Environment of East China Sea and Yellow Sea

Environment of Ariake Sound

Primary Production Estimation by Satellite Ocean Color

Influence of Typhoon on Ocean Primary Production

Environment of Ise Bay

East China Sea and Yellow Sea are enclosed seas surrounded by Japan, China and Korea with wide and shallow continental shelf area. It is expected that freshwater input from rivers of surrounded land influence to the environmental condition. Rapid development of those countries causes eutrophication of the river by agricultural and urban waist. and climate change and water usage also make variation of amount of freshwater. Those changes influences environment of the East China Sea and Yellow Sea. Recent massive occurrence of large jellyfish, seaweed and red tides may be related to those environmental changes. We mostly study dynamics of phytoplankton, main primary producer of marine environment, with satellite ocean color data and ship data, to understand the relationship to the environmental changes.（Figure is monthly satellite chlorophyll-a concentration estimated by ocean color remote sensing.）

Ariake Sound has been one of the most productive bay in Japan; however, frequent occurrence of red tides and low oxygen water and decline of fisheries productivity have been reported. Dyke construction in Isahaya Bay started on 1998 may have relationship, although real reason is still not identified. It is known that water in Ariake Sound is turbid because strong tidal mixing makes resuspension silt; however, increase of transparency has been reported recently. We now focus the relationship between turbidity and primary production and using satellite remote sensing and ship observations to observe red tide, primary production and turbidity. (Figure indicates distribution of red tide occurred during winter from 2000 to 2001.)

Primary production in the ocean is supported by microscopic phytoplankton, and the produced amount of organic carbon is suggested to be similar to the amount by plant on land. Produced organic matter supports lives in the ocean and ecosystem, including fisheries. It also plays important role for material cycling on earth because part of the organic matter sink deeper layer of the ocean and enhances CO2 uptake by ocean. It is difficult to estimate primary production of large ocean. Method to estimate primary production by satellite remote sensing data is an important topic of this laboratory. (Figures indicate global chlorophyll-a, sea surface temperature, photosynthetically active radiation and primary production estimated by Global Imager of Advanced Earth Observation Satellite-II)

Recently, it is suggested that global warming may increase the number of typhoon and enhance the magnitude. Typhoon perturbs sea surface and supplies nutrient rich deeper water to light abundant surface layer. Primary production is enhanced by the passing of typhoon, and CO2 may be absorbed by the sea. Increase of phytoplankton and enhancement of primary production by typhoon is studied with ocean color satellite data.（Figure indicates low sea surface temperature and high chlorophyll-a along the track of typhoon Meari on 2004 in the East China Sea.）

Ise Bay, Japan, is an eutrophic bay by human activities, and red tide and low oxygen water occurs every year. There are many activities to make better environment of the bay, but it is still not easy to detect the change. We will start the study of this area. （Figure indicates satellite chlorophyll-a distribution in Ise Bay on April 11, 2009）