03116nas a2200229   4500008004100000022001300041245015000054210006900204260001000273300001400283490000700297520237700304653001202681653001802693653001102711653001702722100002202739700002502761700002402786700002302810856005302833       2004                        eng d  a0377839800aEnvironmental and biological effects on the stable isotope composition of recent deep-sea benthic foraminifera from the western Mediterranean Sea0 aEnvironmental and biological effects on the stable isotope compo  cApril  a129–1520 v513 aThe influence of microhabitat, organic matter flux, and metabolism on the stable oxygen and carbon isotope composition of live (Rose Bengal stained) and dead (empty tests) deep-sea benthic foraminifera from the Gulf of Lions (western Mediterranean Sea) have been studied. The total range of observed foraminiferal isotope values exceeds 1.0‰ for δ 18 O and 2.2‰ for δ 13 C demonstrating a wide range of coexisting disequilibria relative to δ 18 O of equilibrium calcite ( δ 18 O EQ ) and δ 13 C of bottom water dissolved inorganic carbon ( δ 13 C DIC ). The mean δ 18 O values reveal strongest disequilibria for the studied epifaunal to shallow infaunal species ( Cibicidoides pachydermus , Uvigerina mediterranea , Uvigerina peregrina ) while values approach equilibrium in deep infaunal species ( Globobulimina affinis , Globobulimina pseudospinescens ). The mean δ 13 C values decrease with increasing average living depths of the different species, thus reflecting a dominant microhabitat (pore water) signal. At the axis of the Lacaze-Duthier Canyon a minimum δ 13 C DIC pore water gradient of approximately −2.1‰ is assessed for the upper 6 cm of the surface sediment. Although live individuals of U. mediterranea were found in different depth intervals their mean δ 13 C values are consistent with calcification at an average living depth around 1 cm. The deep infaunal occurrence of U. mediterranea specimens suggests association with macrofaunal burrows creating a microenvironment with geochemical characteristics similar to the topmost centimeter. This also explains the excellent agreement between stable isotope signals of live and dead individuals. The ontogenetic enrichment in both δ 18 O and δ 13 C values of U. mediterranea suggests a slow-down of metabolic rates during test growth similar to that previously observed in planktic foraminifera. Enhanced organic carbon fluxes and higher proportion of resuspended terrestrial organic material at the canyon axis are reflected by δ 13 C values of U. mediterranea on average 0.58‰ lower than those from the open slope. These results demonstrate the general applicability of the δ 13 C signal of this species for the reconstruction of past organic matter fluxes in the Mediterranean Sea. Further studies on live specimens are needed for a more quantitative paleoceanographic approach.10ahabitat10ainvertebrates10amarine10amicrohabitat1 aSchmiedl, Gerhard1 aPfeilsticker, Martin1 aHemleben, Christoph1 aMackensen, Andreas  uhttp://dx.doi.org/10.1016/j.marmicro.2003.10.001