ON THE TROPHIC FATE OF PHAEOCYSTIS-POUCHETII (HARIOT) .4. THE FORMATION OF MARINE SNOW BY P-POUCHETI

The formation of aggregates by Phaeocystis was investigated in coastal waters of northern Norway and in laboratory experiments. No evidence was found to support the hypothesis formulated by Wassmann et al. [(1990); Mar, Ecol. Prog. Ser. 66: 183-195] that Phaeocystis blooms are terminated by the formation of Phaeocystis aggregates from senescent colonies. Although Phaeocystis was observed to form aggregates in some instances, senescent colonies did not appear to have a higher sticking efficiency than growing ones. At senescence Phaeocystis colonies appeared to disintegrate. Further laboratory studies revealed that dissolved carbohydrates derived from the colonial matrix of Phaeocystis formed mucous particles which attached to siliceous fibers and glued them together. Detrital mucous flocs also formed from a natural particle assemblage and dissolved carbohydrates accumulated during the Phaeocystis bloom when rotated. We develop the hypothesis that cells and colonies of Phaeocystis may not contribute significantly to vertical flux, but that the sedimentation of mucous flocs presents a secondary pathway by which carbon assimilated during Phaeocystis blooms may sink to greater depth.