To constrain the use of, and better calibrate benthic foraminiferal carbon-isotope based proxies (δ13C) 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 δ13C. The one-to-one relationship between the δ13C of Cibicidoides wuellerstorfi and Cibicides lobatulus tests and the δ13CDIC of bottom water in Nordic Seas was reconfirmed. We also confirmed an almost constant δ13C of live specimens of infaunal species Melonis zaandamae, Nonion labradoricum, and Globobulimina affinis independent of their subbottom sampling depth and pore water δ13CDIC at any given site. This is in contrast to the wide range of intraspecific δ13C values of both, epifaunal as well as infaunal species, observed between sites. We did not find significant correlations between foraminiferal δ13C minus site-specific δ13CDIC (Δδ13CFor −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 Δδ13CFor −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 δ13C, whereas on the other hand they document the independence of epifaunal and infaunal species δ13C of TOC contents in well-ventilated bottom water and organic-rich surface sediment. Generally, species' mean δ13C reflects their average living depths (ALD5) such that epifaunal and shallow infaunal species depict highest, and deep infaunal species, lowest δ13C values. Mean Δδ13CFor −DIC values of neither epifaunal C. lobatulus and C. wuellerstorfi (− 0.05 ± 0.06‰) nor of infaunal M. zaandamae (− 2.40 ± 0.07‰), N. labradoricum (− 2.69 ± 0.13‰), and G. affinis (− 3.48 ± 0.15‰) 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 δ13CDIC; the latter possibly partly due to methanotrophic oxidation. The δ13C values of deep infaunal N. labradoricum and G. affinis minus epifaunal δ13C values (Δδ13CNlab − Cib and Δδ13CGaff − Cib), seem to decrease with increasing TOC and MOC contents. However, only the Δδ13CNlab − Cib values correlate significantly with MOC contents and thus marine primary productivity. Dissolved oxygen concentrations, estimated on the basis of Δδ13CGaff − Cib values, of > 230 μmol/kg are in accordance with reported well-oxygenated bottom water conditions at all stations.