Biochemical fractionation of primary production by phytoplankton in Belgian coastal waters during short- and long-term incubations with 14C-bicarbonate

Abstract

Short- and long-term, light-dark, time-course studies of radiocarbon accumulation in the major intracellular end-products of photosynthesis (proteins, polysaccharides, lipids, small metabolites) and extracellular monomers and polymers were conducted at natural light intensity in Belgian coastal waters and in the English Channel on Phaeocystis poucheti colonies growing under depleted and non-limited, inorganic nitrogen concentration. Evidence is given that the exopolymeric substances which compose the colony envelope, massively secreted during the photoperiod, are used during the dark, together with the intracellular reserve products, to cover the carbon and energetic needs of the colonies either for the maintenance or for pursuing protein synthesis, according to the external inorganic nitrogen level.