Rates of carbon fixation, organic carbon release and translocation in a reef-building foraminifer, Marginopora vertebralis

Rate measurements obtained in this study and the population densities of foraminifera reported elsewhere suggest that such organisms may well exceed the hermatypic corals in their contribution to reef biogensis and energy fluxes. The average rates at which M, vertebralis photosynthetically fixes carbon into particulate organic carbon, dissolved organic carbon, and shell carbonate, per square centimetre of organism, were estimated to be 50, 1 .5, and 26 ng C min-1 respectively. Exogenously supplied dissolved organic carbon was taken up by M. vevtebralis at a rate of 0.05 ng C min-I in the light, and 0.09 ng C min-I in the dark per square centimetre of organism. The turnover time of particulate organic carbon (91 h) was measured in a long-term in situ incubation during which 19% of the radioactivity lost from the particulate organic carbon entered the calcareous foraminifera1 shell.