Productivity and nutrient limitation of epiphytes on the leaves of the seagrass Thalassia hemprichii in Kenting

• Main Authors: Pei-Yu Su, 蘇姵瑜
• Other Authors: 林幸助
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/60514756849151950680

碩士 === 國立中興大學 === 生命科學系所 === 100 === As one of the most popular tourist attractions of Taiwan, the marine ecosystems of Kenting had suffered massive sewage discharge which leads to an increase of epiphytes growing on the seagrass bed. The eutrophication might ultimately exert a negative effect on seagrass growth. In order to estimate the productivity and nutrient limitation of the epiphytes at different sites and in different seasons, oxygen microsensor was used in Nanwan, Dakwan, Wanliton, and Haikou of Kenting for epiphytes measurement. The production of seagrass was higher than the production of epiphytes at almost every sites in Kenting. Among all sites, sewage site of Nanwan and Wanliton had the highest epiphytes production. According to our results, light and temperature were the major affecting factors of epiphytes productivity, therefore epiphytes productivity in Kenting was the lowest in winter. In addition, 6 ％ of seagrass beds primary production was contributed from the Thalassia hemprichii epiphytes in Kenting. This indicated that epiphytes on seagrass leaves are important primary producers in seagrass ecosystems. Seasonal variation was observed in epiphytes composition on seagrass leaves. In winter the dominant epiphyte species was Hincksia mitchelliae, Centroceras clavulatum was the dominant epiphyte species in spring, coralline algae and Ulothrix flaccida were the summer dominant species, and Ulothrix flaccida and Enteromorpha intestinalis were dominated in fall. Our results indicated significant seasonal and site effects on the epiphytes productivity. Nitrogen, phosphorus, and nitrogen and phosphorus limitation occurred at sewage site and control site of Nanwan and control of Dakwan. sewage site of Dakwan and Wanliton were mainly limited by nitrogen, while Haikou was mainly phosphorus limited. We found that N:P molar ratio and nutrient limitation of seagrass beds had no clear trend. Furthermore, in Wanliton the dominant epiphyte species was green algae which had nitrogen limitation durning the summer and fall. In Haikou the dominant epiphyte species was coralline algae which had phosphorus limited durning the summer and fall.. The sewage site and control site of Nanwan and Dakwan had no clear trend. Therefore, sweage discharge should be managed strictly and long-term monitoring of seagrass beds are needed in order to effectively conserve seagrass beds in Kenting, especially in summer and fall.