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(1997). Longitudinal distribution of plankton in a shallow reservoir of Broa in Brazil. SIL Proceedings, 1922-2010: Vol. 26, No. 2, pp. 553-557.

緩速ろ過池砂層内における抑留物質の深度分布を調査して、砂層内における抑留物質の浄化作用について評価した結果、以下のことが明らかになった。1) 懸濁物質は砂層上部の表層でほとんど捕捉されるが、砂層内に侵入した懸濁物質も砂層上層で抑留された。ろ過継続日数が通常の倍でも抑留物質の侵入度合は変わりがなかった。2) 砂層内での抑留物質の減少率は、クロロフィルa>フエオフイチンa>全有機炭素の順であった。このことから、抑留物質に対する分解能が物質によって異なることが考えられた。3) 藻類体の砂層内への侵入度合は、染屋浄水場よりも石舟浄水場の方が高かった。このことから、浄水場によってろ過池砂層内の懸濁物質の侵入程度が異なることが判明した。

A long-lived, heavy freshwater red tide of Pyridinium occurred in a newly built water supply reservoir, between late February and late May, 1972 and 1973, starting and spreading from the entrance region. The densities of the alga reached at least 9.3 x 104 cells per ml and at least 2, 700 μg chlorophyll- a per liter at a wind drift. The red tide is attributed to the increase of solar radiation, the hardness of water and the sewage drains from towns and croplands. The water mass containing a dense algal bloom was an excellent receiver of the solar radiation. This flagellate acted as an accumulater of nutrients at the entrance region of the reservoir.

The study on the freezing-out phenomena of lake water is carried out in two mountain lakes, Lake Suwa and Lake Haruna in the central part of Japan. The reduction rates were measured concerning the following components : dissolved oxygen, carbon dioxide, ions (Cl, Na, Mg, and Ca), dissolved organic carbon, particulate organic carbon and nitrogen, and bacterial number. Substances in solution in the waters freeze out to 80%. The freezing-out of dissolved oxygen and carbon dioxide was also observed. This may account for the significant accumulation of dissolved gases immediately under the ice at the distinct inverse stratification in Lake Suwa. This accumulation was not observed at a volcanic lake of Haruna. In Lake Suwa a trend of the decrease of concentration was observed in the ice from its upper layer to the bottom. In Lake Haruna the opposite tendency was observed. The viable number of bacteria reduces by factor 103 or more in freezing.

The distribution of chlorophylla and photosynthetic characterestics of phytoplankters were investigated along 155°W between 50°N and 15°S during the KH-69-4 cruise of the R. V. Hakuhō Maru (Aug. 12–Nov. 13, 1969). High concentrations of chlorophylla (more than 0.2 mg Chla/m3) were observed above the depths of 150 m at all stations except in 17°N, 5°S and 15°S. North of 20°N, the depths of chlorophyll accumulation shifted from near the surface to 50–100 m with southwards. In the equatorial region, chlorophyll accumulation centered at a depth of about 70 m and ranged vertically between 10 and 150 m. In all cases in the present study area, chlorophyll accumulation occurred within the euphotic zone (above the depth corresponding to 1% of the surface illumination), and except in the subarctic and some equatorial waters, this was usually prevalent in the lower half of the euphotic zone.