東京都の防火用水池における生物生産の研究 : V.PhytoplanktonのProductivityの季節変化(1)

抄録

(1) The seasonal changes in phytoplankton productivity were investigated by means of both Winkler and chlorophyll methods at three fire pools (40m^2,2.5m in depth) in Tokyo from 1951 to 1953. (2) The gross production was large at the upper layers and small at the lower layers. The difference was small in winter and large in summer, and was comparatively small in pool A and large in pools B and C. At the surface layer, the production was small in winter ; and two maximum values were seen in spring and in autumn, or sometimes once in summer. The above phenomena were seen from the results obtanied by both methods. The values measured by the Winkler method showed different tend encies at 1m and 2m layers in pools B and C. (3) By the Winkler method, the respiration was large in summer and small in winter. It showed almost the same value at upper and lower layers in A, while in B and C it was markedly large at upper layers and small at lower layers. By the chlorophyll method, a marked parallel relationship between the seasonal changes in gross production and respiration were seen, and the value of respiration was much smaller than that measured by the Winkier method. (4) The net production measured by the Winkler method showed positive values at surface layer all the year round, and negative values at 2m layer of A and 1m layer of B and C in summer and winter. At 2m layer of B and C negative values were seen almost in every season. The values determined by the chlorophyll method showed that the positive net production was seen at 2m layer of B and C in spring and autumn. (5) The gross production per unit area measured by both methods showed mostly two maxima in spring and in autumn, and two minima in winter and in mid-summer. This was seen especially markedly when measured by the chlorophyll method. The respiration was found to be large in summer and small in winter when measured by the Winkler method, while by the chlorophyll method it was large in spring and autumn. As for the net production, the tendency was the same as in the case of gross production, It showed negative value in winter and summer by the Winkler method, while by the chlorophyll method it showed always the positive vaiue. (6) The production per unit area showed no remarkable difference among the three pools, increasing year by year. Mean value of the gross production measured by the Winkler method amounted to 1.25〜2.50O_2g/m^2/day, of which 70〜90 per cent was lost by respiration, consequently the net production was 5〜30O_2g/m^2/day. As for the values obtained by the chlorophyll method, the gross production was almost the same as the result by the Winkler method. In this case, however, the respiration amounted only 20 per cent of the gross production, and the net production was 40〜80O_2g/m^2/day. (7) The energy efficiency of the gross production (assimilation/solar energy) was low in summer and high in spring and autumn (especially high in autumn), and its annual average value of every pool was 0.26〜0.45 per cent. Respiration was 0.25〜0.27 per cent by the Winkler method, being 3〜8 times as much as the value by the chlorophyll method. The net production measured by the chlorophyll method was 3〜6 times as much as the values by the Winkler method. (8) As the range of photosynthetic activity under field conditions, 2.0〜100.0O_2mg/Chl. mg/day in Lake Suwa were measured. In general these large values were seen in eutrophic lakes. (9) The advantages of both methods were comparatively examined. Also the comparison with the C^<14> method was made. It was concluded that the method must be chosen in accordance with the trophic state of the waters.