Pathways of carbon assimilation in phytoplankton from the Antarctic

• Main Authors: A. E. Smith, I. Morris
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 1980
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.614.8234; http://www.aslo.org/lo/toc/vol_25/issue_5/0865.pdf

The assimilation of [14C]bicarbonate into the major end-products of photosynthesis was measured at five stations in the Southern Ocean. Under conditions of low light intensity and low temperature ( oOC) and higher light intensities incorporation into lipid accounted for ~20 % of the fixed carbon, the synthesis of polysaccharide and (to a lesser extent) protein being more prominent. Populations showing high rates of incorporation of 14C into lipid have high PC:Chl ratios, high PC:PN ratios, and low C-specific rates of ‘“C assimilation. All populations were dominated by diatoms. High concentrations of nitrate, phosphate, and silicate argue against the concept of nutrient limi-tation. This pattern of photosynthesis differs from that observed in many other parts of the oceans. It is suggested that the prominent synthesis of lipid is a response to extremely low temperatures and is enhanced by the additional stress of low light intensities. Morris et al. (1974) suggested that the routine 14C technique for measuring pri-mary productivity of phytoplankton pop-ulations could be expanded relatively simply to permit measurements of the synthesis of the major end-products of photosynthesis. Convenient differential solvent extraction techniques could sep-arate fractions containing low molecular weight metabolites, lipids, polysaccha-rides, and protein. Such an approach has been applied to seasonal changes in the temperate waters of the Gulf of Maine (Morris and Skea 1978). Smith and Morris (1980) give a preliminary report of the application of this technique to phyto-plankton of the waters surrounding Ant-arctica. We thank G. Franceschini for supply-ing the data on daily irradiance levels, S. El-Sayed for supplying data on the nu-trient concentrations, and M. K. Kenni-cutt II for supplying data on lipid con-tent.