富營養珊瑚礁中觀生態池內氮的收支模式

Nitrogen Budgets in Nutrient Enriched Coral Reef Mesocosms

人類行爲產生的廢水排放流入海洋，常導致海水中含有大量的營養鹽，形成沿岸優養化，造成藻類優勢。本研究整合珊瑚礁中觀生態池模擬台灣墾丁南灣海域優養化的實驗數據，並回顧前人對於各種藻類吸收營養鹽的研究，計算在富營養的環境下，珊瑚礁生態系統對於氮元素（N）的收支模式，並比較中觀生態池中主要物種在第1天及第75天氮的吸收與儲存量。結果顯示中觀生態池無人爲添加營養鹽的控制組有40-46% N被綠藻吸收，有15% N被珊瑚吸收；營養鹽添加組中雖僅有2-20% N被綠藻吸收，但只有0.37% N被珊瑚吸收。海葵和浮游藻類無論是在控制組或是營養鹽添加組中吸收量都＜1% N。實驗75天後在生物量的表現上，控制組中珊瑚生物量上升了8%，但綠藻下降了7%；在營養鹽添加組中珊瑚生物量下降了66%，綠藻則上升了67%。本研究顯示在富營養的珊瑚礁環境下，綠藻是主要吸收添加N的物種，且會累積在其生物量上而造成藻類優勢。

Waste water produced by human activities causes nutrient enrichment in the coastal zone, resulting in algal bloom by stimulating the growth of macroalgae. We used the results of a nutrient enrichment experiment of coral reef mesocosms, of which coral reefs were from the Nanwan Bay of the southern Taiwan. Nitrogen budgets were calculated and responses of the major biotic components to the nutrient enrichment were compared. Results showed that in the controlled mesocosms, N uptakes were 40-46% by green algae and 15% by corals without obvious difference between the 1(superscript st) day and the 75(superscript th) day of the experiment. On the 75(superscript th) days of the experiment, the coral biomass increased 8% but green algae decreased 7% in the controls, while the coral biomass decreased 66% but green algae increased 67% in the enriched mesocosms. The N uptakes by sea anemones and phytoplankton were negligible in both controlled and enriched mesocosms. The results demonstrated that green algae up took most of the added N and accumulated it in its biomass in the nutrient enriched condition.