Detection of coral distribution change in recent decades with satellite remote sensing

Coral reef is a very important ecosystem in Sanya Bay and it has been studied for years only with in situ observations. However, these in situ observations generally have point information and lack the spatial resolution. Recently in order to make clear coral reef spatial distribution and variation in Sanya Bay, Hainan, satellite data of Landsat, QuickBird, CBERS (China-Brazil Earth Resources Satellite program) and historical in situ observation data are used to retrieve and validate the information of coral reef. Based on the retrieved information, coral reef coverage and variation were studied in the paper. Satellite remote sensing results showed that area of coral reef distribution along coast of Dongmao (east) Islands and Ximao (west) islands in Sanya Bay reduced greatly in recent years, which coincides with variation trends of in situ observation data in the whole Sanya Bay. While analyzing the reason for coral reduction it was found that coral distribution in Sanya Bay conversely correlated with anthropic activities, such as digging coral reef for making lime and land use change. These activities change the water quality and sediment type which lead to the change in coral distribution.