Biogeochemistry and microbiology of high Arctic marine sediment ecosystems—Case study of Svalbard fjords

Abstract

Fjord ecosystems of the high Arctic are distinct from fjords of temperate latitudes due to the influence of glaciers, icebergs, sea ice, and the permanently low temperatures. The sediment microbiology and biogeochemical processes were analyzed during an international research program with multiple field studies in Svalbard, situated between the Barents Sea and the Arctic Ocean. We here describe the physical and geochemical setting and the predominant microbiological processes in several fjords. Physiological studies of sediments and pure cultures show how the predominantly psychrophilic bacteria are adapted to the near‐zero temperature. The microbial communities include bacteria responsible for organic matter hydrolytic degradation, fermentation, and terminal oxidation to CO2. These processes drive the cycling of carbon, sulfur, iron, and manganese. The balance between the dominant sediment microbial processes changes along transects out through the fjords, reflecting the varying impact of the glacier‐derived rock flour, rich in metal oxides at the head, and the plankton‐derived, labile, marine organic matter at the mouth. Due to accelerated warming of Arctic ecosystems, glaciers are retreating with impacts on the physical, chemical, and biological functioning of the fjord sediment ecosystems.

Benthic iron flux influenced by climate‐sensitive interplay between organic carbon availability and sedimentation rate in Arctic fjords

“…Short (20–30 cm) sediment cores were retrieved at 10 stations in Kongsfjorden and six stations in Lilliehöökfjorden aboard the RS Teisten in early June 2017 using a Haps coring device (Kanneworff and Nicolaisen 1983). Several of the coring sites have been sampled during previous expeditions, and parallel cores have been investigated in other studies (see Jørgensen et al 2021; Laufer et al 2020). Once the Haps cores were on the deck, the overlying water was siphoned off with minimal disturbance of the SWI, and 2‐D Fe sensors were immediately inserted near the center of the cores.…”

Novel taxa of Acidobacteriota implicated in seafloor sulfur cycling

“…Marine sediments were collected from Smeerenburgfjorden, Kongsfjorden and Van Keulenfjorden, of Svalbard, Norway, in July 2016 and/or June 2017 with the vessel "MS Farm". Extensive biogeochemical data for these sites is available from previous studies [38][39][40][41][42]. Maps of sample locations are presented in Michaud et al [41].…”

Element cycling and aquatic function in a changing Arctic

“…However, despite relatively high productivity and permanently low temperatures, microbial communities of Arctic sediments appear highly efficient in remineralizing deposited organic material. The involved pathways for organic carbon mineralization and carbon sequestration rates in the Arctic appear similar to those at warmer latitudes (Glud et al 1998;Jørgensen et al 2021). This partly reflects the activity of well-adapted microbial communities that maintain high metabolic rates and growth yields at low ambient temperature (Sagemann et al 1998;Robador et al 2015;Scholze et al 2021).…”

“…As noted, glacier dynamics and the position of the glacial terminus is fundamental to the biological and biogeochemical function of many Arctic fjords. Detailed long-term investigations in Svalbard have clearly documented how spatiotemporal dynamics in glacial-induced upwelling, surface production and deposition shape the benthic communities and the relative importance of the respective diagenetic pathways for carbon mineralization (Jørgensen et al 2021). Reduced benthic supply of metal oxides and enhanced marine influence following glacial retreat is expected to transform benthic redox conditions from well-oxidized iron-rich environments to sulfidic sediments (Jørgensen et al 2021), which will have detrimental environmental consequences for benthic and coastal food webs.…”