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  • 1
    Publication Date: 2019-03-20
    Description: Remane's Artenminimum at the horohalinicum is a fundamental concept in ecology to describe and explain the distribution of organisms along salinity gradients. However, a recent metadata analysis challenged this concept for protists, proposing a species maximum in brackish waters. Due to data bias, this literature‐based investigation was highly discussed. Reliable data verifying or rejecting the species minimum for protists in brackish waters were critically lacking. Here, we sampled a pronounced salinity gradient along a west‐east transect in the Baltic Sea and analyzed protistan plankton communities using high‐throughput eDNA metabarcoding. A strong salinity barrier at the upper limit of the horohalinicum and 10 psu appeared to select for significant shifts in protistan community structures, with dinoflagellates being dominant at lower salinities, and dictyochophytes and diatoms, being keyplayers at higher salinities. Also in vertical water column gradients in deeper basins (Kiel Bight, Arkona and Bornholm Basin) appeared salinity as significant environmental determinant influencing alpha‐ and beta‐diversity patterns. Importantly, alpha‐diversity indices revealed species maxima in brackish waters, i.e., indeed contrasting Remane's Artenminimum concept. Statistical analyses confirmed salinity as the major driving force for protistan community structuring with high significance. This suggests that macrobiota and microbial eukaryotes follow fundamentally different rules regarding diversity patterns in the transition zone from freshwater to marine waters.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2015-03-26
    Description: The sea ice structure of the Arctic Ocean has changed measurably in the last decades. Sea ice decline and warming of the surface water layers may affect composition and diversity of protist communities living in the sea ice interface and the pelagic realm. Samples from different habitats were analyzed (1) to investigate the impact of sea ice on the protists and, (2) to elucidate cryo-pelagic coupling. Samples were collected from melt ponds, sea ice, under-ice water and water column during two RV Polarstern cruises to the Central Arctic Ocean in August - September 2011 & 2012. Automated ribosomal intergenic spacer analysis (ARISA) from 182 samples and Illumina-sequencing of 57 samples revealed a high heterogeneity between different melt pond and sea ice samples, whereas samples from the water column were more homogeneous. However, different sea ice habitats showed similar patterns in protist community structure at the same station, indicating intensive sea-ice-water-exchange during melting and freezing processes. These results illustrate that the high biodiversity in the Central Arctic is mainly governed by the sea ice origin compared to the oceanic currents.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , NonPeerReviewed
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  • 3
    Publication Date: 2017-02-21
    Description: Sea ice is one of the main features influencing the Arctic marine protist community composition and diversity in sea ice and sea water. We analyzed protist communities within sea ice, melt pond water, under-ice water and deep-chlorophyll maximum water at eight sea ice stations sampled during summer of the 2012 record sea ice minimum year. Using Illumina sequencing, we identified characteristic communities associated with specific habitats and investigated protist exchange between these habitats. The highest abundance and diversity of unique taxa were found in sea ice, particularly in multi-year ice (MYI), highlighting the importance of sea ice as a unique habitat for sea ice protists. Melting of sea ice was associated with increased exchange of communities between sea ice and the underlying water column. In contrast, sea ice formation was associated with increased exchange between all four habitats, suggesting that brine rejection from the ice is an important factor for species redistribution in the Central Arctic. Ubiquitous taxa (e.g. Gymnodinium) that occurred in all habitats still had habitat-preferences. This demonstrates a limited ability to survive in adjacent but different environments. Our results suggest that the continued reduction of sea ice extent, and particularly of MYI, will likely lead to diminished protist exchange and subsequently, could reduce species diversity in all habitats of the Central Arctic Ocean. An important component of the unique sea ice protist community could be endangered because specialized taxa restricted to this habitat may not be able to adapt to rapid environmental changes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 4
    Publication Date: 2017-06-15
    Description: The ongoing decrease in sea ice thickness and extent is expected to have significant implications for protists in the Arctic Ocean. We analyzed protist community composition and diversity in water and sea ice samples to elucidate the impact of sea ice retreat and sea ice origin. Samples were collected during 2 summer periods with contrasting sea ice concentrations (2011 and 2012). The results are based on a combination of ARISA and sequencing of the 18S rRNA V4 gene region. We show for the first time that the regions of ice floe origin play a fundamental role in structuring the sea ice community. Community structure of pelagic protists correlated signifi- cantly with sea ice concentrations, water masses and sampling regions. Both habitats differed in protist diversity and composition between years and were less diverse during the recorded sea ice minimum year 2012. A reduction in protist diversity was especially true for rare sea ice algae in 2012, which suggests that sea ice algae might be more vulnerable to climate change. In the future Arctic, changes in protist diversity can be expected due to sea ice decline and a temporal and spatial shift in sea ice formation
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 5
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Paramecium nephridiatum Gelei. 1925, was rediscovered. It is a euryhaline brackish-water species that morphologically resembles Paramecium woodruffi. but with multiple contractile vacuole pores. The general morphology, morphometry. and random amplified polymorphic DNA (RAPD) fingerprint patterns are presented for a number of the stocks collected around the world.
