ABUNDANT COLONIZATION OF CALCAREOUS FORAMINIFERA, CIBICIDOIDES WUELLERSTORFI AND PYRGO, AT 4000 M (STATION M) IN THE PACIFIC OCEAN

After one year on the seafloor at 4000 m water depth, five SEA³s (Seafloor Epibenthic Attachment Cubes) were colonized by ~500 foraminifera, ~80% of which were calcareous species. Although calcareous specimens are not typically abundant in sediments from this water depth in the Pacific, living calcareous epibenthic foraminifera may be more abundant near the CCD than previously thought. At such depths, the physiological requirements of building and maintaining a calcareous skeletal structure may severely impact the ability of foraminifera to be competitive. It is therefore surprising that calcareous foraminifera dominated multiple substrate experiments at Station M in the Pacific. Genetic analyses of the dominant, calcareous trochospiral epibenthic foraminiferal species, show that they cluster with Cibicidoides wuellerstorfi. Pyrgo sp., another calcareous foraminiferal species, was also abundant on the plastic mesh of the SEA³s. These results indicate that some deep-sea calcareous taxa are able to thrive under low pH conditions in modern oceans and may have implications for reconstructions of the past and future projections.