Outline of Main Research Theme for
Research Vessel “MIRAI” during fiscal year 2008

1. Cruise Code :
MR08-05

2. Main research theme:
The study of ecosystem and materials’ cycle in the North Pacific

3. Objectives:
Based on previous biogeochemical studies, it has been verified that the biological activity (the biological pump) plays an important role in absorbing atmospheric CO2 in the northwestern North Pacific. On the other hand, mechanism of carbon and other material cycle and its change in the mesopelagic layer or twilight zone (100 ? 1000 m) have been still unclear. It is possible that activity of zooplankton and heterotrophic bacteria in the twilight zone deeply affect on change in materials (regeneration and repackage). In addition, it has been proposed that zooplankton diurnal/ontogenetic vertical migration and its fecal pellet contribute to carbon vertical transport more considerably than we expected. However observation on relation of zooplankton / bacteria activity with carbon cycle has been insufficient.
In this study, seasonal and annual biological and chemical oceanographic data are obtained and the role of zooplankton and heterotrophic bacteria in carbon cycle in the northwestern North Pacific is verified.

4. Outline of observation:
During this cruise, species, vertical distribution, diurnal vertical migration and grazing pressure of zooplankton (bacteria if possible) are observed at several stations in the northwestern North Pacific centering time-series station K2 by using plankton net such as IONESS. In addition, dissolved and particulate chemical substances (nutrients, carbon species, pigments, natural radio-nuclides, primary productivity etc.) are observed with using water sampler, in situ pumping system, drifter and mooring system. Based on these observations, the role of zooplankton in carbon cycle in autumn in studied.

5.Main research area:
Northwestern North Pacific

6.Cruise period:
Departure from Dutch Harbor on 13 October 2008
Arrival at Sekinehama on 10 November 2008 (28 days cruise)

7.Ports of call (tentative):
None

8.Proponent of main research theme:
Minoru Kitamura (JAMSTEC Extremobiosphere Research Center)
Shuichi Watanabe (JAMSTEC Mutsu Institute for Oceanography)
Makio Honda (JAMSTEC Mutsu Institute for Oceanography)

9. Contact person for questionnaire on this cruise:
Minoru Kitamura e-mail:
Shuichi Watanabe e-mail:
Makio Honda e-mail:

10. Remarks :
This cruise is devoted to international programs such as IMBER (Integrated Marine Biogeochemistry and Ecosystem Research), SOLAS (Surface Ocean Low Atmospheric Study) and PICES-CC (The North Pacific Marine Science Organization - Carbon and Climate).