Culture experiments using a diatom,
Phaeodactylum tricornutum, were conducted to make clear the significance of influence of physico-chemical elements, such as light intensity and nutrient concentration, on the variations of organic composition of pariculate matters in the sea.
The alga was cultured under four or five levels of light intensity in two series of condition of nutrient concentration, of which in series-1 inorganic nutrients were added only at the beginning of culture, while in series-2 they were added not only at the beginning but also occasionally added to keep them rich during the experiment. Masurements of photosynthetic activity of the culture and determinations of organic constituents of algal cells were intermittently carried out during the experiments.
The results obtained are summarized as follows: 1) When the alga is cultured under the condition of low light intensity-low nutrient concentration (series-1 experiment), photosynthetic activity under low light intensity increases with an increase of culture period. Contents of chlorophyll
a, proteinous amino acid and reserved carbohydrate are also observed to increase. 2) Under the condition of high light intensity-low nutrient concentration (series-1 experiment), the contents of chlorophyll
a and proteinous amino acid decrease, but those of lipid and carbohydrate are observedto show a little increase. 3) Under the condition of high nutrient concentration (series-2 experiment), the light intensities give little difference to the variations of organic composition and photo-synthetic activity, in contrast to the preservation of high contents of proteinous amino acid under any light intensities.
It is, therefore, evident that the significant influence of light intensity on the variations of organic composition of the alga is remarkable under the condition of low nutrient concentration.
View full abstract