水棲生物の重金属蓄積に関する研究-II

Abstract

Former studies on “green oyster” were all done on the samples which had abnormally accumulated copper and zinc in aquatic environment. We have no information on the accumulating process of cpper and zinc in normal oysters which were transplanted to the water area producing green oyster. In the previous paper, the author reported the evident difference between the contents of copper in oysters collected at southern coast of Nobeoka Bay (S-group) and the adjacent waters to north of Nobeoka Bay (N-group). The oysters collected at the former were all regraded as green oyster. Therefore, normal oysters at Urashiro Bay (one of N-group) were transplanted to Akamizu Inlet (one of S-group), where we examined the variation of copper and zinc accumulation in the meat of oysters. The variation of accumulated quantity of copper and zinc in oysters during 125 days from July to November in 1965 is reported in this paper. The technical terms concerned with the accumulation used in this paper is defined as follows: 1) Normal accumulation indicated the phenomenon of the increase and decrease of heavy metals in organisms which the metabolism of heavy metals at normal physiological condition bring on. 2) Abnormal accumulation indicates the phenomenon of the increase of heavy metals in organisms brought by the influence of abnormal environmental factors. 3) Moreover, abnormal accumulation shows continual increase of heavy metals in organisms by abnormal accumulating phenomenon, therefore, the quatity of Absolute abnormal accumulation is calculated by subtracting the quantity of normal accumulation from the quantity of abnormal accumulation. In this paper, the normal accumulation refers to the copper and zinc accumulation in oysters at Urashiro Bay, the control field, and the abnormal accumulation refers to the copper and zinc accumulation in oysters at Akamizu Inlet, the test field. The quantity of absolute abnormal accumulation is calculated by subtracting the normal accumulation of copper and zinc at Urashiro Bay from the abnormal accumulation of copper and zinc at Akamizu Inlet. The normal oysters were transplanted to the water area of green oyster, and the variation of accumulative quantity of copper and zinc in the meat of oysters, and the influence of normal accumulation upon the abnormal accumulation, were discussed, and we obtained following results: 1) The quantity of copper in abnormal accumulation increases in the exponential function type, log Y=1.4399+0.0069X, and that of zinc indicates sigmoid type (Fig. 1, 2, 3). 2) The critical points (Fig. 4) are remarked on the variation of quantity of absolute abnormal accumulation of copper and zinc. The regression lines are straight over and under of the points. It appears that the normal accumulation has influence upon the variation of quantity of absolute abnormal accumulation of copper and zinc. 3) It is clear that the absorption and accumulation of copper and zinc are not done in same mechanism in oysters, that each of these metals has its peculiarity in the metabolism of oysters, and that the ratio of zinc to copper in oysters becomes smaller in the process of abnormal accumulation of copper and zinc.