Studies on transparent exopolymer particles (TEP) produced by Phaeocystis sp. (Prymnesiophyceae) in the Ross Sea, Antarctica

Transparent exopolymer particles (TEP) produced by Phaeocystis sp. (Prymnesiophyceae) were studied quantitatively in cultures and in the Ross Sea, Antarctica for the first time. Concentration of TEP produced by Phaeocystis were generally higher than those produced by diatoms, and were functions of growth rate and photosynthetic response, which were tightly coupled with irradiance and salinity. These two factors, therefore, influenced the production of TEP in culture. In the Ross Sea TEP concentrations were primarily a function of chlorophyll, and were minimal at chlorophyll levels below 3 μg I^-1 but increased rapidly above this concentration. This two-state system indicated TEP formation might involve a coagulation mechanism, a possibility supported by a correlation between TEP concentrations and wind stress. Distributions of TEP were studied during a Phaeocystis bloom, and the different vertical distribution patterns between TEP and chlorophyll result in a maxima in the TEP; chlorophyll ratio in the bottom of the water column at most the stations investigated. TEP concentrations were measured repeatedly at the same station but at different times during the cruise, and higher TEP concentrations appeared in a deep layer in later surveys. This evidence supports the hypothesis that mucous floes instead of Phaeocystis sp. colonies contribute significantly to carbon vertical flux because TEP is tightly related with floes. A conceptual model of TEP related to the Phaeocystis sp. blooms and a carbon vertical cycle is suggested.