台灣珊瑚群聚分布及氣候變遷對其衝擊之研究

Abstract

本研究探討氣候變遷及異常氣候對珊瑚礁生態系的衝擊。我們針對台灣沿海及離島地區的六個珊瑚礁區，共十六個樣點，利用穿越線調查130種石珊瑚(或種群)的分布現況。結果顯示台灣海域的珊瑚群聚可分為二大群，北部至東北角海域屬於非礁型珊瑚群聚，東部及南部則屬於珊瑚礁群聚。此外，東北角鶯歌石、宜蘭豆腐岬以及蘭嶼椰油各具有特殊的物種組成及群聚型態。在氣候變遷衝擊模擬方面，我們將本研究資料結合過去研究資料套入物種分布模式 Genetic Algorithm for Rule-set Prediction (GARP)進行模擬。 結果顯示現今台灣的珊瑚群聚分布型態和水溫及海流分布型態相符合，主要是由海流與水溫形塑。其他環境中的物理性因子，例如海浪衝擊、海水濁度及沉積物推積皆會影響珊瑚群聚分布型態。面對氣候變遷及海水暖化的衝擊，短期(2025)內珊瑚的分布範圍會變廣，各地的物種豐度會增加。然而在中(2055)及長期(2085)的影響之下，珊瑚的分布範圍會縮減並往北移，北部、宜蘭以及澎湖地區的物種豐度會增加，但東部與南部各地的物種豐度會相對減少。物種組成及數目的模擬結果顯示，未來珊瑚礁生態功能將逐漸喪失，將更易受到氣候異常的衝擊。根據研究結果，我們建議珊瑚礁保育應將氣候變遷的衝擊造成的珊瑚分布變異納入考量。

Coral reefs are found in all waters around Taiwan except in the sandy areas on the west coast. Approximately 300 scleractinian species are found in Taiwan and its offshore islets. The occurrence and relative abundance of 130 species or species groups in coral communities at 16 sites from 6 reef regions in Taiwan were surveyed by transect method. The result of cluster and MDS analysis shows that coral communities in eastern and southern Taiwan possess similar species compositions, whereas those of north coast and northeastern Taiwan form another group. The other three sites with distinct species compositions were Dofujia of Yilan County, Yinggeshi of northeastern coast, and Yeyou at Lanyu. Using the same set of scleractinian distribution data and data from previous studies, we modeled the spatial relationship of corals with Genetic Algorithm for Rule-set Prediction (GARP), a method for learning the spatial relationships of organisms and its environment, and used it to predict the influences of climate change on coral communities in Taiwan. The results show that the distribution pattern of scleractinian corals in Taiwan is congruent with that of sea surface temperature and ocean currents, suggesting their importance in shaping regional coral communities in Taiwan. Other factors such as wave exposure and sedimentation are in addition important in shaping local coral communities. Under the impact of climate change and projected rise in sea surface temperature, the spatial distribution of corals is likely to expand and the species richness in most areas would increase in the short-term prediction. However, the spatial distribution of corals would contract with species richness in most areas decreasing dramatically in the long-term predictions. Unbalanced changes of coral communities can also be envisaged from the model predictions.