Food-web dynamics and isotopic niches in deep-sea communities residing in a submarine canyon and on the adjacent open slopes

Examination of food webs and trophic niches provide insights into organisms’ functionalecology, yet few studies have examined trophodynamics within submarine canyons, wherethe interaction of canyon morphology and oceanography influences habitat provision and fooddeposition. Using stable isotope analysis and Bayesian ellipses, we documented deep-sea foodwebstructure and trophic niches in Baltimore Canyon and the adjacent open slopes in the USMid-Atlantic Region. Results revealed isotopically diverse feeding groups, comprising approximately5 trophic levels. Regression analysis indicated that consumer isotope data are structuredby habitat (canyon vs. slope), feeding group, and depth. Benthic feeders were enriched in 13C and15N relative to suspension feeders, consistent with consuming older, more refractory organic matter.In contrast, canyon suspension feeders had the largest and more distinct isotopic niche, indicatingthey consume an isotopically discrete food source, possibly fresher organic material. Thewider isotopic niche observed for canyon consumers indicated the presence of feeding specialistsand generalists. High dispersion in δ13C values for canyon consumers suggests that the isotopiccomposition of particulate organic matter changes, which is linked to depositional dynamics,resulting in discrete zones of organic matter accumulation or resuspension. Heterogeneity in habitatand food availability likely enhances trophic diversity in canyons. Given their abundance in theworld’s oceans, our results from Baltimore Canyon suggest that submarine canyons may representimportant havens for trophic diversity