|Budget Amount *help
¥5,800,000 (Direct Cost: ¥5,800,000)
Fiscal Year 2003: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2002: ¥4,600,000 (Direct Cost: ¥4,600,000)
It was considered that microbial production and related microbial population would be much changed in summer time according to the environmental condition of the near bottom area. To create different environmental conditions, 4 isolated containers made of polypropyrene were constructed. The container is cylindrical shape with 50 cm in diameter and 1.3 m in height, and the top side is closed with the same material with a hole of 15cm diameter at the central part. Different size of circular windows were drilled symmetrically at both side of the cylinders of the containers from 50 cm down the top, these were 35, 25,15 and 5 cm in diameter.
The purpose of this study is to set the four different containers at the bottom of the muddy sediment, so that the environmental conditions of the each container would become changed as a result of the difference of the water replacement and oxygen consumption at the bottom. These were placed at the bottom in the sea just In front of Kumamoto Prefectural
Fisheries Research Center in 2002 and 2003 in summer time at the entrance part of Ariake Sea, Kyushu. The tidal range of this area is something like 4-5 meters, almost highest area in Japan. So the containers had to be tied very fast to a lot of sandbags and anchors around the containers.
Experiment in 2002 was conducted from September 10 to October 10. However, it was not successful partly due to the water inflow and oxygen supply from the inflowing water. No environmental gradients were observed among the 4 containers. Experiment in 2003 started in September 5. However, the containers had to be recovered on September 10 due to a very strong typhoon passed close to Kyushu, and restarted again until October 20. Environmental factors, such as temperature, salinity, oxygen and nutrient concentrations, chlorophyll a, in the water, OR P and acid volatile hydrogen sulphide in the sediments, and microbial population, such as direct count of bacteria, heterotrophic flagellates, picoplankton and phytoplankton were measured and observed.
As a conclusion, we were successful to set 4 isolated environmental containers at the bottom of the sea, where tidal range is almost highest in Japan. However, both experiments in 2002 and 2003, expected gradients at the 4 isolated containers were not observed probably due to water inflow and recovery and reset of the containers during typhoon. Less