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. 2021 Dec 11;1(1):76.
doi: 10.1038/s43705-021-00074-4.

The polar night shift: seasonal dynamics and drivers of Arctic Ocean microbiomes revealed by autonomous sampling

Matthias Wietz  1   2 , Christina Bienhold  3   4 , Katja Metfies  5 , Sinhué Torres-Valdés  6 , Wilken-Jon von Appen  7 , Ian Salter  3   8 , Antje Boetius  9   10   11
Affiliations

The polar night shift: seasonal dynamics and drivers of Arctic Ocean microbiomes revealed by autonomous sampling

Matthias Wietz et al. ISME Commun. .

Abstract

The Arctic Ocean features extreme seasonal differences in daylight, temperature, ice cover, and mixed layer depth. However, the diversity and ecology of microbes across these contrasting environmental conditions remain enigmatic. Here, using autonomous samplers and sensors deployed at two mooring sites, we portray an annual cycle of microbial diversity, nutrient concentrations and physical oceanography in the major hydrographic regimes of the Fram Strait. The ice-free West Spitsbergen Current displayed a marked separation into a productive summer (dominated by diatoms and carbohydrate-degrading bacteria) and regenerative winter state (dominated by heterotrophic Syndiniales, radiolarians, chemoautotrophic bacteria, and archaea). The autumn post-bloom with maximal nutrient depletion featured Coscinodiscophyceae, Rhodobacteraceae (e.g. Amylibacter) and the SAR116 clade. Winter replenishment of nitrate, silicate and phosphate, linked to vertical mixing and a unique microbiome that included Magnetospiraceae and Dadabacteriales, fueled the following phytoplankton bloom. The spring-summer succession of Phaeocystis, Grammonema and Thalassiosira coincided with ephemeral peaks of Aurantivirga, Formosa, Polaribacter and NS lineages, indicating metabolic relationships. In the East Greenland Current, deeper sampling depth, ice cover and polar water masses concurred with weaker seasonality and a stronger heterotrophic signature. The ice-related winter microbiome comprised Bacillaria, Naviculales, Polarella, Chrysophyceae and Flavobacterium ASVs. Low ice cover and advection of Atlantic Water coincided with diminished abundances of chemoautotrophic bacteria while others such as Phaeocystis increased, suggesting that Atlantification alters microbiome structure and eventually the biological carbon pump. These insights promote the understanding of microbial seasonality and polar night ecology in the Arctic Ocean, a region severely affected by climate change.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Study area and oceanographic conditions.
a Location of moored Remote Access Samplers in the East Greenland Current (EGC) and the West Spitsbergen Current (WSC) of Fram Strait, indicated in blue and red respectively. The small red arrows illustrate recirculation of Atlantic Water in central Fram Strait. The grayscale gradient indicates the fraction of days with average sea ice cover of >20%. b Water temperature (°C), concentrations of oxygen (µmol L−1) and nitrate (µM), the proportion of Atlantic Water (%), sea ice cover (%), and daylight hours.
Fig. 2
Fig. 2. Year-round microbial community structure and turnover.
a Relative sequence abundances (%) of eukaryotic, bacterial and archaeal taxa over the annual cycle. b, upper panel: Microbial community turnover (taxonomic similarities expressed as 1 minus Jenson-Shannon distance) compared to the first sampling event in relation to daylight hours (top color gradient). b, lower panel: Microbial alpha-diversity (inverse Simpson index). Eukaryotes: purple; bacteria and archaea: green. Lines indicate the seasonal boundaries defined by multivariate evaluation of physicochemical and microbial dynamics (Fig. 3).
Fig. 3
Fig. 3. Microbial and environmental seasonality.
a Principal Component Analysis of environmental conditions. Components 1 and 2 explained 58/26% (WSC) and 60/14% (EGC) respectively, and hence the majority of physicochemical variability. For EGC, label size indicates percent ice cover. Only sampling events with complete environmental data were considered. b Non-metric multidimensional scaling of Hellinger-transformed relative ASV abundances (stress values 0.07, 0.03, 0.13, 0.1 from top to bottom) and corresponding Jensen-Shannon distances between and within seasons (larger numbers designate more dissimilar communities).
Fig. 4
Fig. 4. Microbes as indicators for seasons.
Relative sequence abundances of major microbial families by season and region (see Supplementary Fig. 5a for details).
Fig. 5
Fig. 5. Environmental drivers of community structure.
Partial Least Square regression between environmental parameters and the abundance of microbial families, identifying seasonal groupings in the WSC (a) compared to both seasonal and polar/Atlantic-influenced groupings in the EGC (b). Only correlation coefficients > 0.5 were considered. Temp: water temperature; O2 conc: oxygen concentration; O2 sat: oxygen saturation; PW: proportion of Polar Water; ice cover: percent ice cover on a given sampling event; past ice: percent ice cover integrated over the time between sampling events; CO2: partial CO2 pressure.
Fig. 6
Fig. 6. Autumn and winter dynamics.
a Concentrations of nitrate (squares) and silicate (triangles) in relation to stratification (blue; only available for the WSC). b Microbial genera with increased proportions in autumn or winter. “Winter-ice” eukaryotes are combined (marked by asterisks; see Supplementary Fig. 7a for abundances of each genus). c pH values (only available for the WSC) and proportions of Polar Water.
Fig. 7
Fig. 7. Spring and summer dynamics.
a Relative abundances of dominant eukaryotic and bacterial genera (see Supplementary Fig. 8 for detailed abundances). b Concentrations of chlorophyll, nitrate, phosphate and oxygen.
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References

    1. Cavicchioli R, Ripple WJ, Timmis KN, Azam F, Bakken LR, Baylis M, et al. Scientists’ warning to humanity: microorganisms and climate change. Nat Rev Microbiol. 2019;17:569–86. doi: 10.1038/s41579-019-0222-5. - DOI - PMC - PubMed
    1. Bunse C, Pinhassi J. Marine Bacterioplankton seasonal succession dynamics. Trends Microbiol. 2017;25:494–505. doi: 10.1016/j.tim.2016.12.013. - DOI - PubMed
    1. Buttigieg PL, Fadeev E, Bienhold C, Hehemann L, Offre P, Boetius A. Marine microbes in 4D-using time series observation to assess the dynamics of the ocean microbiome and its links to ocean health. Curr Opin Microbiol. 2018;43:169–85. doi: 10.1016/j.mib.2018.01.015. - DOI - PubMed
    1. Gilbert JA, Steele JA, Caporaso JG, Steinbrück L, Reeder J, Temperton B, et al. Defining seasonal marine microbial community dynamics. ISME J. 2012;6:298–308. doi: 10.1038/ismej.2011.107. - DOI - PMC - PubMed
    1. Cram JA, Chow C-ET, Sachdeva R, Needham DM, Parada AE, Steele JA, et al. Seasonal and interannual variability of the marine bacterioplankton community throughout the water column over ten years. ISME J. 2015;9:563–80. doi: 10.1038/ismej.2014.153. - DOI - PMC - PubMed