Although benthic foraminifera are important components of the marine benthos and are widely used in paleoceanography for reconstructing deep- and bottom-water conditions, relatively little is known about their growth rates in the deep sea. Here we present data for two species, Buliminella tenuata and Nonionella stella, from a coastal upwelling region that show abundance changes reflecting rapid growth of these taxa over a three month interval. Rapid growth indicates that the chemical composition of the calcareous foraminiferal test, which is used extensively in paleoceanography, may reflect environmental conditions over a relatively short interval (i.e., months). This observation suggests that it will be possible to reconstruct seasonal environmental conditions in certain areas of the oceans such as coastal upwelling regions.