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General Session 3: Biological oceanography & global change |
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Geography of biogenic elements in the North Pacific Ocean
Monday 9th @ 1505-1525
Multi-function Hall
Hiroaki Saito* , The University of Tokyo
Yu Umezawa, Nagasaki University
Ryu Nozaki, Nagasaki University
Fuminori Hashihama, Tokyo University of Marine Science and Technology
Hideki Fukuda, The University of Tokyo
Hiroshi Ogawa, The University of Tokyo
Presenter Email: hsaito@aori.u-tokyo.ac.jp
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| Nutrient supply is one of the most important factors controlling marine ecosystem structure and productivity. In most subtropical region, nutrient concentration is below the detection limit of conventional measurement method, and the chlorophyll concentration is low. In addition to their small seasonal variability, subtropical regions have been recognized as homogeneous and stable environment. However, after the development of highly sensitive methods for nutrient measurement such as absorption photometry with LWCC (Liquid Waveguide Capillary Cell), it was found that the variations in nitrate and phosphate concentration were more than 3-order of magnitude within the western subtropical Pacific Ocean. We also applied the LWCC method to particulate forms of P and Si and also for DOP. The detection limits are 1-2 order higher than conventional methods. We used these methods during Hakuho-Maru cruise in the North Pacific Ocean and described geographical variation in the concentration and form of biogenic elements. It is suggested that particulate forms of P and N, including phytoplankton and zooplankton, play an important role as a reservoir and for biogeochemical cycling in the subtropical region of the North Pacific. We will discuss contrastive dynamics of biogenic elemental between subtropical and subarctic ecosystems. |
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