抄録
Iron is an essential element for plant life in the sea and on land. However, in the sea, especially in open ocean, photosynthesis is limited by iron deficiency because of both limited supply from land and rapid oxidation and sedimentation of dissolved iron. Although previous studies demonstrated that marine phytoplankton under such iron stress can grow actively using steelmaking slag as an iron source. In this study, we followed the temporal change in efficiency of the powdered decarburization slag on the growth of the diatoms Thalassiosira oceanica and T. nordenskioeldii in a modified ESAW medium. To avoid limitation in other nutrients than iron, cultures were spiked with macronutrients in excess concentration. The cultures ran at 20°C for T. oceanica and 10°C for T. nordenskioeldii and growth was determined by in vivo fluorescence of the cultures. The results demonstrated that availability of the iron originating from the slag was high for both species. The bioavailability persisted for at least 23 d for T. oceanica and 30 d for T. nordenskioeldii when the slag was initially added at the concentration of 20 mg/L, probably because of slow but continual dissolution of iron from the slag. This indicates that continual positive effect of iron fertilization can be expected by slag input at an interval of a month or more.
