Environmental characterization of a hypersaline coastal lagoon from Landsat-5 Thematic Mapper data

Analysis of two 1994 Landsat-5 Thematic Mapper (TM) images (TM bands 1, 2, 3, 4 and 5) from a shallow coastal lagoon in Brazil yielded high correlations between the digitally processed upwelling radiances and synoptic field measurements of chlorophyll- a and Secchi disk depths in water depths greater than 3.5 m. However, in shallower water, bottom reflectance dominates the optical signal. Here the TM images can be used to identify regions of microphytobenthic communities with different densities (levels of productivity). A principal component analysis (PCA) of TM bands 1, 2 and 3 yielded more consistent correlations with chlorophyll- a and turbidity variability than the raw TM data. PC1 and PC2 correlated with chlorophyll- a and PC1 correlated with Secchi disk depths on both dates.