Japan Geoscience Union Meeting 2014

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Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS25_28AM2] Evolution of the Pelagic Realm

Mon. Apr 28, 2014 11:00 AM - 12:45 PM 411 (4F)

Convener:*Atsushi Matsuoka(Department of Geology, Faculty of Science, Niigata University), Toshiyuki Kurihara(Graduate School of Science and Technology, Niigata University), Yasuhiro Kato(Department of Systems Innovation, Graduate School of Engineering, University of Tokyo), Tetsuji Onoue(Earth and Environmental Sciences, Faculty of Science, Kagoshima University), Katsunori Kimoto(Japan Agency for Marine-Earth Science and Technology), Tatsuo Nozaki(Institute for Research on Earth Evolution, Japan Agency for Marine-Earth Science and Technology), Hayato Ueda(Faculty of Education, Hirosaki University), Kenta Kobayashi(Department of Geology, Faculty of Science, Niigata University), Takashi Hasegawa(Division of Global Environmental Science and Engineering, Graduate School of Natural Science and Technology, Kanazawa University), Chair:Atsushi Matsuoka(Department of Geology, Faculty of Science, Niigata University)

11:00 AM - 11:15 AM

[MIS25-07] Lifestyle of adherent benthic foraminifers in the open ocean based on stable of isotope records

Katsunori KIMOTO1, *Shiro HASEGAWA2, Hiroshi NAMIKAWA3, Minoru KITAMURA2, Hajime KAWAKAMI2, Makio HONDA2 (1.Kumamoto University, 2.Japan Agency for Marine-Earth Science and Technology, 3.National Museum of Nature and Science, Tokyo)

Keywords:adherent benthic foraminifera, Stable isotopes, Lifestyle, Hydrozoan

Colonization of new habitat of benthic foraminifers is related to their diversion, survival strategies and evolutions. However their dispersal mechanisms are not well documented and still poorly understood. Last year, we reported a new lifestyle of neritic benthic foraminifera: They had lived on the stems of hydrozoan attaching to observational moorings in the Pacific Ocean. This is a new insight of dispersal strategy of benthic foraminifera to the open ocean. However there are no evidences whether benthic foraminifera developed their calcareous shells in the water column or not. Here we report the new evidences of benthic foraminiferal lifestyles based on micropaleontological and geochemical methods. Physical and biogeochemical observational mooring systems (POPPS & Sediment trap) were deployed on July, 2012 at the Station S1 (30N, 145E, water depth: 5,900m). Moored periods were from July 2012 to July 2013 (1 year). Hydrozoan attaching on the both mooring systems were observed at the surface of the winch, sensor buoy, sediment trap and float at shallower depths (~200 m) and we could not observed hydrozoan at the 500 m water sediment trap. More than 300 individuals of benthic foraminifers attached of the surface of hydrozoan body. At least, fourteen living benthic foraminifers were identified under the microscope and faunal assemblages were basically same (calcareous, agglutinated, and sessile) with that of previous year. We performed the stable isotope analysis for these calcareous specimens including some porcellanic benthic and planktic foraminifera. As the results, oxygen and carbon isotopes of calcareous benthic foraminifera showed remarkably lighter and heavier values than planktic foraminifera, respectively. It suggested that calcareous benthic foraminifera in this study built their calcareous shells at shallower water depth than planktic species.