Distribution of selected species of living algal symbiont-bearing foraminifera on two Pacific coral reefs

Fifteen species belonging to four families of large, benthic, symbiont-bearing foraminifera were collected alive in coral reef-associated environments on Palau, Western Caroline Islands, and Oahu, Hawaii. Typical habitat was algal veneer over rubble or other hard substrate. R-mode cluster analysis revealed four species clusters around Palau. One cluster, dominated by Calcarinidae, was characteristic of seaward reef flats. The second cluster, made up of Marginopora vertebralis, Amphistegina lobifera and Peneroplis planatus, was characteristic of more protected shoals having water depths of less than 5 m. The third cluster, typified by A. lessonii, characterized reef slopes at 5-20 m. The fourth cluster consisted of more deeply dwelling species, especially A. radiata and Operculina ammonoides. In the samples from Oahu, the calcarinid cluster was absent; M. vertebralis was associated with P. pertusus; A. lessonii was associated with A. lobifera and P. planatus; and A. bicirculata and O. ammonoides typified deeper samples. The depth and habitat zonation exhibited by these species indicate their usefulness as paleoenvironmental indicators and as sediment tracers.