Benthic megafauna in the Arctic Ocean - Future dominion by sea cucumbers?

• Main Authors: Boehringer, Lilian, Bergmann, Melanie, Purser, Autun
• Format: Conference Object
• Language: unknown
• Published: 2022
• Subjects: Arctic; Arctic Ocean; Climate change; Fram Strait; Sea ice
• Online Access: https://epic.awi.de/id/eprint/57394/; https://epic.awi.de/id/eprint/57394/1/ICYMARE22_Lilian_Boehringer.pdf; https://www.icymare.com/wp-content/uploads/2022/09/ICYMARE-2022-Bremerhaven_BoA-1.pdf; https://hdl.handle.net/10013/epic.8661fc74-757e-4d35-b3a6-8f17dfce0810

Benthic megafauna in the Arctic Ocean are important for the functioning of deep-sea ecosystems and influence the global carbon cycle. Food availability, as represented primarily by the phytodetrital flux from surface layers, influences the structure of benthic communities in the Arctic Ocean. Along the highly productive marginal sea-ice zones, benthic communities benefit from enhanced food supply. With the advance in climate change, marginal sea-ice zones are shifting and organisms at the seafloor are faced with changing environmental fluxes. This study was designed in order to deepen our understanding of benthic megafauna community dynamics in the Arctic Ocean, from which to infer predictions about the future. Benthic megafauna was quantified by annotating image data from 2016 to 2021. Image data was derived from three different stations, located in the north (N3), centre (HG-IV) and south (S3) of the HAUSGARTEN observatory in the Fram Strait, and was analysed in context with sea-ice coverage measurements. The benthic megafauna communities showed a shift in dominant functional traits, from sessile suspension feeders, to mobile deposit feeders at all stations over the study period. The dominance of mobile deposit feeders was attributed to one species, the sea cucumber Elpidia heckeri. This species showed increases in density of more than 20% across all three stations during the study period. Variations in phytodetrital quality and quantity are most likely the reasons for these strong density increases of the opportunistic sea cucumber. Additionally, a positive relationship between benthic megafaunal density and the extent of sea-ice coverage at N3 and HG-IV was indicated. From these data, into the future, similar strong variations in deposit feeding holothurian densities are expected, given their ability to quickly respond to changing phytodetrital fluxes. This research shows how valuable long-term image-based data studies are in order to detect trends in the future Arctic Ocean.