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  • 1
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    Microbial Communities in the East and West Fram Strait During Sea Ice Melting Season (2018)
    Frontiers
    In:  Frontiers in Marine Science, 5 . Art.Nr. 429.
    Details
    Publication Date: 2021-02-08
    Description: Climate models project that the Arctic Ocean may experience ice-free summers by the second half of this century. This may have severe repercussions on phytoplankton bloom dynamics and the associated cycling of carbon in surface waters. We currently lack baseline knowledge of the seasonal dynamics of Arctic microbial communities, which is needed in order to better estimate the effects of such changes on ecosystem functioning. Here we present a comparative study of polar summer microbial communities in the ice-free (eastern) and ice-covered (western) hydrographic regimes at the LTER HAUSGARTEN in Fram Strait, the main gateway between the Arctic and North Atlantic Oceans. Based on measured and modeled biogeochemical parameters, we tentatively identified two different ecosystem states (i.e., different phytoplankton bloom stages) in the distinct regions. Using Illumina tag-sequencing, we determined the community composition of both free-living and particle-associated bacteria as well as microbial eukaryotes in the photic layer. Despite substantial horizontal mixing by eddies in Fram Strait, pelagic microbial communities showed distinct differences between the two regimes, with a proposed early spring (pre-bloom) community in the ice-covered western regime (with higher representation of SAR11, SAR202, SAR406 and eukaryotic MALVs) and a community indicative of late summer conditions (post-bloom) in the ice-free eastern regime (with higher representation of Flavobacteria, Gammaproteobacteria and eukaryotic heterotrophs). Co-occurrence networks revealed specific taxon-taxon associations between bacterial and eukaryotic taxa in the two regions. Our results suggest that the predicted changes in sea ice cover and phytoplankton bloom dynamics will have a strong impact on bacterial community dynamics and potentially on biogeochemical cycles in this region.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
    DOI: 10.3389/fmars.2018.00429
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Bacterial Colonization and Vertical Distribution of Marine Gel Particles (TEP and CSP) in the Arctic Fram Strait (2017)
    Frontiers
    In:  Frontiers in Marine Science, 4 (Art.No. 166).
    Details
    Publication Date: 2020-02-06
    Description: Gel particles—a class of abundant transparent organic particles—have increasingly gathered attention in marine research. Field studies on the bacterial colonization of marine gels however are still scarce. So far, most studies on respective particles have focused on the upper ocean, while little is known on their occurrence in the deep sea. Here, we report on the vertical distribution of the two most common gel particle types, which are polysaccharide-containing transparent exopolymer particles (TEP) and proteinaceous Coomassie stainable particles (CSP), as well as numbers of bacteria attached to gel particles throughout the water column, from the surface ocean down to the bathypelagial (〈 3,000 m). Our study was conducted in the Arctic Fram Strait during northern hemispheres' summer in 2015. Besides data on the bacterial colonization of the two gel particle types (TEP and CSP), we present bacterial densities on different gel particle size classes according to 12 different sampling depths at four sampling locations. Gel particles were frequently abundant at all sampled depths, and their concentrations decreased from the euphotic zone to the dark ocean. They were colonized by bacteria at all sampled water depths with risen importance at the deepest water layers, where fractions of bacteria attached to gel particles (%) increased within the total bacterial community. Due to the omnipresent bacterial colonization of gel particles at all sampled depths in our study, we presume that euphotic production of this type of organic matter may affect microbial species distribution within the whole water column in the Fram Strait, down to the deep sea. Our results raise the question if changes in the bacterial community composition and functioning on gel particles occur over depth, which may affect microbial respiration and remineralization rates of respective particles in different water layers.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.3389/fmars.2017.00166
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Inter-Annual Variability of Organic Carbon Concentration in the Eastern Fram Strait During Summer (2009–2017) (2019)
    Frontiers
    In:  Frontiers in Marine Science, 6 . Art.Nr. 187.
