PARTICULATE REFLECTANCE MEASUREMENTS OF PHYTOPLANKTON

A portable reflectometer was used to measure the reflectance of phytoplankton and particulate material on glass fiber filters. Measurements were made on four different classes of phytoplankton as well as particulate material from the Southern California Bight and southern Florida coastal waters. The Kubelka-Munk formulation was used to convert the relative reflectance to apparent absorption, A(r)(lambda) which was then compared with particulate absorption measured with a spectrophotometer, A(s)(lambda). Spectra of A(r)(lambda) and A(s)(lambda) were very similar. The ratio of A(r)(lambda)/A(s)(lambda) was 1.4 for cultured algae and 1.2 in the two field assemblages, but in both cases the ratios were less than the theoretical value of 2. These results were discussed in terms of the optical and geometric path lengths of reflected and transmitted light through particulate material on filters.