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  • 1
    Keywords: Aufsatzsammlung
    Type of Medium: Book
    Pages: S. 159 - 321 , Ill., graph. Darst
    Series Statement: Deep sea research 57.2010,3/4
    Language: English
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  • 2
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    PANGAEA
    In:  Supplement to: Fuchs, Nike; Scalco, Eleonora; Kooistra, W H C F; Assmy, Philipp; Montresor, Marina (2013): Genetic characterization and life cycle of the diatom Fragilariopsis kerguelensis. European Journal of Phycology, 48(4), 411-426, https://doi.org/10.1080/09670262.2013.849360
    Publication Date: 2023-10-28
    Description: The planktonic diatom Fragilariopsis kerguelensis plays an important role in the biogeochemical cycles of the Southern Ocean, where remains of its frustules form the largest deposit of biogenic silica anywhere in the world. We assessed the genetic identity of 26 strains, from cells collected at various sites in the Southern Ocean, using three molecular markers, LSU and ITS rDNA and rbcL. The LSU sequences were identical among the tested strains, ITS sequences were highly similar, and only one base pair difference was detected among the rbcL sequences. These results, together with a large number of successful mating experiments demonstrated that the strains belong to a single biological species. We investigated the mating system and life cycle traits of F. kerguelensis. Cell size diminished gradually in clonal strains. Gamete formation only occurred when strains of opposite mating type - within a cell size range of 7-36 µm - were mixed together. Two binucleate gametes were formed in each gametangium and gamete conjugation produced a zygote that had four nuclei and was surrounded by thin siliceous scales. Two out of the four nuclei subsequently degenerated and the zygote expanded to form an auxospore surrounded by a transverse and a longitudinal perizonium. Staining with the fluorochrome PDMPO provided for the first time a clear demonstration that the longitudinal perizonium is formed after auxospore expansion is complete. Initial cells produced within the mature auxospores were 78-101 µm in length. Various authors have shown that the average valve size of F. kerguelensis varies in sediment samples collected in regions and seasons with different primary production regimes and this parameter has thus been proposed as a biological proxy for palaeo-productivity. A better understanding of the life cycle of F. kerguelensis should help the design of future investigations aimed at testing the link between cell size distribution in the natural environment and the role that environmental factors might have in the regulation of population cell size.
    Keywords: ANT-XXI/3; AWI; Cell division rate; Cell size; Cell size decrease; Cell size decrease per division; Date/Time of event; Event label; Hand net; HN; Latitude of event; Longitude of event; Polarstern; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; PS65/410-2; PS65/420-4; PS65/424-4; PS65 EIFEX; South Atlantic Ocean; Species; SPP1158; Strain
    Type: Dataset
    Format: text/tab-separated-values, 42 data points
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  • 3
    Publication Date: 2019-09-23
    Description: Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence—although each with important uncertainties—lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
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  • 4
    Publication Date: 2014-07-01
    Description: Current sampling of genomic sequence data from eukaryotes is relatively poor, biased, and inadequate to address important questions about their biology, evolution, and ecology; this Community Page describes a resource of 700 transcriptomes from marine microbial eukaryotes to help understand their role in the world's oceans.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 5
    Publication Date: 2017-10-04
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 6
    Publication Date: 2019-07-16
    Description: The Alexandrium tamarense species complex is one of the most studied marine dinoflagellate groups due to its ecological, toxicological and economic importance. Several members of this complex produce saxitoxin and its congeners - potent neurotoxins that cause paralytic shellfish poisoning. Isolates from this complex are assigned to A. tamarense, A. fundyense, or A. catenella based on two main morphological characters: the ability to form chains and the presence/absence of a ventral pore between Plates 1′ and 4′. However, studies have shown that these characters are not consistent and/or distinctive. Further, phylogenies based on multiple regions in the rDNA operon indicate that the sequences from morphologically indistinguishable isolates partition into five clades. These clades were initially named based on their presumed geographic distribution, but recently were renamed as Groups I-V following the discovery of sympatry among some groups. In this study we present data on morphology, ITS/5.8S genetic distances, ITS2 compensatory base changes, mating incompatibilities, toxicity, the sxtA toxin synthesis gene, and rDNA phylogenies. All results were consistent with each group representing a distinct cryptic species. Accordingly, the groups were assigned species names as follows: Group I, A. fundyense; Group II, A. mediterraneum; Group III, A. tamarense; Group IV, A. pacificum; Group V, A. australiense.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 7
