Photosynthetic Characteristics of Picoplankton Compared with Those of Larger Phytoplankton Populations, in Various Water Masses in the Gulf of Maine

AbstractCell numbers of eucaryotes and cyanobacteria in phototrophic picoplankton and ratios of in vivo fluorescence of phycoerythrin: chlorophyll a indicated that chroococcalean cyanobacteria played a more prominent role in phytoplankton communities, at the least productive stations. At stations displaying large vertical density gradients, subsurface maxima of phytoplankton pigments were observed. Ratios of in vivo fluorescence of phycoerythrin: chlorophyll a were always greater at the pigment maximum than at the surface. Cyanobacteria from pigment maxima demonstrated greater phycoerythrin fluorescence intensity and photosynthetic rates than cyanobacteria from the surface. Photosynthetic characteristics of picoplankton ( 3 μm populations. The picoplankton differed from larger phytoplankton, in that (1) their pattern of photosynthetic carbon fixation did not vary significantly with decreasing light intensity, and at optimal intensities ...