Recent carbonate data collected in the North Pacific were combined with the data in the literature in order to understand more clearly the carbonate chemistry in the North Pacific. Our analyses show that inorganic CaCO3 dissolution contributes about 26% of the total inorganic CO2, increase of deep water, after leaving the Southern Ocean. The calcium and alkalinity data indicate a CaCO3 dissolution rate of 0.060±0.010 and 0.053±0.005 μ mol kg-1 yr-1 respectively, for waters deeper than 2, 000m in reference to the Weddell Sea Deep Water. The organic carbon decomposition rate is 0.107±0.012 ± mol kg-1 yr-1 while the oxygen consumption rate is 0.13± 0.002 μ mol kg-1 yr-1. These results which are based on the direct comparison of two water masses agree well with other estimates which are based on methods such as the one-dimensional-diffusion-advection model. Comparison of data along the two sections at 165°E and 150°W shows no significant difference in the ratio of the CaCO3 dissolution rate and the organic carbon decomposition rate. The eastern section, however, has a higher TCO2 input than the western section because of the older age of the deep water along the eastern section.
The sediment cores from Tokyo Bay and Funka Bay were analyzed for U and its isotopic ratio, 234T U/238U, after dissolving them in 0.1M HC1, and 30% H202 in 0.05M HC1. A small fraction of U in the anoxic sediments was dissolved in 0.1M HC1 and even the added yield tracer, 232U, was lost. The isotopic ratio of H2O2 soluble U in the sediments was equal to that of seawater, suggesting that the H2O2 soluble U in the sediments is authigenic. The 6M HC1 solution dissolved part of the lithogenic U besides the authigenic U. The depth profiles of U from the two bays resembled each other. The authigenic U comprised more than half of the total U even at the surface and increased with depth down to 70cm, showing small maxima at about 20cm. The concentration of refractory U was nearly constant with depth and similar to that of the pelagic sediments. The highest U concentration, 6 μg g-1 which was about 5 times that of the pelagic sediments, was observed in the layer between 70 and 160cm depth in Tokyo Bay. The annual sedimentation rates of U in the Tokyo Bay sediments were 2.6 tons at the surface and 7.0 tons at the 70-160cm depth. The increase in U with depth should be due to the deposition of interstitial U either diffusing downward from the surface indicating the trapping of seawater U, or otherwise diffusing upward from the deeper layer indicating the internal cycling of U within the sediments.
In order to point out the potential importance of the Kuroshio front as a feeding ground for the early post larvae of the Japanese sardine, distributions of copepod nauplii-the principal food for the larvae-were investigated. Nauplii were abundant in and near the front and in a warm water mass off Ensyu-nada, where the concentration of chlorophyll a was high. Adult females of Paracalanus sp. were dominant in the copepod group there, and the protein synthesis activity shown by the RNA/DNA ratio was high. It is expected that copepod egg productivity is enhanced in the area where food phytoplankton is abundant, because the RNA/DNA ratio showed a positive correlation to chlorophyll a in situ. In and near the front, high chlorophyll a concentration-which is probably supported by nutrient supply caused by local upwelling and/or eddies at the frontcontributes to the high RNA/DNA ratio of the copepods. The relatively large biomass of copepod nauplii at the front may be supported by female's high egg productivity. It is supposed, as a result, that food availability for the early post larvae of the Japanese sardine is increased in and near the Kuroshio front.
Underwater observations of infaunal amphiurid ophiuroids were made at a depth of about 480 m in Suruga Bay, central Japan, using a free-fall system which consists of time-lapse stereo-photography units and current meters. The megabenthos fauna was characterized by the dominance of infaunal echinoderms; in particular, amphiurid ophiuroids were numerically dominant. The densityand biomass of the amphiurids were 170 m-2 and 37 g m-2, respectively. They buried their discs in the sediment and extended their arm tips out of the sediment surface. They protruded 2.2 arms per individual on the average. Strong bottom currents were observed, and the average velocity was 12 cm sec-1 at 4 m above the sea floor. No arm tip was observed to be raised vertically into the water column for suspension feeding utilizing the bottom current, and amphiurids were considered to be primarily a surface deposit feeder at the present site.