    Publication Date: 2014-09-24
    Description: Ocean iron fertilization experiments enable the quantitative study of processes shaping the structure and functioning of pelagic ecosystems following perturbation under in situ conditions. EIFEX was conducted within a stationary eddy adjacent to the Antarctic Polar Front over 38 days in February/March 2004 and induced a massive diatom bloom. Here, we present the responses in abundance and biomass of all identifiable protozooplankton taxa (heterotrophic protists ranging from 2 to 500 µm) during the bloom. Acantharia, dinoflagellates and ciliates together contributed 〉90% of protozooplankton biomass in the upper 100 m throughout the experiment with heterotrophic nanoflagellates, nassellaria, spumellaria, phaeodaria, foraminifera and the taxopodidean Sticholonche zanclea providing the remainder. Total protozooplankton biomass increased slightly from 1.0 to 1.3 g C m−2 within the fertilized patch and remained at 0.7+0.04 g C m−2 outside it. However, distinct trends in population build-up or decline were observed within the dominant taxa in each group. In general, smaller less-defended groups such as aloricate ciliates and athecate dinoflagellates declined, whereas the biomass of large, spiny and armoured groups, in particular acantharia, large tintinnids and thecate dinoflagellates increased inside the patch. We attribute the higher accumulation rates of defended taxa to selective, heavy grazing pressure by the large stocks of copepods. Of the defended taxa, acantharia had the lowest mortality rates and the highest biomass. Large stocks of tintinnid loricae in the deep water column identify this group as a relevant contributor to deep organic carbon export. Highest accumulation rates (0.11 day−1) were recorded in S. zanclea.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 8
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    International Association for Plant Taxonomy
    In:  EPIC3Taxon, International Association for Plant Taxonomy, 63(4), pp. 932-933, ISSN: 0040-0262
    Publication Date: 2014-10-07
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 9
    Publication Date: 2019-07-16
    Description: Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence—although each with important uncertainties—lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 10
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Harmful Algae 14 (2012): 10-35, doi:10.1016/j.hal.2011.10.012.
    Description: The dinoflagellate genus Alexandrium is one of the major harmful algal bloom (HAB) genera with respect to the diversity, magnitude and consequences of blooms. The ability of Alexandrium to colonize multiple habitats and to persist over large regions through time is testimony to the adaptability and resilience of this group of species. Three different families of toxins, as well as an as yet incompletely characterized suite of allelochemicals are produced among Alexandrium species. Nutritional strategies are equally diverse, including the ability to utilize a range of inorganic and organic nutrient sources, and feeding by ingestion of other organisms. Many Alexandrium species have complex life histories that include sexuality and often, but not always, cyst formation, which is characteristic of a meroplanktonic life strategy and offers considerable ecological advantages. Due to the public health and ecosystem impacts of Alexandrium blooms, the genus has been extensively studied, and there exists a broad knowledge base that ranges from taxonomy and phylogeny through genomics and toxin biosynthesis to bloom dynamics and modeling. Here we present a review of the genus Alexandrium, focusing on the major toxic and otherwise harmful species.
    Description: Support to DMA was provided by the National Institute of Environmental Health Sciences (1-P50-ES012742) and the National Science Foundation through the Woods Hole Center for Oceans and Human Health (OCE-0430724), and by NOAA Grants NA09NOS4780193, NA06OAR4170021 and NA06NOS4780245. Research funding to ADC and previously to TJA was furnished under the PACES Programme (Coast WP2) from the Helmholtz Society initiative Earth and Environment. Support to TJA was obtained by the research funding program LOEWE (Landes-Offensive zur Entwicklung Wissenschaftlich-ökonomischer Exzellenz) of Hesse’s Ministry of Higher Education, Research, and the Arts. Support to EM and YC was provided by grants from the French National Programme “Ecosphère Continentale et Côtière-EC2CO and from the “Fondation pour la Recherche sur la Biodiversité-INVALEX project (AAP-IN-2009- 036).
    Keywords: Alexandrium ; Harmful algal blooms ; HAB ; Biotoxins ; Public health ; Global dispersion
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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