Takahito IKENOUE

Profile

Senior Researcher
Marine Ecosystem Research Group,
Center for Earth Surface System Research,
Research Institute for Global Change (RIGC)

Research Interests

  • Quantification of the roles of siliceous plankton (e.g., radiolarians and phaeodarians) in the vertical transport of carbon and silicon (Biological pump)
  • Quantification of microplastics in the ocean and their sinking dynamics into the deep sea
  • Dynamics of highly radioactive microparticles in the ocean
  • Reconstruction of modern and past climate/environmental changes using biogenic particles in marine sinking particles and microfossils in seafloor sediments

Contact

Marine Ecosystem Research Group, Center for Earth Surface System Research, Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
2-15 Natsushima-cho, Yokosuka, Kanagawa 237-0061, Japan

Career

1984 Born in Morioka, Iwate Prefecture, Japan
2002/3 Graduated from Fukuoka Prefectural Shuyukan High School
2008/3 B.Sc., Department of Earth and Planetary Sciences, Faculty of Science, Kyushu University
2010/3 M.Sc., Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University
2012/4-2013/3 2012/4–2013/3 JSPS Research Fellow (DC2), Graduate School of Science, Kyushu University
2013/3 Ph.D. (Science), Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University
2013/4-2014/3 JSPS Post-doctoral Research Fellow, Kyushu University
2013/4-2014/3 Visiting Researcher, Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
2013/5-2013/11 Guest Researcher, Department of Geology, Natural History Museum, University of Oslo
2014/4-2021/3 Scientist, Central Laboratory, Marine Environment Group, Marine Ecology Research Institute (MERI)
2021/4-2021/11 Scientist, Head Office, Marine Ecology Research Institute (MERI)
2021/12-2025/3 Researcher (Tenure-track), Marine Plastics Research Group (M-Plastics), Marine Biodiversity and Environmental Assessment Research Center (BioEnv), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
2025/4-2025/9 Researcher with Tenure, Marine Plastics Research Group (M-Plastics), Marine Biodiversity and Environmental Assessment Research Center (BioEnv), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
2025/10-2026/3 Senior Researcher with Tenure, Marine Plastics Research Group (M-Plastics), Marine Biodiversity and Environmental Assessment Research Center (BioEnv), Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
2026/4–Present Senior Researcher with Tenure, Marine Ecosystem Research Group (ESS-2), Earth Surface System Research Center, Research Institute for Global Change (RIGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

所属学会

  • American Geophysical Union (AGU)
  • Japan Geoscience Union (JpGU)
  • The Plankton Society of Japan
  • The Oceanographic Society of Japan
  • Paleosciences Society（PALEO）
  • Japan Consortium for Arctic Environmental Research (JCAR)
  • Japan Science Visualization Society (JSVS)
  • Society of Iodine Science (SIS)
  • The Oceanographic Society of Japan, Advisory Group on Marine Environmental Issues
  • The Oceanographic Society of Japan, Ocean Literacy and Education Panel

Committees and Others

2025/11–Present Member, AMAP Litter and Microplastic Expert group (LMEG), Arctic Monitoring and Assessment Programme (AMAP) working group of the Arctic Council
2025/4–Present Editor, Plankton and Benthos Research, The Plankton Society of Japan
2025/4-2026/3 Executive Committee Member, The 24th Microfossil Reference Center Meeting (MRC2026)
2022/6–Present Editorial Board Member of "PALEO", Paleosciences Society
2022/4–Present Councilor, Paleosciences Society
2022/1–Present Member, Advisory Panel on Science Communications (AP-SciCom), The North Pacific Marine Science Organization (PICES)
2021/10-2023/3 Co-advisor (Secondary Supervisor) for Master's Course, Graduate School of Science, Kyushu University
2013/11-2014/3 Executive Committee Member, Micropaleontological Reference Center Workshop 2014 (MRC2014)

Awards

2023/12 The iwate Prefectural Governor's Prize (general category) for research paper on the Sanriku Sea Area, Iwate Prefecture, FY2023 (Title: Study on Radioactive Iodine-129 Concentration Indicators in Seawater Using Kelps from the Coastal Waters of Northern Japan)

