4:30 PM - 4:45 PM
[BCG04-10] Stable isotote signature of Fe to understand the Fe-biocycle in the hydrothermal-vent
Keywords:Iron stable isotope, Fe bio-cycle, deep-sea organisms, multiple collector-ICP-mass spectrometer
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.