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Balaguer J, Koch F, Flintrop CM, Völkner C, Iversen MH, Trimborn S. Iron and manganese availability drives primary production and carbon export in the Weddell Sea. Curr Biol 2023; 33:4405-4414.e4. [PMID: 37769661 DOI: 10.1016/j.cub.2023.08.086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 07/17/2023] [Accepted: 08/30/2023] [Indexed: 10/03/2023]
Abstract
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.
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Affiliation(s)
- Jenna Balaguer
- Marine Botany, University of Bremen, Bremen 28359, Germany; Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven 25570, Germany.
| | - Florian Koch
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven 25570, Germany
| | - Clara M Flintrop
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven 25570, Germany; The Fredy & Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem 91904, Israel; Interuniversity Institute for Marine Sciences, Eilat 88103, Israel
| | - Christian Völkner
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven 25570, Germany
| | - Morten H Iversen
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven 25570, Germany; MARUM Center for Marine Environmental Sciences, University of Bremen, Bremen 28359, Germany
| | - Scarlett Trimborn
- Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven 25570, Germany
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2
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Klawonn I, Van den Wyngaert S, Iversen MH, Walles TJW, Flintrop CM, Cisternas-Novoa C, Nejstgaard JC, Kagami M, Grossart HP. Fungal parasitism on diatoms alters formation and bio-physical properties of sinking aggregates. Commun Biol 2023; 6:206. [PMID: 36810576 PMCID: PMC9944279 DOI: 10.1038/s42003-023-04453-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 01/10/2023] [Indexed: 02/24/2023] Open
Abstract
Phytoplankton forms the base of aquatic food webs and element cycling in diverse aquatic systems. The fate of phytoplankton-derived organic matter, however, often remains unresolved as it is controlled by complex, interlinked remineralization and sedimentation processes. We here investigate a rarely considered control mechanism on sinking organic matter fluxes: fungal parasites infecting phytoplankton. We demonstrate that bacterial colonization is promoted 3.5-fold on fungal-infected phytoplankton cells in comparison to non-infected cells in a cultured model pathosystem (diatom Synedra, fungal microparasite Zygophlyctis, and co-growing bacteria), and even ≥17-fold in field-sampled populations (Planktothrix, Synedra, and Fragilaria). Additional data obtained using the Synedra-Zygophlyctis model system reveals that fungal infections reduce the formation of aggregates. Moreover, carbon respiration is 2-fold higher and settling velocities are 11-48% lower for similar-sized fungal-infected vs. non-infected aggregates. Our data imply that parasites can effectively control the fate of phytoplankton-derived organic matter on a single-cell to single-aggregate scale, potentially enhancing remineralization and reducing sedimentation in freshwater and coastal systems.
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Affiliation(s)
- Isabell Klawonn
- Department of Plankton and Microbial Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775, Stechlin, Germany.
- Department of Biological Oceanography, Leibniz Institute for Baltic Sea Research Warnemünde (IOW), 18119, Rostock, Germany.
| | - Silke Van den Wyngaert
- Department of Plankton and Microbial Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775, Stechlin, Germany
- Department of Biology, University of Turku, 20014, Turku, Finland
| | - Morten H Iversen
- Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, 27570, Bremerhaven, Germany
- Centre for Marine Environmental Sciences (MARUM) and University of Bremen, 28359, Bremen, Germany
| | - Tim J W Walles
- Department of Plankton and Microbial Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775, Stechlin, Germany
| | - Clara M Flintrop
- Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, 27570, Bremerhaven, Germany
- Centre for Marine Environmental Sciences (MARUM) and University of Bremen, 28359, Bremen, Germany
- The Inter-University Institute for Marine Sciences in Eilat, Eilat, 8810302, Israel
| | - Carolina Cisternas-Novoa
- Helmholtz Centre for Ocean Research (GEOMAR), 24148, Kiel, Germany
- Ocean Sciences Centre, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada
| | - Jens C Nejstgaard
- Department of Plankton and Microbial Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775, Stechlin, Germany
| | - Maiko Kagami
- Faculty of Science, Toho University, Funabashi, Chiba, 274‑8510, Japan
- Faculty of Environment and Information Sciences, Yokohama National University, Yokohama, Kanagawa, 240‑8502, Japan
| | - Hans-Peter Grossart
- Department of Plankton and Microbial Ecology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), 16775, Stechlin, Germany
- Institute of Biochemistry and Biology, Potsdam University, 14469, Potsdam, Germany
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3
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Abstract
Understanding the nature of organic matter flux in the ocean remains a major goal of oceanography because it impacts some of the most important processes in the ocean. Sinking particles are important for carbon dioxide removal from the atmosphere and its movement to the deep ocean. They also feed life below the ocean's productive surface and sustain life in the deep sea, in addition to depositing organic matter on the seafloor. However, the magnitude of all of these processes is dependent on the transformation of sinking particles during their journey through the water column. This review focuses on the movement of organic matter from the surface ocean to the deep sea via the biological carbon pump and examines the processes that prevent this downward movement-namely, attenuation via microbial colonization and zooplankton feeding. It also discusses how the depth-specific interactions among microbes, zooplankton, and aggregates determine carbon export as well as nutrient recycling, which in turn impact ocean production and Earth's climate.
