| Summary: | 碩士 === 國立中山大學 === 海洋科學系研究所 === 104 === Thalassia hemprichii and Halophila ovalis are two widely distributed seagrasses in Indo-West Pacific Ocean. In this study we investigated their dispersal mechanisms. Threehypotheses are proposed and tested: 1. dispersal by current 2. transported by birds, 3. transported by fishes. I used plants at different stages-adult plants,seedling,fruits and seeds to test these three hypotheses.Samples of Thalassia hemprichii and Halophila ovalis were collected from Dongsha Atoll in 2013 and 2014.Adult plants of Thalassia hemprichii could remain floating and survive for at least 2 months, longer than the seedlings which could have one month floating stage if unattached to substrate. Fruits of Thalassia hemprichii could remain floating for two weeks and release germinable seeds., but germination rates decline with longer floating time. Adult plants of Halophila ovalis could only float for one weeks before dying. The seeds of Halophila ovalis could pass through animal gastrointestinal tracts and remain competent for germination ,but seeds of Thalassia hemprichii could not. These two seagrasses use different dispersal mechanisms.
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