Takeo Hama

The environments of the ocean are now rapidly changing as a result of processes associated with human activity. Such processes include eutrophication, increasing water temperatures, increasing CO2 concentrations, and decreasing pH. These changes are most likely affecting the composition of biota. Structural changes in oceanic ecosystems will be followed by alterations in biogeochemical cycles, including the rate of fixation of CO2 by photosynthesis, the isolation of abyssal carbon, and the long-term fixation of carbon through the production of refractory dissolved organic matter.

To elucidate the relationships between marine biota and ocean and global environments, we are studying oceanic biological activity in relation to the biogeochemical cycles of bioelements such as carbon, nitrogen, and phosphorus.

The distribution of phytoplankton pigments in the ocean is substantially affected by latitude, because vertical mixing in the cold water regions supplies nutrients to the surface layers. The increase in surface water temperature caused by global warming may cause declines in nutrient supply, phytoplankton biomass, and carbon fixation.