Manganese in the East China Sea and the Yellow Sea

Total dissolvable manganese (TDMn) was measured at 13 stations in the East China Sea and the Yellow Sea. High manganese concentrations of more than 100 nmol/l were observed at stations near the Yangtze River estuary and in the bottom water of the central Yellow Sea, while the manganese concentration dramatically decreased toward the shelf break and reached a constant value less than 5 nmol/l in the Kuroshio water. The manganese concentration increased toward the bottom at almost stations. These data confirm that manganese is released from the seafloor of the continental shelf. Applying a box model to the continental shelf water shallower than 150 m deep, the residence time and the benthic flux of manganese have been calculated to be (140 +/- 62) days, (11 +/- 4) x 10(3) nmol/m(2)/day from the whole bottom area of 0.9 x 10(12) m(2), respectively. The fraction of manganese transported into the East China Sea across the 700 km-long border from outside the sea via the near bottom layer is estimated at 55% of total input to the region. The flux of terrigenous particles exported to the pelagic ocean amounts to 8% of the total suspended load discharged from the Yangtze and Yellow rivers.