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Affiliation(s)
- Morten H Iversen
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany;
- Center for Marine Environmental Sciences (MARUM), University of Bremen, Bremen, Germany
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4
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Pauli NC, Flintrop CM, Konrad C, Pakhomov EA, Swoboda S, Koch F, Wang XL, Zhang JC, Brierley AS, Bernasconi M, Meyer B, Iversen MH. Krill and salp faecal pellets contribute equally to the carbon flux at the Antarctic Peninsula. Nat Commun 2021; 12:7168. [PMID: 34887407 PMCID: PMC8660819 DOI: 10.1038/s41467-021-27436-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2021] [Accepted: 11/15/2021] [Indexed: 11/09/2022] Open
Abstract
Krill and salps are important for carbon flux in the Southern Ocean, but the extent of their contribution and the consequences of shifts in dominance from krill to salps remain unclear. We present a direct comparison of the contribution of krill and salp faecal pellets (FP) to vertical carbon flux at the Antarctic Peninsula using a combination of sediment traps, FP production, carbon content, microbial degradation, and krill and salp abundances. Salps produce 4-fold more FP carbon than krill, but the FP from both species contribute equally to the carbon flux at 300 m, accounting for 75% of total carbon. Krill FP are exported to 72% to 300 m, while 80% of salp FP are retained in the mixed layer due to fragmentation. Thus, declining krill abundances could lead to decreased carbon flux, indicating that the Antarctic Peninsula could become a less efficient carbon sink for anthropogenic CO2 in future.
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Affiliation(s)
- Nora-Charlotte Pauli
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl-von-Ossietzky University of Oldenburg, Carl-von-Ossietzky-Str. 9-11, 26111, Oldenburg, Germany. .,Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570, Bremerhaven, Germany.
| | - Clara M. Flintrop
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany ,grid.7704.40000 0001 2297 4381MARUM and University of Bremen, Leobener Str. 8, 28359 Bremen, Germany
| | - Christian Konrad
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany ,grid.7704.40000 0001 2297 4381MARUM and University of Bremen, Leobener Str. 8, 28359 Bremen, Germany
| | - Evgeny A. Pakhomov
- grid.17091.3e0000 0001 2288 9830Department of Earth, Ocean, and Atmospheric Sciences, University of British Columbia, 2207 Main Mall, Vancouver, British Columbia V6T 1Z4 Canada ,grid.17091.3e0000 0001 2288 9830Institute for the Oceans and Fisheries, University of British Columbia, 2202 Main Mall, Vancouver, British Columbia V6T 1Z4 Canada ,grid.484717.9Hakai Institute, PO Box 25039, Campbell River, British Columbia V9W 0B7 Canada
| | - Steffen Swoboda
- grid.7704.40000 0001 2297 4381MARUM and University of Bremen, Leobener Str. 8, 28359 Bremen, Germany
| | - Florian Koch
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Xin-Liang Wang
- grid.43308.3c0000 0000 9413 3760Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 106 Nanjing Road, Qingdao, 266071 China
| | - Ji-Chang Zhang
- grid.43308.3c0000 0000 9413 3760Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, 106 Nanjing Road, Qingdao, 266071 China
| | - Andrew S. Brierley
- grid.11914.3c0000 0001 0721 1626Pelagic Ecology Research Group, Gatty Marine Laboratory, Scottish Oceans Institute, School of Biology, University of St Andrews, St Andrews, Fife KY16 8LB UK
| | - Matteo Bernasconi
- grid.11914.3c0000 0001 0721 1626Pelagic Ecology Research Group, Gatty Marine Laboratory, Scottish Oceans Institute, School of Biology, University of St Andrews, St Andrews, Fife KY16 8LB UK
| | - Bettina Meyer
- Institute for Chemistry and Biology of the Marine Environment (ICBM), Carl-von-Ossietzky University of Oldenburg, Carl-von-Ossietzky-Str. 9-11, 26111, Oldenburg, Germany. .,Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570, Bremerhaven, Germany. .,Helmholtz Institute for Functional Marine Biodiversity (HIFMB), Ammerländer Heerstraße 231, 26129, Oldenburg, Germany.
