On the “Akasiwo” caused by Diatom at the Nakami

[摘要] The relation between the diatom and the nutrient salts is described in the present paper. Chaetoceras is the most predominant genus in diatom in the water of the Nakami. The quantities of nutrient salts consumed by 10, 000 of Chaetoceras per litre are calculated as following: 1.17mg/L in SiO2 and 0.072mg. in P2O5, and the ratio is 100:6.2, when the amout of solar radiation is 1, 000 gr. cal./cm2. in the open air. It is remarkable from the view-point of limiting factor that the content of silicate in the water of upper layer on 23, Sept. is decreased to zero due to the consumption of diatom while phosphate is increased more or less. On 16, Sept. there was found a vast crowd of resting spores of Chaetoceras (about 14, 000, 000/L.) in the bottom layer of St. 9 where the amount of dissolved O2 was 0.43 c. c./L. It is supposed that one of the main factors to make damage for shell-fish in “Akasiwo” is the scarcity of dissolved O2 caused by the putrefaction of dead diatom.

[学科分类] 大气科学