Stable isotopic signatures of sediment carbon and nitrogen sources and its relation to benthic meiofaunal distribution in the Arctic Kongsfjord

The present study investigated the relationship of sediment attributes to meiofaunal composition pattern and its food source in the Kongsfjord. Sediment in the fjord is dominated with silty clay fractions. Ten meiofaunal groups contributed to the meiofaunal composition in the fjord with the dominance of foraminiferans, nematodes and tintinnids. The total density of fauna ranged from 1 ind./10 cm² to 1,560 ind./10 cm² whereas the biomass ranged from 0.06 ± 0.002 μg/10 cm² to 605.1 ± 7.19 μg/10 cm². On comparing with previous studies, our data exhibited a significant decrease in the overall density and biomass of the meiofauna. Sediment δ¹³C values were relatively low in the fjord that varied from −21.6‰ to −22.9‰, and this could be due to low CO₂ concentrations in the ambient environment. The isotopic value proves that the carbon supply in the fjord sediment is linked to the marine source largely from single-celled phytoplankton in the photic zones. Isotope value of δ¹⁵N increases in the fjord system when marine productivity is relatively high; that also varies from 4.6‰ to 6.8‰, further suggesting that the origin of fjord sediment nitrogen is supplied from the nutrient-rich warm Atlantic water masses contributing to high marine production in the fjord. TOC/TN values in the fjord were lower than 10%, which also supports our hypothesis that Kongsfjord sediment organic matter was received mainly from marine source.