Trophic structure of the abyssal benthic community in the Sea of Japan inferred from stable isotope and fatty acid analyses

Abstract

The abyss of the Sea of Japan represents an example of an isolated deep-sea environment that contains mostly endemic fauna and has a complicated Quaternary history. To determine the trophic structure and sources supporting this abyssal benthic community, the carbon and nitrogen stable isotope ratios and fatty acid (FA) compositions of key invertebrate species and sedimentary organic matter (SOM) were analysed. Samples were collected at a range of depths from 2481 to 3666 m in the deep-water basin of the Sea of Japan in August 2010. Species of the most abundant invertebrates -including polychaetes, sea anemones, peracarid crustaceans, bivalves and brittle stars -showed similar δ 15 N values, corresponding to relatively high and similar trophic positions. Analysis of FA trophic markers showed that all of these equally 15 N-enriched omnivores, carnivores and scavenger species in the Sea of Japan abyssal environment fed mostly on sinking zooplankton animals. The resulting FA profiles of these species showed a high 18:1ω9/18:1ω7 ratio, and the 22:6ω3 and 20:5ω3 polyunsaturated FAs were the most abundant FAs. Only one macrobenthic species, the filter-feeding Thyasira (Parathyasira) sp., had low 22:6ω3 and 20:5ω3 FA proportions, but it exhibited significant levels of 18:2ω6 and 16:1ω10 FAs characteristic of the SOM of the deep waters of the Sea of Japan. These data reveal the dominant role of descending zooplankton as a food resource for mega-and macrobenthos in this marginal deep-water environment. Despite the proximity of the productive shelf area, which exports plant residues to the deep-water basin of the Sea of Japan, we found no isotopic or FA indications of feeding on allochtonous detritus of seagrasses or macroalgae among abyssal consumers. Our data did not support cannibalism as a feeding mode of the abundant abyssal carnivorous polychaetes, as had previously been suggested. Different key invertebrate species of the Sea of Japan abyssal food web occupied similar trophic positions and fed predominantly on descended zooplankton. We suggest that the simple structure of the Sea of Japan abyssal food web, lacking abundant deposit-feeder food chains, is the result of the young evolutionary age of this community rather than the low availability of bottom detritus or the specific structure of the pelagic community that provides abundant downward flow of zooplankton.

Food Sources of Benthic Communities at the Caiwei Guyot and Yap Trench, Northwestern Pacific Ocean: Inferences From Carbon and Nitrogen Isotopes

“…Therefore, based on the observed and inferred C and N isotope values of the zooplankton and the megabenthos, we conclude that zooplankton is likely an important direct food source for the abyssal megabenthos of the northwest Pacific Ocean. This scenario is consistent with observations in other ocean areas (e.g., in the west Antarctic and the Sea of Japan, where studies suggest that zooplankton serve as an important food resource for the deepwater megabenthos; Mincks et al, ; Kiyashko et al, ).…”

“…The implication is that at least some members of the megabenthos are relying significantly on other food sources (e.g., zooplankton or SPOM). Recent work in the Sea of Japan (Kiyashko et al, ) also suggests that sedimentary organic matter is not always an important food source for the megabenthos.…”

“…In deep‐sea communities, a strong positive correlation between consumers' δ 15 N and δ 13 C values indicates that a single primary food source supports the community (Fanelli et al, ; Iken et al, ; Kiyashko et al, ; Polunin et al, ). At our study sites, no such correlation was observed (Figure ).…”

“…Most of the POM produced in surface oceans is remineralized as it sinks through the water column (Koppelmann & Frost, ), which leaves only a small portion to finally reach the sea bottom to sustain the benthic food web. Some additional food may be transferred downward through the water column by descending zooplankton and micronekton (Kiyashko et al, ; Vinogradov & Tseitlin, ).…”

Temporal variation in the fatty acid composition of ovigerous females and embryos of the squat lobsterPleuroncodes monodon(Decapoda, Munididae)

“…In agreement with the fatty acid profiles in both seasons for female Pleuroncodes monodon hepatopancreas, evaluating fatty acid content and composition can be used to determine the type of food that red squat lobster is eating, and it can also be used to elucidate interspecific interactions within the marine food web (e.g. Connelly et al ., 2014; Kiyashko et al ., 2014; Legezżynńska et al ., 2014). In this context, presence of SFA, such as C15:0 and C17:0, indicates that females feed off detritus present in sediments (Volkman et al ., 1998).…”