Abstract
Iron is an essential element for plant growth. But iron is converted into insoluble form because of a pH change; however, most of the dissolved iron has been found to form metal-organic complexes. Fulvic acid and low molecular weight organic acids produced in forests and marsh lands are responsible for dissolving Fe from minerals in rocks or parent material into the soil, and for maintaining its solubility in water. Rivers play an important role in transporting the complex to the sea because their source region is in the mountains and runs through various terrains till it reaches the sea. Recently, research into a transport of iron in the Amur River has been performed as the Amur-Okhotsk Project. Also tree-planting program is in progress in many regions of Japan with reference to fulvic acid. However, the qualitative and quantitative processes of iron transport with fulvic acid from land to sea are not well understood. To gain better understanding of the transport mechanism of fulvic acid from the forest to the sea, we analyzed water and soil sampls along sites in the Obitsu River by fluorescence spectrophotometer. Moreover, we disclosed the relation between net material production and phytoplankton.
