The absorption coefficient of phytoplankton is one of the most important parameters in studies of primary production in the sea and ocean-color remote sensing. This report presents protocol for measuring the absorption coefficient with QFT(quantitative filter technique). The protocol was discussed at three workshops, where some experiments were conducted to standardize its methodology ; (1) with an emphasis on comparisons between spectrophotometers, and techniques for pigment extraction ; (2) comparison between the absorption coefficients of phytoplankton determined by different analytical techniques ; and (3) establishment of a reliable database. In addition, in situ absorption measurement with a submersible spectrophotometer(ac-9, WET Labs)was also discussed at the workshops, and its analytical procedure recommended is briefly reported here. The absorption coefficients as measured with this protocol enable data obtained by different researchers to be compared directly.

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Tide-induced residual flow, M₂ and M₄ tidal currents around Okinawa are caleculated using a horizontal two-dimensional numerical model, and the bottom stress corresponding to that transport is calculated. The estimated direction of bottom sediment trasnport coincides well with the result of field observation in Nakagusuku Bay. The direction of bottom sediment transport around Okinawa is estimated on the basis of calculated results.

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In order to clarify the seasonal variation of residual current and material transportation process in Hiroshima Bay, Japan, the residual current and particle tracking by using Euler-Lagrange model were numerically simulated. The calculated tidal current, water temperature and salinity showed good agreement with the observed ones. The residual current showed a southward flow pattern in the upper layer, northward in the lower layer. The flow structure of residual current in Hiroshima Bay is an estuarine circulation affected by density flow and wind-driven currents. The residual current plays an important role in material transportation in the bay.

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Total oxygen and nitrogen fluxes between sediment and water were measured seasonally by whole core incubation under in situ conditions in the central part of Koajiro Bay, Japan. Concentration profiles of oxygen and nitrogen at the sediment-water interface were measured simultaneously, and diffusive fluxes through the interface were calculated from the concentration gradient at the interface with molecular diffusion coefficients. The depthe distribution of oxygen consumption rates within the sediment were also calculated from the obtained concentration profiles. There was a temporary increase in organic matter content at the sediment surface(0∼5 mm)in April(Fig.10(a)). The total oxygen flux, always toward the sediment increased from February to April and again to August, and showed a clear seasonal chage(Fig.10(b)). the total oxygen flux exhibited a significant positive correlation with temperature, but not with the organic matter content at the sediment surface(0∼5 mm). Ammonium was always released from the sediment(Fig.10(c)), and the total ammonium flux also showed a clear seasonal change similar to the total oxygen flux(Fig.10(c)), but there was no correlation with temperature nor with organic matter content. From the comparison of the total flux, the diffusive flux and depth integration of oxygen consumption(Tables 1, 2, and 3, Fig.14), molecular diffusion seemed to be the most important transport process of oxygen and ammonium between sediment and water throughout the year. The value of 5.2 was estimated as the C : N tatio of the organic matter actually being decomposed in the sediment from the ratio between total fluxes of oxygen and ammonium(Fig.15).

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Variabilities of current and water temperature in the bottom layer(760 m depth)at the mouth of Tokyo Bay are investigated using observed data from 1995 to 1999. Variabilities with the tidal periods of 6 hours, 12 hours and 24 hours, and several days periods of 3-4 days and 9-10 days are dominant in both current and water temperature. Tidal fluctuation of water temperature with the amplitude of about 0.3°C is generated by the tidal current which ascends and decends the shelf slope. Variations of the residual flow along the isobath and water temperature with the period of 3.8 days are generated by the fluctuation of the warm water originated from the Kuroshio.

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The absorption coefficient of seawater is one of the most crucial parameters in studies of primary production in the sea and ocean-color remote sensing. A considerable number of studies have been done on the measurement of the absorption coefficient so far. This article is a reviw of the principle and problems of each method of absorption measurement, and a step toward a protocol for measuring the absorption coefficient of plytoplankton

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The author described his studies on deep circulation using diagnostic models and in situ observations. A diagnostic model is proposed for calculation of a three-dimensional velocity field from observed temperature and salinity data. Tracking of water particles in the model reveals the deep waters in most of the major basins originate from the North Atlantick. Observation with moored current meters and CTD casts were carried out east of Japan, and the structure of deep currents above the trench is described ; the current above the western flank flows southward and that above the eastern flank flows northward. The northward transport is over 10 Sv. The difference of the transport at 30, 34, and 38°N suggests the existence of inflow from the east and recirculation below the Kuroshio Extension.

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