Sammendrag
We explore the trophic ecology of heterotrophic fauna associated with a high temperature
(HT) vent, 2 low temperature vents, a ‘near-HT vent’ habitat and a non-vent site situated at
upper bathyal depths on the southern Mohn’s Ridge in the Arctic Ocean. Only a single taxon (the
gastropod Pseudosetia griegi) was found at the high temperature vent habitat. Their mean δ13C
values were significantly lighter than conspecifics from a low temperature vent habitat within the
same vent field, reflecting the incorporation of sulfide oxidizing bacteria into the biomass of the
animals. The majority of fauna from the low temperature, near-HT, and non-vent habitats had
isotopic signatures indicative of assimilation of photosynthetic material. However, we found
remarkably diverse isotopic compositions among the fauna sampled here, with a small sub-set of
fauna at each site possessing C and N isotopic signatures indicative of incorporation of chemo -
synthetic production. Moreover, when isotopic signatures of similar taxa were compared from the
same sample, δ13C signatures suggested a high degree of trophic complexity can exist over relatively
small spatial scales at vent habitats on the southern Mohn’s Ridge. The high contribution of
photosynthetic food material to faunal diets and variability in food types may result from the upper
bathyal venting depth and sedimentary nature of the vents. We hypothesize that the upper
bathyal depth of active venting may lead to iron enhancement of surface photosynthetic production,
especially in high nutrient areas, which ultimately sinks to the seabed where it is incorporated
by fauna around the vents.
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