The use of optical attenuance meters for biological measurements

Different biological and other suspended particles in sea water show different light absorption spectra. So one should get some more informations on the particles themselves if one measures in situ with high precision the attenuation coefficients and with further increased precision the direct differences of the attenuations at two or more wavelengths . In practice such differences must be measured in one same water sample at the same time on the same light path. This paper deals with a newly developed type of in situ measuring instrument by which such measurements can be achieved with very high resolution and accuracy. Not only the differences but also the attenuations and are available from the same sensor. Such data may well serve for studying the distribution of biological and other particulate matter in the ocean. A number of profiles from recent cruises show remarkable results, which will be reported on.