- 學位論文
澎湖海域亞熱帶石珊瑚群聚之研究
Studies on Subtropical Scleractinian Coral Communities in Penghu Archipelago
摘要
位於北回歸線上的澎湖群島，極南至極北的距離約70公里，在此海域生長著許多底棲生物群聚，其中包括了亞熱帶及邊緣性的「珊瑚群聚」及「珊瑚礁」。許多物理及生物因子都會影響石珊瑚的生長與分佈，物理因子例如：溫度、沉積物、颱風、光照(濁度)、鹽度、營養鹽、潮流、海洋酸化導致珊瑚骨骼鈣化速率降低等等；生物因子例如：競爭、幼生入添、捕食者的劇增以及功能群或關鍵物種的消失等等因素。位於亞熱帶及邊緣區的石珊瑚群聚(珊瑚礁)可以作為研究石珊瑚面臨逆境時，群聚變遷、後續的回覆性及抵抗逆境能力等的極佳試驗場所。 為了解澎湖群島石珊瑚群聚的分布和特徵，吾人在2004-2005年間以佈放橫截線配合數位攝影機調查紀錄該群島不同海域（北部、東部、內海及南部）的石珊瑚群聚發育現況，再以「逢機灑點計數試算表」軟體（CPCE）將影像紀錄轉換成量化的資料。以類群分析（clustering）及多向度空間分析法（MDS）所得結果發現，東部及北部海域的石珊瑚群聚結構相似可劃歸為一群，內海及南部海域則各自獨立形成另外兩群。東部及北部海域的石珊瑚群聚主要以軸孔珊瑚小群體或是片段為主體，表示該海域可能面臨頻繁的環境擾動。內海的石珊瑚群聚以耐污濁的物種為主，顯示高沉積率及低光照度對此處珊瑚分布影響甚大。南部海域的石珊瑚群聚則具有較高的物種多樣性及覆蓋率，顯示此處是適合石珊瑚生長的良好環境，主要因子可能是較高的水溫及低沉積速率。另外，以相似度分析方法（SIMPER）所得結果也支持上述類群分群及多向度空間分析的結果。在物種組成方面，南部海域以分枝狀軸孔珊瑚為優勢種；內海海域以管孔珊瑚及分枝狀表孔珊瑚為優勢種；而東部與北部海域則以菊珊瑚科及片珊瑚科的種類為主。美麗軸孔珊瑚在所有調查地點的較淺區都是豐度最高的物種，每個調查地點或海域則是各自擁有獨特的物種組成，也造成了彼此之間的差異。 極端溫度向來被認為是影響珊瑚生長及分布最重要的因素。2007-2008年冬天澎湖群島發生寒害侵襲，造成各類珊瑚礁生物大量死亡的事件。現地水溫資料顯示，比過去三年冬季水溫平均值要低的水溫持續了三週，同時發生四年來最低的水溫紀錄。南部海域的最低水溫比最北的姑婆嶼高了約攝氏3-4度。2008年4~5月在姑婆嶼、澎澎灣、青灣內灣、嶼坪、七美等地點的調查結果，與2005年與的資料比較，所有調查地點的活體珊瑚覆蓋率都明顯下降，而「新近死亡珊瑚」的比例則明顯升高。分枝狀的軸孔珊瑚及細枝鹿角珊瑚是此次寒害受創最嚴重的物種。本論文提出「寒潮持續度週」（DCW）指數作為石珊瑚群聚遭受寒害影響的指標，初步結果顯示，當DCW>1.0 即有可能對珊瑚群聚造成重大傷害，此值是否可作為寒害預警指標，尚待進一步驗證。 為了推動海洋保護區的劃設，本論文也針對澎湖海域12調查地點保育價值做出評價，依據以往的監測結果發現，青灣內灣具有相當高的活體珊瑚覆蓋率、高物種及棲地多樣性，亦即具有高保育價值。因此，針對劃設海洋保護區的全面考量，進行青灣內灣的生態資源詳細調查及當地居民的社經現況普查。漁業現況調查結果發現，當地大多是休閒漁業及自給式漁業，具有低收益、低投資、高度天候依存等特性。社經調查結果發現保護區劃設對於鄰近村里沒有直接的利益衝突，而且大部分居民贊成保護區劃設，而海域棲地環境的破壞，例如：錨害以及結螺的啃食，都需要持續的管理介入改善及監測。當然社區的主動參予可使保護區發揮功能，持續的環境教育則對於促進大眾認知有幫助。本章提出澎湖地區劃設海洋保護區或禁漁區的標準作業規範，有助於漁業管理機關做為未來施政時的參考。 綜合而論，澎湖群島多樣的石珊瑚群聚與其特有的地理及海域環境條件有關，並且具有亞熱帶珊瑚群聚變動劇烈的特性，過低海溫或冷水入侵是重大干擾因子，對該海域珊瑚群聚造成重大傷害，然而，後續的群聚回復力及抗拒力，以及功能群改變對群聚變動的影響，甚至於這種亞熱帶珊瑚群聚在全球變遷衝擊之下的反應等，都是值得繼續研究的課題。
並列摘要
To reveal the distributional pattern of scleractinian communities, a video-transect method together with CPCe (Coral Point Count with Excel) analysis were applied to study the coral communities in four sectors: North, East, South, and Inner sea in Penghu Archipelago in 2004-05. The results of cluster analysis showed that coral communities in East and North sectors were grouped together, while those in Inner and South sectors remained as independent groups. Coral communities in North and East sectors were dominated by small colonies and fragments of Acropora spp. indicating that these areas possibly suffering frequent disturbances. Coral communities in Inner sector were dominated by turbidity-tolerant species suggesting that high sedimentation and low light-intensity were possibly the major factors structuring the coral community. Coral communities in South sector were characterized by high species diversity and coral cover, indicating a favorable environment for coral growth and reef development. Results of SIMPER analysis showed that Acropora spp. dominated the South sector, Goniopora sp. and branching Montipora sp. were abundant in Inner sector, while faviids and pectiniids were common