Educational Activities

Graduate School: Biological Oceanography, Marine Ecology, Ecological Methods

Research Activities

1. Zooplankton diversity in oceans
We investigate species diversity with metagenetic approaches. Copepods are the most dominant crustacean zooplankton in the ocean and are distributed throughout the water column with a high diversity of species (over 2500). Copepod species have been identified by morphological characters and are recognized as a taxa of a well-established taxonomy. However, identification of species requires specialized knowledge and time, and unfortunately basin-scale species diversity and community structures have rarely been studied. Pyrosequencing technology has enabled us to investigate the community structures and species diversity of marine copepods and other organisms very efficiently. We are currently developing methods using 28S rRNA. These technologies can also be applied to the identification of gut content and egg and larval stages. These targets are impossible to identify with conventional morphological characters. We hope we can elucidate early life histories and predator-prey relationships.
2. Biogeochemical cycles and the role of plankton
We have been working on the role of iron as a trace nutrient in oceans. We carried out three iron fertilization experiments in the subarctic Pacific from 2001 to 2004 and found that iron is a limiting nutrient for phytoplankton (especially diatom) production. We are also interested in unpredictable events (from organisms) related to typhoons, dust deposition, and islands on biological production in the subtropical Pacific, which is considered an ocean desert. We have found that these events enhance the local primary production and presumably modify the ecosystem dynamics.

Literature

1) Tsuda, Takeda, Saito, Nishioka, Nojiri, Kudo, Kiyosawa, Shiomoto, Imai, Ono, Shimamoto, Tsumune, Yoshimura, Aono, Hinuma, Kinugasa, Suzuki, Sohrin, Noiri, Tani, Deguchi, Tsurushima, Ogawa, Fukami, Kuma, and Saino. A mesoscale iron enrichment in the western subarctic Pacific induces large centric diatom bloom. Science, 300: 958-961.
2) Boyd, Law, Wong, Nojiri, Tsuda, Levasseur, Takeda, Rivkin, Harrison, Strzepek, Gower, McKay, Abraham, Arychuk, Barwell-Clarke, Crawford, Crawford, Hale, Harada, Johnson, Kiyosawa, Kudo, Marchetti, Miller, Needoba, Nishioka, Ogawa, Page, Robert, Saito, Sastri, Sherry, Soutar, Sutherland, Taira, Whitney, Wong, and Yoshimura: The decline and fate of an iron-induced subarctic phytoplankton bloom. Nature, vol. 428, pp. 549-553, 2004.
3) Boyd, Jickells, Law, Blain, Boyle, Buesseler, Coale, Cullen, de Baar, Follows, Harvey, Lancelot, Levasseur, Owens, Pollard, Rivkin, Sarmiento, Schoemann, Smetacek, Takeda, Tsuda, Turner, and Watson: Mesoscale iron enrichment experiments 1993-2005: Synthesis and future direction. Science, vol. 315, pp. 612-617, 2007.
4) Tsuda, Takeda, Saito, Nishioka, Kudo, Nojiri, Suzuki, Uematsu, Wells, Tsumune, Yoshimura, Aono, Aramaki, Cochlan, Hayakawa, Imai, Isada, Iwamoto, Johnson, Kameyama, Kato, Kiyosawa, Kondo, Levasseur, Machida, Nagao, Nakagawa, Nakanishi, Nakatsuka, Narita, Noiri, Obata, Ogawa, Oguma, Ono, Sakuragi, Sasakawa, Sato, Shimamoto, Takata, Trick, Watanabe, Won, and Yoshie: Evidence for the grazing hypothesis: Grazing reduces phytoplankton responses of the HNLC ecosystem to iron enrichment in the western subarctic Pacific (SEEDS II). J. Oceanogr., vol. 63, pp. 983-994, 2007.
5) Moore, Mills, Arrigo, Berman-Frank, Bopp, Boyd, Galbraith, Geider, Guieu, Jaccard, Jickells, La Roche, Lenton, Mahowald, Maranon, Marinov, Moore, Nakatsuka, Oschlies, Saito, Thingstad, Tsuda, and Ulloa: Processes and patterns of oceanic nutrient limitation, Nature Geoscience, DOI: 10.1038/NGEO1765, 2013.

Other Activities

North Pacific Marine Science Organization (PICES) BIO committee chair (2010-present), Oceanographic Society of Japan, vice-president (2011-2013).

Future Plan

We aim to detect global-scale ecosystem changes in oceans with the hope that our products will help ensure the sustainable use of oceans.

Messages to Students

Please come to our laboratory and join our cruises to the open Pacific Ocean and feel the importance and vulnerability of life in the oceans.

URL

http://www.ecosystem.aori.u-tokyo.ac.jp/plankton/english.html