| | - Morten H. Iversen
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany ,grid.7704.40000 0001 2297 4381MARUM and University of Bremen, Leobener Str. 8, 28359 Bremen, Germany
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Fadeev E, Rogge A, Ramondenc S, Nöthig EM, Wekerle C, Bienhold C, Salter I, Waite AM, Hehemann L, Boetius A, Iversen MH. Sea ice presence is linked to higher carbon export and vertical microbial connectivity in the Eurasian Arctic Ocean. Commun Biol 2021; 4:1255. [PMID: 34732822 PMCID: PMC8566512 DOI: 10.1038/s42003-021-02776-w] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 10/09/2021] [Indexed: 01/04/2023] Open
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.
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Affiliation(s)
- Eduard Fadeev
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany ,grid.419529.20000 0004 0491 3210Max Planck Institute for Marine Microbiology, D-28359 Bremen, Germany ,grid.10420.370000 0001 2286 1424Present Address: Department of Functional and Evolutionary Ecology, University of Vienna, A-1090 Vienna, Austria
| | - Andreas Rogge
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany ,grid.9764.c0000 0001 2153 9986Institute for Ecosystem Research, Kiel University, D-24118 Kiel, Germany
| | - Simon Ramondenc
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany
| | - Eva-Maria Nöthig
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany
| | - Claudia Wekerle
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany
| | - Christina Bienhold
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany ,grid.419529.20000 0004 0491 3210Max Planck Institute for Marine Microbiology, D-28359 Bremen, Germany
| | - Ian Salter
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany ,grid.424612.7Faroe Marine Research Institute, FO 100 Tórshavn, Faroe Islands
| | - Anya M. Waite
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany ,Ocean Frontier Institute, NS, B3H 4R2 Halifax, Canada
| | - Laura Hehemann
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany
| | - Antje Boetius
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany ,grid.419529.20000 0004 0491 3210Max Planck Institute for Marine Microbiology, D-28359 Bremen, Germany ,grid.7704.40000 0001 2297 4381MARUM and University of Bremen, D-28359 Bremen, Germany
| | - Morten H. Iversen
- grid.10894.340000 0001 1033 7684Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, D-27570 Bremerhaven, Germany ,grid.7704.40000 0001 2297 4381MARUM and University of Bremen, D-28359 Bremen, Germany
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6
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Thiele S, Basse A, Becker JW, Lipski A, Iversen MH, Mollenhauer G. Microbial communities in the nepheloid layers and hypoxic zones of the Canary Current upwelling system. Microbiologyopen 2018; 8:e00705. [PMID: 30311417 PMCID: PMC6528590 DOI: 10.1002/mbo3.705] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2018] [Revised: 07/04/2018] [Accepted: 07/06/2018] [Indexed: 11/24/2022] Open
Abstract
Eastern boundary upwelling systems (EBUSs) are among the most productive marine environments in the world. The Canary Current upwelling system off the coast of Mauritania and Morocco is the second most productive of the four EBUS, where nutrient‐rich waters fuel perennial phytoplankton blooms, evident by high chlorophyll a concentrations off Cape Blanc, Mauritania. High primary production leads to eutrophic waters in the surface layers, whereas sinking phytoplankton debris and horizontally dispersed particles form nepheloid layers (NLs) and hypoxic waters at depth. We used Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD‐FISH) in combination with fatty acid (measured as methyl ester; FAME) profiles to investigate the bacterial and archaeal community composition along transects from neritic to pelagic waters within the “giant Cape Blanc filament” in two consecutive years (2010 and 2011), and to evaluate the usage of FAME data for microbial community studies. We also report the first fatty acid profile of Pelagibacterales strain HTCC7211 which was used as a reference profile for the SAR11 clade. Unexpectedly, the reference profile contained low concentrations of long chain fatty acids 18:1 cis11, 18:1 cis11 11methyl, and 19:0 cyclo11–12 fatty acids, the main compounds in other Alphaproteobacteria. Members of the free‐living SAR11 clade were found at increased relative abundance in the hypoxic waters in both years. In contrast, the depth profiles of Gammaproteobacteria (including Alteromonas and Pseudoalteromonas), Bacteroidetes, Roseobacter, and Synechococcus showed high abundances of these groups in layers where particle abundance was high, suggesting that particle attachment or association is an important mechanisms of dispersal for these groups. Collectively, our results highlight the influence of NLs, horizontal particle transport, and low oxygen on the structure and dispersal of microbial communities in upwelling systems.
