涠洲岛活珊瑚覆盖率变化的仿真分析

为了更好地理解环境参数对珊瑚礁生态的影响，以涠洲岛为研究区域，结合历史文献所记载的活珊瑚覆盖率（Live Coral Cover, LCC）资料，利用MODIS 2003-2015年遥感观测获取的环境参数，即叶绿素a质量浓度（Chl-a）、海表温度（SST）和光合有效辐射（PAR），探讨LCC变化与环境参数之间的关系，并建立了LCC变化模型。首先计算出每个环境参数3~10个月的移动平均值，并用皮尔逊相关系数计算得到与LCC变化相关性最大的环境参数值；然后考虑环境参数值之间、前后不同年份的LCC之间可能存在的自相关性，利用主成分分析法消除这些自相关之后，再利用非线性约束优化方法估计LCC与环境参数值关系的经验模型。该模型的系数为Chl-a（-0.109 04）、SST（-0.061 62）和PAR（0.013 58），据此推测，人类活动所造成的海水富营养化可能是涠洲岛LCC下降的最主要原因。最后，对涠洲岛珊瑚礁未来的发展与变化进行仿真和预测，结果表明：涠洲岛在环境不变的条件下其LCC会稳定在10%左右，而在当前气候变暖的条件下其珊瑚有可能会在2120年左右存在开始消失的风险。

Simulation of Living Coral Cover Changes around the Weizhou Island

Owing to their extensive biodiversity-rich ecosystems, coral reefs are called the “tropical rainforests of the sea.” They are of great importance as they can help to maintain the ecological balance, biological resources, and species diversity on Earth. However, coral reefs are globally threatened by many factors, including human activities and climate change, and the live coral cover (LCC), regarded as the best measure of coral reef health, is declining. Therefore, it is necessary to manage and protect coral reefs when they are exploited and utilized. Such management and protection should be based on an understanding of the knowledge of the impacts of the environment on the ecological status of the coral reef. To aid our understanding of this knowledge, studies were conducted at The Weizhou Island. The corresponding live coral cover (LCC) data recorded in the historic documents and three environmental parameters obtained by MODIS (2003-2015), i.e. chlorophyll- a concentration (Chl-a), sea surface temperature (SST), and photosynthetically active radiation (PAR), were used to explore the relationship between the LCC and the environmental parameters. First, several environmental parameter statistics that have the greatest impact on LCC were calculated and chosen, and then principal component analysis (PCA) was used to remove the redundant information. Thereafter, to overcome the difficult caused by the absence of LCC data in some years for the study sites, a nonlinear constrained optimization method was used to construct the relationship between the LCC and the environmental parameter statistics. The coefficients of the environmental parameter statistics were found to be -0.109 04, -0.061 62, and 0.013 58 for Chl-a, SST, and PAR, respectively. These values indicate that the Chl-a around the Weizhou Island had the most negative impact on LCC, followed by SST, whereas PAR has the least negative impact on LCC. Finally, the future development of the LCC around the Weizhou Island was simulated. Accordingly, the LCC around the Weizhou Island was seen to become stable at approximately 10% if the environmental conditions remain constant. However, owing to the current climate warming trends, it is possible that the corals will begin to disappear in approximately 2120. Therefore, although the Weizhou Island is considered as one of the refuges of corals from global warming under the “Refuge Hypothesis” , the corals around the Weizhou Island are still at risk of disappearing as the global climate continues to become warmer. These factors were rarely considered in previous studies, so this study is an innovative application of remote sensing to the research on coral reefs.