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  • 1
    Publication Date: 2023-12-14
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉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.〈/p〉
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: Federal Ministry of Education and Research (BMBF)
    Description: Helmholtz‐Gemeinschaft
    Keywords: ddc:577.7 ; eastern Fram Strait ; sea ice dynamics ; zooplankton population dynamics
    Language: English
    Type: doc-type:article
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  • 2
    Publication Date: 2014-11-11
    Description: Phytoplankton blooms in surface waters of the oceans are known to influence the food web and impact microbial as well as zooplankton communities. Numerous studies have investigated the fate of phytoplankton-derived organic matter in surface waters and shelf sediments, however, little is known about the effect of sinking algal biomass on microbial communities in deep-sea sediments. Here, we analyzed sediments of four regions in the Southern Atlantic Ocean along the Antarctic Polar Front that had different exposures to phytoplankton bloom derived organic matter. We investigated the microbial communities in these sediments using high-throughput sequencing of 16S rRNA molecules to determine microorganisms that were active and catalyzed reporter deposition fluorescence in situ hybridization to infer their abundance and distribution. The sediments along the Antarctic Polar Front harbored microbial communities that were highly diverse and contained microbial clades that seem to preferably occur in regions of high primary productivity. We showed that organisms affiliated with the gammaproteobacterial clade NOR5/OM60, which is known from surface waters and coastal sediments, thrive in the deep-sea. Benthic deep-sea NOR5 were abundant, diverse, distinct from pelagic NOR5 and likely specialized on the degradation of phytoplankton-derived organic matter, occupying a similar niche as their pelagic relatives. Algal detritus seemed to not only fuel the benthic microbial communities of large areas in the deep-sea, but also to influence communities locally, as we found a peak in Flavobacteriaceae-related clades that also include degraders of algal biomass. The results strongly suggest that phytoplankton-derived organic matter was rapidly exported to the deep-sea, nourished distinct benthic microbial communities and seemed to be the main energy source for microbial life in the seafloor of vast abyssal regions along the Antarctic Polar Front.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
    Publication Date: 2024-03-01
    Description: Next to iron (Fe), recent phytoplankton-enrichment experiments identified manganese (Mn) to (co-)limit Southern Ocean phytoplankton biomass and species composition. Since taxonomic diversity affects aggregation time and sinking rate, the efficiency of the biological carbon pump is directly affected by community structure. However, the impact of FeMn co-limitation on Antarctic primary production, community composition, and the subsequent export of carbon to depth requires more investigation. In situ samplings of 6 stations in the understudied southern Weddell Sea revealed that surface Fe and Mn concentrations, primary production, and carbon export rates were all low, suggesting a FeMn co-limited phytoplankton community. An Fe and Mn addition experiment examined how changes in the species composition drive the aggregation capability of a natural phytoplankton community. Primary production rates were highest when Fe and Mn were added together, due to an increased abundance of the colonial prymnesiophyte Phaeocystis antarctica. Although the community remained diatom dominated, the increase in Phaeocystis abundance led to highly carbon-enriched aggregates and a 4-fold increase in the carbon export potential compared to the control, whereas it only doubled in the Fe treatment. Based on the outcome of the FeMn-enrichment experiment, this region may suffer from FeMn co-limitation. As the Weddell Sea represents one of the most productive Antarctic marginal ice zones, our findings highlight that in response to greater Fe and Mn supply, changes in plankton community composition and primary production can have a disproportionally larger effect on the carbon export potential.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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