Phytosynthesis Regulation of Phytoplankton by Organic Complexation of Iron

Storing carbon dioxide in the oceans is expected to provide a useful means of tackling climate change. Especially, the availability of iron to marine phytoplankton has received considerable attention. There is a hypothesis that fertilizing the oceans with iron may help to reduce carbon dioxide in the atmosphere, because they increase the amount of carbon dioxide absorbed by phytoplankton in the oceans. In this study, we present data on the effect of the chemical form of iron on the growth of phytoplankton in artificial seawater media, in which we have varied the composition of dissolved iron species using synthetic chelators. It was found that chemical forms of iron in the culture media influenced the cell growth of phytoplankton. Under low-iron conditions, the phytoplankton growth was affected by the concentrations of synthetic chelators in the culture media. Under high-iron conditions, there was little difference in growth rates of phytoplankton between chelators in the media. On the basis of the data obtained, we discuss equilibrium conditions controlling the phytoplankton growth in the cultures.