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 mo re than 100 nmol/l were observed at stations near the Yangtze River es tuary and in the bottom water of the central Yellow Sea, while the man ganese concentration dramatically decreased toward the shelf break and reached a constant value less than 5 nmol/l in the Kuroshio water. Th e manganese concentration increased toward the bottom at almost statio ns. 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 fl ux 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 n ear bottom layer is estimated at 55% of total input to the region. The flux of terrigenous particles exported to the pelagic ocean amounts t o 8% of the total suspended load discharged from the Yangtze and Yello w rivers.