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Daniel Vaulot - One of the best experts on this subject based on the ideXlab platform.
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Annual phytoplankton dynamics in coastal waters from Fildes Bay, Western Antarctic Peninsula
Scientific Reports, 2021Co-Authors: Nicole Trefault, Dominique Marie, Adriana Lopes Dos Santos, Catherine Gérikas Ribeiro, Rodrigo De La Iglesia, Mario Moreno-pino, Génesis Parada-pozo, Antonia Cristi, Daniel VaulotAbstract:Year-round reports of phytoplankton dynamics in the West Antarctic Peninsula are rare and mainly limited to microscopy and/or pigment-based studies. We analyzed the phytoplankton community from coastal waters of Fildes Bay in the West Antarctic Peninsula between January 2014 and 2015 using metabarcoding of the nuclear and plastidial 18/16S rRNA gene from both size-fractionated and flow cytometry sorted samples. Overall 14 classes of photosynthetic eukaryotes were present in our samples with the following dominating: Bacillariophyta (diatoms), Pelagophyceae and Dictyochophyceae for division Ochrophyta, Mamiellophyceae and Pyramimonadophyceae for division Chlorophyta, Haptophyta and Cryptophyta. Each metabarcoding approach yielded a different image of the phytoplankton community with for example Prymnesiophyceae more prevalent in plastidial metabarcodes and Mamiellophyceae in nuclear ones. Diatoms were dominant in the larger size fractions and during summer, while Prymnesiophyceae and Cryptophyceae were dominant in colder seasons. Pelagophyceae were particularly abundant towards the end of autumn (May). In addition of Micromonas polaris and Micromonas sp. clade B3, both previously reported in Arctic waters, we detected a new Micromonas 18S rRNA sequence signature, close to, but clearly distinct from M. polaris , which potentially represents a new clade specific of the Antarctic. These results highlight the need for complementary strategies as well as the importance of year-round monitoring for a comprehensive description of phytoplankton communities in Antarctic coastal waters.
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Annual phytoplankton dynamics in coastal waters from Fildes Bay, Western Antarctic Peninsula.
2020Co-Authors: N. Trefaut, Dominique Marie, Rodrigo De La Iglesia, Mario Moreno-pino, Antonia Cristi, A. Lopes Dos Santos, C. Gerikas Ribeiro, Daniel VaulotAbstract:Year-round reports of phytoplankton dynamics in the West Antarctic Peninsula are rare and mainly limited to microscopy and/or pigment-based studies. We analyzed the phytoplankton community from coastal waters of Fildes Bay in the West Antarctic Peninsula between January 2014 and 2015 using metabarcoding of the nuclear and plastidial 18/16S rRNA gene from both size-fractionated and flow cytometry sorted samples. Each metabarcoding approach yielded a different image of the phytoplankton community with for example Prymnesiophyceae more prevalent in plastidial metabarcodes and Mamiellophyceae in nuclear ones. Overall 14 classes of photosynthetic eukaryotes were present in our samples with the following dominating: Bacillariophyta (diatoms), Pelagophyceae and Dictyochophyceae for division Ochrophyta, Mamiellophyceae and Pyramimonadophyceae for division Chlorophyta, Prymnesiophyceae and Cryptophyceae. Diatoms were dominant in the larger size fractions and during summer, while Prymnesiophyceae and Cryptophyceae were dominant in colder seasons. Pelagophyceae were particularly abundant towards the end of autumn (May). In addition of Micromonas polaris and Micromonas sp. clade B3, both previously reported in Arctic waters, we detected a new Micromonas 18S rRNA sequence signature, close to but clearly distinct from M. polaris, which potentially represent a new clade specific of the Antarctic. These results highlight the need for complementary strategies as well as the importance of year-round monitoring for a comprehensive description of phytoplankton communities in Antarctic coastal waters.