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Affiliation(s)
- Stefan Thiele
- Max-Planck-Institute for Marine Microbiology, Bremen, Germany.,Friedrich Schiller University, Jena, Germany
| | - Andreas Basse
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.,MARUM and University of Bremen, Bremen, Germany
| | - Jamie W Becker
- Department of Biology, Haverford College, Haverford, Pennsylvania
| | - Andre Lipski
- Department of Food Microbiology and Hygiene, Rheinische Friedrich-Wilhelms Universität Bonn, Bonn, Germany
| | - Morten H Iversen
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.,MARUM and University of Bremen, Bremen, Germany
| | - Gesine Mollenhauer
- Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.,MARUM and University of Bremen, Bremen, Germany
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Yilmaz P, Iversen MH, Hankeln W, Kottmann R, Quast C, Glöckner FO. Ecological structuring of bacterial and archaeal taxa in surface ocean waters. FEMS Microbiol Ecol 2012; 81:373-85. [PMID: 22416918 DOI: 10.1111/j.1574-6941.2012.01357.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 12/02/2011] [Accepted: 03/04/2012] [Indexed: 11/30/2022] Open
Abstract
The Global Ocean Sampling (GOS) expedition is currently the largest and geographically most comprehensive metagenomic dataset, including samples from the Atlantic, Pacific, and Indian Oceans. This study makes use of the wide range of environmental conditions and habitats encompassed within the GOS sites in order to investigate the ecological structuring of bacterial and archaeal taxon ranks. Community structures based on taxonomically classified 16S ribosomal RNA (rRNA) gene fragments at phylum, class, order, family, and genus rank levels were examined using multivariate statistical analysis, and the results were inspected in the context of oceanographic environmental variables and structured habitat classifications. At all taxon rank levels, community structures of neritic, oceanic, estuarine biomes, as well as other exotic biomes (salt marsh, lake, mangrove), were readily distinguishable from each other. A strong structuring of the communities with chlorophyll a concentration and a weaker yet significant structuring with temperature and salinity were observed. Furthermore, there were significant correlations between community structures and habitat classification. These results were used for further investigation of one-to-one relationships between taxa and environment and provided indications for ecological preferences shaped by primary production for both cultured and uncultured bacterial and archaeal clades.
