Study of Oceanographic Environments of sea of Harima during Red Tides period by means of Multi Platform Remote Sensing
Seijiro Hayakawa, Takeshi Doihara, Kiichi Hirono
Asia Air Survey Co., Ltd. Tokyo, Japan
Abstract
Red tides due to
Chattonella-antiqua were the cause of damages to the young Yellow Tail raising industries in Sea of Harima, Japan, during the summer (from July through August) of 1987.
Recently, Red tides due to
C. antiqua, frequently occur all over Sea of Harima. Oceanographic environmental parameters which are responsible for the explosive increase in
C. antiqua, however, have not yet been identified.
The difference between sea surface temperature (SST) distribution during two periods, the summer of 1987 and 1985 when Red tides did not occur so much, was studied by means of comparison between NOAA AVHRR data. And weather observation date during those two periods was also compared.
To analyze NOAA AVHRR data acquired in different stage of tides, SST distribution changes due to the ebb and flow was estimated by means of Airborne Multi Spectral Scanner (MSS) data (thermal channel) acquired in time to the tidal cycle.
It is clearly seen on NOAA AVHRR data that the homogeneous water body spread all over Sea of Harima at the period of bloom in 1987. It is noticed that oceanic environments such as upwelling from the bottom due to the strong winds, mixing and spreading of eutrophic water with a plenty of sunlight during the summer of 1987 were different from those of 1985. And those conditions are considered to be necessary to cause Red Tides due to
C. antiqua in Sea of Harima.
Intorduction
Sea of Harima is located in the eastern part of the Seto Inland Sea, Japan (Fig. 1). This area is one of the most eutrophic coastal sea in Japan.
Recently, Red tides due to
C. antiqua frequently occur all over Sea. of Harima. During the summer (from July through August) of 1987, Red tides due to
C. antiqua caused great damages to the young Yellow Tail raising industries in Sea of Harima.
As increase in occurrence of Red tides, the many kinds of study to analyze the relation between oceanographic environments and occurrence of Red tides have been done. FUKASE et al., (1980F) concluded that the upwelling due to the water flow through Kii Channel caused Red tides. And YANAGI (1980) concluded that the upwelling due to the wind caused Red tides. The most important factor of explosive increase in
C.antiqua, However, have not yet been cleared. To study Red Tides phenomena, it is necessary to analyze Red tides from an extensive environmental aspect.
Selecting SST as one of parameter representing oceanic environments, the difference between SST distribution during two periods, the summer of 1987 and 1985 when Red tides did not occur so much, was studied by means of comparison between NOAA AVHRR data.
To compare these NOAA AVHRR data acquired in different stage of tides, the extent of mixing area around Naruto Channel due to the ebb and flow had been estimated by Airnorne MSS data collected at times of slacks and maximum tidal streams
Upwelling associated with the wind was mentioned as an important factor for occurrence of Red tides by YANAGI(1981), IOI et al., (1981). The difference between weather condition which may have caused upwelling during the summer of 1987 and /or 1985 was studied.