    Type of Medium: Electronic Resource
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  • 6
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    Alfred Wegener Institute for Polar and Marine Research
    In:  In: The Expedition PS93.2 of the Research Vessel POLARSTERN to the Fram Strait in 2015. , ed. by Bornemann, H. Berichte zur Polar- und Meeresforschung = Reports on Polar and Marine Research, 693 . Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, pp. 38-42.
    Publication Date: 2016-06-02
    Type: Book chapter , NonPeerReviewed
    Format: text
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  • 7
    Publication Date: 2016-09-22
    Description: © 2009 The Authors. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Biology 7 (2009): 72, doi:10.1186/1741-7007-7-72.
    Description: Recent advances in sequencing strategies make possible unprecedented depth and scale of sampling for molecular detection of microbial diversity. Two major paradigm-shifting discoveries include the detection of bacterial diversity that is one to two orders of magnitude greater than previous estimates, and the discovery of an exciting 'rare biosphere' of molecular signatures ('species') of poorly understood ecological significance. We applied a high-throughput parallel tag sequencing (454 sequencing) protocol adopted for eukaryotes to investigate protistan community complexity in two contrasting anoxic marine ecosystems (Framvaren Fjord, Norway; Cariaco deep-sea basin, Venezuela). Both sampling sites have previously been scrutinized for protistan diversity by traditional clone library construction and Sanger sequencing. By comparing these clone library data with 454 amplicon library data, we assess the efficiency of high-throughput tag sequencing strategies. We here present a novel, highly conservative bioinformatic analysis pipeline for the processing of large tag sequence data sets.The analyses of ca. 250,000 sequence reads revealed that the number of detected Operational Taxonomic Units (OTUs) far exceeded previous richness estimates from the same sites based on clone libraries and Sanger sequencing. More than 90% of this diversity was represented by OTUs with less than 10 sequence tags. We detected a substantial number of taxonomic groups like Apusozoa, Chrysomerophytes, Centroheliozoa, Eustigmatophytes, hyphochytriomycetes, Ichthyosporea, Oikomonads, Phaeothamniophytes, and rhodophytes which remained undetected by previous clone library-based diversity surveys of the sampling sites. The most important innovations in our newly developed bioinformatics pipeline employ (i) BLASTN with query parameters adjusted for highly variable domains and a complete database of public ribosomal RNA (rRNA) gene sequences for taxonomic assignments of tags; (ii) a clustering of tags at k differences (Levenshtein distance) with a newly developed algorithm enabling very fast OTU clustering for large tag sequence data sets; and (iii) a novel parsing procedure to combine the data from individual analyses. Our data highlight the magnitude of the under-sampled 'protistan gap' in the eukaryotic tree of life. This study illustrates that our current understanding of the ecological complexity of protist communities, and of the global species richness and genome diversity of protists, is severely limited. Even though 454 pyrosequencing is not a panacea, it allows for more comprehensive insights into the diversity of protistan communities, and combined with appropriate statistical tools, enables improved ecological interpretations of the data and projections of global diversity.
    Description: The International Census of Marine Microbes and the W.M. Keck Foundation award to the Marine Biological Laboratory at Woods Hole (MA) supported the pyrosequencing part of this study. Further financial support came from a grant from the Deutsche Forschungsgemeinschaft to TS (STO414/3-1). Support for the unpublished work on Cariaco Basin protists came from NSF MCB-0348407 to VE (collaborative project with S Epstein at Northeastern University, Boston, MA, USA). Financial support to AC was provided by NSF MCB-0348045. Financial support to RC was provided by the ANR-Biodiversité project Aquaparadox.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 8
    Publication Date: 2017-01-05
    Description: Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Extremophiles 13 (2009): 151-167, doi:10.1007/s00792-008-0206-2.
