Abstract: In order to clarify the spatiotemporal distribution of Sargassum horneri, and approach the possible measures to ecologically protect and restore macroalgal bed, an investigation was conducted on the seasonal distribution of S. horneri from seedling to maturing stages in Gouqi Island of East China by the method of underwater quadrat sampling. From seedling to maturing stages, the average loss rate of S. horneri density reached 61%, which was mainly determined by the wave action that moved the S. horneri from its substrate, and to some extent, affected by the density restriction mechanism. Most of the individuals were found within a water depth of 121-547 cm during seedling stage, and a water depth of 132-461 cm during maturing stage. The width of S. horneri vertical distribution not only decreased from seedling stage to maturing stage, but also varied obviously among sampling sites, which was related to the effects of environmental factors. In addition, wave exposure had important effects on the distribution of S. horneri, especially on the upper limit of distribution. The growth rate of S. horneri had a correlation with seawater transparency. Wave action could result in the resuspension of sediments, which affected the light intensity, and thus, restrained the growth of S. horneri. It was unclear whether the decrease of light intensity would result in the death of S. horneri. Further researches would be needed on the relationships between light intensity and S. horneri growth density to understand the upward distribution mechanism of S. horneri.

Key words: Laodelphax striatellus, buprofezin, resistance screening, risk assessment, cross-resistance, biochemical resistance mechanism.