The influence of microhabitats on the carbon isotopic composition of deep‐sea benthic foraminifera

We report δ 13 C and δ 18 O 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 δ 13 C profiles to evaluate the importance of environmental (microhabitat) effects on the carbon isotopic composition of benthic foraminifera. The δ 13 C values of infaunal taxa are consistently lower than those of epifaunal taxa, suggesting that microhabitat effects on test composition do exist. The δ 13 C differences between foraminiferal carbonate and bottom water dissolved inorganic carbon are not correlated with the δ 18 O differences between benthic foraminifera tests and equilibrium calcite, but they do correlate with variations in the chemistry of sediment pore waters. However, interspecific δ 18 O differences as well as δ 13 C differences between species with similar vertical distributions in the sediments indicate that taxon‐specific “vital” effects also influence test composition.