Effects of naphthalene on metabolic rate and ammonia excretion of juvenile Florida pompano, Trachinotus carolinus Thaís da Cruz Alves dos Santos ⁎ , Phan Van Ngan, Maria José de Arruda Campos Rocha Passos, Vicente Gomes Instituto Oceanográfico, Universidade de São Paulo, Praça do Oceanográfico 191, Cidade Universitária, São Paulo, SP, CEP: 05508-900, Brazil Received 19 August 2005; received in revised form 8 January 2006; accepted 28 February 2006 Abstract Bioassays were performed to determine the level of 96h-LC50 of naphthalene in Trachinotus carolinus and to investigate the effects of different concentrations of naphthalene, after acute (50-min and 24-h) and chronic (12-day) exposures, on the physiological parameters of the species. The 96h-LC50 at 24 °C was 2.83 ppm of naphthalene. Fish after acute exposures show a tendency to increase specific oxygen consumption by virtue of naphthalene concentrations. After chronic exposures, however, a decrease was observed at the highest concentration evidencing a narcotic effect of naphthalene. Ammonia excretion was reduced significantly, as compared to that of the controls, in all the exposed organisms. The O:N ratio indicated a tendency of using lipidic substrate to supply metabolic demands after long term exposition to naphthalene or to high concentrations of the pollutant. The effects caused by naphthalene were time and dose dependent for Florida pompanos. © 2006 Elsevier B.V. All rights reserved. Keywords: Ammonia excretion; O:N ratio; Oxygen consumption; Naphthalene; Trachinotus carolinus 1. Introduction Despite the availability of many studies on hydro- carbon toxicity over marine organisms, relatively little is known about its physiological effects on them. Physi- ological mechanisms relating to toxicity are difficult to determine mainly when the experimental compound is a poorly defined mixture of many elements, such as the often-used water soluble fraction of crude or refined petroleum (Hargreaves et al., 1982). The polycyclic aromatic hydrocarbons (PAHs) are important constituents of petroleum, and naphthalene has been one of the most intensively studied PAHs because of its high toxicity, lower sensitivity to photo-oxidation, high persistence in water and low molecular weight (Vijayavel et al., 2004). Naphthalene, a two-ring PAH, is an ubiquitous pollutant introduced into the aquatic environ- ment mainly as a result of discharges from coal tar production and distillation processes (ATSDR, 1995) as well as of petroleum products and by-product spillages (Irwin et al., 1997; Pacheco and Santos, 2001). PAHs accumulate rapidly in aquatic organisms and attain levels higher than those detected in the environment, in such a way as to affect their normal vital functions as well as the process of energy allocation (Kulkarni and Masurekar, Journal of Experimental Marine Biology and Ecology 335 (2006) 82 – 90 www.elsevier.com/locate/jembe ⁎ Corresponding author. Tel.: +55 11 30916548; fax: +55 11 30916607. E-mail address: thaiss@usp.br (T.C.A. Santos). 0022-0981/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jembe.2006.02.019