Japan Geoscience Union Meeting 2016

Presentation information

International Session (Oral)

Symbol B (Biogeosciences) » B-CG Complex & General

[B-CG04] Earth and Planetary Science Frontiers for Life and Global Environment

Sun. May 22, 2016 3:30 PM - 5:00 PM 201A (2F)

Convener:*Yohey Suzuki(Graduate School of Science, The University of Tokyo), Yoshinori Takano(Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Shingo Kato(Japan Agency for Marine-Earth Science and Technology), Katsunori Yanagawa(Graduate School of Social and Cultural Studies, Kyushu University), Tadashi Yokoyama(Department of Earth and Space Science, Graduate School of Science, Osaka University), Chair:Yohey Suzuki(Graduate School of Science, The University of Tokyo), Shingo Kato(Japan Agency for Marine-Earth Science and Technology)

4:30 PM - 4:45 PM

[BCG04-10] Stable isotote signature of Fe to understand the Fe-biocycle in the hydrothermal-vent

*Yuko Yamagata1, Yu-ki Tanaka1, Chong Chen2, Takashi Toyofuku2, Takafumi Hirata1 (1.Graduate School of Science, Kyoto University, 2.Japan Agency for Marine-Earth Science and Technology(JAMSTEC))

Keywords:Iron stable isotope, Fe bio-cycle, deep-sea organisms, multiple collector-ICP-mass spectrometer

Recent progresses in isotope analysis based on the mass spectrometry technique enabled us to detect small changes of the many elements in the periodic table. Among the elements, stable isotope studies using Fe has been widely adopted to understand both the mechanism of Fe metabolism in marine organisms and the bio-cycling of Fe in marine environment. Iron is typical essential inorganic nutrients for all plants and animals. For the land organisms, the Fe isotope ratios varies significantly with increase of the trophic level (Walczyk and Blanckenburg, 2002, 2005). In strike contrast, for marine organisms, because of very limited availability of Fe in seawater, the intake efficiency for Fe could be higher than those for the terrestrial animals. Higher intake efficiency of Fe can results in smaller magnitude of isotopic fractionation through dietary process, and therefore, the difference in the Fe isotope ratios for marine organisms of lower trophic levels were close to the seawater sample (Jong et al., 2007; Bergquist and Boyle, 2006). Moreover, there were no significant difference in the Fe isotope ratios (<0.5‰) for high trophic level marine organisms between muscle and liver (Yamagata, in prep). These studies revealed that magnitude of the isotope effects on Fe can reflect both the nutritional status of Fe in animals and the availability of Fe in marine environments. To investigate this, we have measured the 56Fe/54Fe and 57Fe/54Fe for deep-sea organisms in hydrothermal field for understanding Fe bio-cycle which has both characteristics of environment, terrestrial and marine.
In this study, Chrysomallon squamiferum called “Scaly-foot“ gastropod (n=5) and Gigantopelta aegis (n=5) from a deep-sea hydrothermal field at the Longqi vent field, Southwest Indian Ridge, were subsidized to the Fe isotope ratio analysis. The Chrysomallon squamiferum has unique scale made of iron sulphide on its foot (Suzuki et al., 2006). The Gigantopelta aegis, collected in the identical locations for the Chrysomallon squamiferum, has a thick iron oxide coating on the shell. Both the Chrysomallon squamiferum and Gigantopelta aegis has sulphur-oxidizing bacteria in oesophageal gland to form a symbiotic relation. Sclerite samples and soft body samples of muscle, ctnidium, blood, heart, and oesophageal gland were decomposed, and the Fe was extracted by anion-exchange chromatography. The Fe isotopic ratios were analyzed by a multiple collector-ICP-mass spectrometer (MC-ICP-MS) technique (Nu Plasma II) equipped with a desolvating sample introduction system and pseudo high resolution mode.
The resulting Fe isotope ratios demonstrated the distinct variations in the 56Fe/54Fe and 57Fe/54Fe ratios for Chrysomallon squamiferum and Gigantopelta aegis samples. The resulting δ56Fe values for all soft body samples collected from the Chrysomallon squamiferum were systematically higher than those for the Gigantopelta aegis, whereas no significant difference in the δ56Fe values could be found for oesophageal gland samples collected from Chrysomallon squamiferum and Gigantopelta aegis samples. It should be noted that the δ56Fe for all the soft body samples from the Chrysomallon squamiferum was rather higher than those for symbiotic bacteria. This can reflect both very high intake efficiency of Fe from marine environments and the small contribution of Fe intake through the symbiotic bacterial for the Chrysomallon squamiferum. The Fe isotope signature obtained here demonstrate the clear difference in the Fe metabolism between Chrysomallon squamiferum and sulphur-oxidizing bacteria. The details of the mechanism why separate the δ56Fe values of these two samples will be discussed in this presentation.