Publications (Peer-reviewed)

  • 31. Ikenoue, T., Ogawa, N.O., Nomaki, H., Kimoto, K., Honda, M.C., Ohkouchi, N., Fujiki, T. (2025) New evaluation of particulate organic carbon fluxes of submillimeter-sized phaeodarians in the mesopelagic twilight zone of the western North Pacific Ocean. Progress in Earth and Planetary Science 12, 79, doi: 10.1186/s40645-025-00753-z. https://doi.org/10.1186/s40645-025-00753-z
  • 30. Sambandam, M., Mishra, P., Ikenoue, T., Nakajima, R., Itoh, M., Dhineka, K., Kaviarasan, T., Marigoudar, S.R. (2025) Microplastic contamination in the western Arctic water column: A transition from pristine to polluted. Chemosphere 384, 144577, doi:10.1016/j.chemosphere.2025.144577. https://doi.org/10.1016/j.chemosphere.2025.144577.
  • 29. Watanabe, E., Ueno, H., Kodaira, T., Murata, A., Nishino, S., Ikenoue, T., Yamamoto, M., Nomura, D., Abe, H., Kawaguchi, Y., Hirano, D., Zhang, Y., Yasunaka, S. (2025) Arctic marine environments regulated by ocean transport and air‒sea‒land interaction: Findings from the ArCS II Ocean Research Program, Polar Science 45, 101205. doi: 10.1016/j.polar.2025.101205. https://doi.org/10.1016/j.polar.2025.101205
  • 28. Dhineka, K., Mishra, P., Ikenoue, T., Nakajima, R., Itoh, M., Sambandam, M., Kaviarasan, T., and Marigoudar, S.R. (2024) Arctic Threads: Microplastic Fibres in Chukchi and Beaufort Sea Sediments, Marine Pollution Bulletin 208, 116954, doi: 10.1016/j.marpolbul.2024.116954. https://doi.org/10.1016/j.marpolbul.2024.116954
  • 27. Ikenoue, T., Nakajima, R., Osafune, S., Siswanto, E., Honda, M.C. (2024) Vertical flux of microplastics in the deep subtropical Pacific Ocean: moored sediment-trap observations within the Kuroshio Extension recirculation gyre. Environmental Science & Technology 58(36), 16121-16130, doi: 10.1021/acs.est.4c02212. https://doi.org/10.1021/acs.est.4c02212.
  • 26. Ikenoue, T., Nakajima, R., Mishra, P., Ramasamy, E.V., Fujiwara, A., Nishino, S., Murata, A., Watanabe, E., Itoh, M. (2023) Floating microplastic inventories in the southern Beaufort Sea, Arctic Ocean. Frontiers in Marine Science 10, 1288301, doi:10.3389/fmars.2023.1288301. https://doi.org/10.3389/fmars.2023.1288301
  • 25. Ikenoue, T., Bjørklund, K.R., Krabberød, A.K., Nishino, S., Wassmann, P. (2023) Radiolaria and Phaeodaria (siliceous Rhizaria) in south-western and northern Norwegian fjords during late summer 2016: dominant species and biomass in shallow-water assemblages. Polar Research 42, 9584, doi:10.33265/polar.v42.9584. https://doi.org/10.33265/polar.v42.9584
  • 24. Ikenoue, T., Nakajima, R., Fujiwara, A., Onodera, J., Itoh, M., Toyoshima, J., Watanabe, E., Murata, A., Nishino, S., Kikuchi, T. (2023) Horizontal distribution of surface microplastic concentrations and water-column microplastic inventories in the Chukchi Sea, western Arctic Ocean. Science of the Total Environment 855, 159564, doi: 10.1016/j.scitotenv.2022.159564. https://doi.org/10.1016/j.scitotenv.2022.159564
  • 23. Ikenoue, T., Yamada, M., Ishii, N., Kudo, N., Shirotani, Y., Ishida, Y., Kusakabe, M. (2022) Cesium-137 and 137Cs/133Cs atom ratios in marine zooplankton off the east coast of Japan during 2012–2020 following the Fukushima Dai-ichi nuclear power plant accident. Environmental Pollution 311, 119962, doi: 10.1016/j.envpol.2022.119962. https://doi.org/10.1016/j.envpol.2022.119962
  • 22. Ikenoue, T., Otosaka, S., Honda, M.C., Kitamura, M., Mino, Y., Narita, H., Kobayashi, T. (2022) Neocalanus cristatus (Copepoda) from a deep sediment-trap: abundance and implications for ecological and biogeochemical studies. Frontiers in Marine Science9, 884320, doi: 10.3389/fmars.2022.884320. https://doi.org/10.3389/fmars.2022.884320
