A new method for measuring spectral absorption coefficients of marine particles

A new method has been developed to measure the light absorption coefficients of marine particles. The procedure, adapted from one proposed earlier for microscopic observation of nanoplankton, consists of concentrating particles onto a Nuclepore filter, transferring the filtered material to a glass microscope slide using liquid nitrogen freezing, and finally measuring the particle absorption spectrum on the slide. Measurements on various phytoplanktonic species show that the transfer efficiency is 94-98% and that no alteration of absorption spectra occurs. Our new method has been tested successfully on both phytoplankton-dominated and detritus-dominated field samples. In comparison with the widely used glass-fiber filter technique, the major advantage of our procedure is to provide more accurate absorption coefficients, since the pathlength amplification effect CB factor) and its attached uncertainties are completely eliminated.