Takeshi Ikeda

Prevention of ocean acidification-induced disturbance of the marine silicon cycle

Grant No.：JPMJPR23G1

Researcher

Takeshi Ikeda

Outline

Ocean acidification caused by increasing carbon dioxide emissions can disturb the marine silicon cycle, which, in turn, can affect the global carbon cycle. It has been speculated that more microorganisms are involved in the biogeochemical silicon cycle than previously thought. In this research project, I intend to revisit the marine silicon cycle while considering previously unrecognized microorganisms, to understand the effects of ocean acidification on the global silicon and carbon cycles and to sustain the healthy silicon cycle.

Shinya Iwasaki

History of deep seawater carbon storage in the Pacific Southern Ocean

Grant No.：JPMJPR23G2

Researcher

Shinya Iwasaki

Outline

Deep ocean carbon reservoir plays a vital role in the global carbon cycle, contributing to dynamic change in atmospheric carbon dioxide concentration during the glacial and interglacial periods. However, little quantitative evidence exists of carbon storage in the deep ocean during the glacial period. Here, I apply a newly developed method to assess foraminiferal test dissolution as a proxy for paleo-carbonate ion concentrations. Utilizing the new proxy, I evaluate the variation in the deep seawater carbon storage in the Southern Pacific, which contributes to understanding the process of carbon sequestration in the deep ocean since the last interglacial period.

Hisashi Endo

A novel dynamics analysis of marine plankton based on genetic information in the dissolved fraction of seawater

Grant No.：JPMJPR23G3

Researcher

Hisashi Endo

Outline

Phytoplankton and other microscopic organisms are the main players in the biogeochemical cycles in the ocean. To understand the future of marine ecosystems, it is essential to understand the responses of eukaryotic microorganisms, which are estimated to number more than 100,000 species, to environmental change. This project aims to establish an environmental impact assessment method that simultaneously measures the growth and mortality of all planktonic species using comprehensive and quantitative analysis of cell-free RNA in dissolved fractions of seawater, and to elucidate the response of marine ecosystems under climate change.

Hidetaka Kobayashi

Elucidating the mechanisms of transient changes in the millennial-scale ocean carbon cycle

Grant No.：JPMJPR23G4

Researcher

Hidetaka Kobayashi

Outline

This study conducts numerical experiments using a model of the ocean carbon cycle to investigate the mechanisms of changes in ocean carbon storage over millennial timescales, focusing on continental weathering, sea level change and seafloor sedimentation processes, from past glacial-interglacial cycles to thousands of years into the future.

Yoshiko Kondo

Role and importance of vitamin B12 in controlling marine primary production

Grant No.：JPMJPR23G5

Researcher

Yoshiko Kondo

Outline

This project will investigate the dynamics of vitamin B12 in both coastal and open ocean areas and verify the state of vitamin B12 limitation in the natural phytoplankton communities through onboard incubation experiments. In the field observation, this project will not only investigate vitamin B12, but also trace metal elements such as iron, which are necessary for phytoplankton growth, and the composition of biological communities. This project will comprehensively analyze the results and elucidate the role and importance of vitamin B12 in the material cycles in the ocean.

Tatsuya Sakamoto

Understanding the impact of global warming on sardine and anchovy ecologies based on fossil isotope analyses

Grant No.：JPMJPR23G6

Researcher

Tatsuya Sakamoto

Outline

How will global warming change the ecology of sardines, which form the basis of marine ecosystems? In this study, I approach this question by analysing the stable isotope ratios of fossil fish otoliths, bivalves and foraminifera from terrestrial strata recently discovered in Kanagawa Prefecture (Paleo-Tokyo Bay). The growth and migration history of sardine and anchovy at that time and the marine environmental conditions will be reconstructed, which will make it possible to clarify the effects of global warming on their distribution and abundance.

Shintaro Takao

Development of high spatiotemporal observation system of photosynthetic activity for the assessment of climate change impacts

Grant No.：JPMJPR23G7

Researcher

Shintaro Takao

Outline

There is deeply concern about the effects of extreme ocean events, such as marine heatwaves, that have become more frequent in recent years on planktonic ecosystems and the air-sea exchange of carbon dioxide (CO2). In this project, I will develop a high spatiotemporal observation system to elucidate interactions among extreme ocean events, the partial pressure of CO2 in surface water, and physiological characteristics of phytoplankton, and to evaluate their impacts on the ocean carbon cycle creating the world’s first dataset that simultaneously captures seasonal variations in the partial pressure of CO2 and photosynthetic activity of phytoplankton in the North Pacific Ocean.

Shotaro Takano

Quantitative understanding of trace metal cycling in the ocean based on multi-elemental analysis

Grant No.：JPMJPR23G8

Researcher

Shotaro Takano

Outline

Trace metals in seawater are essential nutrients or toxins for phytoplankton, so the cycle of trace metals and carbon in the ocean is closely interrelated. This study aims to quantitatively understand the processes of supply, transport, and removal of dissolved and particulate trace metals in the ocean by analyzing concentrations and isotope ratios of multi-elements in atmospheric aerosols, phytoplankton, seawater, suspended particles in seawater, and sediment.

Masumi Hasegawa-Takano

Role of bacteria in the carbon storage process in the mangrove forest

Grant No.：JPMJPR23G9

Researcher

Masumi Hasegawa-Takano

Outline

The mangrove forest storages significant amounts of carbon and thus attracts considerable attention as a blue carbon ecosystem. In this study, I investigate the bacterial community composition and physiological functions of bacteria in the mangrove forest that support its high carbon sequestration capacity, through both metagenomic analyses and culture experiments. These results contribute to the assessment and prediction of potential impacts of environmental fluctuations on mangrove ecosystems.

Takako Masuda

Reassessing marine biological productivity using single cell analysis

Grant No.：JPMJPR23GA

Researcher

Takako Masuda

Outline

I aim to visualize and quantify CN uptake activity by phytoplankton on a cell-by-cell basis using stable isotopes (13C15N) combined with secondary ion mass spectrometry (NanoSIMS). The obtained results will be compared with the bulk results. I will try to visualize 13C utilization in the organic state for picoplankton. Finally, I will apply the above results to a model to estimate primary production in the offshore waters of the Tohoku region.