This Research Planning Grant will concentrate on developing techniques for measuring the growth rate of calcareous algae in carbonate reefs of Panama. It has been hypothesized that these algae may contribute a substantial amount to the total amount of carbon fixed into calcite in reef settings. The author will monitor the growth rate of individual algae and calculate the number of calcite particles produced and their ultimate fate--whether they are preserved in the sediment, thus burying carbon in the sediment or altered, thus releasing carbon back into the water. The long- range goal is to determine whether atmospheric levels of CO2 might be affected by changes in algal production resulting from sealevel variations.