The Experts below are selected from a list of 2004 Experts worldwide ranked by ideXlab platform
Bente Edvardsen - One of the best experts on this subject based on the ideXlab platform.
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Taxonomic reassignment of Pseudohaptolina birgeri comb. nov. (Haptophyta)
Phycologia, 2020Co-Authors: Catherine Gérikas Ribeiro, Daniel Vaulot, Ian Probert, Adriana Lopes Dos Santos, Bente EdvardsenAbstract:The haptophyte genus Pseudohaptolina (formerly Chrysochromulina clade B1-3) currently harbours two species: Pseudohaptolina arctica and Pseudohaptolina sorokinii. In addition, Chrysochromulina birg...
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:: Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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Seasonal Dynamics of Haptophytes and dsDNA Algal Viruses Suggest Complex Virus-Host Relationship
Viruses, 2017Co-Authors: Torill Vik Johannessen, Elianne Dunthorn Egge, Gunnar Bratbak, Aud Larsen, Antonio Pagarete, Bente Edvardsen, Ruthanne SandaaAbstract:Viruses influence the ecology and diversity of phytoplankton in the ocean. Most studies of phytoplankton host–virus interactions have focused on bloom-forming species like Emiliania huxleyi or Phaeocystis spp. The role of viruses infecting phytoplankton that do not form conspicuous blooms have received less attention. Here we explore the dynamics of phytoplankton and algal viruses over several sequential seasons, with a focus on the ubiquitous and diverse phytoplankton division Haptophyta, and their double-stranded DNA viruses, potentially with the capacity to infect the haptophytes. Viral and phytoplankton abundance and diversity showed recurrent seasonal changes, mainly explained by hydrographic conditions. By 454 tag-sequencing we revealed 93 unique haptophyte operational taxonomic units (OTUs), with seasonal changes in abundance. Sixty-one unique viral OTUs, representing Megaviridae and Phycodnaviridae, showed only distant relationship with currently isolated algal viruses. Haptophyte and virus community composition and diversity varied substantially throughout the year, but in an uncoordinated manner. A minority of the viral OTUs were highly abundant at specific time-points, indicating a boom-bust relationship with their host. Most of the viral OTUs were very persistent, which may represent viruses that coexist with their hosts, or able to exploit several host species.
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Haptophyta
Handbook of the Protists, 2016Co-Authors: Wenche Eikrem, Linda K. Medlin, Ian Probert, Jorijntje Henderiks, Sebastian Rokitta, Björn Rost, Jahn Throndsen, Bente EdvardsenAbstract:Haptophyta are predominantly planktonic and phototrophic organisms that have their main distribution in marine environments worldwide. They are a major component of the microbial ecosystem, some form massive blooms and some are toxic. Haptophytes are significant players in the global carbonate cycle through photosynthesis and calcification. They are characterized by the haptonema, a third appendage used for attachment and food handling, two similar flagella, two golden-brown chloroplasts, and organic body scales that serve in species identification. Coccolithophores have calcified scales termed coccoliths. Phylogenetically Haptophyta form a well-defined group and are divided into two classes Pavlovophyceae and Coccolithophyceae (Prymnesiophyceae). Currently, about 330 species are described. Environmental DNA sequencing shows high haptophyte diversity in the marine pico- and nanoplankton, of which many likely represent novel species and lineages. Haptophyte diversity is believed to have peaked in the past and their presence is documented in the fossil record back to the Triassic, approximately 225 million years ago. Some biomolecules of haptophyte origin are extraordinarily resistant to decay and are thus used by geologists as sedimentary proxies of past climatic conditions
Elianne Dunthorn Egge - One of the best experts on this subject based on the ideXlab platform.
