ABSTRACT

Seawater samples collected in a coastal area in Funka Bay, Hokkaido, were analyzed for manganese, iron and aluminum in particulate form and for the total concentrations of manganese and iron. A marked contrast was found in the seasonal variations of their distribution with high concentrations of particulate aluminum in winter and total manganese in summer. The causes of the seasonal variations are the dissolution of manganese from the sea floor and the influx of terrigenous material probably transported by the winter monsoon, although resuspension of particles from the bottom and in situ biological decomposition contribute somewhat to the variations in the lower layers of the bay water. When the particulate matter becomes incorporated into the bottom sediments, the proportions of metals lost from the particles are calculated to be more than 76% for manganese and 57% for iron. The rates of resupply to the coastal water estimated from the particulate flux are calculated to be 0.5 and 10g/m²/yr for manganese and iron, respectively.