JOURNAL OF PLANKTON RESEARCH | VOLUME 25 | NUMBER 10 | PAGES 1227-1235 | 2003
© Oxford University Press
Physiology of diatom Skeletonema costatum (Grev.) Cleve photosynthetic extracellular release: evidence for a novel coupling between marine bacteria and phytoplankton
American College of Management and Technology, Cira Carica 4, 20000 Dubrovnik, Croatia and 1 Umr Physiologie Et Biotechnologie Vegetales Ibvm Centre De Recherches Inra De Bordeaux, 71 Avenue Eduard Bourleaux, Bp 8133883, Villenave D’Ornon Cedex, France
* Corresponding Author: stasa{at}acmt.hr
The photosynthesis of cellular materials by phytoplankton is accompanied by release of organic molecules from the algal cells into the water. The patterns of carbon fixation in particulate and dissolved pools were investigated in Skeletonema costatum cultured under 12 h light/12 h dark cycles. The short-term production (1–15 min) of particulate organic carbon (POC) and extracellular organic carbon (EOC) compounds was studied by measuring the uptake of 14C-labelled sodium bicarbonate and its subsequent incorporation and release into organic compounds. Slightly modified traditional 14C radiotracer protocols were used, including separation by electrophoresis and thin-layer chromatography and detection by autoradiography. Results indicated that there was a distinct difference between radiolabelled compounds in the POC and EOC pools. Several metabolites found in the EOC pool were not present in the POC pool, indicating the active release of these products from the cells into the ambient water during short-term incubations, and indicating that inorganic carbon fixation pathways in marine autotrophs might be partly extracellular.