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:: Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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Seasonal Dynamics of Haptophytes and dsDNA Algal Viruses Suggest Complex Virus-Host Relationship
Viruses, 2017Co-Authors: Torill Vik Johannessen, Elianne Dunthorn Egge, Gunnar Bratbak, Aud Larsen, Antonio Pagarete, Bente Edvardsen, Ruthanne SandaaAbstract:Viruses influence the ecology and diversity of phytoplankton in the ocean. Most studies of phytoplankton host–virus interactions have focused on bloom-forming species like Emiliania huxleyi or Phaeocystis spp. The role of viruses infecting phytoplankton that do not form conspicuous blooms have received less attention. Here we explore the dynamics of phytoplankton and algal viruses over several sequential seasons, with a focus on the ubiquitous and diverse phytoplankton division Haptophyta, and their double-stranded DNA viruses, potentially with the capacity to infect the haptophytes. Viral and phytoplankton abundance and diversity showed recurrent seasonal changes, mainly explained by hydrographic conditions. By 454 tag-sequencing we revealed 93 unique haptophyte operational taxonomic units (OTUs), with seasonal changes in abundance. Sixty-one unique viral OTUs, representing Megaviridae and Phycodnaviridae, showed only distant relationship with currently isolated algal viruses. Haptophyte and virus community composition and diversity varied substantially throughout the year, but in an uncoordinated manner. A minority of the viral OTUs were highly abundant at specific time-points, indicating a boom-bust relationship with their host. Most of the viral OTUs were very persistent, which may represent viruses that coexist with their hosts, or able to exploit several host species.
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Comparing high-throughput sequencing and scanning electron microscopy to investigate haptophyte communities in Oslofjorden (Skagerrak)
2016Co-Authors: Sandra Gran Stadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:Comparing high-throughput sequencing and scanning electron microscopy to investigate haptophyte communities in Oslofjorden (Skagerrak)
Sandra Granstadniczenko - One of the best experts on this subject based on the ideXlab platform.
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:: Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
Luka Šupraha - One of the best experts on this subject based on the ideXlab platform.
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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haptophyte diversity and vertical distribution explored by 18s and 28s ribosomal rna gene metabarcoding and scanning electron microscopy
Journal of Eukaryotic Microbiology, 2017Co-Authors: Sandra Granstadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:: Haptophyta encompasses more than 300 species of mostly marine pico- and nanoplanktonic flagellates. Our aims were to investigate the Oslofjorden haptophyte diversity and vertical distribution by metabarcoding, and to improve the approach to study haptophyte community composition, richness and proportional abundance by comparing two rRNA markers and scanning electron microscopy (SEM). Samples were collected in August 2013 at the Outer Oslofjorden, Norway. Total RNA/cDNA was amplified by haptophyte-specific primers targeting the V4 region of the 18S, and the D1-D2 region of the 28S rRNA. Taxonomy was assigned using curated haptophyte reference databases and phylogenetic analyses. Both marker genes showed Chrysochromulinaceae and Prymnesiaceae to be the families with highest number of Operational Taxonomic Units (OTUs), as well as proportional abundance. The 18S rRNA data set also contained OTUs assigned to eight supported and defined clades consisting of environmental sequences only, possibly representing novel lineages from family to class. We also recorded new species for the area. Comparing coccolithophores by SEM with metabarcoding shows a good correspondence with the 18S rRNA gene proportional abundances. Our results contribute to link morphological and molecular data and 28S to 18S rRNA gene sequences of haptophytes without cultured representatives, and to improve metabarcoding methodology.
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Comparing high-throughput sequencing and scanning electron microscopy to investigate haptophyte communities in Oslofjorden (Skagerrak)
2016Co-Authors: Sandra Gran Stadniczenko, Elianne Dunthorn Egge, Luka Šupraha, Bente EdvardsenAbstract:Comparing high-throughput sequencing and scanning electron microscopy to investigate haptophyte communities in Oslofjorden (Skagerrak)
Yongsong Huang - One of the best experts on this subject based on the ideXlab platform.
