Since the Sea of Japan Proper Water is formed inside the closed basin, it is straightforward to use the mass-balance method to estimate the Redfield ratios and the dissolution and decomposition rates of particulate matter. The resulting Ca/Si/C/O/N/P ratios for waters deeper than 2000 m are 23¿9/57¿2/98¿6/125¿5/13¿0.9/1¿0.04, in good agreement with the traditional C/O/N/P values of 106/138/16/1. The calcium and alkalinity data indicate a CaCO3 dissolution rate of 0.22¿0.13 and 0.16¿0.05 &mgr;mol kg-1 yr-1 respectively. The organic carbon (OC) decomposition rate is 0.89¿0.05 &mgr;mol kg-1 yr-1 while the oxygen consumption rate is 1.13¿0.04 &mgr;mol kg-1 yr-1. The nitrate, phosphate and silicate regeneration rates are, respectively, 0.12¿0.008, 0.0091¿0.0004 and 0.52¿0.02 &mgr;mol kg-1 yr-1. These rates are much higher than found elsewhere in the open oceans. The Ca/Si/C/O/N/P ratios for waters immediately beneath the thermocline (300--600) are 0¿8/22¿2/88¿9/121¿7/14.7¿1.3/1¿0.04. The C/P ratio is lower than the traditional Redfield ratio but the N/P ratio is in very good agreement. The regeneration rates are as follows: IC=0¿0.4, OC=3.7¿0.4, O=5.1¿0.3, N=0.62¿0.06, P=0.042¿0.002 and Si=0.93¿0.05 &mgr;mol kg-1 yr-1, respectively. These values indicate that the decomposition rate of organic matter is about five times higher in the upper water than in the deeper water. ¿ American Geophysical Union 1996