Deposit-feeding of <i>Nonionellina labradorica</i> (foraminifera) from an Arctic methane seep site and possible association with a methanotroph

Abstract. Several foraminifera are deposit feeders that consume organic detritus (dead particulate material with entrained bacteria). However, the role of such in benthic food web remains understudied. Foraminifera feeding on methanotrophic bacteria, which 13C-depleted, may cause negative cytoplasmic and/or calcitic δ13C values. To test whether foraminiferal diet includes methanotrophs, we performed a short-term (20 h) experiment Nonionellina labradorica from an active Arctic methane-emission site (Storfjordrenna, Barents Sea) using marine methanotroph Methyloprofundus sedimenti and analysed N. cytology via transmission electron microscopy (TEM). We hypothesised M. would be visible post-experiment degradation vacuoles, as evidenced by their ultrastructure. Sediment grains (mostly clay) occurred inside one or several vacuoles all foraminifers. In 24 % specimens also contained although none could confirmed to offered sedimenti. Observations apertural area after 20 h incubation revealed three putative close clay particles, based bacterial ultrastructural characteristics. Furthermore, noted absence endobionts examined but presence kleptoplasts, were often partially degraded. sum, suggest can consumed untargeted grazing seeps generally classified feeder at this site.