Estimation of past aquatic environment interms of shells in coastal zone and development of rehabilitation methods

以菲律宾蛤仔(Ruditapes Philippinarum)为例，探讨了贝类生长线在评价日本有莱科湾水域环境中的适用性。贝壳的生长线是由内部(生理)反应和外部应力共同作用形成的。生长线的距离，即生长率，除了取决于前面提到的食物、缺氧和有害物质的暴露量外，还取决于水温和物理干扰，而不是取决于亮度的变化。贝壳每年被物理和生物腐蚀17%，也就是说，有莱克湾每10年就有80%被腐蚀。因此，埋藏在沉积物中的贝壳可用于估算过去的水环境。Δ^14C可以用来估计有莱克湾的生长期。该方法适用于估算壳体的物理扰动。需要进一步研究以评估营养不良、缺氧等造成的影响。

Applicability of growth line of shells to estimate aquatic environment in terms of Ruditapes philippinarum (short neck clam) in Ariake Bay, Japan is investigated. The growth line of the shell is formed by both internal (physiological) reaction and external stresses. The distance of growth lines, that is, growth rate is shown to depend on water temperature and physical disturbance in addition to the amount of food, anoxia and exposure of harmful substances which are stated already, but not to depend on change of brightness. The shell is corroded physically and biologically by 17% per year, that is, 80% per 10 years in Ariake Bay. Therefor embedded shells in sediments are available to estimate past aquatic environment. Δ^14C is available to estimate growing its period in Ariake Bay. The proposed method is applicable to estimate physical disturbance for shells. Further research is needed for estimation of impacts by malnutrition, anoxia, etc.