南灣珊瑚礁海域浮游生物群聚呼吸率及有機碳循環之研究

Abstract

本研究主要利用2005年五月至2007年一月、共八個航次之研究調查，探討南灣海域上層水體的浮游生物群聚呼吸率(Community respiration rate；CR)和有機碳循環，並結合其它生地化參數進行分析，以期了解影響CR時空變化的主因。結果顯示南灣海域上層水體群聚呼吸率的變化範圍介於1.7~ 213 mg C m-3 d-1之間，進一步分析結果顯示南灣珊瑚礁海域水體中的CR可能主要受控於水體中浮游生物群聚生物量(尤其是浮游植物)及其生產力的多寡，此推測可由CR與葉綠素甲濃度(1.8~67 mg Chl m-2)及初級生產力(PP；43~569 mg C m-2 d-1)積分值間的顯著相關(p＜0.05)得到佐證。此外，分析結果也顯示細菌生物量(11~1313 mg C m-2)與生產力(18~823 mg C m-2 d-1)和有機碳濃度(顆粒態有機碳、溶解態有機碳)間的積分值也有顯著關係(p＜0.01)；此結果顯示在此珊瑚礁海域中異營性細菌的生長可能受限於有機碳量的多寡。而PP與CR的平均比值(P/R ratio)為0.38 ± 0.51，顯示南灣海域上層水體為異營性生態系，此結果建議本水體需有外源性(allochthonous)有機碳的補充，以平衡因浮游生物群聚呼吸作用所消耗的碳。推測本珊瑚礁海域高生產力底棲系統的珊瑚及底棲生物的泌液，為此外源性有機碳的最可能來源。

The purpose of this study is to understand potential factors impact on planktonic community respiration (CR) and organic carbon cycle in the water column of coral reef ecosystem in the Nan-Wan Bay, southern Taiwan. Results showed that CR varied between 1.7~ 213 mg C m-3 d-1 during study period. Further analysis showed that the rate was mainly determined by biomass and production of planktonic community, especially phytoplankton. This assumption can be evident by significant relationships observed between integrated values over euphotic zone of CR versus chlorophyll a (Chl-a; 1.8~67 mg Chl m-2) and primary production (PP; 43~569 mg C m-2 d-1; all p< 0.05). In addition, Results also showed that integrated bacterial biomass (BB; 11~1313 mg C m-2) and production (BP; 18~823 mg C m-2 d-1) were significantly regressed against both dissolved and particulate organic carbon (all p<0.01). It suggests that growth of heterotrophic bacteria in this coral reef system might be limited by the amount of organic substrates. The mean ratio of primary production to community respiration (i.e., P/R ratio) was 0.38 ± 0.51, and this indicates that the ecosystem of water column in the Nan-Wan Bay is heterotrophic. This result also suggests that allochthonous organic carbon is needed to support the organic carbon consumption, and organic exudates from the benthos, e.g., corals, might be the most important source in this coral reef ecosystem.