In order to clarify the budgets of organic matter and nutrient in Osaka Bay, distributions of salinity, total suspended matter(TSM), particulate organic carbon(POC), particulate organic nitrogen(PON), particulate phosphorus(PP), dissolved inorganic nitrogen(DIN) and dissolved inorganic phosphorus(DIP) were investigated in Osaka Bay and the Kii Channel in summer(August 29 and September 5)and winter(December 11 and 17)in 1996. The budgets of TSM, POC, PON, PP, DIN and DIP in summer and winter were estimated by box model analysis. The mean net generation rates of POC, PON and PP in the surface layer during summer and winter were 1, 300, 175 and 27 t d^-1 respectively. These values of POC, PON and PP were larger than those supplied from the land and others by factors of 10, 8, and 17, respectively. This means that large amounts of POC, PON and PP were produced in the water column in the bay. The amounts of each decomposed in the bay were about 60% of the totals, while 20∼30% were transported outside the bay. On the other hand, the mean net generation rates of DIN and DIP in the lower layer(middle and bottom layers)during summer and winter were 130 and 17 t d^-1 respectively. In summer, the DIN and DIP transports from the lower layer to the surface layer were 171 and 31 t d^-1 respectively. They are utilized by primary production in the surface layer and, therefore, the residence times of total nitrogen and total phosphorus were prolonged in Osaka Bay.

View full abstract

Sea surface current observation with HF radar was carried out in the southern part of Tokyo Bay, Japan, in December 1998. The residual current during neap tide was dominant compared with that during spring tide. A numerical experiment reproduced well the variability of the residual current field observed with HF radar. The difference of residual current between spring and neap tides mainly depends on the strength of tidal mixing. It is also suggested that the increase of fresh water input should have a significant influence on the residual current field.

View full abstract