Marine ecologists increasingly use trait-based approaches to assess ecosystem change and compare distinct habitats. To contrast scavenging benthic communities and feeding responses to food sources from mid- (Placentia Bay, Newfoundland, Canada) and high-latitude (Nain, Labrador, Canada) food webs, we deployed Baited Remote Underwater Video systems with fish, jellies, and kelp baits separately at each location. We annotated maxN (i.e., maximum number of individuals per time unit) per species and considered their traits (i.e., size, mobility, feeding structure, trophic position, and feeding style). We compared trait and species diversity across location and baits. Locations and treatments were functionally diverse, whereas species-based comparisons were limited. Three main functional roles emerged: (1) “Large, highly motile predators” (e.g., gadids) dominated Placentia Bay and preferred fish bait; (2) “Sloppy feeders” (e.g., rock crab) broke down fish bait, facilitating access by predators; and (3) “Slow species” (e.g., echinoderms) consumed lower-nutrition foods, specifically jellies and kelp. Low functional dispersion (i.e., breadth of functional roles) in Nain likely reflected environmental filtering through colder temperatures and scarcity of food, whereas high functional originality (i.e., one or a few species per functional role) suggested greater sensitivity to species loss. Higher species richness and Shannon diversity in fish treatments occurred only in Placentia Bay. Overall, scavengers in both systems used lower-quality food such as jellies, highlighting their trophic worth and the value of multiple bait types in capturing trophic diversity. Integrating trait-based and species diversity approaches enables comprehensive comparisons across systems, supporting conservation and management. • The use of a trait-based approach facilitates effective comparisons between ecosystems with different species composition. • Harsh environmental conditions in Nain sustain a less functionally diverse food web that is more sensitive to species loss. • Despite a low nutritional value, jellies attract scavengers within an hour, prooving their role in benthic food webs at temperate and high latitudes. • Slower-paced scavengers can benefit from jelly-falls but more mobile species outcompete them in fish-falls. • Species traits and optimization of diet can explain food choices by different functional roles, their behaviour, and interaction among species.
Neus et al. (Sat,) studied this question.