Ecological Study on the Decay and Replenishment of Sargassum horneri in the Intertidal Zone of Gouqi Island

Sargassum horneri is one of the important species in the seaweed field in China, which plays an important role in supporting the marine environment and fishery resources. In order to find out whether the Sargassum horneri is a perennial problem and the tolerance temperature of Sargassum horneri, based on the field intertidal monitoring and observation, the ecological process of Sargassum horneri’s decline period in natural habitat was explored by recording the biological parameters such as plant height, trunk diameter, fixator attachment area and water temperature data. The results showed that: (1) at the end of May, Sargassum horneri in the intertidal zone of Gouqi Island began to enter the decline period after breeding and the decline of Sargassum horneri showed obvious seasonal variation (P<0.05) . The water temperature during the summer has become the key factor to determine the perennial of Sargassum horneri. In July, the temperature in the intertidal zone of Gouqi Island reached more than 25 ℃. With the increase of temperature, all the fixators of 76 strains of Sargassum horneri decayed and fell off, and they could not spend the summer for nutritional reproduction. Therefore, it was judged that the Sargassum horneri in the intertidal zone of Gouqi Island in Zhejiang Province were annual. (2) When the water temperature was above 25 ℃, the Sargassum horneri fixator began to break and rot, and could not survive. The tolerance temperature range of the ecological amplitude of mature Sargassum horneri in the intertidal zone of Gouqi Island, Zhejiang Province is 7.1~25 ℃. (3) The decay time of intertidal Sargassum horneri is relatively short, which is mainly based on the fact that after the reproduction of intertidal Sargassum horneri, the adhesion of the fixator is reduced and the adhesion area is small, and the adhesion is weak. Under the action of waves and currents, the fixator is easier to fall off and lose, and the decay and apoptosis time is faster. (4) In May, faced with the situation of low growing algae, the intertidal Sargassum horneri are still able to carry out sexual reproduction and release spores that firmly adhere to the surrounding parent body. By aggregating the seedling population, they reduce the exposure to air and light damage during low tide, and cause competition for growth resources, which is an important survival and competition strategy for them. Sargassum horneri utilize survival and competition strategies to maintain the reproduction of their population, and on this basis, they continue to expand their distribution range. The above research results provide a reference value for understanding whether the Sargassum horneri are perennial, analyzing the life history of Sargassum horneri, for its artificial development and marine ecological environment protection and provide a scientific basis for the restoration and reconstruction of degraded Sargassum horneri population.