A new method for the satellite remote sensing of ocean biological activity is presented.In contrast to existing algorithms,our method analyses weak narrow-band reflectance structures of chlorophyll and pigments in the red spectral range.It is based on differential optical absorption spectroscopy (DOAS),which is usually applied for the analysis of atmospheric trace gas absorptions.Since the spectra of atmospheric absorption and spectral reflectance are simultaneously included in the analysis,the effects of atmospheric absorption are automatically corrected.The derived global maps of the ocean biological activity represent the spatial distribution and seasonal cycle.High biological activity is found e.g.at the mouths of big rivers,in the Black sea and the Caspian sea as well as around corral reefs north of Australia.Our results indicate the need for a more detailed and comprehensive data base of ocean reflectance spectra with at least moderate resolution (about 1nm).After such improved spectra become available,a more sensitive and more specific data analysis should be possible.