  • 21. Ikenoue, T., Kimoto, K., Nakamura, Y., Bjørklund, K.R., Kuramoto, N., Ueki, M., Ota, Y., Onodera, J., Harada, N., Honda, M.C., Sato, M., Watanabe, E., Itoh, M., Nishino, S., Kikuchi, T. (2021) New evaluation of species-specific biogenic silica flux of radiolarians (Rhizaria) in the western Arctic Ocean using microfocus X-ray computed tomography. Limnology and Oceanography 66(11), 3901–3915, doi: 10.1002/lno.11928. https://doi.org/10.1002/lno.11928
  • 20. Ikenoue, T., Takehara, M., Morooka, K., Kurihara, E., Takami, R., Ishii, N., Kudo, N., Utsunomiya, S. (2021) Occurrence of highly radioactive microparticles in the seafloor sediment from the Pacific coast 35 km northeast of the Fukushima Daiichi Nuclear Power Plant. Chemosphere 267, 128907, doi: 10.1016/j.chemosphere.2020.128907. https://doi.org/10.1016/j.chemosphere.2020.128907 .
  • 19. Ikenoue, T., Kusakabe, M., Yamada, M., Oikawa, S., Misonoo, J. (2020) Temporal variation of iodine-129 concentrations in kelps (Saccharina) from coastal waters off northern Japan. Marine Pollution Bulletin 161, 111775, doi:10.1016/j.marpolbul.2020.111775. https://doi.org/10.1016/j.marpolbul.2020.111775.
  • 18. Hernández-Almeida, I., Björklund, K.R., Diz, P., Kruglikova, S., Ikenoue, T., Matul, A., Saavedra-Pellitero, M., Swanberg, N. (2020) Life on the ice-edge: Paleoenvironmental significance of the radiolarian species Amphimelissa setosa in the northern hemisphere. Quaternary Science Reviews 248, 106565, doi: 10.1016/j.quascirev.2020.106565. https://doi.org/10.1016/j.quascirev.2020.106565
  • 17. Ikenoue, T., Kimoto, K., Okazaki, Y., Sato, M., Honda, C. M., Takahashi, K., Harada, N., Fujiki, T. (2019) Phaeodaria: An important carrier of particulate organic carbon in the mesopelagic twilight zone of the North Pacific Ocean. Global Biogeochemical Cycles 33(8), 1146–1160, doi:10.1029/2019GB006258. https://doi.org/10.1029/2019GB006258
  • 16. Ikenoue, T., Bjørklund, K. R., Fujiwara, A., Uchimiya, M., Kimoto, K., Harada, N., Nishino, S. (2019) Horizontal and vertical distribution of polycystine radiolarians in the western Arctic Ocean during the late summers of 2013 and 2015. Polar Biology42(2), 285–305, doi: 10.1007/s00300-018-2421-3. https://doi.org/10.1007/s00300-018-2421-3.
  • 15. Takata, H., Johansen, M. P., Kusakabe, M., Ikenoue, T., Yokota, M., Takaku, H. (2019) A 30-year record reveals re-equilibration rates of 137Cs in marine biota after the Fukushima Dai-ichi nuclear power plant accident: Concentration ratios in pre-and post-event conditions. Science of the total environment 675, 694-704, doi:10.1016/j.scitotenv.2019.04.015. https://doi.org/10.1016/j.scitotenv.2019.04.015
  • 14. Ikenoue, T., Ishii, N., Kusakabe, M., Takata, H. (2018) Contribution of 137Cs-enriched particles to radiocesium concentrations in seafloor sediment: Reconnaissance experiment. PLOS ONE 13(9), e0204289, doi: 10.1371/journal.pone.0204289. https://doi.org/10.1371/journal.pone.0204289
  • 13. Takata, H., Kusakabe, M., Inatomi, N., Ikenoue, T. (2018) Appearances of Fukushima Daiichi Nuclear Power Plant-Derived 137Cs in Coastal Waters around Japan: Results from Marine Monitoring off Nuclear Power Plants and Facilities, 1983–2016. Environmental Science & Technology 52(5), 2629–2637, doi: 10.1021/acs.est.7b03956.  https://doi.org/10.1021/acs.est.7b03956
  • 12. Kusakabe, M., Inatomi, N., Takata, H., Ikenoue, T. (2017) Decline in radiocesium in seafloor sediments off Fukushima and nearby prefectures. Journal of Oceanography 73(5), 529–545, doi: 10.1007/s10872-017-0440-2. https://doi.org/10.1007/s10872-017-0440-2
