Carbon flow in an experimental microbial ecosystem

Abstract

Good introduction on bacterial feeding on EOC. Three chemostat cultures were followed to elucidate the growth of bacteria on organic exudates of autotrophs. The cultures consisted of A (autotrophs), AB (auto + bact) and ABF (auto+bact+flagellates). Due to size restrictions herbivory by the flagellates can be exluded. They found that there C-budget was 'closed' and therefore conclude that their assumptions are valid. EOC (excreted organic carbon) only increased in the A-culture after the exponential growth phase of the autotrophs (and coincident depletion of nutrients, mainly P). EOC in the other cultures remained fairly constant. A connection between algae survival and bacterial growth was found. After a long discussion they hypothesize that this may be due to the consumption of exudates by bacteria, which might limit algae survival. The growth of bacteria could be attributed to EOC production by algae. Most of the bacterial C was mineralized by respiration by flagellates and therefore the net community carbon production was fairly low. The main effect of the microbial loop was that by the grazing of bacteria by flagellates, inorganic nutrients became available to induce a second algal bloom.