Detecting coral bleaching using high-resolution satellite data analysis and 2-dimensional thermal model simulation in the Ishigaki fringing reef, Japan
Detecting coral bleaching using high-resolution satellite data analysis and 2-dimensional thermal model simulation in the Ishigaki fringing reef, Japan
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DOI：
10.1007/s00338-011-0860-1
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发表时间：
2012-06-01
期刊：
影响因子：
3.5
通讯作者：
Kayanne, H.
中科院分区：
文献类型：
--
作者：
Dadhich, A. P.;Nadaoka, K.;Kayanne, H.
2007年，在日本石垣岛东南海岸发育良好的缘礁区观察到高温导致的大规模珊瑚死亡。为了分析珊瑚对热应力的响应，珊瑚覆盖使用Quickbird数据进行了检查，在漂白事件之前和之后穿过礁坪，并进行了礁尺度水平二维热模型模拟。Quickbird数据由空间分辨率为2.4米的多光谱图像和空间分辨率为0.6米的全色融合多光谱图像组成。观察到的珊瑚覆盖的变化意味着部分漂白珊瑚的PAN + MSS的划定更精确。使用PAN + MSS（93%）实现的分类准确性优于使用MSS（88%）获得的分类准确性（上级）。现场水温观测和二维热模式模拟结果表明，2007年7月下旬内礁区水温波动较大。不同的热应力指数，包括每日平均温度，每日最高温度过高，和每日积温，进行了检查，以确定一个合适的指数，代表珊瑚覆盖的热应力的严重程度。结果表明，在白化季节的最高海面温度期间发生的日积温提供了最好的预测漂白。水温，水深，珊瑚斑块大小的变化影响漂白的严重程度，因此，这些变量的空间依赖性进行了研究，使用莫兰的我和拉格朗日乘数检验。一项关于珊瑚斑块大小对珊瑚白化的影响的调查表明，大的珊瑚斑块受到的影响小于小的珊瑚斑块，小的珊瑚斑块更有可能遭受白化和珊瑚死亡。
In 2007, high-temperature-induced mass coral mortality was observed in a well-developed fringing reef area on the southeastern coast of Ishigaki Island, Japan. To analyze the response of the corals to thermal stress, the coral cover was examined using Quickbird data, taken across the reef flat just before and after the bleaching event and performing a reef scale horizontal 2-dimensional thermal model simulation. The Quickbird data consisted of multispectral (MSS) imagery, which had a spatial resolution of 2.4 m, and panchromatic (PAN)-fused multispectral imagery, which had a 0.6-m spatial resolution. The observed changes in coral cover implied that the delineation of partially bleached coral was more precise with PAN + MSS. The classification accuracy achieved using PAN + MSS (93%) was superior to that obtained using MSS (88%). The in situ water temperature observations and 2-dimensional thermal model simulation results indicated that the water temperature fluctuated greatly in the inner reef area in late July 2007. Different thermal stress indices, including daily average temperature, daily maximum excess temperature, and daily accumulated temperature, were examined to define a suitable index that represented the severity of the thermal stress on coral cover. The results suggested that the daily accumulated temperature that occurred during the maximum sea surface temperature period of the bleaching season provided the best predictor of bleaching. The changes in water temperature, bathymetry, and coral patch size affected the severity of bleaching; therefore, the spatial dependence of these variables was examined using Moran's I and Lagrange multiplier tests. An investigation of the effect of coral patch sizes on coral bleaching indicated that large coral patches were less affected than the small patches, which were more likely to suffer bleaching and coral mortality.