  • 11. Ikenoue, T., Takata, H., Kusakabe, M., Kudo, N., Hasegawa, K., Ishimaru, T. (2017) Temporal variation of cesium isotope concentrations and atom ratios in zooplankton in the Pacific off the east coast of Japan. Scientific Reports 7, 39874, doi:10.1038/srep39874. https://doi.org/10.1038/srep39874
  • 10. Takata, H., Kusakabe, M., Inatomi, N., Ikenoue, T., Hasegawa, K. (2016) The contribution of sources to the sustained elevated inventory of 137Cs in offshore waters east of Japan after the Fukushima Dai-ichi Nuclear Power Station Accident. Environmental Science and Technology 50(13), 6957–6963, doi:10.1021/acs.est.6b00613. https://doi.org/10.1021/acs.est.6b00613
  • 9. Ikenoue, T., Okazaki, Y., Takahashi, K. (2016) Bering Sea radiolarian biostratigraphy and paleoceanography at IODP Site U1341 during the last four million years. Deep-Sea Research Part II: Topical Studies in Oceanography 125–126, 38–55, doi:10.1016/j.dsr2.2015.03.004. https://doi.org/10.1016/j.dsr2.2015.03.004
  • 8. Ikenoue, T., Bjørklund, K. R., Dumitrica, P., Krabberød, A. K., Kimoto, K., Matsuno, K., Harada, N. (2016) Two new living Entactinaria (Radiolaria) species from the Arctic province: Joergensenium arcticum n. sp. and Joergensenium clevei n. sp. Marine Micropaleontology 124, 75–94, doi:10.1016/j.marmicro.2016.02.003. https://doi.org/10.1016/j.marmicro.2016.02.003
  • 7. Takata, H., Hasegawa, K., Oikawa, S., Kudo, N., Ikenoue, T., Isono, R. S., Kusakabe, M. (2015) Remobilization of radiocesium on riverine particles in seawater: The contribution of desorption to the export flux to the marine environment. Marine Chemistry 176, 51–63, doi: 10.1016/j.marchem.2015.07.004. https://doi.org/10.1016/j.marchem.2015.07.004
  • 6. Ikenoue, T., Bjørklund, K. R., Kruglikova, S. B., Onodera, J., Kimoto, K., Harada, N. (2015) Flux variations and vertical distributions of siliceous Rhizaria (Radiolaria and Phaeodaria) in the western Arctic Ocean: indices of environmental changes. Biogeosciences 12(6), 2019–2046, doi:10.5194/bg-12-2019-2015. https://doi.org/10.5194/bg-12-2019-2015
  • 5. Ikenoue, T., Ueno, H., Takahashi, K. (2012) Rhizoplegma boreale (Radiolaria): a tracer for mesoscale eddies from coastal areas, Journal of Geophysical Research-Oceans 117(C4), C04001, doi: 10.1029/2011JC007728. https://doi.org/10.1029/2011JC007728
  • 4. Ikenoue, T., Takahashi, K., Tanaka, S. (2012) Fifteen year time-series of radiolarian fluxes and environmental conditions in the Bering Sea and the central subarctic Pacific, 1990–2005, Deep-Sea Research II: Topical Studies in Oceanography 61–64, 17–49, doi: 10.1016/j.dsr2.2011.12.003. https://doi.org/10.1016/j.dsr2.2011.12.003
  • 3. Takahashi, K., Asahi, H., Okazaki, Y., Onodera, J., Tsutsui, H., Ikenoue, T., Kanematsu,Y., Tanaka, S., Iwasaki S. (2012) Museum archives of the 19 years long time-series sediment trap samples collected at central subarctic Pacific Station SA and Bering Sea Station AB during 1990-2010. Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and Planetary Sciences 32(4), 1–38, doi: 10.5109/21002. https://doi.org/10.5109/21002
  • 2. Ikenoue, T., Takahashi, K., Sakamoto, T., Sakai, S., Iijima, K. (2011) Occurrences of radiolarian biostratigraphic markers Lychnocanoma nipponica sakaii and Amphimelissa setosa in Core YK07-12 PC3B from the Okhotsk Sea. Memoirs of the Faculty of Science, Kyushu University. Series D, Earth and Planetary Sciences 32(3), 1–10, doi: 10.5109/19193. https://doi.org/10.5109/19193
  • 1. Ikenoue, T., Takahashi, K., Ishitani, Y., Tanaka, S. (2010) Seasonal flux changes of radiolarians at Station K2 in the Western Subarctic Gyre. Oceanography in Japan 19(4), 165–185, doi: 10.5928/kaiyou.19.4_165. (In Japanese with English abstract) https://doi.org/10.5928/kaiyou.19.4_165

