THE INFLUENCE OF MICROHABITATS ON THE CARBON ISOTOPIC COMPOSITION OF DEEP-SEA BENTHIC FORAMINIFERA

We report delta C-13 and delta O-18 values for Rose Bengal-stained benthic foraminifera from a set of box cores from continental margin environments in the Atlantic and Pacific oceans. These isotopic results are compared with foraminiferal distribution data and pore water delta C-13 profiles to evaluate the importance of environmental (microhabitat) effects on the carbon isotopic composition of benthic foraminifera. The delta C-13 values of infaunal taxa are consistently lower than those of epifaunal taxa, suggesting that microhabitat effects on test composition do exist. The delta C-13 differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the delta O-18 differences between benthic foraminifera tests and equilibrium calcite, but they do correlate with variations in the chemistry of sediment pore waters. However, interspecific delta O-18 differences as well as delta C-13 differences between species with similar vertical distributions in the sediments indicate that taxon-specific "vital" effects also influence test composition.