MR02-K01

Observational studies on Primary Productivity in the Equatorial Pacific Ocean

The equatorial Pacific has distinguished characteristics, those are it occupies a large region of the world's ocean and the warmest water of the planet exists there. The western equatorial Pacific contains so-called warn water pool. Nitrate is depleted there and primary production is small. In the central and eastem equatorial Pacific, vertical flux of nutrients is enhance due to Quasi-stationary up welling caused by equatorial divergence and consequently chlorophyll a concentration and primary production rate increased along the equator. However, primary production and biomass are not as high as would be expected from the flux of nutrients could support. This is called high nutrient low chlorophyll situation. Since this east to west asymmetry is affected by ENSO event, there is a significant variability in physical characters on seasonal-interannual scale with impact to biogeochemistry, as well potentially with the similar scale of variability. The objective of our cruise is to investigate the, mechanism of this biogeochemical variability especially in the western equatorial Pacific.

We will make a comprehensive observation to investigate carbon cycle especially in a biological aspect. Our observation will include:

-Hydrocast for physical, chemical and biological parameters such as salinity, nutrients, dissolved inorganic carbon, plant pigments and so on.

-Atmospheric and oceanic CO2 measurements.

-In situ and simulated in situ incubation for primary productivity and new productivity.

-Sediment trap moorings to observe export production.

-Distribution of phytoplankton and zoo plankton.

-ETC.

The western Equatorial pacific (145E - 165W on the Equator)

Sekinehama - Hachinohe - Honolulu - Guam - Hachinohe - Sekinehama

Takeshi KAWANO (Ocean Science)