Books

  • Beautiful Tiny Creatures in Water: Encyclopedia of Small Benthos and Plankton with Color Illustrations, Asakura Publishing Co., Ltd. (2025) (Role: Contributor, "Phaeodaria" pp. 108-115)
  • 50 Questions about Marine Organisms and Radioactivity, Seiyamado Shoten (2024) (Role: Contributor)
  • Plankton: Jellyfish, Water Fleas, and Tiny Aquatic Creatures (Shogakukan's Illustrated Encyclopedia NEO POCKET), Shogakukan Inc. (2024) (Role: Supervisor (editorial), "Phaeodaria and Radiolarians" pp. 138-143)

Research Grants

2023/4-2026/3 JSPS Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), "Quantitative evaluation of microplastic abundance and sinking flux in the seawater of the western Arctic Ocean" (Principal Investigator: Takahito IKENOUE)
2020/4-2022/3 JSPS Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), "Elucidation of the role of phaeodarians in the biological pump of the seasonal sea ice zone in the Indian sector of the Southern Ocean" (Principal Investigator: Takahito IKENOUE)
2017/4-2020/3 JSPS Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (C), "Elucidation of the role of siliceous shell plankton on the silicon cycle in the north and south polar regions" (Principal Investigator: Takahito IKENOUE, Co-Investigator: Katsunori KIMOTO)
2017/4-2018/2 The Sasakawa Scientific Research Grant, The Japan Science Society, "Quantitative evaluation of the role of large unicellular eukaryotes, phaeodarians, in the carbon and silicon cycles: Time-series flux variations in the western North Pacific from 2014 to 2016" (Principal Investigator: Takahito IKENOUE)
2014/4-2017/3 JSPS Grants-in-Aid for Scientific Research, Grant-in-Aid for Young Scientists (B), "An exploration of environmental indices in the Arctic Ocean based on horizontal distribution of radiolarian skeletal structures" (Principal Investigator: Takahito IKENOUE)
2012/4-2014/3 JSPS Grants-in-Aid for Scientific Research, Grant-in-Aid for JSPS Fellows, "How much do phaeodarians contribute to the marine carbon cycle?" (Principal Investigator: Takahito IKENOUE)