Dynamic analysis of eutrophic waters in an inner bay based on satellite image analysis and on field investigations of sediments and benthos

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During the research period, we carried out water quality measurement at about 30 locations in Mikawa Bay on the dates August 21, 1998 November 19 1998, and September 9 1999, when the satellite Landsat took the picture of Mikawa Bay area. The water quality indexes we measured are chlorophyll-a, water temperature, transparency, DO and SS. On August 21 1998, sediments and benthos in the bay were also surveyed. Furthermore, investigations on the population of amphioxus (Branchchiostoma belcheri) and on chlorophyll concentration were carried out off the Enshu coast during the periods July 31-August 5 1998 and June 17 - June 22 1999.Regarding the remote sensing of the chlorophyll concentration, we obtained corresponding Landsat data from Remote Sensing Technology Center of Japan and studied the possibility of the prediction comparing with the measured data. As a result, we developed a new simple formula for the prediction of chlorophyll concentration, which employs bands 1 and 3 the TM data. It also revealed that the formula does not have high accuracy and is not always applicable especially in summer. More consideration on the atmosphere correction will be required.The sea bottom in Mikawa Bay is almost covered by organic mud and the low possibility of existence of living amphioxus is indicated. We then investigated the population of amphioxus off the Enshu coast and found strong correlation between its population and characteristics of sea bottom materials especially grain size, which indicates that changes in bottom materials in Mikawa Bay due to the eutrophication gave signification influences on the benthos in the bay.