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Successional blooms of alkenone-producing haptophytes in Lake George, North Dakota: Implications for continental paleoclimate reconstructions
Limnology and Oceanography, 2019Co-Authors: Susanna Theroux, Yongsong Huang, Jaime L. Toney, Robert A. Andersen, Paul Nyren, Rick Bohn, Jeffrey M. Salacup, Leslie G. Murphy, Linda Amaral-zettlerAbstract:Alkenone‐derived paleotemperature reconstruction holds great promise in lake environments. However, the occurrence of multiple species of alkenone‐producing haptophyte algae in a single lake can complicate the translation of alkenone unsaturation to temperature if each species requires an individual temperature calibration. Here, we present the first systematic monitoring of two alkenone‐producing haptophytes throughout the course of a seasonal cycle in Lake George, North Dakota, using a combined approach of DNA sequencing and alkenone lipid characterization. Field sampling revealed a nonoverlapping haptophyte succession, with both an early and late season haptophyte bloom event. Culturing experiments demonstrated that the two haptophyte species responsible for these blooms had statistically similar alkenone‐temperature responses, although the culture‐based calibrations were distinct from the in situ calibration. Bloom timing of each haptophyte species corresponded to surface‐water temperatures that differed by more than 10°C, revealing that changes in bloom intensities for each species will skew the sediment‐inferred temperatures to a different stage of the growth season. These results highlight the importance of accounting for bloom timing when interpreting alkenone‐derived temperatures in sediment cores, especially in lakes that experience large seasonal fluctuations in water column temperature and salinity.
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Changes in long chain alkenone distributions and Isochrysidales groups along the Baltic Sea salinity gradient
Organic Geochemistry, 2019Co-Authors: Jérôme Kaiser, Yinsui Zheng, Helge W Arz, Karen J. Wang, Linda Amaral-zettler, Derek M. Rott, Yongsong HuangAbstract:Abstract Isochrysidales species of the phylum Haptophyta are the exclusive producers of C37 to C42 long chain alkyl ketones, also called long chain alkenones (LCAs). While LCA distributions are known to vary with temperature and salinity, it is difficult to tease apart the direct effects of environmental parameters vs changes in the LCA-producing organisms. The Baltic Sea surface salinity gradient, which ranges from oligohaline (0.5–5 g/kg) to polyhaline (18–30 g/kg), represents a unique opportunity to study the relationships between salinity changes, species distribution and LCA biomarkers in a single ecosystem. LCA biomarkers revealed the presence of the three known Isochrysidales groups (Groups I, II and III) in Baltic Sea surface sediments, and the presence of Groups I and II were further confirmed with DNA sequencing. Group III Isochrysidales were present in the mixoeuhaline Skagerrak based on LCA signature alone. Groups I and II Isochrysidales were found for the first time in the Baltic Sea using a combination of LCAs and DNA biomarkers, solving an eighteen-year long mystery of Baltic Sea LCA-producing haptophyte identity. Group II Isochrysidales, which have a large salinity tolerance range, were spread over the Skagerrak and the complete Baltic Sea, but were characteristic for the central Baltic Sea. Oligohaline Group I Isochrysidales were representative for the northern Baltic Sea. However, evidence of Group I Isochrysidales in the central and southern Baltic Sea suggests a possible transport by surface currents since this group is typically confined to oligohaline conditions. Testing the recently developed ratio of isomeric C37 ketones (RIK37) against the Baltic Sea surface salinity gradient revealed a significant positive correlation. This may represent a salinity proxy reflecting the amount of Group I Isochrysidales relative to Group II Isochrysidales in oligohaline environments. The present study elucidates for the first time the identity and the spatial distribution of LCA producers thriving in a large and stable brackish environment.
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Production and temperature sensitivity of long chain alkenones in the cultured haptophyte Pseudoisochrysis paradoxa
Organic Geochemistry, 2013Co-Authors: Susanna Theroux, Jaime L. Toney, Linda A. Amaral-zettler, Yongsong HuangAbstract:The alkenone unsaturation index (U37K or U37K′) serves as a critical tool for reconstructing temperature in marine environments. Lacustrine haptophyte algae are genetically distinct from their ubiquitous and well studied marine counterparts, and the unknown species-specific genetic imprints on long chain alkenone production by lacustrine species have hindered the widespread application of the U37K temperature proxy to lake sediment records. The haptophyte Pseudoisochrysis paradoxa produces alkenones but its U37K calibration has never been determined. It has an alkenone fingerprint abundant in tetraunsaturated alkenones, a hallmark of lacustrine environments. We present here the first calibration of the U37K index to temperature for a culture of P. paradoxa. We found that the U37K index accurately captured the alkenone response to temperature whereas the U37K′ index failed to do so, with U37K′ values below 0.08 projecting to two different temperature values. Our results add a fifth species-specific U37K calibration and provide another line of evidence that different haptophyte species require different U37K calibrations. The findings also highlight the necessary inclusion of the C37:4 alkenone when reconstructing temperatures from P. paradoxa-derived alkenone records.
