Description: The ocean moderates the world's climate through absorption of heat and carbon, but how much carbon the ocean will continue to absorb remains unknown. The North Atlantic Ocean west (Baffin Bay/Labrador Sea) and east (Fram Strait/Greenland Sea) of Greenland features the most intense absorption of anthropogenic carbon globally; the biological carbon pump (BCP) contributes substantially. As Arctic sea-ice melts, the BCP changes, impacting global climate and other critical ocean attributes (e.g. biodiversity). Full understanding requires year-round observations across a range of ice conditions. Here we present such observations: autonomously collected Eulerian continuous 24-month time-series in Fram Strait. We show that, compared to ice-unaffected conditions, sea-ice derived meltwater stratification slows the BCP by 4 months, a shift from an export to a retention system, with measurable impacts on benthic communities. This has implications for ecosystem dynamics in the future warmer Arctic where the seasonal ice zone is expected to expand.

Description: Bacterial diversity and function across time and space in the Arctic Ocean, including the Polar Night, remain virtually unknown. In the FRAM Observatory, we study microbial composition and genetic potential in ice-covered and ice-free regions of the Fram Strait, the major gateway between the Arctic and Atlantic Oceans. A continuous amplicon time-series, derived from moored autonomous samplers, revealed marked taxonomic and functional seasonality among bacterial communities in the ice-free West Spitsbergen Current, with distinct succession of taxonomic modules. PacBio long-read metagenomes showed peaks of proteorhodopsin- and DMSP-utilizing genes in late summer, whereas winter mixing of the water column covaried with ammonia- and nitrite-metabolizing bacterial genes. In the ice-covered East Greenland Current, taxonomic and functional diversity varied less with seasons, with prominent influence of ice cover and polar water masses. For instance, high-ice conditions coincided with higher number of peptidoglycan-utilizing genes. Continuous observations were contextualized with five-year amplicon data from summertime samples collected across Fram Strait, integrating seasonal and interannual patterns of bacterial community dynamics. This fundamental baseline information helps understanding ecological and biogeochemical processes in a marine region severely affected by climate change.

Description: Science communication is becoming increasingly important to connect academia and society, and to counteract fake news among climate change deniers. Online video platforms, such as YouTube, offer great potential for low-threshold communication of scientific knowledge to the general public. In April 2020 a diverse group of researchers from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research launched the YouTube channel "Wissenschaft fürs Wohnzimmer" (translated to "Sitting Room Science") to stream scientific talks about climate change and biodiversity every Thursday evening. Here we report on the numbers and diversity of content, viewers, and presenters from 2 years and 100 episodes of weekly livestreams. Presented topics encompass all areas of polar research, social issues related to climate change, and new technologies to deal with the changing world and climate ahead. We show that constant engagement by a group of co-hosts, and presenters from all topics, career stages, and genders enable a continuous growth of views and subscriptions, i.e. impact. After 783 days the channel gained 30,251 views and 828 subscribers and hosted well-known scientists while enabling especially early career researchers to improve their outreach and media skills. We show that interactive and science-related videos, both live and on-demand, within a pleasant atmosphere, can be produced voluntarily while maintaining high quality. We further discuss challenges and possible improvements for the future. Our experiences may help other researchers to conduct meaningful scientific outreach and to push borders of existing formats with the overall aim of developing a better understanding of climate change and our planet.

Description: Unravelling the relationship between biological diversity and ecosystem resilience is a timeless topic dating back to Alexander von Humboldt’s expeditions in the early 19th century. While global oceanographic expeditions and basin-wide transects show positive correlations between microbial diversity and temperature or productivity, they often lack temporal replication, and include few high latitude observations especially during winter months. Here, using seasonal amplicon sequence data from six time-series in the northern and southern hemispheres, we show that on a multiannual basis marine microbial alpha-diversity (species richness and evenness) correlate most strongly with day length, rather than with temperature and chlorophyll a (as proxy for primary production), independent of the targeted 16S rRNA hypervariable region. By integrating data from 2003 to 2020, our evidence suggests that microbial diversity and annually recurring community composition are governed by similar principles, from subtropic to polar oceans. These global trends are consistent regardless of the collection methods, DNA extraction chemistry, sequencing technologies or bioinformatic pipelines. Hence, to understand drivers of marine microbial diversity, larger-scale studies need to embed their analyses into the context of regional seasonal variations. Overall, our synthesis reframes the fundamental drivers of marine microbial diversity as phenological, and suggests that although the state of the temperature and chlorophyll spectra should be considered, it is regular sampling over seasonal cycles that can disentangle these effects. Our findings support the idea that microbial diversity patterns and ecosystem stability are regulated by holistic feedback systems. Or as Alexander von Humboldt already stated, Nature is interconnected, linking ‘the little things’ with global interactions and patterns will allow us to place the observed microbial diversity into the bigger picture.

