Water colour variation analysis of the coastal waters surrounding Xiamen Island of SE China by multispectral and multitemporal remote sensing measurements
环厦门海域水色变化的多光谱多时相遥感分析

The water colour variations of the coastal waters around Xiamen Island from 1989 to 2003 has been analysed through image-spectrum-based models without using in situ data. A water-thematic image processing procedure for Landsat TM/ETM and SPOT 5 imagery has been proposed and applied to detect spatial and temporal dynamics of suspended solid- and chlorophyll-a-concentrations in the coastal waters. The study shows that the suspended solid concentration (SSC) is the most important parameter to affect water colour, while chlorophyll-a concentration (CAC) is a particularly good estimator of the water trophic level. The image-spectrum-based algorithms can fast and efficiently reveal the spatial and temporal variations of water colour during a long period of time and are especially useful when lack of historical concurrent in situ data. The results from multitemporal change detection indicate that the SSC in the coastal waters has significantly increased during the study years and CAC has also greatly increased in some areas such as the Maluan Bay. In particular, the high SSC water only accounted for 0.2 % of the study ocean area in 1989 but increased up to 10.2 % of the area in 2003. It is concluded that a huge number of suspended solids loaded in the Jiulong River was the major terrestrial input, and the most important factor resulting in the pollution of the coastal waters when discharging of the loads in the estuary area. In addition, the booming aquiculture development was another important factor attributed to the pollution.