Abstract
A suite of lipid biomarkers plus compound-specific carbon isotopes of major sterols were determined in muscle tissues across increasing sizes of northern Neptune whelks Neptunea heros, developing eggs and potential diets to link trophic patterns, metabolism and carbon sources on the Chukchi Sea shelf. Analysis of primary prey included the northern clam Astarte borealis, water column particulate organic matter (POM) and surface sediments near the collection sites. Sterols specific to major algal groups along with algal-derived polyunsaturated fatty acids (C20:5n-3, C20:4n-3, C22:6n-3) in whelk muscle tissue reflected the importance of algal primary production to benthic consumers and its direct incorporation. Compound-specific carbon isotope values of cholesterol and Δ5,7-sterols present in foot muscle of N. heros also suggest a transition from scavenging/detrital feeding in smaller juveniles to predatory consumption by larger adults. Sexually mature adult female N. heros (shell lengths >10 cm) contained lower sterol concentrations compared to smaller whelks, which may reflect reduced consumption rates or lipid translocation during the annual reproductive cycle. Analysis of N. heros eggs at 3 developmental stages ranging from internal egg masses to mature egg cases showed significant transfer of algal-derived sterols and fatty acids which were conserved during egg maturation. The suite of individual lipid signatures and δ13C sterol values observed in N. heros suggest that the northern Neptune whelk relies on both direct lipid incorporation as well as metabolic modification of algal-derived food sources for sterol requirements that transition as animals mature and become predatory consumers.
Highlights
The Arctic Chukchi Sea represents a transition region between the North Pacific and the Arctic, where the advection of warm, nutrient-rich water as well as primary and secondary producers transported from the Bering Sea are mixed over its shallow shelf (Grebmeier et al 2018)
This study examined diet and metabolism reflected in the abundance and distribution of lipid markers in N. heros and several potential diets
Summed seen in adult muscle tissues, ranging from 21−24% of sterol concentrations in N. heros ranged from 3.88− the total sterols
Summary
The Arctic Chukchi Sea represents a transition region between the North Pacific and the Arctic, where the advection of warm, nutrient-rich water as well as primary and secondary producers transported from the Bering Sea are mixed over its shallow shelf (Grebmeier et al 2018). Northward flow across the shallow (50 m) Chukchi shelf follows several paths northward, with primary production strongly influenced by local winds and historic ice cover over 7−8 months of the year. The freshly produced primary production reaching the seabed supports high biodiversity and species richness of benthic communities in the Chukchi Sea continental shelf and a tight coupling between pelagic and benthic realms (Grebmeier et al 1989, Iken et al 2010). The rapid sedimentation to the benthos provides a supply of labile organic matter influencing benthic biomass, trophic structure and organic carbon (OC) cycling on the shelf (Feder et al 2005, 2011)
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