Anthropogenic and naturally-produced organobrominated compounds in bluefin tuna from the Mediterranean Sea
Introduction
Brominated flame retardants (BRFs), such as polybrominated diphenyl ethers (PBDEs), have been the focus of an increasing number of studies during the last decade because of their potential for bioaccumulation and contamination in the environment and food webs (de Wit, 2002, Alaee et al., 2003, Law et al., 2003) and because of their potential health effects (ATSDR, 2004, Birnbaum and Staskal, 2004). PBDEs are synthetic compounds, commercially available as mixtures with different degree of bromination (Penta-, Octa- and Deca-BDE), used in a variety of products such as plastics, textiles and electrical equipment. In 2004, the Penta- and Octa-BDE mixtures were banned by the European Union (Directive, 2003/11/EC). The Deca-BDE mixture was banned in 2008 (Betts, 2008). Recently (May 2009), the Penta- and Octa-BDE mixtures were added to the Stockholm convention list.
Several structural PBDE analogues, such as the methoxylated PBDEs (MeO-PBDEs), have recently been evidenced in fish and marine mammals (Pettersson et al., 2004, Sinkkonen et al., 2004, Valters et al., 2005, Covaci et al., 2008; Weijs et al., 2009). MeO-PBDEs are naturally-produced in the marine environment by sponges or algae (Vetter et al., 2002, Malmvarn et al., 2005). More than 4000 halogenated naturally-produced compounds have been found in the marine environment (Gribble, 2000), while only a few of them, such as MeO-PBDEs, polybrominated hexahydroxanthene derivatives (PBHDs), 2,4,6-tribromoanisole (TBA) and a mixed halogenated compound (MHC-1), have been measured at high concentrations in marine organisms, including top-predators (Vetter et al., 2001, Vetter et al., 2002, Vetter et al., 2008, Melcher et al., 2005, Hiebl et al., 2006, Melcher et al., 2007). Yet, only a few papers reported on concentrations of PBDEs and MeO-PBDEs in Mediterranean Sea organisms (Pettersson et al., 2004, Corsolini et al., 2008, Covaci et al., 2008).
The present work focuses on bluefin tuna (Thunnus thynnus) from the Mediterranean Sea, an economically and gastronomically relevant species. Tuna populations are variable according to the season, the Mediterranean area being massively populated during warmer seasons (Medina et al., 2002, Sara and Sara, 2007). Remarkably, populations have considerably decreased in the last decades (almost by 80%) most likely due to over-fishing by industrial fisheries (Chase, 2002, Corsolini et al., 2007, Sara and Sara, 2007). The bluefin tuna is a good example of a flexible species, capable of adapting to its environment which changes rapidly due to their temporal migration. Moreover, this species is also suitable for aquaculture. They feed on crustaceans, small fishes and cephalopods in their juveniles stages, and rely on large cephalopods and pelagic fishes as adults (Corsolini et al., 2007, Sara and Sara, 2007). Because of all these confounding factors, these animals may exhibit different bioaccumulation profiles, which make this species interesting from an ecotoxicological point of view.
This paper aims at assessing the presence of anthropogenic and naturally-produced organobrominated compounds in bluefin tuna from the Mediterranean Sea. Differences in concentrations and accumulation profiles of these brominated compounds between wild and farmed tuna were investigated. Moreover, the daily human intake of brominated compounds was estimated from the ingestion of Mediterranean tuna and its contribution to the total diet was evaluated.
Section snippets
Sample collection
Muscle samples from 26 bluefin tuna (12 males and 14 females between 2–13 years old) were collected in the Mediterranean Sea (South Thyrrenian Sea) during 2003 by different fishing techniques. Twenty wild animals were used from which 10 were caught by longline fishing (baited hooks hanging from a single line) and 10 by “mattanza” technique (net chambers). Six tuna originated from a fish farming area from the same area. Fishes were dissected and muscle samples were frozen at −20 °C until analysis.
Lipid content
Lipid percentages differed according to the origin of the tuna samples (Table 1). Farmed tunas presented higher values probably due to a combination of an intensive diet (mostly based on herring) and a lower activity compared to their wild counterparts. A narrow range (between 27% and 37%, mean 32%, RSD < 12%) was observed for farmed tuna due to the identical conditions in which they were kept. A wider lipid content range was found in wild fishes with percentages ranging from 2.7% to 30%, but
Acknowledgements
Miren Pena acknowledges the Spanish Science and Innovation Ministry (MICINN) for financial support via a FPU grant and aid AP2006-02137. Miren Pena and Lourdes Ramos thank MICINN for financial support (CTQ-2006-14993/BQU). Liesbeth Weijs is financially supported by the Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen). Adrian Covaci is financially supported by a postdoctoral fellowship from the Research Scientific Foundation – Flanders (FWO).
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