Chemical speciation of arsenic in the livers of higher trophic marine animals Reiji Kubota, Takashi Kunito, Shinsuke Tanabe * Center for Marine Environmental Studies (CMES), Ehime University, Tarumi 3-5-7, Matsuyama 790-8566, Japan Abstract Concentrations of total arsenic and individual arsenic compounds were determined in livers of cetaceans (Dall’s porpoise and short-finned pilot whale), pinnipeds (harp and ringed seals), sirenian (dugong), and sea turtles (green and loggerhead turtles) to characterize arsenic accumulation profiles in higher trophic marine animals. Hepatic arsenic concentrations in sea turtles were highest among the species examined. Chemical speciation of arsenic revealed that arsenobetaine was the major arsenic compound in almost all the species. In contrast, arsenobetaine was a minor constituent in dugong. Dimethylarsinic acid, methylarsonic acid, arsenocholine, tetramethylarsonium ion, arsenite, and an unidentified arsenic compound were also detected as minor constituents. However, the composition of arsenic compounds was different among these species. These results might reflect the differences in the metabolism of arsenic and/or the compositions of arsenic compounds in their preys. To our knowledge, this is the first report on the large variation in the composition of arsenic species in liver of marine mammals and sea turtles. Ó 2002 Elsevier Science Ltd. All rights reserved. Keywords: Arsenic; Marine mammals; Sea turtles; Pacific Ocean; Chemical speciation; HPLC/ICP-MS 1. Introduction Marine environment is important for global cycling of arsenic. Inorganic arsenic in seawater is biotrans- formed into organoarsenic compounds by marine biota and more than 20 organoarsenic compounds have been identified (Francesconi and Edmonds, 1997). In gen- eral, marine algae accumulate inorganic arsenic from seawater and convert it to arsenosugars, followed by further transformation into arsenobetaine through the marine food chain (Francesconi and Edmonds, 1997). Because the toxicity and behavior of arsenic depends on their chemical forms, chemical speciation of arsenic is essential to understand the metabolism and toxic effects in higher trophic marine animals feeding on the lower trophic marine organisms with high arsenic con- centration (a few ppm to several hundred ppm (Phillips, 1990)). Nevertheless, little is known about the accumu- lation and chemical speciation of arsenic in higher trophic marine animals. In this study, concentrations of total arsenic and in- dividual arsenic compounds were determined in the liver, which plays an important role in arsenic metabolism (Vahter, 1999), of seven species of higher trophic marine animals to characterize the accumulation features. 2. Materials and methods 2.1. Samples Liver tissues of cetaceans (Dall’s porpoise and short- finned pilot whale), pinnipeds (harp and ringed seals), sirenian (dugong), and sea turtles (green and loggerhead turtles) were used in this study. Dall’s porpoise (Pho- coenoides dalli; n ¼ 1) was collected from Otsuchi, Japan, in 2000, short-fined pilot whale (Globicephala macrorhynchus; n ¼ 1) from Ayukawa, Japan, in 1985, harp seal (Phoca groenlandica; n ¼ 1) and ringed seal (P. hispida; n ¼ 1) from Pangnirtung, Canada, in 1999, dugong (Dugong dugon n ¼ 1) from Okinawa, Japan, in 1982, green turtle (Chelonia mydas; n ¼ 1) from Yaey- ama Islands, Japan, in 1996, and loggerhead turtle (Caretta caretta; n ¼ 1) from the North Pacific in 1990. These samples used in this study were obtained from * Corresponding author. Tel./fax: +81-89-946-9904. E-mail address: shinsuke@agr.ehime-u.ac.jp (S. Tanabe). 0025-326X/02/$ - see front matter Ó 2002 Elsevier Science Ltd. All rights reserved. PII:S0025-326X(02)00055-3 www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 45 (2002) 218–223