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Affiliation(s)
- Pelin Yilmaz
- Max Planck Institute for Marine Microbiology, Bremen, Germany
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8
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Wohlrab S, Iversen MH, John U. A molecular and co-evolutionary context for grazer induced toxin production in Alexandrium tamarense. PLoS One 2010; 5:e15039. [PMID: 21124775 PMCID: PMC2993940 DOI: 10.1371/journal.pone.0015039] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 10/14/2010] [Indexed: 12/29/2022] Open
Abstract
Marine dinoflagellates of the genus Alexandrium are the proximal source of neurotoxins associated with Paralytic Shellfish Poisoning. The production of these toxins, the toxin biosynthesis and, thus, the cellular toxicity can be influenced by abiotic and biotic factors. There is, however, a lack of substantial evidence concerning the toxins' ecological function such as grazing defense. Waterborne cues from copepods have been previously found to induce a species-specific increase in toxin content in Alexandrium minutum. However, it remains speculative in which context these species-specific responses evolved and if it occurs in other Alexandrium species as well. In this study we exposed Alexandrium tamarense to three copepod species (Calanus helgolandicus, Acartia clausii, and Oithona similis) and their corresponding cues. We show that the species-specific response towards copepod-cues is not restricted to one Alexandrium species and that co-evolutionary processes might be involved in these responses, thus giving additional evidence for the defensive role of phycotoxins. Through a functional genomic approach we gained insights into the underlying molecular processes which could trigger the different outcomes of these species-specific responses and consequently lead to increased toxin content in Alexandrium tamarense. We propose that the regulation of serine/threonine kinase signaling pathways has a major influence in directing the external stimuli i.e. copepod-cues, into different intracellular cascades and networks in A. tamarense. Our results show that A. tamarense can sense potential predating copepods and respond to the received information by increasing its toxin production. Furthermore, we demonstrate how a functional genomic approach can be used to investigate species interactions within the plankton community.
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Affiliation(s)
- Sylke Wohlrab
- Department of Ecological Chemistry, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany.
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9
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Gärdes A, Iversen MH, Grossart HP, Passow U, Ullrich MS. Diatom-associated bacteria are required for aggregation of Thalassiosira weissflogii. ISME J 2010; 5:436-45. [PMID: 20827289 DOI: 10.1038/ismej.2010.145] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Aggregation of algae, mainly diatoms, is an important process in marine systems leading to the settling of particulate organic carbon predominantly in the form of marine snow. Exudation products of phytoplankton form transparent exopolymer particles (TEP), which acts as the glue for particle aggregation. Heterotrophic bacteria interacting with phytoplankton may influence TEP formation and phytoplankton aggregation. This bacterial impact has not been explored in detail. We hypothesized that bacteria attaching to Thalassiosira weissflogii might interact in a yet-to-be determined manner, which could impact TEP formation and aggregate abundance. The role of individual T. weissflogii-attaching and free-living new bacterial isolates for TEP production and diatom aggregation was investigated in vitro. T. weissflogii did not aggregate in axenic culture, and striking differences in aggregation dynamics and TEP abundance were observed when diatom cultures were inoculated with either diatom-attaching or free-living bacteria. The data indicated that free-living bacteria might not influence aggregation whereas bacteria attaching to diatom cells may increase aggregate formation. Interestingly, photosynthetically inactivated T. weissflogii cells did not aggregate regardless of the presence of bacteria. Comparison of aggregate formation, TEP production, aggregate sinking velocity and solid hydrated density revealed remarkable differences. Both, photosynthetically active T. weissflogii and specific diatom-attaching bacteria were required for aggregation. It was concluded that interactions between heterotrophic bacteria and diatoms increased aggregate formation and particle sinking and thus may enhance the efficiency of the biological pump.
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Affiliation(s)
- Astrid Gärdes
- Jacobs University Bremen, School of Engineering and Science, Bremen, Germany
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10
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Abstract
BACKGROUND Vitamin A reduces the pathophysiological effects of endotoxin in animals, but the mechanism and the lowest effective dose are not clear. METHODS An intravenous bolus of endotoxin 20 microg. kg(-1) was given to 30 rabbits. In 10 of them, 1000 IE. kg(-1) retinyl palmitate was injected intravenously 1 h before the endotoxin and in another 10 rabbits 1 h after the endotoxin. A one-compartment open model was fitted to the time-concentration profile of endotoxin in plasma. RESULTS The half-life of endotoxin was half as long when vitamin A was given for prophylaxis (median 35 min) and for treatment (33 min) than in the controls (67 min; p < 0.004). The plasma concentrations of immunoglobulin G and M endotoxin-core antibodies, the leucocyte count and the acid-base balance did not differ between the groups during the experiment, but the pyrogenic reaction was more pronounced in the controls. CONCLUSION A fairly low dose of vitamin A reduced the half-life of endotoxin.
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Affiliation(s)
- M H Iversen
- Department of Anaesthesia, Stockholm Söder Hospital, S-11 883 Stockholm, Sweden
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