Consumer isoscapes reveal heterogeneous food webs in deep-sea submarine canyons and adjacent slopes

• Published in: Progress in oceanography 2024-04, Vol.223, p.103231, Article 103231
• Main Authors: Demopoulos, Amanda W.J., Smith, Brian J., Bourque, Jill R., Chaytor, Jason D., McClain-Counts, Jennifer, Prouty, Nancy, Ross, Steve W., Brooke, Sandra, Duineveld, Gerard, Mienis, Furu
• Format: Article
• Language: English
• Subjects: Deep sea; Food web; Isoscapes; Slopes; Stable-isotope analysis; Submarine canyon; U.S. Mid Atlantic
• ISSN: 0079-6611; 1873-4472
• DOI: 10.1016/j.pocean.2024.103231

•Deep-sea habitats are typically food limited.•Stable carbon and nitrogen isotopes are useful tools to track food resources and trophic levels.•Isoscapes help track spatial variation in resource use across canyon and slope environments.•Deep-sea isoscapes provide avenue to understand shifting baselines with climate change. The deep sea is the largest biome on earth, but one of the least studied despite its critical role in global carbon cycling and climate buffering. Deep-sea organisms largely rely on particulate organic matter from the surface ocean for energy – these organisms in turn play critical roles in energy transport, transformation, storage, and sequestration of carbon. Within the deep sea, submarine canyons are amongst the most complex and dynamic environments in our oceans, where varied morphology, powerful currents, and variable nutrient conditions influence the distribution of species and transport of organic material throughout the water column and the seafloor. Significant habitat heterogeneity provides ideal substrates for cold-water corals, making submarine canyons of interest to conservation and management. However, how these and other topographic features in the deep ocean influence energy flow and trophic pathways is poorly known. Thus, submarine canyons serve as model systems to track variability in organic material flux and consequential utilization and assimilation by the benthos. In this study, we used an extensive stable isotope dataset to examine food-web structure in Baltimore and Norfolk submarine canyons and compared them to their adjacent slopes located along the U.S. Atlantic margin. Linear models were used to construct geospatially-explicit consumer isoscapes that predicted variation in carbon and nitrogen isotopes across the canyon-slope seascape, providing a predictive map from which to test hypotheses on the distribution and flow of energy resources, relevant to understanding whole community function. Communities were composed of isotopically diverse feeding groups with photosynthetically-derived organic carbon providing the basal food resource. Canyon communities were distinct from the slope, with canyon consumers significantly 13C-depleted, indicating a greater supply and/or utilization of fresh organic matter compared to the slope. Isoscapes for benthic and suspension feeders were distinct, possibly due to the consumption of different quality organic matter sources (fresh = suspension feeders, old = benthic feeders),