Variation of the vertical thermal structure in the sea is discussed from BT traces obtained at Stations T (29°N, 135°E) and V (34°N, 164°E) in relation to meteorological conditions. In summer, the thickness of surface homogeneous layer at Stations T and V has a tendency to increase with increase in wind speed. But, in October, the thickness of surface homogeneous layer increases with time independent of wind speed. The general increase in the thickness of surface homogeneous layer in October seems to be attributed to the heat loss from the sea surface. It is interesting to note that the thickness of surface homogeneous layer has a tendency to decrease with decrease in wind speed. This phenomenon occurs remarkably after the passage of typhoon. Sometimes we find secondary or transient thermoclines in the sea near the surface. We discussed the genesis and the development of the transient thermocline.

View full abstract

The measurement of the size distribution of photosynthesizing phytoplankton was repeated at 8 stations in the Indian Ocean and one station in the South China Sea The sample waters were taken from 0, 25 and75 m depth. After incubating by ¹⁴C tank technique, the sample waters were filtered through XX17 net, Millipore HA, AA and SM filter respectively, and the precipitates were counted by windowless G. M. counter. The chlorophyll-a contents of each fraction were also determined after the filtration through the same filters with ¹⁴C technique.
Concerning the photosynthetic activity, the results obtained in this cruise were essentially same to those determined in the last cruise. Namely, the photosynthetic activity caught by XX17 net (90μ pore size) takes only a small part of the total activity and increases with depth, whereas the phytoplankton with the size between 0.8 and 90μ play the most part of the activity. The smallest size fraction with the size smaller than 0.8μ has a considerable activity for the surface water, but it decreases with depth.
Though there were no marked differences among the rates of dark fixation of carbon for each fraction of same sample water, the highest rate of dark fixation was generally found in the smallest size. The size fractionation of the chlorophll-a content seems to give a imilar inclination with that of photosynthesis. But the details were obscure because of the difficulties of measuring the extreme low concentration of pigments in the tropical water.
The photosynthetic activity by unit amount of chlorophyll-a was the highest in the fraction retained by AA filters, whereas it was the lowest in XX17 net retained samples. The low photosynthetic rates were also found in most of the samples taken from 75m depth.

View full abstract

The bacteriological samples of gastrointestinal contents from the whales in the Antarctic Ocean stored at -5° and -20° respectively were examined. The number of heterotrophic bacteria in the gastrointestinal contents of baleen whales stored for 4 to 5 months at -5° were from 10⁵ to 10⁶ cells per ml of stomach contents, and from 10³ to 10⁶ cells per ml of intestinal contents. In the samples stored at -20° bacteria in the stomach contents were generally more than that in the intestinal contents. On the other hand, no marked difference in the bacterial population between the two samples was seen in samples stored at -5°. As the chitinoclastic bacteria that survive at low freezing temperature can be detected only in the stomach contents, the bacterial flora of stomach and intestines of the same whale in the Antarctic Ocean may be different.

View full abstract

The marine bacterium and protozoan, isolated at Aburatsubo Inlet in June, multiplied in the sea water with glucose and nitrate. The multiplication of the bacteria was not rapid in the solution, whereas the protozoa were considered to multiply rapidly in the solution after the logarithmic phase of the bacteria. As brine shrimp does grow little in the system with the nutrient of the bacteria and glucose, the cell substances of protozoan which utilized glucose and nitrate together with the bacterial cell substances are responsible for the growth of brine shrimp.

View full abstract