Mapping Bottom Type and Water Depth in Shallow Coastal Waters with Satellite Remote Sensing

Species composition of benthic macroalgal cover and the changes therein are indicators of the trophic state of aquatic ecosystems. On the other hand, mapping and knowledge of water depth in shallow water areas, not accessible by hydrographical ships, is important for several reasons. This study assessed the suitability of high spatial resolution multispectral and medium spatial resolution hyperspectral data for mapping water depth and benthic macroalgal cover in shallow coastal waters of the Baltic Sea. Results of this study indicate that use of multispectral satellite data with high spatial resolution is preferable to using hyperspectral medium resolution data in mapping benthic macroalgal cover in areas where the spatial heterogeneity is very high. In case of a single image and availability of in situ data, multispectral high spatial resolution (2.4 in) satellite QuickBird can provide more detailed information about benthic cover than was assumed based on the shape of reflectance spectra of different bottom types and spectral resolution of the sensor. Depth maps of shallow (less than 3 metres) waters proved to be reliable except in turbid water areas with no bottom visibility.