Study of Oceanographic Environments of sea of Harima during Red Tides period by means of Multi Platform Remote Sensing
Fig. 3 shows the weather condition around Sea of Harima in July and August of 1985 and 1987.
From these data, the following were emphasized:
- In the summer of 1987, at previous period of the
bloom (11-16) July), the range of the wind speed which blew from
south-south-east at Tokushima was from 5 to 7 m sec-1 . It is considered
that strong winds were blowing over the Sea of Harima. When the young
Yellow Tail raising industries were damaged exceedingly (from the end of
July to the beginning of August ) , wind speed was weaker and hours of
sunlight was ling every day.
- In the summer of 1985 (From 1 of July to 5 of
August),, the winds was weaker than that of the same period of 1987.
Discussion
According to weather observation data, strong winds were blowing over the Sea of Harima at previous period of the bloom of 1987. Consequently it was possible that this wind might have caused the upwelling of bottom water which contained nutrients and benthic
C. antiqua cells abundantly and the mixing near the surface. After that, wind speed was weak and hours of sunlight was long. So, the mixed eutrophic water with benthic
C. antiqua cells might be spread in the surface layer with a plenty of sunligh. On the other hand according to NOA AVHRR data, the pattern of SST distribution obtained during the summer of 1987 was more homigeneous, and the difference of minimum and maximum temperature was approximately 2 to 3' c while it was 4 to 5 c in 1985. It is considered that these sea condition that cannot deny the above-metioned inference, can be responsible for the rapid growth to
C. antiqua.
During the summer of 1985, the winds might not be so strong enough to cause upwelling. And on account of the existence of the clockwise moving pattern clearly seen in 1985, spreading of homigeneous water which was mixed with eutrophic bottom water can not be admitted. It is considered that these weather and sea condition were not suitable for the explosive increase in
C. antique.
Conclusion
Using Multi-Platform remote sensing and weather observation data, oceanographic environments of Sea of Harima in the summer of 1987 (Red tides occurred) were compared with these of 1985 ( not occurred). As a results of this study, 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 in Sea of Harima.
In the case of this study, there was no other data useful in regard to ocean environments at the previous period of
C. antiqua blooming, but NOAA AVHRR data and weather observation data. Therefore, simultaneously obtained data by shipboard, such as, nutrients, salinity, vertical temperature distribution, with remote sensing were expected to indentify the relationship parameters in the future.
