To constrain the use of, and better calibrate benthic foraminiferal carbon-isotope based proxies (delta C-13) we analyzed live (Rose Bengal stained) benthic foraminifera from fjords, outer shelves, and the upper continental slope of SW-Svalbard. We further investigated whether the presence of widespread methane seepage altered benthic foraminiferal delta C-13. The one-to-one relationship between the delta C-13 of Cibicidoides wuellerstorfi and Cibicides lobatulus tests and the delta C-13(DIC) of bottom water in Nordic Seas was reconfirmed. We also confirmed an almost constant delta C-13 of live specimens of infaunal species Melonis zaandamae, Nonion labradoricum, and Globobulimina affinis independent of their subbottom sampling depth and pore water delta C-13(DIC) at any given site. This is in contrast to the wide range of intraspecific delta C-13 values of both, epifaunal as well as infaunal species, observed between sites. We did not find significant correlations between foraminiferal delta C-13 minus site-specific delta C-13(DIC) (Delta delta C-13(For) - (DIC)) of the investigated species and the total organic carbon (TOC) contents of surface sediments. On the contrary, a distinct relationship is observed between high marine organic carbon (MOC) contents and low Delta delta C-13(For) - (DIC) values of N. labradoricum and, to a lesser extent, G. affinis. These findings are important because on the one hand they confirm a systematic influence of the availability of labile MOC on deep infaunal species delta C-13, whereas on the other hand they document the independence of epifaunal and infaunal species delta C-13 of TOC contents in well-ventilated bottom water and organic-rich surface sediment. Generally, species' mean delta C-13 reflects their average living depths (ALD(5)) such that epifaunal and shallow infaunal species depict highest, and deep infaunal species, lowest delta C-13 values. Mean Delta delta C-13(For) - (DIC) values of neither epifaunal C. lobatulus and C. wuellerstorfi (-0.05 +/- 0.06 parts per thousand) nor of infaunal M. zaandamae (-2.40 +/- 0.07 parts per thousand), N. labradoricum (-2.69 +/- 0.13 parts per thousand), and G. affinis (-3.48 +/- 0.15 parts per thousand) seem to be significantly influenced by strongly elevated methane concentrations in the water column, widespread gas seepage at the sea floor, and low pore-water delta C-13(DIC), the latter possibly partly due to methanotrophic oxidation. The delta C-13 values of deep infaunal N. labradoricum and G. affinis minus epifaunal delta C-13 values (Delta delta C-13(Nlab) - (Cib) and Delta delta C-13(Gaff) - (Cib)), seem to decrease with increasing TOC and MOC contents. However, only the Delta delta C-13(Nlab) - (Cib) values correlate significantly with MOC contents and thus marine primary productivity. Dissolved oxygen concentrations, estimated on the basis of Delta delta C-13(Gaff) - (Cib) values, of > 230 mu mol/kg are in accordance with reported well-oxygenated bottom water conditions at all stations.