Halogenated Bipyrroles and Methoxylated Tetrabromodiphenyl Ethers in Tiger Shark (Galeocerdo cuvier) from the Southern Coast of Japan

Abstract

Naturally produced halogenated bipyrroles (HBPs) and methoxylated tetraBDEs (MeO-tetraBDEs) are lipophilic and persistent, and therefore may bioaccumulate with higher trophic levels. In this study, the livers of tiger shark (Galeocerdo cuvier) collected from the southern coast of Japan were investigated for size-related bioaccumulation of natural HBPs and MeO-tetraBDEs in comparison with anthropogenic PCBs and PBDEs. Heptachloro-1'-methyl-1,2'-bipyrrole (Cl7-MBP) and hexahalogenated 1,1'-dimethyl-2,2'-bipyrrole (Br4Cl2-DBP) were present at similar concentration ranges (4-4400 ng/g lipid) in the liver and increased with increasing body length. Two MeO-tetraBDEs, 6-methoxy-2,2',4,4'-tetrabromodiphenyl ether(6-MeO-BDE47), and 2'-methoxy-2,3',4,5'-tetrabromodiphenyl ether (2'-MeO-BDE68) were present at 4- to 6-fold higher concentrations (88 and 58 ng/g lipid, respectively) than BDE-47. In mature tiger sharks, 2,2'-dimethoxy-3,3',5,5'-tetrabromobiphenyl (2,2'-diMeO-BB80) was present at a median concentration of 330 ng/g lipid. Concentrations of 6-MeO-BDE47 were positively correlated to body length (P < 0.01), but no such correlation was observed for 2'-MeO-BDE68 and 2,2'-diMeO-BB80. The concentration ratios (patterns) of PBDE-like natural products in tiger sharks were largely different from that found in other species, such as the bull shark (Carcharhinus leucas), the silvertip shark (Carcharhinus albimarginatus), and the sandbar shark (Carcharhinus plumbeus). The present study suggests thatthe concentrations of natural HBPs in the liver are size (age)-dependent whereas MeO-tetraBDEs have species-specific biomagnification potentials.