Benthic scavenger community composition and carrion removal in Arctic and Subarctic fjords

Abstract

In high latitude coastal regions, benthic scavenger communities are largely composed of invertebrates that play a key role in the cycling of organic matter. Factors including temperature and depth can structure Arctic and Subarctic fjord benthic communities, but the response of scavenging communities to these factors is poorly known. To address this, we compared scavenging fauna in eight fjords with different physical characteristics in Svalbard and northern Norway using time-lapse imagery of scavengers consuming Atlantic herring (Clupea harengus) bait. Fjords influenced by relatively warm Atlantic waters, both in Norway and Svalbard, had high scavenger richness. However, Svalbard fjords with negative bottom temperatures had the lowest species richness and were dominated by lysianassoid amphipods and ophiuroids. In these cold Svalbard fjords, the mean carrion removal rates were almost 20 times higher than mean values noted elsewhere, except in the warm Norwegian fjord Kaldfjorden. Amphipods and ophiuroids quickly reduced the bait to bones (207.6–304.7 g removed per hour (g h−1); mean 290.6 ± 7.3 g h−1, n = 4) in cold Svalbard fjords. In the warmer Svalbard fjords, carrion removal rates were low (0–51.5 g h−1; mean 14.6 ± 9.0 g h−1, n = 5). Carrion removal rates in Kaldfjorden were higher than other Atlantic Water influenced fjords (132.1 and 372.5 g h−1, n = 2) owing to the scavenging activity of Atlantic cod (Gadus morhua). The results demonstrate potential ecosystem responses to warming in Arctic and Subarctic fjords, particularly effects related to range expansion of boreal species.

Shallow-Water Scavengers of Polar Night and Day – An Arctic Time-Lapse Photography Study

“…Also, by comparison with lower latitudes in the deep sea, shallow-water (12 m depth) polar scavenging is slow (Smale et al, 2007). In a recent study performed in Kongsfjorden at 360 m, consumption rate was recorded to be an order of magnitude faster (i.e., 0.5 g min −1 , Dunlop et al, 2020) than that recorded in our study. Differences between bait types were slightly less pronounced than differences between the seasons (Sqrt, Table 3).…”

“…This study provides insights into the over-wintering strategies of bottom fauna, temporal turnover in scavengers present at carrion, scavenging community dynamics, and nutrient cycling and functioning of shallow-water ecosystems during polar night. Given the many limitations of the current study (e.g., a single study site, a single replicate camera system per bait type within each season, a relatively short physical distance of 25 m between the bait types), the general lack of such shallow-water seasonal data, the rapid change of Arctic systems due to climate warming (Overland et al, 2019), and the consequent modifications to carrion decomposition efficiency and energy flow (Dunlop et al, 2020), clearly more comprehensive investigations are needed. The high Arctic fjords of Svalbard Archipelago, which may represent an area similar in its environmental parameters to what might be expected for most Arctic coastal areas in the second half of this century (Piskozub, 2017), could serve as a potential model system.…”

“…There are few studies describing shallow-water assemblages of scavengers from higher latitudes, especially during the polar night (but see e.g., Legeżyńska et al, 2000Legeżyńska et al, , 2012Smale et al, 2007;Nygård et al, 2012;Dunlop et al, 2020), which, until recently (Berge et al, 2015a,b), was one of the last unexplored areas in time and space for the marine realm, probably as a consequence of logistic constraints. Thus, our understanding of marine scavenging fauna comes primarily from lower latitudes and/or deep-sea ecosystems, as necrophagy becomes a more prominent strategy with increasing depth, due to declining food availability (Stockton and DeLaca, 1982; see also Dunlop et al, 2018 and references therein).…”

Scavenger gastropod devouring a common lamellibranch bivalve in an estuary of Northeast Brazil

“…Marine scavenger metazoans include a considerable diversity of taxonomic groups that play an important role in ecological interactions, providing the rapid removal, cycling and dispersing of carrion in seas and oceans throughout the world (De Broyer et al, 2004;Ates, 2017;Depestele et al, 2019;Dunlop et al, 2020;Carreira-Flores et al, 2023).…”

“…Benthic scavenger communities are composed of a large diversity of highly efficient scavenger invertebrates, such as actiniarian cnidarians, decapod, peracarid and amphipod crustaceans, asteroid, ophiuroid and echinoid echinoderms, and gastropod mollusks, living in different tropical to polar seafloor habitats from shallow water to the deep ocean (Moore and Howarth, 1996;Ramsay et al, 1998;De Broyer et al, 2004;Schlacher et al, 2013;Ates, 2017;Depestele et al, 2019;Dunlop et al, 2020;Hyndes et al, 2022).…”