Temporal And Spatial Variation Of Sea Surface Temperature And Ecological Impacts In Coral Reef Areas Of The South China Sea Based On Remote Sensing

As one of the most important parameters of marine water,Sea surface temperature(SST)is a very important data in coral reef remote sensing and ecological survey,which can directly reflect the thermal environment of coral reef ecosystem and is often used to monitor and predict the occurrence of coral bleaching.The advantage of retrieving SST by satellite remote sensing is that it can realize large-scale synchronous measurement and is very suitable for application in the South China Sea(the SCS)which is far from mainland.It can also effectively grasp the changes of SST in the research period,which is of practical significance to the management and protection of coral reef ecosystem.This paper is mainly based on two kinds of remote sensing data,one is the OISST V2 monthly average SST dataset provided by NOAA,another is the MODIS nightly SST dataset provided by Ocean Color.Based on the data processing,the SSTA and SST fields are established to analyze the spatial and temporal variation of sea surface temperature and the calculation of SST thermal accumulation in coral reef area.The results are as follows:(1)The time scale statistics of SST at coral reef areas of Dongsha,Xisha and Nansha Islands showed that:First,SST of the three reefs showed a trend of warming up,but the range of warming was different.The warming trend of SST in Dongsha coral reef area was the most significant(about 0.216?/10a).However,the following trends were 0.18?/10a at Xisha reef area and 0.096?/10a at Nansha reef area,respectively.Second,the SST in the Xisha and Nansha reef areas were in the optimum growth temperature of hermatypic corals in the whole year.There were about 4 months lower SST for hermatypic corals in the Dongsha reef area.The hottest month were focused on July(Dongsha),June(Xisha)and May(Nansha),respectively.Third,the range of SST above the suitable SST for coral growth would occur at the three reef regions.The year of 1998,2010,and 2015 are three year of higher SST at these reef areas.(2)The EOF analysis of the OISST V2 monthly anomaly field showed that the first mode reflects the main distribution and variation characteristics of SST in the SCS from 1982 to 2015.The spatial distribution of the first mode showed that the variation of SST in the SCS was in the same phase,and the amplitude decreased from the northwest to the southeast.The wavelet analysis of the first modal time coefficient showed that there are interannual modes of 2?3 years and 5-7 years,and the main period was 5 years,corresponding to the average period of the El Nino event.The correlation analysis between SSTA over the SCS and the index of Nino3.4 showed that the average incidence was 0.655,and the highest correlation degree was 0.723.The SSTA over the SCS was lag of Nino3.4 about 7?8 months.(3)Based on the calculation of thermal stress indexes such as HotSpots with MODIS SST fusion dataset in May of 2014?2016,it was found that thermal pressure was highly heterogeneous in space between Zhubi Reef and Mischief Reef.On the whole,the HotSpots and weekly heat accumulation of Zhubi reef were higher than that in Mischief reef.We concluded that the thermal stress of Zhubi Reef was higher than that of Mischief Reef.To a certain extent,the index of DHWM was up for the fact that underestimated thermal stress by CRW on the coral reef ecosystem of Nansha.