Field Test on Breeding Technique of the Zoogamy for Acropora tumidaFumihito IWASE, Susumu NAKANO, Hiroshi AKI, Naoya OKADA and Rika SHIMIZU This study is aimed for establishment of the breeding technique by the zoogamy of Acropora tumida. The natural restoration works for coral communities has been carried out in the Takegashima underwater park located in Southeast Shikoku. A breeding by the zoogamy is effective for the restoration of the coral. Therefore we conducted field works about the growth process of this coral from eggs to juveniles. As a result of investigation of three years, we obtained some important ecological characteristics of this coral, such that laying eggs occurs about on July 3 in lunar calendar.
After the Nankai earthquake in 1946, the resultant flooding lasted for a long time, because seawater remained on land after the tsunami in Kochi city. Large-scale flooding occurred in Ishinomaki city immediately after the Great East Japan Earthquake in 2011. Long-term flooding may hamper disaster responses such as rescue and recovery activities. This paper studied the risks of long-term flooding after the Nankai earthquake in Tokushima city based on a paleographical survey and numerical analysis. The paleographical survey identified statements such as “seawater sometimes flowed onto the land at the full tide,” suggesting occurrences of long-term flooding after previous Nankai earthquakes. The numerical analysis separately calculated values inside and outside the levee.
The tsunami waveforms outside the analysis area obtained by tsunami numerical simulation was used as the boundary condition of the inland flow modeling, that is water was introduced inside the levee when the tsunami water level exceeded the upper end of the levee. The two layers of ground surface and the drain were defined to calculate the flow, including water exchange between the two layers, and the water was drained forcefully outside the levee using a drainage pump. The possibility of long-term flooding in the analysis area is suggested when a large-scale earthquake occurs in the Nankai trough.
The main object of this research settles on the improvement plans for environment on a coral sea area around Awa-Takegashima underwater park in The East Shikoku distinct. Many people have pointed out the decrease and the change on the coral around this park in the past thirty years since 1972,when this sea area was designated for one of the underwater parks. We investigated the social, the nature and the stream conditions around this sea area.
The aim of this study is the development of a method to evaluate a suitable habitat condition of a colony of Acropora tumida which is a kind of stony coral. We improved the HSI model which was often used in a quantitative ecological assessment and suggested the PHSI model which was introduced a probabilistic way of thinking. We can evaluate the optimum habitat condition of coral more precisely than the conventional HSI model by applying the PHSI model to an ecological assessment. We estimated the distribution of a colony of Acropora tumida in 1975 by using the PHSI model in which three physics factors was involved and the estimated distribution well coincided with the observed one. In addition, it was found that the average PHSI value of the object sea area has decreased gradually since 1985. And, the present value was approximately 60% in comparison with that in 1970.
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