Abstract
Thermal environment of the tidal flat is one of the major parts of the contaminated geo-environment of the Ariake Sea. The activities of marine ecosystem in tidal flats depend strongly on the thermal environment. In order to get a clear idea about the thermal environment of the tidal flats of the Ariake Sea, two study areas, Iida and Higashiyoka tidal flats were selected. By installing five nos. of thermocouple (Tokyo Sokki co., Model no.: N004853) at different specified depths ( 0.10 m,0.20 m,0.50 m,1.0 m and 2.0 m) connected with data logger (TDS-530) were used to observe diurnal variation of temperature during the 1st April to 8th April, 2006 at Higashiyoka tidal flat. The measured temperature was stored automatically at 1 h interval in the data logger. To observe seasonal variation of temperature in different depths , temperature was measured by inserting the thermocouple at 0.10 m depths interval in the last week of every month at both study areas in the Ariake sea tidal flat. The diurnal temperature variation was more visible near the surface (0.10 m and 0.20 m) indicating the influence of solar radiation in that portion, however in the deeper region (1.0 m and 2.0 m depth) the temperature was dominated by thermal properties of the mud. From seasonal variation of temperature it was seen that during spring and summer heat was transferred from subsurface to the deeper area but during winter and autumn opposite phenomenon was observed. A correlation is proposed to get the temperature profile in the tidal flat in different seasons.
Highlights
The Ariake Sea which is situated in the south western part of Kyushu island, is one of the best-known semi-closed shallow seas in Japan
The cause for the declination of the fishery products is the unfavorable geoenvironmental condition of the Ariake Sea created by acid treatment practice for the Porphyra sp. cultivation [4, 7].During the period of the cultivation (December-March), the acid is used as the disinfectant acid to treat the Porphyra sp. cultivated in the sea and to provide some nutrient phosphorus to it
The solar radiation affected the soil temperature more than the deeper part of the tidal mud. This type of diurnal trend of temperature agrees with the findings in Baeksu tidal flat in Korea [9]
Summary
The Ariake Sea which is situated in the south western part of Kyushu island, is one of the best-known semi-closed shallow seas in Japan. According to Saga agricultural and forestry statistical society (SAFSS), Japan 2006, the conditions of Sinonovacula constricta, living in the depth of 0-0.70 m of the mud, was very bad as 1.7 x 105 kg catch in 1976 dropped to practically nil by 1992. Cultivated in the sea and to provide some nutrient phosphorus to it This organic acid provides ample of foods for the sulphate reducing bacteria living in the mud and increase the sulphide content in the mud. As a matter of fact that, no study had been carried out before to get the information about the thermal properties or the temperature profile in the Ariake Sea tidal mud.
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