Subproject A01 Ocean Province
Group A01-1 New Ocean Provinces from Physical Oceanography
Our hypothesis is that physical oceanographic phenomena such as mode water formations and variations of mesoscale eddies likely enhance biogeochemical processes, and the areas in which these phenomena occur characterize a new ocean province. To examine this hypothesis, our group takes the following three approaches: (1) analyses of data from the global database, (2) across-basin observations in the North Pacific, and (3) ecosystem modeling. A special focus is to specify the spatial resolution at which the three approaches intersect. The first step is to clarify the global distribution of mode waters and mesoscale eddies and their physical structure by using data from satellite altimetry and Argo floats. This is followed by in situ observations in the target areas stated in the first step. The in situ observations investigate the intensity of vertical mixing, mode water properties, and their modification processes. A new ocean province is derived from these results and verified by satellite ocean color data and outputs from the lower-trophic ecosystem model. Furthermore, by applying the integrated ocean ecosystem model from the lower-trophic ecosystem to migratory fishes, we evaluate the importance of the new province at a higher trophic level.
Group A01-2 New Ocean Provinces from the Geography of Biogenic Elements
The supply and concentration of biogenic elements (C, N, P, Si, O) are essential factors that control marine biogeography. Marine organisms, in addition to physical transportation and chemical transformation processes, regulate the concentration of biogenic elements. Understanding the distribution and dynamics of biogenic elements is essential to distinguish ocean provinces as well as physical oceanographic property and biogeography. The goal of this study is to establish new ocean provinces based on the geography of biogenic elements for governance and sustainable use of marine ecosystem services. To reach this goal, our group will develop highly sensitive methods for the measurement of dissolved and particulate forms of biogenic elements and will apply the methods during meridional- and trans-Pacific cruises. The dust flux of biogenic elements will also be estimated by satellite remote sensing and the numerical model SPRINTERS. With these measurement data, we will develop a 3-D map of the distribution of biogenic elements in the Pacific Ocean.
Group A01-3 Establishment of New Ecozones in the Oceans by Meta-genetic Community Analysis
The goal of our group is to establish new ecological realms (i.e., ecozones) of the oceans based on the biogeography of bacteria, phytoplankton, and zooplankton by implementing high-throughput next-generation sequencing techniques. For bacteria, the community structures are determined by partial sequencing of the 16S rRNA gene, which enables us to identify key species of eubacteria and archaea as well as their roles in the bacterial community. For phytoplankton, we primarily focus on the geographical diversity of their eukaryotic groups, which are diverse lineages with species that can be cryptic or difficult to identify by using DNA barcoding techniques. For zooplankton, first we develop a method to identify the species of pelagic copepods, which are the most dominant and diverse group in the community, by using a metagenomic analysis of the 28S rRNA gene. The new ecozones of these organisms are examined on a basin or global scale and then compared with each other. These outputs augment the description and prediction of ocean conditions and the establishment of general laws for the biogeography of pelagic organisms.