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Plastid 16S rRNA Gene Diversity among Eukaryotic Picophytoplankton Sorted by Flow Cytometry from the South Pacific Ocean
2015Co-Authors: Xiao Li Shi, David J. Scanlan, Daniel VaulotAbstract:The genetic diversity of photosynthetic picoeukaryotes was investigated in the South East Pacific Ocean. Genetic libraries of the plastid 16S rRNA gene were constructed on picoeukaryote populations sorted by flow cytometry, using two different primer sets, OXY107F/OXY1313R commonly used to amplify oxygenic organisms, and PLA491F/OXY1313R, biased towards plastids of marine algae. Surprisingly, the two sets revealed quite different photosynthetic picoeukaryote diversity patterns, which were moreover different from what we previously reported using the 18S rRNA nuclear gene as a marker. The first 16S primer set revealed many sequences related to Pelagophyceae and Dictyochophyceae, the second 16S primer set was heavily biased toward Prymnesiophyceae, while 18S sequences were dominated by Prasinophyceae, Chrysophyceae and Haptophyta. Primer mismatches with major algal lineages is probably one reason behind this discrepancy. However, other reasons, such as DNA accessibility or gene copy numbers, may be also critical. Based on plastid 16S rRNA gene sequences, the structure of photosynthetic picoeukaryotes varied along the BIOSOPE transect vertically and horizontally. In oligotrophic regions, Pelagophyceae, Chrysophyceae, and Prymnesiophyceae dominated. Pelagophyceae were prevalent at the DCM depth and Chrysophyceae at the surface. In mesotrophic regions Pelagophyceae were still important but Chlorophyta contribution increased. Phylogenetic analysis revealed a new clade of Prasinophyceae (clade 16S-IX), which seems to be restricted to hyper-oligotrophic stations. Our data suggest that a single gene marker, even as widely used as 18S rRNA
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a small flagellate isolated from the English Channel
2015Co-Authors: Wenche Eikrem, Mikel Latasa, Khadidja Romari, Florence Le Gall, Jahn Throndsen, Daniel VaulotAbstract:spherical, measure 3–6 m and have two markedly unequal flagella as well as two yellow-brown chloroplasts. The long hairy flagellum pulls the cells through the water and the short flagellum is acronematic. Their morphology and fine structure indicate a close relationship with the Heterokonts. Phylogenetic analysis of the small subunit of the ribosomal RNA gene clearly places F. parvula within the class Dictyochophyceae and more precisely the order Dictyochales, despite the absence of the external skeleton characteristic of this order. The pigment suite consists of chlorophylls a, c2, c3, 19 butanoyloxy-fucoxanthin, fucoxanthin, diadinoxanthin and -carotene. This pigment composition is typical of the class Pelagophyceae
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Composition of the summer photosynthetic pico and nanoplankton communities in the Beaufort Sea assessed by T-RFLP and sequences of the 18S rRNA gene from flow cytometry sorted samples
The ISME Journal, 2012Co-Authors: Sara Balzano, Priscillia Gourvil, Dominique Marie, Daniel VaulotAbstract:The composition of photosynthetic pico and nanoeukaryotes was investigated in the North East Pacific and the Arctic Ocean with special emphasis on the Beaufort Sea during the MALINA cruise in summer 2009. Photosynthetic populations were sorted using flow cytometry based on their size and pigment fluorescence. Diversity of the sorted photosynthetic eukaryotes was determined using terminal-restriction fragment length polymorphism analysis and cloning/sequencing of the 18S ribosomal RNA gene. Picoplankton was dominated by Mamiellophyceae, a class of small green algae previously included in the prasinophytes: in the North East Pacific, the contribution of an Arctic Micromonas ecotype increased steadily northward becoming the only taxon occurring at most stations throughout the Beaufort Sea. In contrast, nanoplankton was more diverse: North Pacific stations were dominated by Pseudo-nitzschia sp. whereas those in the Beaufort Sea were dominated by two distinct Chaetoceros species as well as by Chrysophyceae, Pelagophyceae and Chrysochromulina spp.. This study confirms the importance of Arctic Micromonas within picoplankton throughout the Beaufort Sea and demonstrates that the photosynthetic picoeukaryote community in the Arctic is much less diverse than at lower latitudes. Moreover, in contrast to what occurs in warmer waters, most of the key pico- and nanoplankton species found in the Beaufort Sea could be successfully established in culture.
Christopher J. Gobler - One of the best experts on this subject based on the ideXlab platform.
