BIOOPTICAL CHARACTERISTICS OF COASTAL WATERS - ABSORPTION-SPECTRA OF PHYTOPLANKTON AND PIGMENT DISTRIBUTION IN THE WESTERN NORTH-ATLANTIC

The vertical structure in fluorescence and beam attenuation (at 660 nm) is related to local hydrographic features and the composition of photosynthetic pigments for the Gulf of Maine region at the end of summer. Phytoplankton and covarying material appear to be the major factors affecting the beam attenuation coefficient through changes in species composition and pigment concentration and through photoadaptation. The specific absorption coefficient of phytoplankton at 440 nm decreased significantly from stratified waters in the open ocean to the well-mixed area in the central part of the Georges Bank. We combined detailed pigment analysis with measurement of in vivo phytoplankton absorption spectra and consequently have interpreted the variability in the specific absorption spectra of phytoplankton in terms of changes in the pigment composition. We found major regional differences in the phytoplankton absorption spectra linked to regional differences in the phytoplankton community.