Carbon budget of the planktonic food web in an atoll lagoon (Takapoto, French Polynesia)

The structure and functioning of the planktonic food web were characterized in the lagoon of Takapoto Atoll (French Polynesia). Several variables were estimated over several weeks in April 1996 and 1997: carbon stocks of different planktonic compartments, phytoplankton particulate net production (PPNP), release of dissolved organic carbon (DOC) from phytoplankton, bacterial production and metabolic activity, and sinking of particles. The carbon stocks and flows were used to build up a quantitative description of the planktonic food web. The heterotrophic bacterial community was characterized by high biomass, low production and a small proportion of actively respiring cells. This was consistent with the observed low consumption of bacteria by protozoa. The relatively high PPNP was mostly due to cyanobacteria