in North and East sectors. A. muricata is the most widely distributed species in shallow zone. Temperature extremes have traditionally been regarded as the most important factor that affects the distribution and development of reefs. A chill event occurred in winter 2007-2008 and resulted in severe mass mortalities of reef organisms in Penghu Archipelago. The in situ seawater temperature profiles showed that, unusually low SSTs persisted for three weeks and low temperature extremes (LTE) in past three winters were also recorded. The LTEs in South sector (Yupin and Chimei) were about 3-4℃ higher than that of Gupo in North sector. Comparisons of live coral cover (LCC) between 2005 and 2008 showed that significant reduction in LCC and increase of recently dead corals were observed. Branching Acopora spp. and Pocillopora damicornis were the most vulnerable species in the chill event. An index, degree chilling weeks (DCW), was proposed for predicting the impacts of cold sea temperatures. The preliminary data showed that DCW = 1.0 was possibly the threshold of forecasting a chill event. In order to promote the establishment of the first marine protected area (MPA) in Taiwan, the conservation values of 12 reef sites in Penghu Archipelago were evaluated. The results together with a surveillance programme revealed that the Chinwan Inner Bay (CIB) possesses the best coral community in Penghu Archipelago with the highest coral cover, high species diversity and habitat types, as well as a high conservation value. Utilization of biological resources and socio-economic factors of CIB were investigated by intensive field surveys and a complete visit-and-poll survey respectively. Most of the fishing at CIB is for recreational purposes and is characterized by low investment, low harvest rates, high dependence on weather conditions, and self-consumption. The socio-economic data showed that there was basically no direct conflict of interests with local communities at two neighbouring villages, and most local residents indicated that they would support the MPA proposal. A blueprint for a CIB MPA based on the results of these biological and socio-economic investigations is proposed. The involvement of local communities is key to the success of this MPA and environmental education is recommended to promote public awareness. In conclusion, diverse coral communities exist in Penghu Archipelago and the patterns of community structure are closely related to the unique oceanographic and geographic settings. These subtropical coral communities are characterized by catastrophic changes and the intrusion of cold water or the persistence of unusually low temperature is one of the major disturbance factors. The community dynamics following the disturbance such as resilience and resistance as well as the influences of functional groups and the impacts of climate change on these subtropical communities remain to be studied.