Remote sensing and zonation of seagrasses and algae along the Kenyan coast

Little information has been published on space-borne remote sensing of seag rasses, and no information is available about the distribution of seagrasse s and algae in East Africa. Through satellite remote sensing this study inv estigates the distribution of these plants along a southern section of the Kenyan coast. The visible bands (red, green and blue) and the near infra-re d band of a Landsat Thematic Mapper image acquired in 1992 were combined in order to detect seagrasses and algae in 10 sectors along the section of th e coast. Ground truthing was done at three locations along the same section . Results indicate that two distinct zones of vegetation can be recognised, and ground truthing reveals their identity is rocky substrate with mostly algae and seagrasses, respectively. The extent of the vegetation in the two zones has been quantified in square kilometres for the 10 sectors. However , care is needed in the interpretation of the satellite images when dealing with artefacts such as clouds. The zonation of the algal vegetation is dis cussed for one of the study sites.