Information on the spatial location and extent of changes in the marine vegetation resulting from natural or human impacts, it is essential for the management of nearshore environment. Satellite remote sensing has been used as an effective tool to monitor and manage them, especially effective for lo...
Information on the spatial location and extent of changes in the marine vegetation resulting from natural or human impacts, it is essential for the management of nearshore environment. Satellite remote sensing has been used as an effective tool to monitor and manage them, especially effective for long-term changes of coastal environment. However, studies regarding distribution of marine vegetation in Korea have only been conducted through SCUBA diving or direct sampling method, thus it is limited in the long-term perspective on dynamics of marine vegetation. In this study, time-series satellite images were used to detection of the long-term changes of marine vegetation distribution. In chapter 2, the temporal changes of seagrass beds were detected from the analysis of satellite data over the 24 years (1990-2013). In addition, most of the seagrass beds were destroyed after typhoon passed the study site in 2012, therefore I evaluated the impacts of typhoons on disturbance of seagrass beds. To examine the long-term changes of seagrass beds, four types of satellite images (Landsat TM/ETM+, Aster, Spot-4, and Kompsat-2) were used within Mahalanobis Distance Classification (MDC) algorithm. The average of seagrass beds was 4.6 km2, and it was consistently before seagrass die-off in 2012. From the result of the spatial extent changes in seagrass beds beforehand and after the typhoon passed, typhoon had little impact on the distribution of seagrass beds. Unlikely the other typhoons, Typhoon Sanba only passed the study site during low tide. Therefore, these findings indicate that the water column buffer did not have any effect, and it led to seagrass die-off. In chapter 3, time-series satellite data were used to track the distribution and transport of rafting macroalgae in the southwestern coast of Korea (eastern YS). In addition, because the rafting Ulva and Sargassum appear simultaneously in one ecoregion, I try to discriminate between them by the satellite images. MODIS and Landsat TM/ETM+ images were used to detect rafting Ulva and Sargassum in the YS and ECS. Furthermore, surface currents were analyzed using the ROMS model to investigate the connection between the pathway of two rafting macroalgae and surface currents in the YS and ECS. From the satellite image observation, rafting Ulva and Sargassum in the eastern YS originated from the Jiangsu province of China and northern part of Taiwan, respectively. Also, the surface current in the YS and ECS were consistent with transport pathway of rafting macroalgae. This combined approach, using satellite data and current model, provide a robust proof for reveal the origin and distribution of Ulva and Sargassum rafts in the southwestern coast of the Korean peninsula. Because the Ulva and Sargassum species do not have large difference in the reflectance spectra, it is able to discriminate between them as only large-scale patches. In the future, it can distinguish more accurate by high spectral resolution image.
In short, satellite remote sensing is effective tool for estimate the spatial and temporal dynamics of marine vegetation, and provide useful information particularly in seagrass die-off and macroalgae bloom events. Nevertheless, long-term ecology research is lacking in the Korean coasts, long-term ecological data were derived from time-series satellite images. Therefore, these studies provide important information to understanding ecological characteristics of marine vegetation and effective manage them.
Information on the spatial location and extent of changes in the marine vegetation resulting from natural or human impacts, it is essential for the management of nearshore environment. Satellite remote sensing has been used as an effective tool to monitor and manage them, especially effective for long-term changes of coastal environment. However, studies regarding distribution of marine vegetation in Korea have only been conducted through SCUBA diving or direct sampling method, thus it is limited in the long-term perspective on dynamics of marine vegetation. In this study, time-series satellite images were used to detection of the long-term changes of marine vegetation distribution. In chapter 2, the temporal changes of seagrass beds were detected from the analysis of satellite data over the 24 years (1990-2013). In addition, most of the seagrass beds were destroyed after typhoon passed the study site in 2012, therefore I evaluated the impacts of typhoons on disturbance of seagrass beds. To examine the long-term changes of seagrass beds, four types of satellite images (Landsat TM/ETM+, Aster, Spot-4, and Kompsat-2) were used within Mahalanobis Distance Classification (MDC) algorithm. The average of seagrass beds was 4.6 km2, and it was consistently before seagrass die-off in 2012. From the result of the spatial extent changes in seagrass beds beforehand and after the typhoon passed, typhoon had little impact on the distribution of seagrass beds. Unlikely the other typhoons, Typhoon Sanba only passed the study site during low tide. Therefore, these findings indicate that the water column buffer did not have any effect, and it led to seagrass die-off. In chapter 3, time-series satellite data were used to track the distribution and transport of rafting macroalgae in the southwestern coast of Korea (eastern YS). In addition, because the rafting Ulva and Sargassum appear simultaneously in one ecoregion, I try to discriminate between them by the satellite images. MODIS and Landsat TM/ETM+ images were used to detect rafting Ulva and Sargassum in the YS and ECS. Furthermore, surface currents were analyzed using the ROMS model to investigate the connection between the pathway of two rafting macroalgae and surface currents in the YS and ECS. From the satellite image observation, rafting Ulva and Sargassum in the eastern YS originated from the Jiangsu province of China and northern part of Taiwan, respectively. Also, the surface current in the YS and ECS were consistent with transport pathway of rafting macroalgae. This combined approach, using satellite data and current model, provide a robust proof for reveal the origin and distribution of Ulva and Sargassum rafts in the southwestern coast of the Korean peninsula. Because the Ulva and Sargassum species do not have large difference in the reflectance spectra, it is able to discriminate between them as only large-scale patches. In the future, it can distinguish more accurate by high spectral resolution image.
In short, satellite remote sensing is effective tool for estimate the spatial and temporal dynamics of marine vegetation, and provide useful information particularly in seagrass die-off and macroalgae bloom events. Nevertheless, long-term ecology research is lacking in the Korean coasts, long-term ecological data were derived from time-series satellite images. Therefore, these studies provide important information to understanding ecological characteristics of marine vegetation and effective manage them.
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