水中施肥に関する研究-IV : 黄化現象を呈したテングサ漁場への施肥

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Two experiments carried out repeatedly in 1960 and 1961 on the effect of nitrogenous manure to the yellowed Gelidium beds along the coasts of the Izu Peninsula, Middle Honshu, resulted in a remarkable recovery of the healthy reddish color of the algal thalli. Thus the manuring method reported in this paper is proved effective and practicable for improving the growth of Gelidium in the sea. The results obtained in those experiments are summarized as follows: 1) The rate of thallus weight increase of the agar seaweed within the manured area was 2.9-5.4 times as high as that in the control area. 2) The content of the nitrogenous component of the agar seaweed within the manured area increased by 0.5 percent in total-N and 0.4 percent in protein-N, both in proportion to the dry weight, as compared with its content before manuring. 3) The range of effective area of a perforated polyethylene bag containing the manure as much as 0.5 kg in net weight was 0.62-2.1m2, so that the appropriate number of the manure bags to be thrown upon a Gelidium bed would be 0.5-1.7 per one square meter. 4) The rate of manure absorption of the agar seaweed in the experimental ground was 0.8-4.7 percent. 5) The frequent occurrence of the yellowed agar seaweed in summer may be attributable to the deficiency of nitrogen in sea-water due to the active metabolism of nitrogen induced by higher water temperature and brighter sunlight.
公益社団法人日本水産学会の論文