Determination of food sources for nematodes in the Kuril Basin and eastern slope of the Kuril Islands by stable isotope and fatty acid analyses

Abstract

Little is known about the diet and feeding strategies of deep-sea nematodes. In this study, we investigated the trophic ecology of several macrobenthic nematode species in the abyssal zone of the Sea of Okhotsk and adjacent northwest Pacific by means of stable isotope and fatty acid analyses. A wide range of δ13C and δ15N values was found, with δ13C values ranging from −37.8 to −16.4‰ and δ15N values ranging from 5.7 to 19.2‰. The fatty acid composition of the nematode species demonstrated high variation. Planktonic FAs were found in high abundance in the nematodes at all stations, with values ranging from 31% to 34% (Metoncholaimus sp.) to 59% (Synonchinae gen. sp.). The abundance of bacterial FAs ranged from 13% to 22%. The isotopic and FA signatures exhibited a wide range of food sources in the nematode diet and highlighted the importance of sediment bacteria in the diet. The depleted isotopic signatures coupled with the increased abundance of bacterial FAs suggest that chemosynthetically derived organic matter can be an important carbon source for macrobenthic nematodes in the Kuril Basin.