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  • 1
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 7 ( 2020-6-19)
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2020
    detail.hit.zdb_id: 2757748-X
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  • 2
    In: Biogeosciences, Copernicus GmbH, Vol. 16, No. 11 ( 2019-06-04), p. 2247-2268
    Abstract: Abstract. The relative abundance of individual archaeal membrane lipids, namely of glycerol dialkyl glycerol tetraethers (GDGTs) with different numbers of cyclopentane rings, varies with temperature, which enables their use as a paleotemperature proxy index. The first GDGT-based index in marine sediments called TEX86 is believed to reflect mean annual sea surface temperature (maSST). The TEX86L is an alternative temperature proxy for “low-temperature” regions (〈15 ∘C), where the original TEX86 proxy calibration shows a larger scatter. However, TEX86L-derived temperatures still display anomalous estimates in polar regions. In order to elucidate the potential cause of the disagreement between the TEX86L estimate and SST, we analyzed GDGT fluxes and TEX86L-derived temperatures in sinking particles collected with time-series sediment traps in high-northern- and high-southern-latitude regions. At 1296 m depth in the eastern Fram Strait (79∘ N), a combination of various transporting mechanisms for GDGTs might result in seasonally different sinking velocities for particles carrying these lipids, resulting in strong variability in the TEX86L signal. The similarity of flux-weighted TEX86L temperatures from sinking particles and surface sediments implies an export of GDGTs without alteration in the Fram Strait. The estimated temperatures correspond to temperatures in water depths of 30–80 m, where nitrification might occur, indicating the favorable depth habitat of Thaumarchaeota. In the Antarctic Polar Front of the Atlantic sector (50∘ S), TEX86L-derived temperatures displayed warm and cold biases compared to satellite-derived SSTs at 614 m depth, and its flux-weighted mean signal differs from the deep signal at 3196 m. TEX86L-derived temperatures at 3196 m depth and the surface sediment showed up to 7 ∘C warmer temperatures relative to satellite-derived SST. Such a warm anomaly might be caused by GDGT contributions from Euryarchaeota, which are known to dominate archaeal communities in the circumpolar deep water of the Antarctic Polar Front. The other reason might be that a linear calibration is not appropriate for this frontal region. Of the newly suggested SST proxies based on hydroxylated GDGTs (OH-GDGTs), only those with OH-GDGT–0 and crenarchaeol or the ring index (RI) of OH-GDGTs yield realistic temperature estimates in our study regions, suggesting that OH-GDGTs could be applied as a potential temperature proxy in high-latitude oceans.
    Type of Medium: Online Resource
    ISSN: 1726-4189
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2019
    detail.hit.zdb_id: 2158181-2
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  • 3
    In: Limnology and Oceanography, Wiley, Vol. 68, No. S1 ( 2023-06)
    Abstract: The collection of zooplankton swimmers and sinkers in time‐series sediment traps provides unique insight into year‐round and interannual trends in zooplankton population dynamics. These samples are particularly valuable in remote and difficult to access areas such as the Arctic Ocean, where samples from the ice‐covered season are rare. In the present study, we investigated zooplankton composition based on swimmers and sinkers collected by sediment traps at water depths of 180–280, 800–1320, and 2320–2550 m, over a period of 16 yr (2000–2016) at the Long‐Term Ecological Research observatory HAUSGARTEN located in the eastern Fram Strait (79°N, 4°E). The time‐series data showed seasonal and interannual trends within the dominant zooplankton groups including copepoda, foraminifera, ostracoda, amphipoda, pteropoda, and chaetognatha. Amphipoda and copepoda dominated the abundance of swimmers while pteropoda and foraminifera were the most important sinkers. Although the seasonal occurrence of these groups was relatively consistent between years, there were notable interannual variations in abundance, suggesting the influence of various environmental conditions such as sea‐ice dynamic and lateral advection of water masses, for example, meltwater and Atlantic water. Statistical analyses revealed a correlation between the Arctic dipole climatic index and sea‐ice dynamics (i.e., ice coverage and concentration), as well as the importance of the distance from the ice edge on swimmer composition patterns and carbon export.
    Type of Medium: Online Resource
    ISSN: 0024-3590 , 1939-5590
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2033191-5
    detail.hit.zdb_id: 412737-7
    SSG: 12
    SSG: 14
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  • 4
    Online Resource
    Online Resource
    Frontiers Media SA ; 2023
    In:  Frontiers in Marine Science Vol. 10 ( 2023-7-11)
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 10 ( 2023-7-11)
    Abstract: Marine sinking particles sequester atmospheric carbon dioxide to the deep ocean via the biological carbon pump. Understanding how environmental shifts drive changes in the microbial composition of particles, and how these affect the export of organic matter from the surface to the deep ocean, is critical, especially in the rapidly changing Arctic Ocean. Here, we applied next generation sequencing of the 18S and 16S rRNA genes to sediment trap samples from around 200 m water depth in the eastern Fram Strait, covering a time frame of more than one decade (2000-2012). The aim was to characterize their microbial composition during annual highest particulate organic carbon flux events. The bimodal annual spring and summer export fluxes were representative of the strong seasonality in the region. Furthermore, the study period was characterized by considerable interannual variation, marked especially by a warm water anomaly between 2005 and 2007. During this period changes in the hydrography and sea ice cover also led to measurable changes in the microbial composition of particles. The warm water period was marked by a decrease in diatoms affiliated with Chaetoceros , an increase of small phytoplankton and an increase in sequence abundance of the bacterial taxa Oceanospirillales , Alteromonadales and Rhodobacterales on the particles. The resulting changes in microbial composition and the associated microbial network structure suggest the emergence of a more developed retention system in the surface ocean. Our results provide the first long-term assessment of the microbial composition of sinking particles in the Arctic Ocean, and stress the importance of sea ice and hydrography for particle composition and subsequent flux of organic matter to deeper waters.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
    detail.hit.zdb_id: 2757748-X
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  • 5
    In: Communications Biology, Springer Science and Business Media LLC, Vol. 4, No. 1 ( 2021-11-03)
    Abstract: Arctic Ocean sea ice cover is shrinking due to warming. Long-term sediment trap data shows higher export efficiency of particulate organic carbon in regions with seasonal sea ice compared to regions without sea ice. To investigate this sea-ice enhanced export, we compared how different early summer phytoplankton communities in seasonally ice-free and ice-covered regions of the Fram Strait affect carbon export and vertical dispersal of microbes. In situ collected aggregates revealed two-fold higher carbon export of diatom-rich aggregates in ice-covered regions, compared to Phaeocystis aggregates in the ice-free region. Using microbial source tracking, we found that ice-covered regions were also associated with more surface-born microbial clades exported to the deep sea. Taken together, our results showed that ice-covered regions are responsible for high export efficiency and provide strong vertical microbial connectivity. Therefore, continuous sea-ice loss may decrease the vertical export efficiency, and thus the pelagic-benthic coupling, with potential repercussions for Arctic deep-sea ecosystems.
    Type of Medium: Online Resource
    ISSN: 2399-3642
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2919698-X
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