Diel patterns of carbon incorporation into biochemical constituents of Synechococcus spp. and larger algae in the Northwest Atlantic Ocean

Diel patterns of ¹⁴C-bicarbonate incorporation in>5 m algal communities were compared with those in cyanobacterial populations of Synechococcus spp. (0.6 to 1.0 m), collected from the surface and/or chlorophyll maximum at three stations in the Northwest Atlantic Ocean (a neritic front; in Warm-Core Eddy 84-E; and Wilkinson's Basin) from 21 July to 8 August, 1984. Cell constituents were chemically separated into four fractions: lipids, low molecular weight (LMW) metabolites, polysaccharides/nucleic acids, and proteins. The in situ diel pattern of ¹⁴C assimilation was virtually the same for >5 m algal communities adapted to different environments. Protein synthesis appeared to continue at a reduced rate at night using energy derived from the catabolism of polysaccharides and the mobilization of LMW compounds. Synechococcus spp. populations exhibited inherent physiological differences in their in situ diel pattern of carbon fixation from that in>5 m algal communities taken from the same water mass. There was no nighttime protein-synthesis in Synechococcus spp. The relative proportion of ¹⁴C-protein remained constant over night, while that of ¹⁴C-polysaccharides/nucleic acids declined and that of labelled LMW metabolites increased. Daytime light-intensity manipulations did not alter the diel pattern of carbon fixation in any of the>5 m algal assemblages, while changes in the carbon metabolism of surface and shadeadapted Synechococcus spp. populations could be rapidly induced by altering the light intensity.Bigelow Laboratory Contribution No. 86004