Outline

This project will monitor the fluctuations in seaweed bed ecosystems on the Sanriku Coast to determine what human efforts are effective in restoring abundant coastal zones. Optimal aquaculture methods for oysters, scallops, wakame etc. on the Sanriku Coast will be proposed. In addition, quantitative evidence showing that the forests are the ocean’s best friend will be presented.

Subtopic (1) Monitoring of changes in coastal environments, and use of the results to develop methods for coastal sea management

Description of Research (FY 2014 – 2016 Achievements)

We used satellite image analysis and ground surveys to study changes in representative ecotones formed by the tsunami and changes in the number of aquaculture rafts. We also investigated the relationship between preys and growth of non-fed aquaculture organisms in Shizugawa Bay, provided these data to an ecosystem model that has been developed by Topic 5, and verified the results obtained with the model. In addition, we co-organized and run the Council for Future Environments in Shizugawa Bay with local related groups.

Description of Research (FY 2017 Plan)

We will use satellite image analysis and ground surveys to study changes in representative ecotones formed by the tsunami and changes in the number of aquaculture rafts. We will also provide data such as seaweed beds needed for the ecosystem model developed by Topic 5 and study deployment of the rafts and carrying capacity of the rafts and so on. needed for the model. We will also run the Council for Future Environments in Shizugawa Bay with local related groups.

Subtopic (2) Determination of the mechanisms of nutrient transfer among forests, rivers and oceans

Description of Research (FY 2014 – 2016 Achievements)

We studied the changes in the quantity and quality of nutrients brought by rivers resulting from differences in land use patterns. We also estimated the annual load flux from the rivers flowing into Shizugawa Bay, based on a consideration of seasonal differences in water quality and flow rate. In addition, we estimated the nutrient discharge potential of land areas and monitored the distribution and cyclic processes of nutrients in seaweed beds and salt marshes. Through experiments both at the site and in the laboratory, we analyzed nutrient circulation in relation to oysters. Furthermore, we also estimated the quantity of water flowing in from outside the bay and the quantity of nutrients flowing in from the open ocean.

Description of Research (FY 2017 Plan)

We will estimate the nutrient concentrations needed in each season by phytoplankton, adherent microalgae, benthic microalgae, large ocean plants and other primary producers and quantify the contribution of nutrient inflow from rivers and the open ocean. We will also analyze the stable isotope ratio in the soft body parts of microalgae and oysters (primary food candidates) to search for candidate foods that are important for oyster growth.

Subtopic (3) 1 Determination of the role of organic matter in substance transfer between forests and oceans

Description of Research (FY 2014 – 2016 Achievements)

We conducted studies throughout the year of Shizugawa Bay in Miyagi Prefecture as well as rivers flowing into the bay, forests, rice paddies and so on, and determined the properties of trace metals (iron, etc.) and organic matter and determined the spatio-temporal fluctuations of these substances. We also conducted experiments of iron intake by microalgae to determine the spatio-temporal fluctuations in the utility of iron in the bay. In addition, we made a quantitative assessment of the flux in the inflow of trace metals from land areas and iron intake by microalgae so on.

Description of Research (FY 2017 Plan)

We will continue to focus on organic matter and physiochemical conditions in conducting tests of the intake of trace metals (iron, etc.) by algae and studies in the Shizugawa Bay region. Together with the results of the studies conducted up through the previous fiscal year, we will focus on Shizugawa Bay and the rivers that flow into the bay and assess the properties of trace metals and organic matter, the spatio-temporal fluctuations in these substances, and the resulting response of primary producers in the bay. We will also pursue a quantitative analysis of trace metals in the bay and quantitatively assess the dynamics of trace metals in the Shizugawa Bay region, including marine algae and other cultivation areas.

Subtopic (3) 2 Determination of the role of organic matter in material transport between forests and oceans

Description of Research (FY 2014 – 2016 Achievements)

In Shizugawa Bay, we investigated the distribution of organic matter originating from rivers, marine algae and seagrass beds, and also examined food resource assimilated by oysters and benthos by carbon stable isotope ratio and fatty acid analyses. We found that the reduced desity of oyster culture significantly has enhanced the oyster growth and mitigated the environmental impacts of oyster feces and pseudofeces in bottom layers. In addition, we sysnthesized data on the particulate organic matter transport from ivers and offshore, and provided them to Subtheme Groupe 4 to contribute to developping the simulation model for particulate organic matter dynamics in the bay.

Description of Research (FY 2017 Plan)

We will identify the particulate organic matter dynamics in oyster aquaculture farms in Shizugawa Bay, and assess effects of oyster aquaculture on oxygen consumption in bottom layer seeawater and sediment properties. We also will further examine nutirtional contributions of terrestrial origin organic matter on primary consumptions in the bay by appplying analyses of fatty acid compositions and carbon and nitrogen stable isotopes.