TROPICAL GEOGRAPHY ›› 2019, Vol. 39 ›› Issue (3): 329-336.doi: 10.13284/j.cnki.rddl.003143

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Simulation of Living Coral Cover Changes around the Weizhou Island

Zhang Huiya1,2, Huang Rongyong1bc,2 and Yu Kefu1bc,2   

  1. (1.a.School of Resources, Environment and Materials; b. Coral Reef Research Center of China; c. School of Marine Sciences, Guangxi University, Nanning 530004, China; 2. Guangxi Laboratory on the Study of Coral Reefs in the South China Sea, Nanning 530004, China)
  • Received:2019-02-24 Revised:2019-05-23 Online:2019-05-05 Published:2019-05-05

Abstract:

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.

Key words: Live Coral Cover, MODIS, remote sensing, simulation, the Weizhou Island