrove areas, which are widely distributed along the Brazilian coast. The aim of this study was to investigate the effects of salinity (9, 15, 25, and 35 ppt) on the activities of glutathione S- transferase (GST), glucose 6-phosphate dehydrogenase (G6PDH), catalase (CAT), and acetylcholinesterase (AChE) in the digestive gland of this species after exposure to diesel oil for 7 days at nominal concentrations of 0.01, 0.1, and 1 ml L 1 and after depuration for 24 h and 7 days. GST activity increased in a diesel oil concentration-dependent manner at salinities 25 and 15 ppt and remained slightly elevated even after depuration periods of 24 h and 7 days. No changes were observed in the activities of G6PDH, CAT, and AChE in the oysters exposed to diesel and depurated. Based on these results, GST activity in the digestive gland of C. rhizophorae might be used as a biomarker of exposure to diesel oil in sites where the salinity is between 15 and 25 ppt, values usually observed in mangrove ecosystems. r 2005 Elsevier Inc. All rights reserved. Keywords: Mangrove oyster; Crassostrea rhizophorae; Diesel; Salinity; Glutathione S-transferase; Biomarkers 1. Introduction Coastal regions are frequently impacted by human exploration of natural resources. Many foreign organic and inorganic compounds may enter the marine environment through discharge of domestic sewage and industrial effluents, harbor activities, and applica- tion of biocides, deteriorating the quality of the aquatic environment. Polycyclic aromatic hydrocarbons (PAHs) are present in the marine environment due to their widespread occurrence in petroleum, coal, soot, air pollutants, and oil spillages (Walker et al., 1996), and carcinogenic properties have been associated with the exposure to these compounds (Reynaud et al., 2002). The impact of these contaminants in biological systems can be evaluated through biomarkers related to xenobiotic biotransformation and excretion mechan- isms. Biotransformation of xenobiotics may enhance the production of reactive oxygen species (ROS) and electrophilic intermediates derived from the parent chemical. These intermediates can be conjugated with endogenous molecules such as reduced glutathione (GSH) through the action of glutatione S-transferase (GST) (Livingstone, 1985). This conjugation mechanism produces more hydrophilic xenobiotics yielding expel- lable metabolites (Mannervik and Danielson, 1988). ARTICLE IN PRESS www.elsevier.com/locate/ecoenv 0147-6513/$ - see front matter r 2005 Elsevier Inc. All rights reserved. doi:10.1016/j.ecoenv.2004.12.008 Ã Corresponding author. Fax: +55 48 331 9672. E-mail address: bainy@mbox1.ufsc.br (A.C.D. Bainy).