Effects of preservation period of fertilized eggs and high concentrations of nitrogen in nutrient sources on germling growth of Sargassum horneri

Abstract

The effects of high concentrations of nitrogen sources on the germling growth of Sargassum horneri were investigated for the restoration of coastal barren ground using fertilization materials containing high concentrations of nitrogen. Moreover, the safekeeping period of fertilized eggs of S. horneri was studied to elucidate performance stability as an appropriate method using fertilized eggs. The fertilized eggs of S. horneri that had been preserved in a refrigerator for approximately 170 days were able to grow and demonstrate the same growth curve as those that had been preserved for shorter periods. This demonstrates that our culture method can be applied to examine the effects of nitrogen sources on the germling growth of S. horneri. The addition of over 2 mg N L−1 of ammonium (NH4–N) or nitrite (NO2–N) clearly inhibited growth, and the addition of 50 mg N L−1 of NH4–N or NO2–N had lethal effects on the germling growth of S. horneri. The addition of 1 mg N L−1 of NH4–N or NO2–N did not clearly promote or inhibit growth. The addition of 50 mg N L−1of nitrate (NO3–N) did not inhibit growth. It is expected that the effects of NH4–N or NO2–N on seaweed growth depends on the concentration level, growth stage of the seaweed, and seaweed species. On the basis of our results, nitrogen fertilizers that contain high concentrations of some nitrogen sources should be carefully considered before they are applied to restore barren ground in nutrient-deficient coastal areas.