Mapping the distribution of an invasive marine alga (Codium fragilespp.tomentosoides) in optically shallow coastal waters using the compact airborne spectrographic imager (CASI)

We collected 19 bands of ocean colour data (spanning 391–904 nm) at 1 m2 spatial resolution from Mahone Bay on the south coast of Nova Scotia during July 2001 with an airborne hyperspectral sensor (CASI). The data were classified using 16 different protocols in an effort to accurately map benthic communities over 7 km2 of seabed to 6 m water depth. The primary objective was to depict the spatial pattern of invasion of the rocky subtidal zone by an introduced macroalga: Codium fragile. The best classification results were obtained using the first three axes of a principal component analysis of all 19 spectral channels and the maximum likelihood classification of four classes of benthic community (i.e., those dominated by Codium meadow, kelp bed, Codium–kelp mix, and sand) at three depth strata using an added bathymetry channel and no correction for water-column attenuation. The overall accuracy obtained for the entire visible seabed of the bay was 83.30% (Kappa statistic = 0.82). User's and producer's accu...