Journal of Oceanography, Vol. 61 (No. 3), pp. 455-463, 2005
Ishigaki Tropical Station, Seikai National Fisheries Research Institute, Fukai-Ota, Ishigaki 907-0451, Japan
(Received 19 August 2002; in revised form 14 August 2004; accepted 2 September 2004)
Abstract: The concentration level of cadmium (Cd) and the regeneration related to phosphate (PO4) were examined at two stations (CM10, CM12) in the eastern Japan Basin in July 1998. The observed Cd concentrations were around 0.2-0.3 nM and 0.5-0.6 nM in the surface and deep layers (Japan Sea Proper Water; JSPW), respectively; the concentration of Cd in the JSPW was much lower than that in the Pacific deep water, which is attributed to its specific formation system (which driven by the winter convection of the surface layer within the Japan Sea, thereafter descending to the deep layer) connected with the relatively active vertical mixing in the Japan Sea. A plot of Cd against PO4 showed good linearity with positive y-intercept values, suggesting that the excess Cd was apparently not available in the biogeochemical cycle. The molecular ratios of consumed O2 to regenerated Cd and PO4 in the JSPW were 688,000, 140 and 881,000, 146 for CM10 and CM12, respectively, and a lower preformed Cd concentration (around 0.37 nM) was also estimated in the JSPW, different from that of the North Pacific deep water (613,000 for Cd, 170 for PO4, and 0.64 nM of preformed Cd).