台湾地区生物礁及其生境

Biotic reefs and reef biotops in Taiwan Region

台湾岛位于亚洲大陆板块与菲律宾海板块的交界处,是在中新世晚期经由板块碰撞而形成的大陆边缘岛屿。台湾岛形成初期,由于地形陡峭,地表的侵蚀速率高,在高沉积速率的环境中,并不利于碳酸盐沉积物的形成,因此甚少珊瑚礁沉积,及至更新世和全新世才有比较具规模的珊瑚礁形成。台湾地区的更新世珊瑚礁主要分布在台湾岛西南部高雄地区和南部恒春地区;其中,高雄地区大岗山、小岗山、半屏山和寿山等地的珊瑚礁,可能是在逆断层前移的背斜脊高区上沉积形成,或与冷泉碳酸盐提供珊瑚礁发育的硬底质有关。台湾岛南端恒春地区的珊瑚礁则是在更新世晚期的温暖浅海环境中沉积形成。台湾地区大部分的生物礁于全新世沉积形成,此时期海平面上升,沉积速率降低,浅海环境适宜,因而有利于生物礁形成;但是由于各地环境条件的差异,礁的型态也不同;台湾岛南部恒春半岛、绿岛、兰屿、澎湖列岛南部和小琉球等地有较具规模的珊瑚礁发育,约有造礁珊瑚200～300种;台湾岛东部及澎湖列岛北部仅有块状礁或斑礁形成,造礁珊瑚约有150种;台湾岛北部和东北部浅海则有造礁珊瑚约100种,但因侵蚀作用强烈,并不成礁,属于"非礁型珊瑚群聚"。另外,在台湾岛西北部海岸则有以无栉珊瑚藻为主体所形成的藻礁。台湾地区各地的全新世生物礁,由于沉积时间很短,同时受到台湾地区高上升速率与高侵蚀速率的影响,礁体的厚度不足,并广泛被抬升成为海岸地带的上升礁,且与潮下带的现生珊瑚礁互相连续。台湾岛海域造礁珊瑚的属种特别丰富,高达近300种,约占全球珊瑚物种的三分之一,主要系因邻近全球珊瑚物种多样性最高的珊瑚大三角,而且黑潮流经台湾地区大部分海域,把热带物种幼苗携带过来,因而造就了台湾岛海域的生物多样性。

Taiwan is an uplifted island on Asia continental margin formed during the arc-continent collision between the Philippine Sea Plate and Asia Continental Plate in the Late Miocene. In early stage（Mio-Pliocene）of Taiwan Island,the deposition of carbonate reefs was prohibited by high erosion rate of mountain areas and high sedimentation rate in the sea. Major biotic reefs were formed during the Pleistocene and Holocene when the marine environment was favorable for the growth of reef-building organisms. The carbonate reefs in Kaohsiung,southwestern Taiwan Island,including Dagangshan,Xiaogangshan,Banpingshan and Shoushan,were possibly formed on anticlinal ridges raised above the adjacent sea floor by thrust-front migration in a foreland setting or on the hardgrounds provided by cold-seep carbonates. The Late Pleistocene reef limestone in Hengchun,southern Taiwan Island,was formed in a shallow-water environment when the sea condition was warm and favorable. Most biotic reefs in Taiwan Region were formed in the Holocene when the sea level was high,sedimentation rate was relatively low,and sea condition was favorable. However,due to the differences of environmental conditions,various types of biotic reefs were formed in different areas. Well-developed coral reefs occurred in coastal areas of southern Taiwan Island,Ludao,Lanyu,southern Penghu Archipelago and Xiaoliuchiu,where approximately 200～300 species of reef-building corals were recorded. Patch reefs occurred in coastal areas of eastern Taiwan Island and northern Penghu Archipelago with about 150 species of reef-building corals. Non-reefal coral communities existed in coastal areas of northern and northeastern Taiwan Region where about 100 species of reef-building corals were recorded,but no significant reef deposition was formed due to strong bio-and physical erosions. Besides,algal reefs deposited mainly by crustose coralline algae occurred in coastal areas of northwestern Taiwan Island. Because of the high uplifting rate of land and high erosion rates induced by storms,most Holocene reefs in Taiwan Island have been uplifted as emergent reefs in coastal zones and the thickness of reefs is relatively low. However,with approximately 300 species of reef-building corals,the species diversity of coral reefs in Taiwan Island is very high,mainly because its proximity to the Coral Triangle and the prevail of Kuroshio Current that transports larvae of tropical marine organisms to Taiwan Region.