[AOS30-P07] Marine Environmental Changes Caused by Destruction and Reconstruction of the Bay-mouth Breakwater
Keywords:Water exchange, Bay-mouth breakwater, Kamaishi Bay, Great East Japan Earthquake
Before the Great Earthquake (in 2009), the bay-mouth breakwater had a negative effect on the marine environment in the bay, although it provided a calm environment there. That is, oxygen deficiency occurred at the inner foot of the bay-mouth breakwater during the season of stratification, especially in the fall season, where a stagnant region formed. This is because water exchange between inside and outside the bay was prevented by the bay-mouth breakwater. Just after the Great Earthquake (in 2011), on the other hand, the oxygen deficiency is reduced, since the stagnant water tended to be removed by the water exchange between inside and outside the bay. At present (in and after 2015), however, the oxygen deficiency is reappearing, because the water exchange begins to be prevented again by the bay-mouth breakwater that is being reconstructed. In other words, the marine environment is getting worse again in the lower layer in Kamaishi bay.