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Comparative molecular microbial ecology of the spring haptophyte bloom in a greenland arctic oligosaline lake.
Frontiers in microbiology, 2012Co-Authors: Susanna Theroux, Yongsong Huang, Linda A. Amaral-zettlerAbstract:The Arctic is highly sensitive to increasing global temperatures and is projected to experience dramatic ecological shifts in the next few decades. Oligosaline lakes are common in arctic regions where evaporation surpasses precipitation, however these extreme microbial communities are poorly characterized. Many oligosaline lakes, in contrast to freshwater ones, experience annual blooms of haptophyte algae that generate valuable alkenone biomarker records that can be used for paleoclimate reconstruction. These haptophyte algae are globally important, and globally distributed, aquatic phototrophs yet their presence in microbial molecular surveys is scarce. To target haptophytes in a molecular survey, we compared microbial community structure during two haptophyte bloom events in an arctic oligosaline lake, Lake BrayaSo in southwestern Greenland, using high-throughput pyrotag sequencing. Our comparison of two annual bloom events yielded surprisingly low taxon overlap, only 13% for bacterial and 26% for eukaryotic communities, which indicates significant annual variation in the underlying microbial populations. Both the bacterial and eukaryotic communities strongly resembled high-altitude and high-latitude freshwater environments. In spite of high alkenone concentrations in the water column, and corresponding high haptophyte rRNA gene copy numbers, haptophyte pyrotag sequences were not the most abundant eukaryotic tag, suggesting that sequencing biases obscured relative abundance data. With over 170 haptophyte tag sequences, we observed only one haptophyte algal Operational Taxonomic Unit, a prerequisite for accurate paleoclimate reconstruction from the lake sediments. Our study is the first to examine microbial diversity in a Greenland lake using next generation sequencing and the first to target an extreme haptophyte bloom event. Our results provide a context for future explorations of aquatic ecology in the warming arctic.
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phylogenetic diversity and evolutionary relatedness of alkenone producing haptophyte algae in lakes implications for continental paleotemperature reconstructions
Earth and Planetary Science Letters, 2010Co-Authors: Jaime L. Toney, Susanna Theroux, William J Dandrea, Linda A Amaralzettler, Yongsong HuangAbstract:Alkenones have been found in an increasing number of lakes around the world, making them a promising new tool for continental paleoclimate reconstruction. However, individual lakes may harbor different species of haptophyte algae with different sensitivities to temperature variations, thus presenting a significant challenge to the use of lacustrine alkenones for paleotemperature reconstructions. To explore the extent of lacustrine haptophyte diversity, we conducted the first comprehensive phylogenetic and geochemical survey of lacustrine alkenone producers. We sampled 15 alkenone-containing lake surface sediments from a variety of geographic locales and inferred identities of environmental sequences using 18S ribosomal RNA (rRNA) gene-based phylogenies. For two lakes, BrayaSo in southwest Greenland and Tso Ur on the Tibetan Plateau, we also analyzed both surface and downcore sediments to characterize haptophyte populations through time. In parallel with phylogenetic analyses, we determined the alkenone distributions (including C37/C38 ratios, and the presence/absence of C38 methyl ketones and C40 compounds) in all the samples. The resulting alkenone profiles from this study do not all align with traditional “marine” versus “coastal/lacustrine” alkenone profiles. Additionally, our genetic data indicate the presence of multiple haptophyte species from a single lake sediment sample; these distinct haptophyte populations could not be discerned from the alkenone profiles alone. These results show that alkenone profiles are not a reliable way to assess the haptophyte algae in lakes and that DNA fingerprinting is a preferred approach for species identification. Although closely related haptophyte species or subspecies may not warrant different temperature calibrations, our results emphasize the importance of genetic data for inferring haptophyte identities and eventually selecting alkenone–temperature calibrations for paleoclimate reconstructions.
