Observation with a moored Acoustic Doppler Current Profiler (ADCP) set to a very short measurement interval revealed vertical propagation of near-inertial internal waves (NIW) in the abyssal Yamato Basin in the Japan Sea. Flow and temperature measurements showed a sinusoidal variation having near-inertial period associated with NIW. From the polarization of flow vectors, vertical and horizontal wave numbers of the NIW were estimated to be 1.741×10^-3m^-1 and 2.563×10^-4m^-1 respectively. Phase propagation of the NIW was downward at speed of 5.34×10^-2ms^-1 indicating an upward group velocity. Back-tracing of the energy ray path of NIW passing through the observation point shows that the observed NIW were the bottom-reflected waves. The bottom reflected waves were the downward-propagating NIW generated in the upper layer. An event of clockwise rotation of wind vectors was suggested as a cause of the observed NIW.

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Lagoon Notoro-ko is a large brackish lake on the Okhotsk Sea coast of Hokkaido. It is completely covered with sea ice during winter and hydrographic and biological conditions during this season are unknown. Previous investigations done in warm seasons indicate that the lagoon water is almost the same as the Okhotsk Sea water because there are few inflows from the land. We conducted a winter investigation into the temporal changes of microalgal chlorophyll a in the sea ice and water column beneath it during the period from February 6 to March 18, 2008. Of the surface PAR, 1% penetrated to 6–10 m depth in the water column beneath the ice, where 0.4–6.0 mg/m³ chlorophyll a was detected. Integrated chlorophyll a in 18 m ranged 8.7–119.1 mg/m². In contrast, chlorophyll a levels in 20–31 cm thick ice ranged 2.5–11.6 mg/m², relatively less than in the water column. However, because chlorophyll a was largely concentrated in the bottom-most part of the ice, it might be available to grazers in the underlying water. During ice melting, a large proportion of the populations released from the ice likely sunk to the sea bottom rather than remaining in the water column.

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We investigated seasonal variations of population structure and depth distribution of Calanus sinicus in northern Kagoshima Bay. Animals were abundant during April to June when chlorophyll a concentrations were high. Young copepodites or adults appeared over the seasons, however, copepodite stage 5 dominated when the population abundance was the lowest during August 2009 and July 2010. We found little indication of seasonal vertical migration since all developmental stages occurred above 50 m and below 100 m throughout the year. RNA:DNA ratios revealed no significant decline throughout the year. These results suggest that Calanus sinicus reproduces throughout the year and does not experience a deep-water dormancy period in northern Kagoshima Bay.

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