A fertilizer, composed of iron oxides as a source of Fe and compost as humic substance (HS) source, was developed to restore seaweed beds on the barren coasts. However, reasons of Fe elution had been continued for a few years still, not elucidated. Based on the detected biomarker of microbial activities in HS from the fertilizer, we focused on the roles of HSs effect in microbial activities. Microorganisms were isolated from the fertilizer in the barren coast and inoculated to artificial seawater that contained hematite as a model of iron oxide. The effect of anthraquinone-2,7-disulfonate (AQDS) as a model of HS, on the Fe elution was investigated. <i>E. oxidotolerans</i> (T-2-2) was isolated as a major microorganism. Tests for Fe elution were conducted by inoculating T-2-2 in postgate B medium, and the eluted iron was analyzed by ICP-AES. In the presence of both T-2-2 and AQDS (Fig. 1, Kinetics of iron elution from hematite), Fe elution was reached the highest level after 9 days of incubation and then decreased until 30 days. In the absence or presence of T-2-2 alone, trace amounts of Fe were eluted during 30 days of incubation. Only T-2-2 and humic substances, iron cannot be found in this sample. The organic acids production such as oxalic and citric acids also show the highest concentration related to high activities of iron elution. These results suggest that Fe elution into seawater can be due to microbial activities and humic substances can enhance the microbial elution of Fe.

Effect of humic analogue on microbial leaching of iron from hematite into seawater

253rd National Meeting (2017)

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