Coccolithophores are important microorganism for the carbon and sulfur cycles. Coccolithophores bloom was found on 3 October 2007 in Suruga Bay. The seasonal appearance of coccolithophores and the relationship between nutrients are as follows.1. Coccolithophores generally increased in spring and showed the maximum in May. In spring they distributed more offshore surfaces than coastal area. The whole cell density decreased in summer and became the peak in October. 2. The dominant species was Emiliania huxleyi. 3. Increase of coccolithophores at the forehead of stratification appeared after the bloom of small diatoms. As for the nutrients, phosphate and silicate were less than the half of saturation constant of diatoms, while nitrate still remained, of which concentration sufficient for coccolithophores to increase.

The study was carried out to investigate the dynamics of the fresher-water plumes by Fuji River outflow by using the field measurements in the inner pert of Suruga Bay. The Fuji River water spreads over a deep continental slope as a surface-advected plume and extends several km. According to the three dimensional current data collected using shipboard acoustic Doppler current profiler (ADCP), anticyclonic eddy at the river mouth is not generated. It was found that the intrusion of Kuroshio warm water prevented the spreading of the Fuji river water to east area of inner part of bay. Residual current, such as wind driven current or intrusion of the oceanic current, have a strong effect to the fresher-water plume.

In order to estimate the quantification of the material flux or material circulation, it is necessary to separate the tidal flow from the observation raw date measured by Acoustic Doppler Current Profiler (ADCP). This study was carried out to examine a method of separating the discontinuous current data collected using shipboard ADCP. To apply a harmonic analysis to discontinuous data brings up some questions about separation of tidal and residual current. In this study, even if increase the number of the observation data, the harmonic analysis is that M2 and S2 constituents cannot be separated. Since internal wave was dominant in this study area, the analysis period affects the result of harmonic analysis.

The water mass structure in Suruga Bay is strongly influenced by open-ocean water. In particular, it is suggested that intermittent intrusions of the Kuroshio water generate characteristic circulations in the surface layer of the bay. In this study, we investigated the processes of the intrusions of open-ocean water into the bay and related generation of bay-scale cyclonic and anti-cyclonic circulation patterns. In doing so, we used an ocean simulation product with observational data constraint on meso and larger scales and with a resolution fine enough to resolve the smaller-scale intrusion structure. Cyclonic and anti-cyclonic circulation patterns as suggested by previous observational studies were detected as positive and negative first leading empirical orthogonal function (EOF) modes of the velocity field in Suruga Bay. The time scale of occurrences of these patterns was estimated as about 1 month, which was consistent with short-term Kuroshio fluctuations as reported in previous studies. Conditions favorable for generating these patterns were analyzed for three typical Kuroshio path periods individually. As suggested by previous studies, relatively strong northward flow to the west of Zeni-su generally promoted the open-ocean water intrusions into the eastern bay mouth, leading the cyclonic circulation in Suruga Bay. Our results showed that the correlation of this relation was significant for each Kuroshio path period. The open-ocean water intrusion increased the surface-layer temperature in Suruga Bay by about 0.7°C on average. On the other hand, the anti-cyclonic circulation pattern in Suruga Bay tended to be generated with relatively weak northward flow to the west of Zeni-su during the large meander Kuroshio path period, whereas this relation was rather weak during other periods. These results were mostly supported by available observations and would be useful for integrating our understanding of the influences of the western boundary current fluctuations on the circulation and temperature variations in proximal bays.

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