Studies on the Coral Communities in Yenliao Bay, Northern Taiwan

• Main Authors: Ming-Jay Ho, 何旻杰
• Other Authors: Chang-Feng Dai
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/72403218783163545247

博士 === 國立臺灣大學 === 海洋研究所 === 102 === Coral communities in Yenliao Bay were characterized by low coral cover, low species diversity and limited reef-building activities due to its subtropical and marginal environment for reef corals. To better understand the dynamics of these coral communities, a long-term monitoring study by permanent belt quadrats at semi-annual intervals was conducted on three rocky reefs in Yenliao Bay, northern Taiwan, from 2003-2009. The objectives of this study were (1) to examine the general characteristics of the scleractinian coral communities, (2) to examine the dynamics and long-term changes of coral communities, (3) to study the recruitment pattern and recruitment rate of scleractinian corals, (4) to investigate the possible environmental factors related to the changes of coral communities in Yenliao Bay. Multidimensional Scaling (MDS) analysis of coral communities among 12 consecutive surveys showed distinct temporal variations and the major change occurred between July 2005 and November 2005 which was coincident with major typhoon disturbances in summer 2005. Coral species with different growth forms varied greatly in partial and whole colony mortalities due to their susceptibility to typhoon disturbances. Foliaceous and encrusting corals such as Montipora, Pachyseris, and Hydnopora species suffered higher mortality, while massive corals including Favia, Favites, Cyphastrea, and Montastrea species suffered lower mortality after typhoon disturbances. Coral recruitment in these subtropical coral communities was studied by settlement plates from May 2006 to September 2009. The results showed that coral recruits occurred in summer and early autumn only and the most common taxa were Pocilloporidae (52~90%) and Acroporidae (10~41%). The number of coral recruits on top and vertical surfaces was negatively correlated with depths suggesting that light intensity is possibly the primary factor controlling settlement and survival of coral recruits in these subtropical coral communities. In addition, there was a large variation of recruitment rates (recruits/m2) among years. The high recruitment rates in 2006 and 2007 were comparable with those of tropical reefs suggesting that recruitment might not be a limiting factor for the maintenance and development of coral communities in Yenliao Bay. Studies on the relationships between coral coverage and environment factors showed that the concentrations of phosphate, total nitrogen, and total phosphorus were positively correlated with the changes of coral coverage among years in Yenliao Bay. This suggests that nutrients enrichment might be beneficial for coral growth through the enhancement of photosynthesis of zooxanthellae in subtropical environment where light intensity is relatively low. In conclusion, this study demonstrated that the subtropical coral communities in Yenliao Bay were susceptible to typhoon disturbances and large changes might occur among years. Typhoon disturbances induced differential mortality to coral species related to their growth forms, hence resulted in the changes of coral communities. The recovery and maintenance of coral communities was possibly not limited by recruitment since the high recruitment rates were comparable with those of tropical reefs. Besides, nutrients enrichment might be beneficial to the recovery of coral communities since there were consistent positive correlations between dissolved inorganic nutrients and coral coverage among years. Since marginal coral areas might act as refuges for tropical reef corals to face with the threats of climate change, this study can contribute to our knowledge of coral community dynamics in marginal environment and benefit the management and conservation of coral community facing the increasing environmental stresses in the future.