Comparison of Trophic Magnification Slopes of Mercury in Temperate and Tropical Regions Case Studies on the Oregon Coast, USA, Sanriku Coast, Japan, and Jakarta Bay, Indonesia Adi Slamet Riyadi, 1,2 Takaaki Itai,* 1 Daisuke Hayase, 1 Tomohiko Isobe, 1,3 Sawako Horai, 1,4 Todd W. Miller, 1 Koji Omori, 1 Agus Sudaryanto, 2 Muhammad Ilyas, 2 Iwan Eka Setiawan, 2 and Shinsuke Tanabe 1 1 Center for Marine Environmental Studies (CMES), Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577 2 Agency for the Assessment and Application of Technology (BPPT), Jl. MH. Thamrin 8 Jakarta 10340, Indonesia 3 Center for Environmental Health Sciences, National Institute for Environmental Studies (NIES), 16-2 Onogawa, Tsukuba, Ibaraki 305-8506 4 Department of Regional Environment, Tottori University, 4-101 Koyamacho-Minami, Tottori 680-8551 (E-mail: itai@sci.ehime-u.ac.jp) The trophic magnification slope (TMS) of mercury has been reported from >130 aquatic systems in the world. However, data from the Asia-Pacific region is quite lacking despite the need for estimation of Hg exposure via fish consumption in many of those regions in the world. Here we provide TMS values from three marine regions in the Pacificrim, Oregon coast, USA, Sanriku coast, Japan, and Jakarta Bay, Indonesia. A decreasing trend of TMS from temperate to tropical regions was found in this study. Mercury (Hg) isawidely recognized global pollutant due to its potential for long-range transport and high biomagnification potential as methylmercury (MeHg). 1 Recent development of numerical modeling coupling atmosphere-ocean Hg dynamics has predicted high deposition of Hg in east to south-east Asia due to its high emission from China and artisinal goldmining. 2,3 Once deposited into ecosystems, inorganic Hg may be converted to MeHg, which bioaccumulates in aquatic food webs. 4 Fishes inhigh trophic position generally show high MeHg level thereby being the biggest source of MeHg exposure to humans. 5 Therefore, increas- ing deposition of Hg in the North Pacific cannot be overlooked by concerned governments in Asia-Pacific as their people constantly consume fish as an important source of animal protein. 6 In order to predict MeHg level by coupling atmosphere-ocean dynamics models, the trophic magnification factor of total Hg (THg) and MeHg through the food web should be known. Statistical investigation has been recently developed by compiling literature data from various freshwater and marine water systems. 7 The study showed an increasing trend of trophic magnification slope (TMS), the slope of regression curve between δ 15 N and Log[THg], with latitude. However, the underlying mechanism of this trend is under debate. Additionally, data from Asian tropical/temperate regions are lacking (two fresh water sites in China and Masan Bay, Korean marine site, Masan Bay) in Lavoie et al. despite 127 studies (n = 101 in freshwater, n = 26 in marine water) being covered from the entire world. 7-9 Apart from Lavoie et al., as far as we know, only 2 reports have been published from Asian marine sites, 10,11 while freshwater systems in China have recently been investigated. 12 In this study, we provide TMS and trophic magnification factor (TMF) from three regions in the Pacificrim, Oregon coast, Sanriku coast, and Jakarta Bay. We chose these three regions based on their oceanographic characteristics. The Oregon coast (43-48°N along the west coast of North America) is in the cold temperate region. The California Current is predominant in this region and shows high productivity due to up-welling. 13 The Sanriku coast is located on the temperate western Pacific (39°N, 142°E) where the warm Kuroshio current and cold Oyashio current are flowing here converting this region into a highly productive and thus a good fishing ground. 14 Jakarta Bay (6°S, 107°E) is a representative tropical eutrophic marine bay. 15 After calculating trophic magni- fication parameters, factors controlling these are discussed by comparing other studies focusing on oceanographic properties. Nine species of animals(n = 67) were collected from North- ern California to the Oregon coast from June to September 2007, 15 species (n = 111) were purchased from the Sanriku coast in September 2007, and 26 species (n = 57) were collected from Jakarta Bay during August 2010. In the Oregon and Sanriku coasts, zooplankton was collected by plankton net. All animals were dissected and freeze dried for 24 h. Muscletissue from fish and large crustacean were used while mantletissue was used for cephalopod samples. Wholetissues of small fish, small crustacean and zoo plankton were homogenized. Detailsof species are listed in Table S1. For the THg analysis, ca 0.2g of powdered dry sample was digested by a microwave system (Start D, Milestone) using HNO 3 (Wako pure) in Teflon vials. Concentration of mercury was determined by cold vapor-atomic absorption spectrometry (CV- AAS, Hiranuma HG-400 series). Methyl mercury was selectively extracted with toluene followed by back-extraction to a 4mM thiosulfate solution. The aliquot was digested with the microwave system followed by the determination by CV-AAS. For the isotope ratio analysis, subsamples were dried for 24 h at 60 °C and ground into powder with a mortar and pestle. The solvent-extractable lipid fraction was removed from the subsample and the lipid-free residues were centrifuged using microtubes and dried at room temperature and later at 60 °C for 24 h. One milligram powder subsamples were packed into 4-6 mm tin capsules for stable isotope measurements. Stable isotopes were measured using ANCA-SL mass spectrometer (PDZ Europa Ltd.). Isotope ratios of carbon (δ 13 C) and nitrogen (δ 15 N) are expressed as the deviation from standards in parts per thousand (‰) according to the following equation: X ¼ ½ðR sample =R standard Þ 1 1000 ð1Þ where X is 15 N or 13 C and R is the corresponding ratio 15 N/ 14 N or 13 C/ 12 C. Standard for 15 N and 13 C are atmospheric N (air) and the PDB standard, respectively. TMSs and TMFs were calculated as follows. The definition of TMS are the slope (b) of regression of eq 2. Log 10 ½Hg¼  15 N ðbÞþ a ð2Þ CL-150579 Received: June 14, 2015 | Accepted: July 28, 2015 | Web Released: August 7, 2015 1470 | Chem. Lett. 2015, 44, 1470–1472 | doi:10.1246/cl.150579 © 2015 The Chemical Society of Japan