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  • 1
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    CAMBRIDGE UNIV PRESS
    In:  EPIC3Antarctic Science, CAMBRIDGE UNIV PRESS, 25(6), pp. 741-751, ISSN: 0954-1020
    Publication Date: 2019-07-16
    Description: We determined the composition and structure of late summer eukaryotic protist assemblages along a west–east transect in the Amundsen Sea. We used state-of-the-art molecular approaches, such as automated ribosomal intergenic spacer analysis (ARISA) and 454-pyrosequencing, combined with pigment measurements via high performance liquid chromatography (HPLC) to study the protist assemblage. We found characteristic offshore and inshore communities. In general, total chlorophyll a and microeukaryotic contribution were higher in inshore samples. Diatoms were the dominant group across the entire area, of which Eucampia sp. and Pseudo-nitzschia sp. were dominant inshore and Chaetoceros sp. was dominant offshore. At the most eastern station, the assemblage was dominated by Phaeocystis sp. Under the ice, ciliates showed their highest and haptophytes their lowest abundance. This study delivers a taxon detailed overview of the eukaryotic protist composition in the Amundsen Sea during the summer 2010.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    CAMBRIDGE UNIV PRESS
    In:  EPIC3Antarctic Science, CAMBRIDGE UNIV PRESS, 26(5), pp. 545-553, ISSN: 0954-1020
    Publication Date: 2019-07-17
    Description: The diet of Antarctic salps was elucidated by investigating their gut content using “Automated Ribosomal Intergenic Spacer Analysis” and 454-pyrosequencing. Salp samples were collected during the Lazarev Krill Study in the Western Weddell Sea (summer 2005/06 and 2007/08, fall 2004, and winter 2006). Two salp species, Salpa thompsoni and Ihlea racovitzai, both occur in the Southern Ocean, can overlap geographically and seasonally. Here we provide evidence that despite the non-selective feeding mechanism, the two co-occuring salp species might have different niches within one given habitat. ARISA-patterns of 93 salp gut content samples revealed strong differences between the two salp species, even at the same sampling site. These differences were confirmed by 454-pyrosequencing of the V4-18S rDNA of ten salps. The pyrosequencing data indicate that flagellates, in particular dinophyceae constitute a high proportion of the sequence reads identified in the gut content of both salp species. However, within the dinophyceae differences in the read composition were detected between the two salp species. This supports the findings of a previous study where fatty acid signatures indicate a flagellate based diet of salps, even though microscopic analyses identified diatoms as the dominant component of salp gut contents.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
    Publication Date: 2021-12-15
    Description: Over the past decades, two key grazers in the Southern Ocean (SO), krill and salps, have experienced drastic changes in their distribution and abundance, leading to increasing overlap of their habitats. Both species occupy different ecological niches and long-term shifts in their distributions are expected to have cascading effects on the SO ecosystem. However, studies directly comparing krill and salps are lacking. Here, we provide a direct comparison of the diet and fecal pellet composition of krill and salps using 18S metabarcoding and fatty acid markers. Neither species’ diet reflected the composition of the plankton community, suggesting that in contrast to the accepted paradigm, not only krill but also salps are selective feeders. Moreover, we found that krill and salps had broadly similar diets, potentially enhancing the competition between both species. This could be augmented by salps’ ability to rapidly reproduce in favorable conditions, posing further risks to krill populations.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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  • 4
    Publication Date: 2024-03-28
    Description: The Arctic Ocean is experiencing unprecedented changes because of climate warming, necessitating detailed analyses on the ecology and dynamics of biological communities to understand current and future ecosystem shifts. Here, we generated a four-year, high-resolution amplicon dataset along with one annual cycle of PacBio HiFi read metagenomes from the East Greenland Current (EGC), and combined this with datasets spanning different spatiotemporal scales (Tara Arctic and MOSAiC) to assess the impact of Atlantic water influx and sea-ice cover on bacterial communities in the Arctic Ocean. Densely ice-covered polar waters harboured a temporally stable, resident microbiome. Atlantic water influx and reduced sea-ice cover resulted in the dominance of seasonally fluctuating populations, resembling a process of “replacement” through advection, mixing and environmental sorting. We identified bacterial signature populations of distinct environmental regimes, including polar night and high-ice cover, and assessed their ecological roles. Dynamics of signature populations were consistent across the wider Arctic; e.g. those associated with dense ice cover and winter in the EGC were abundant in the central Arctic Ocean in winter. Population- and community-level analyses revealed metabolic distinctions between bacteria affiliated with Arctic and Atlantic conditions; the former with increased potential to use bacterial- and terrestrial-derived substrates or inorganic compounds. Our evidence on bacterial dynamics over spatiotemporal scales provides novel insights into Arctic ecology and indicates a progressing Biological Atlantification of the warming Arctic Ocean, with consequences for food webs and biogeochemical cycles.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , peerRev
    Format: application/pdf
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