Description: Bei "Wissenschaft fürs Wohnzimmer" nimmt Euch Matthias Wietz, Meeresbiologe vom Alfred-Wegener-Institut, mit nach Spitzbergen - dem Land der Eisbären und endlosen Gletscher! Matthias zeigt Einblicke ins Forscherleben 1000km vorm Nordpol, wie man Belugas zum Fliegen bekommt, und was wir dadurch übers Wechselspiel zwischen Ozean und Atmosphäre lernen.

Description: The functional diversity of microbes along the seasonal extremes in the Arctic Ocean including the Polar Night are virtually unknown. Here, using PacBio long-read metagenomes derived from automated samplers over an annual cycle, we elucidate functional microbial seasonality in the Fram Strait in the context of a high-resolution amplicon time-series. In the ice-free West Spitsbergen Current, the transition from the phototrophy-dominated spring and summer ecosystem states to the dark winter was evident in bacterial genomes. Proteorhodopsin- and DMSP-utilizing genes peaked in late summer, marking a transition phase. Winter mixing of the water column covaried with microbial taxa encoding ammonia- and urea-metabolizing genes, with probable implications for nitrogen recycling and the following phytoplankton bloom. In the ice-covered East Greenland Current, functional diversity varied with the extent of ice cover and polar water masses. During intermittent low-ice conditions in winter, the metagenomic repertoire resembled that during summer, indicating rapidly (i.e. within weeks) shifting ecosystem states with ice cover. Overall, we provide a baseline to understand ecological and biogeochemical processes in a region severely affected by climate change, with implications for the present and future Arctic Ocean.

Description: Dimethyl sulphide (DMS) plays an important role in the atmosphere by influencing the formation of aerosols and cloud condensation nuclei. In contrast, the role of methanethiol (MeSH) for the budget and flux of reduced sulphur remains poorly understood. In the present study, we quantified DMS and MeSH together with the trace gases carbon monoxide (CO), isoprene, acetone, acetaldehyde and acetonitrile in North Atlantic and Arctic Ocean surface waters, covering a transect from 57.2° N to 80.9° N in high spatial resolution. Whereas isoprene, acetone, acetaldehyde and acetonitrile concentrations decreased northwards, CO, DMS and MeSH retained significant levels at high latitudes, indicating specific sources in polar waters. DMS was the only compound with higher average in polar (31.2 ± 9.3 nM) than in Atlantic waters (13.5 ± 2 nM), presumably due to DMS originating from sea ice. At eight sea-ice stations north of 80° N, in the diatom-dominated marginal ice zone, vertical profiles showed a marked correlation (R2 = 0.93) between DMS and chlorophyll a. Contrary to previous measurements, MeSH and DMS did not co-vary, indicating decoupled processes of production and conversion. The contribution of MeSH to the sulphur budget (represented by DMS+MeSH) was on average 20 % (and up to 50 %) higher than previously observed in the Atlantic and Pacific Oceans, suggesting MeSH as a significant source of sulphur possibly emitted to the atmosphere. The potential importance of MeSH was underlined by several correlations with bacterial taxa, including typical phytoplankton associates from the Rhodobacteraceae and Flavobacteriaceae families. Furthermore, the correlation of isoprene and chlorophyll a with Alcanivorax indicated a specific relationship with isoprene-producing phytoplankton. Overall, the demonstrated latitudinal and vertical patterns contribute to the understanding of central marine trace gases from chemical, atmospheric and biological perspectives.