Diffusion chamber studies of carbon flux from living algae to heterotrophic bacteria

The flux of recently photosynthetically fixed, dissolved organic carbon (PDOC) from phototrophs to heterotrophic microorganisms was measured directly in microplankton samples from Lake Kinneret using a diffusion chamber technique. The minimum amounts of PDOC incorporated into small <3 µm heterotrophs during a 12 h light period ranged from 0.8 to 38.4 µg (C) l^-1, or from 0.2% to 6% of net primary productivity. Although quantitatively small in comparison with total photosynthetic fixation, this PDOC flux could yield about 2 to 3 × 10⁶ bacterial cells.ml^-1 daily. This experimental is consistent with previous estimates of algal PDOC release in this lake.