Utilization of Dissolved Organic Carbon by Natural Populations of Epibenthic Salt Marsh Diatoms¹

Natural populations of pennate diatoms collected from the mudflats of a Georgia salt marsh were cleansed by differential centrifugation and tested for their ability to assimilate and respire 14 C‐acetate, lactate and glucose at 1 μM concentrations. A correction was made for contaminating bacterial activity. Utilization rates were measured in the light and dark and in the presence of a second substrate. Mean incorporation rates were (in pmol ·μg chl a −1 · h −1 ± SE): acetate, 117 ± 37; lactate, 53.7 ± 20.4; glucose 13.0 ± 5.8. Using a carbon/chlorophyll ratio of 53.2 and a generation time of 48 h we calculate these algae could obtain up to 1% of their carbon heterotrophically if several usable substrates were each available at 1 μM concentrations.