The Canadian Beaufort Shelf trophic structure: evaluating an ecosystem modelling approach by comparison with observed stable isotopic structure

• Published in: Arctic science Vol. 8; no. 1; pp. 292 - 312
• Main Authors: Hoover, C., Giraldo, C., Ehrman, A., Suchy, K.D., MacPhee, S.A., Brewster, J., Reist, J.D., Power, M., Swanson, H., Loseto, L.
• Format: Journal Article
• Language: English
• Published: Ottawa Canadian Science Publishing NRC Research Press 01.03.2022; NRC Research Press
• Subjects: Ablation; Anadromous fishes; Anadromous species; Biomass; Climate change; Continental shelves; Diet; Ecosystem models; Ecosystems; Energy resources; Fish; Food chains; Food webs; Isotopes; Latitude; Life Sciences; Marine mammals; Modelling; Plankton; Polar bears; Predators; River ecology; Sea ice; Stable isotopes; Taxa; Trophic levels; Trophic structure; Beaufort Sea; Arctic region; Mackenzie River
• ISSN: 2368-7460; 2368-7460
• DOI: 10.1139/as-2020-0035

Climate-driven impacts on marine trophic pathways worldwide are compounded by sea-ice loss at northern latitudes. For the Arctic, current information describing food-web linkages is fragmented, and there is a need for tools that can describe overarching trophic structure despite limited species-specific data. Here, we tested the ability of a mass-balanced ecosystem model (Ecopath with Ecosim, EwE) to reconstruct the trophic hierarchy of 31 groups, from primary producers to polar bears, in the Canadian Beaufort Sea continental shelf. Trophic level (TL) estimates from EwE were compared with those derived from two nitrogen stable isotope (SI) modelling approaches (SI linear and scaled) to assess EwE accuracy, using a data set of 642 δ 15 N observations across 282 taxa. TLs from EwE were strongly, positively related to those from both SI models (R 2  > 0.80). EwE performed well (within 0.2 TL) for groups with relatively well-known diets or for taxa characterized by fewer trophic connections (e.g., primary consumers). Performance was worse (>0.5 TL) for species groups aggregated at coarse taxonomic levels, those with poorly documented diets, and for anadromous fishes. Comparisons with SI models suggested that the scaled approach can overestimate the TL of top predators if ecosystem-specific information is not considered.