湖沼の植物プランクトンの光合成の二三の性質

Abstract

The relation of photosynthesis of natural phytoplankton to each environmental factor was discussed in detail on the basis or laboratory experiments.1.In eutrophic lake water, or in water enriched with nutrient salts, light saturation of photosynthesis occurred at about 15klux. in Cyanophyceae communities, at about 10klux. in Chlorophyceae, and at 7klux. in Bacillariophyceae. Such light saturation, however, was found at low light intensity of about 4klux. with phytoplankton in oligotrophic lake water.2. The highest photosynthetic activity of phytoplankton of about 8mg. O2/chl. mg./hr. was measured in natural waters of eutrophic lakes. The activity in mesotrophic lake was about 4mg. O2/chl. mg./hr. and the lowest was 2mg. O2/chl. mg./ hr. in oligotrophic lakes.3. The effect of supply of nutrient salts on photosynthesis of phytoplankton was not so remarkable in eutrophic lake waters as in oligotrophic ones. However, nutrient materials in water were exhausted sometimes even in eutrophic water in summer and autumn, and the deficiency in such materials would be able to limit the primary production of lakes severely.4. Potential photosynthetic activity of phytoplankton was almost constant throughout the year, except for two spells in March and in August when heavy altering of constitutent phytoplankters were going.