Benthic megafauna in the Arctic Ocean - Dynamics in temporal community composition

• Main Authors: Boehringer, Lilian, Purser, Autun, Bergmann, Melanie
• 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/57395/; https://epic.awi.de/id/eprint/57395/1/MIW22_Poster_Topic1_BOEHRINGER_Lilian_A0.pdf; https://cloud.ifremer.fr/index.php/s/ZPdojxkhBe87YtP; https://hdl.handle.net/10013/epic.108b4202-2bfc-4706-a6f3-dddc47045a00

Benthic megafauna in the Arctic Ocean plays a pivotal role in the functioning of deep-sea ecosystems and influences the global carbon cycle. The structure of benthic communities in the Arctic Ocean is primarily determined by food availability and therefore by phytodetrital flux from surface layers. Hence, highly productive marginal sea-ice zones provide high food supply for benthic communities. With the advance in climate change, marginal sea-ice zones are shifting and organisms are faced with changing phytodetrital fluxes. This study was designed to increase the understanding of benthic megafauna community dynamics in the Arctic Ocean and infer predictions about the future. Therefore, the benthic megafauna was quantified at three stations, with contrasting extent of sea-ice coverage, located in the north (N3), centre (HG-IV) and in the south (S3) of the HAUSGARTEN observatory in the Fram Strait. Image data from different years between 2016 and 2021 were annotated and 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. The dominance of mobile deposit feeders was attributed to one species, the sea cucumber, Elpidia heckeri. Additionally, a positive relation between benthic megafaunal density and the extent of sea-ice coverage at N3 and HG-IV was indicated. Variations in phytodetrital quality and quantity are most likely the reasons for these strong density increases of the opportunistic sea cucumber. For the future, similarly strong variations in deposit feeding holothurian densities are expected, given their ability to quickly respond to changing phytodetrital fluxes. The results also indicate that benthic megafauna community composition as a whole is likely to exhibit strong variations in density and diversity. This research shows how valuable image data from time-series studies are in order to detect long-term trends in the future Arctic Ocean.