    Details
    Publication Date: 2022-01-31
    Description: The Arctic Ocean plays a key role in regulating the global climate, while being highly sensitive to climate change. Temperature in the Arctic increases faster than the global average, causing a loss of multiyear sea-ice and affecting marine ecosystem structure and functioning. As a result, Arctic primary production and biogeochemical cycling are changing. Here, we investigated inter-annual changes in the concentrations of particulate and dissolved organic carbon (POC, DOC) together with biological drivers, such as phyto- and bacterioplankton abundance in the Fram Strait, the Atlantic gateway to the Central Arctic Ocean. Data have been collected in summer at the Long-Term Ecological Research observatory HAUSGARTEN during eight cruises from 2009 to 2017. Our results suggest that the dynamic physical system of the Fram Strait induces strong heterogeneity of the ecosystem that displays considerable intra-seasonal as well as inter-annual variability. Over the observational period, DOC concentrations were significantly negatively related to temperature and salinity, suggesting that outflow of Central Arctic waters carrying a high DOC load is the main control of DOC concentration in this region. POC concentration was not linked to temperature or salinity but tightly related to phytoplankton biomass as estimated from chlorophyll-a concentrations (Chl-a). For the years 2009–2017, no temporal trends in the depth-integrated (0–100 m) amounts of DOC and Chl-a were observed. In contrast, depth-integrated (0–100 m) amounts of POC, as well as the ratio [POC]:[TOC], decreased significantly over time. This suggests a higher partitioning of organic carbon into the dissolved phase. Potential causes and consequences of the observed changes in organic carbon stocks for food-web structure and CO2 sequestration are discussed.
    Type: Article , PeerReviewed
    Format: text
    Format: other
    DOI: 10.3389/fmars.2019.00187
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Bacterial Colonization and Vertical Distribution of Marine Gel Particles (TEP and CSP) in the Arctic Fram Strait (2017)
    Frontiers
    In:  EPIC3Frontiers in Marine Science, Frontiers, 4(166), pp. 1-14, ISSN: 2296-7745
    Details
    Publication Date: 2017-07-03
    Description: Gel particles—a class of abundant transparent organic particles—have increasingly gathered attention in marine research. Field studies on the bacterial colonization of marine gels however are still scarce. So far, most studies on respective particles have focused on the upper ocean, while little is known on their occurrence in the deep sea. Here, we report on the vertical distribution of the two most common gel particle types, which are polysaccharide-containing transparent exopolymer particles (TEP) and proteinaceous Coomassie stainable particles (CSP), as well as numbers of bacteria attached to gel particles throughout the water column, from the surface ocean down to the bathypelagial (〈 3,000 m). Our study was conducted in the Arctic Fram Strait during northern hemispheres' summer in 2015. Besides data on the bacterial colonization of the two gel particle types (TEP and CSP), we present bacterial densities on different gel particle size classes according to 12 different sampling depths at four sampling locations. Gel particles were frequently abundant at all sampled depths, and their concentrations decreased from the euphotic zone to the dark ocean. They were colonized by bacteria at all sampled water depths with risen importance at the deepest water layers, where fractions of bacteria attached to gel particles (%) increased within the total bacterial community. Due to the omnipresent bacterial colonization of gel particles at all sampled depths in our study, we presume that euphotic production of this type of organic matter may affect microbial species distribution within the whole water column in the Fram Strait, down to the deep sea. Our results raise the question if changes in the bacterial community composition and functioning on gel particles occur over depth, which may affect microbial respiration and remineralization rates of respective particles in different water layers.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Location Call Number Limitation Availability
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    PAPER (OA)
  • 5
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    Models of Plankton Community Changes during a Warm Water Anomaly in Arctic Waters Show Altered Trophic Pathways with Minimal Changes in Carbon Export (2017)
    Frontiers
    In:  EPIC3Frontiers in Marine Science, Frontiers, 4(160), pp. 1-19, ISSN: 2296-7745
    Details
    Publication Date: 2017-10-24
    Description: Carbon flow through pelagic food webs is an expression of the composition, biomass and activity of phytoplankton as primary producers. In the near future, severe environmental changes in the Arctic Ocean are expected to lead to modifications of phytoplankton communities. Here, we used a combination of linear inverse modeling and ecological network analysis to study changes in food webs before, during, and after an anomalous warm water event in the eastern Fram Strait of the West Spitsbergen Current (WSC) that resulted in a shift from diatoms to flagellates during the summer (June–July). The model predicts substantial differences in the pathways of carbon flow in diatom- vs. Phaeocystis/nanoflagellate-dominated phytoplankton communities, but relatively small differences in carbon export. The model suggests a change in the zooplankton community and activity through increasing microzooplankton abundance and the switching of meso- and macrozooplankton feeding from strict herbivory to omnivory, detritivory and coprophagy. When small cells and flagellates dominated, the phytoplankton carbon pathway through the food web was longer and the microbial loop more active. Furthermore, one step was added in the flow from phytoplankton to mesozooplankton, and phytoplankton carbon to higher trophic levels is available via detritus or microzooplankton. Model results highlight how specific changes in phytoplankton community composition, as expected in a climate change scenario, do not necessarily lead to a reduction in carbon export.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
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