| Summary: | 自工業革命以來，大氣中二氧化碳(carbon dioxide, CO2)濃度迅速上升，導致海洋酸化(ocean acidification, OA)及暖化，使海洋生態系面臨威脅。高生產力的海草常生活在沿岸珊瑚礁生態系，能吸收海水中的CO2、調節酸鹼值及霰石飽和溶解度(ΩAr)。本研究目的是利用中觀生態池，探討未來面臨OA及海水暖化，海草是否具有維持珊瑚鈣化作用的能力。並透過淨系統生產量(net ecosystem production, NEP)探討中觀生態池的環境因子與生物因子之交互影響。實驗設計3組無海草組及3組具海草的珊瑚礁，進行4個酸化及升溫階段。以CO2分壓400 ppm做為未酸化情境；800 ppm做為OA情境。第一階段為未酸化及25˚C；第二階段為OA及25˚C；第三階段為OA及升溫至28˚C；第四階段為OA及升溫至31 ˚C。研究結果顯示在OA的環境下，海草組的珊瑚鈣化速率於OA(25˚C)和OA(28˚C)都高於無海草組。此外，OA環境使大型藻類增生，無海草之大型藻生長速率有高於有海草的趨勢。因此OA(25˚C)使無海草組的淨系統生產量(net ecosystem production, NEP)顯著上升，但OA對於海草組的NEP則沒有影響。無海草組和海草組面臨酸化環境下的升溫，系統呼吸量(ecosystem respiration)都隨溫度升高而逐漸上升，但總初級生產量(gross primary production)於OA(28˚C)達到最高後於OA(31˚C)下降。因31˚C的高溫環境降低大型藻類的生長速率並且提高死亡率。無海草組於OA(31˚C)急劇下降了 0.93±0.22 g O2 m-2 d-1，而海草組則是下降了0.68±0.13 g O2 m-2 d-1。未來OA和31˚C暖化，具海草之生態環境仍能維持珊瑚之鈣化速率，且抑制大型藻類增生的趨勢，使得NEP幅度下降幅度較小，因此海草具有穩定珊瑚礁生態系之功能。 Since the Industrial Revolution, the concentration of carbon dioxide (CO2) in the atmosphere has risen rapidly, resulting in ocean acidification (OA) and warming, which has threatened coastal ecosystems. Highly productive seagrasses usually live adjacent to or among coral reefs and can absorb CO2 in seawater, regulate the pH and the aragonite saturation state (ΩAr). The purpose of this study was to use coral reefs mesocosms to examine the effects of seagrasses on coral reef ecosystems under OA and warming. The net ecosystem production (NEP) was used to determine the functioning of the mesocosms. Three mesocosms without seagrass and three mesocosms with seagrass were designed to conduct four stages of OA and warming experiments. A non-acidified CO2 partial pressure of 400 ppm was used as control and 800 ppm was used as the OA scenario. The first stage was unacidified and 25˚C; the second stage was OA and 25˚C; the third stage was OA and warmed up to 28˚C; the fourth stage was OA and the temperature was raised to 31˚C. The results showed that under the OA scenario, the coral calcification rates with seagrasses were higher in OA (25˚C) and OA (28˚C) than without seagrasses. In addition, the OA scenario proliferated the macroalgae, and the growth rate of macroalgae without seagrasses was higher than that with seagrasses. Therefore, OA (25˚C) significantly increased the NEP of the mesocosms without seagrasses, but OA had no effect on the NEP of the mesocosms with seagrasses. Ecosystem respiration (ER) increased gradually with increasing temperature under the scenario of OA, but gross primary production (GPP) in OA (28˚C) reached the maximum, then dropped in OA (31˚C). Due to the high temperature environment of 31 ̊C, the growth rate of macroalgae reduced and the mortality increased. The mesocosms without seagrasses dropped sharply at OA (31˚C) by 0.93±0.22 g O2 m-2 d-1, while the mesocosms with seagrasses decreased moderately by 0.68±0.13 g O2 m-2 d-1. Under the condition of OA and warming in the future, seagrasses can maintain the calcification rate of corals. Seagrasses can inhibit the growth of macroalgae, caused the magnitude of NEP declined less and maintain the stability of coral reef ecosystems at a high temperature of 31˚C. 第一章、前言 1 1. 氣候變遷 1 2. 海洋酸化的影響 2 3. 海水暖化的影響 3 4. 珊瑚礁生態系的現況 3 5. 熱帶海草床的重要性 4 6. 熱帶海草對珊瑚礁的生態服務 6 7. 系統代謝 6 8. 研究目的 7 9. 研究假說 9 第二章、 材料方法 10 1. 實驗對象與採樣地點 10 2. 中觀生態池之設置與生物組成 11 3. 生態池之操作模式 15 3.1. 生態池的監控系統(Apex AquaController, Neptune System) 15 3.2. CO2釋放方式 15 4. 實驗設計 16 5. 環境因子測定 18 5.1. 水質 18 5.2. 光度 18 5.3. 海水碳化學 19 5.4. 營養鹽 20 6. 生物因子測定 21 6.1. 海草 21 6.1.1. 植株密度與密度變化率 21 6.1.2. 葉片光合作用光效能 21 6.1.3. 葉片生長速率 23 6.1.4. 葉片生產力 23 6.1.5. 植株生物量 23 6.2. 珊瑚 24 6.2.1. 珊瑚光合作用光效能 24 6.2.2 珊瑚鈣化速率 24 6.3. 浮游藻與附著微藻之生物量 24 6.4. 大型藻類生長速率 25 7. 系統代謝 25 8. 統計分析 27 8.1. 重複量數二因子變異數分析 27 8.2. 重複量數單因子變異數分析 28 8.3. 變異係數(coefficient of variation, CV) 28 第三章、結果 29 1. 環境因子 29 1.1. 水質 29 1.2. 光度 30 1.3. 海水碳化學 30 1.4. 營養鹽 31 2. 海草泰來草 42 2.1. 植株密度與密度變化率 42 2.2. 葉片光合作用光效能 42 2.3. 葉片生長速率 42 2.4. 葉片生產力 43 2.5. 植株生物量 43 3. 其它生物因子 51 3.1. 珊瑚 51 3.1.1. 珊瑚光合作用光效能 51 3.1.2. 珊瑚鈣化速率 51 3.2. 浮游藻與附著微藻之生物量 51 3.3. 大型藻類生長速率 52 4. 系統代謝 58 4.1. 系統呼吸量 58 4.2. 總基礎生產量 58 4.3. 淨系統生產量 59 4.4. P/R比值 59 4.5. 系統代謝參數變異係數 60 第四章、討論 66 1. 海洋酸化與暖化時海草床對於環境因子之影響 66 2. 海洋酸化與暖化對海洋初級生產者之影響 67 2.1. 海草 67 2.2. 大型藻類 70 3. 氣候變遷與海草床對珊瑚之影響 70 4. 從物種反應到生態系統變化-系統代謝 76 5. 氣候變遷與珊瑚礁物種交互作用之概念模式 77 第五章、結論 80 第六章、參考文獻 81 第七章、附錄 93 附錄 1、墾丁國家公園之採集許可證(2017/03/16-2017/03/17) 93 附錄 2、實驗第一階段無酸化(25˚C)和第二階段OA(25˚C)，無海草和海草組生態池內大型藻生長狀況之比較 94 附錄 3、中觀生態池內常見的大型藻類物種 95 第八章、會議記錄 96
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