On the basis of the field observations of water quality characteristics of the Seto Inland Sea by Hashimoto et al. (1996), the seasonal variations in standing stocks of DIN, PON, DIP, POP and Si, and the characteristics of lower trophic level ecosystem in the Seto Inland Sea are discussed. The standing stock ratios of DIP, DOP, and POP are almost same, about 30%, on annual average. Primary production is generally limited by DIP in the eastern part of the Seto Inland Sea, and by DIN in the western part.

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Using temperature and salinity data obtained by intensive field observation in Ise Bay on October 29 and 30, 1994, the residual current is simulated with a diagnostic numerical model. The computed currents agree well quantitatively with the data measured by ADCP. The clockwise gyres in the inner (north) and the central (western) bay areas, which have been found in earlier observations, are clearly reproduced. The computed residual current structure in the bay is as follows. The denser water intrudes into the lower layer from the bay mouth and upwells in the northern and western parts of the bay, being affected by the bottom topography. The upwelling induces anti-cyclonic circulation in the upper layer in both the inner and central areas. The anti-clockwise circulation in the middle layer forms between the southward geostrophic current in the southwestern part of the bay and the northward current intruding along the Chita Peninsula. The residual current in Ise Bay is almost geostrophic and the flow structure is an estuarine circulation affected by the earth's rotation. Magnitude of residual current in the upper layer exceeds the tidal current amplitude in the central part of the bay, thus the residual current plays an important role of transport of substance in the bay.

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