    Description: Environmental factors restrict the distribution of microbial eukaryotes but the exact boundaries for eukaryotic life are not known. Here we examine protistan communities at the extremes of salinity and osmotic pressure, and report rich assemblages inhabiting Bannock and Discovery, two deep-sea superhaline anoxic basins in the Mediterranean. Using a rRNA-based approach, we detected 1538 protistan rRNA gene sequences from water samples with total salinity ranging from 39 g/kg to 280 g/Kg, and obtained evidence that this DNA was endogenous to the extreme habitats sampled. Statistical analyses indicate that the discovered phylotypes represent only a fraction of species actually inhabiting both the brine and the brine-seawater interface, with as much as 82% of the actual richness missed by our survey. Jaccard indices (e.g., for a comparison of community membership) suggest that the brine/interface protistan communities are unique to Bannock and Discovery basins, and share little (0.8-2.8%) in species composition with overlying waters with typical marine salinity and oxygen tension. The protistan communities from the basins’ brine and brine/seawater interface appear to be particularly enriched with dinoflagellates, ciliates and other alveolates, as well as fungi, and are conspicuously poor in stramenopiles. The uniqueness and diversity of brine and brine-interface protistan communities make them promising targets for protistan discovery.
    Description: This study was supported by grant grant STO414/2-4 of the Deutsche Forschungsgemeinschaft, the EuroDEEP program of the European Science Foundation under 06-EuroDEEP-FP-004 MIDDLE project and NSF-grant MCB- 0348341
    Keywords: Anoxic ; Brine ; Community structure ; Deep-sea ; DHAB ; Hypersaline ; Molecular diversity ; Protists
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 9
    Publication Date: 2016-09-23
    Description: © The Author(s), 2013. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Microbiology 13 (2013): 150, doi:10.1186/1471-2180-13-150.
    Description: Deep hypersaline anoxic basins (DHABs) are isolated habitats at the bottom of the eastern Mediterranean Sea, which originate from the ancient dissolution of Messinian evaporites. The different basins have recruited their original biota from the same source, but their geological evolution eventually constituted sharp environmental barriers, restricting genetic exchange between the individual basins. Therefore, DHABs are unique model systems to assess the effect of geological events and environmental conditions on the evolution and diversification of protistan plankton. Here, we examine evidence for isolated evolution of unicellular eukaryote protistan plankton communities driven by geological separation and environmental selection. We specifically focused on ciliated protists as a major component of protistan DHAB plankton by pyrosequencing the hypervariable V4 fragment of the small subunit ribosomal RNA. Geospatial distributions and responses of marine ciliates to differential hydrochemistries suggest strong physical and chemical barriers to dispersal that influence the evolution of this plankton group. Ciliate communities in the brines of four investigated DHABs are distinctively different from ciliate communities in the interfaces (haloclines) immediately above the brines. While the interface ciliate communities from different sites are relatively similar to each other, the brine ciliate communities are significantly different between sites. We found no distance-decay relationship, and canonical correspondence analyses identified oxygen and sodium as most important hydrochemical parameters explaining the partitioning of diversity between interface and brine ciliate communities. However, none of the analyzed hydrochemical parameters explained the significant differences between brine ciliate communities in different basins. Our data indicate a frequent genetic exchange in the deep-sea water above the brines. The “isolated island character” of the different brines, that resulted from geological events and contemporary environmental conditions, create selective pressures driving evolutionary processes, and with time, lead to speciation and shape protistan community composition. We conclude that community assembly in DHABs is a mixture of isolated evolution (as evidenced by small changes in V4 primary structure in some taxa) and species sorting (as indicated by the regional absence/presence of individual taxon groups on high levels in taxonomic hierarchy).
    Description: This work was funded by NSF grants OCE-0849578 and OCE- 1061774 to VE and support from Carl Zeiss fellowship to AS and from the Deutsche Forschungsgemeinschaft (grants STO414/3-2 and STO414/7-1) to TS.
    Keywords: Ciliates ; Hypersaline ; Deep-sea anoxic basins ; DHABs ; Brine ; Species sorting ; Environmental filtering ; Niche separation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
    Publication Date: 2019-07-16
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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