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Dynamic CO 2 and pH levels in coastal, estuarine, and inland waters: Theoretical and observed effects on harmful algal blooms
Harmful algae, 2019Co-Authors: John A Raven, Christopher J. Gobler, Per Juel HansenAbstract:Abstract Rising concentrations of atmospheric CO2 results in higher equilibrium concentrations of dissolved CO2 in natural waters, with corresponding increases in hydrogen ion and bicarbonate concentrations and decreases in hydroxyl ion and carbonate concentrations. Superimposed on these climate change effects is the dynamic nature of carbon cycling in coastal zones, which can lead to seasonal and diel changes in pH and CO2 concentrations that can exceed changes expected for open ocean ecosystems by the end of the century. Among harmful algae, i.e. some species and/or strains of Cyanobacteria, Dinophyceae, Prymnesiophyceae, Bacillariophyceae, and Ulvophyceae, the occurrence of a CO2 concentrating mechanisms (CCMs) is the most frequent mechanism of inorganic carbon acquisition in natural waters in equilibrium with the present atmosphere (400 μmol CO2 mol−1 total gas), with varying phenotypic modification of the CCM. No data on CCMs are available for Raphidophyceae or the brown tide Pelagophyceae. Several HAB species and/or strains respond to increased CO2 concentrations with increases in growth rate and/or cellular toxin content, however, others are unaffected. Beyond the effects of altered C concentrations and speciation on HABs, changes in pH in natural waters are likely to have profound effects on algal physiology. This review outlines the implications of changes in inorganic cycling for HABs in coastal zones, and reviews the knowns and unknowns with regard to how HABs can be expected to ocean acidification. We further point to the large regions of uncertainty with regard to this evolving field.
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The brown tide algae, Aureococcus anophagefferens and Aureoumbra lagunensis (Pelagophyceae), allelopathically inhibit the growth of competing microalgae during harmful algal blooms
Limnology and Oceanography, 2017Co-Authors: Yoonja Kang, Christopher J. GoblerAbstract:Allelopathy is an ecological strategy that can facilitate the occurrence of algal blooms. Here, we describe the ability of the harmful pelagophytes, Aureoumbra lagunensis isolated from coastal waters of Cuba, Florida, and Texas and Aureococcus anophagefferens (CCMP1785, CCMP1984) isolated from New York, U.S.A., to inhibit the growth of potentially co-occurring phytoplankton. The allelopathic effects of brown tide algae were broad and strong with both whole cells and culture filtrate causing 10–96% reductions in cell abundance relative to controls in 10 phytoplankton strains originating from nine species and eight classes. The inhibition of target phytoplankton was dose-dependent with Aureococcus and Aureoumbra cell densities exceeding 2.5 × 105 cell mL−1 causing significant reductions in abundance of competing phytoplankton. Recently isolated strains of Aureoumbra (2012–2013) were more allelopathically potent than a strain isolated 20 yr ago. Passage of culture filtrate through hydrophobic resins nearly eliminated the effects of allelochemicals on eukaryotic, but not prokaryotic phytoplankton. Allelochemicals were heat-stable, but degraded at 20°C over 2 weeks. Filtrate of each pelagophyte was capable of reciprocally inhibiting the growth of the other pelagophyte indicating each alga synthesizes a unique set of allelochemicals. Filtrate from brown tide cultures and bloom events were capable of significantly reducing densities of natural assemblages of eukaryotic and prokaryotic phytoplankton from bloom-prone waters in New York and Florida, respectively. Collectively, these findings suggest that allelopathic inhibition of competing phytoplankton is an important process that facilitates intensification and persistence of harmful brown tide blooms caused by Aureococcus and Aureoumbra.
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Effect of vitamins B1 and B12 on bloom dynamics of the harmful brown tide alga, Aureococcus anophagefferens (Pelagophyceae)
Limnology and Oceanography, 2013Co-Authors: F. Koch, Sergio A Sañudo-wilhelmy, Nicholas S. Fisher, Christopher J. GoblerAbstract:Most harmful algae require B vitamins. We investigated vitamin use by the B1 and B12 auxotroph, Aureococcus anophagefferens, a harmful alga that dominates plankton communities during dense ‘‘brown tides’’ in North America, Africa, and Asia. B12-depleted cultures of A. anophagefferens (clone CCMP1984) adapted to lower ambient B12 concentrations by reducing half-saturation constants (Ks)ofB12 uptake and increasing maximum uptake rates (Vmax) compared to vitamin-replete cultures. In contrast, Vmax of vitamin B1 was higher in replete compared to the depleted cultures, whereas the Ks values were similar for both. Ks values for B12 (5.0– 21 pmol L21) were similar to or higher than concentrations measured during brown tides, suggesting that B12 may restrict the growth of this alga in the field. Over the course of a dense brown tide (. 106 cells mL21) in Quantuck Bay, New York, vitamin B1 and B12 concentrations declined from . 100 pmol L21 to , 8 pmol L21, suggesting there was rapid uptake by A. anophagefferens and its associated microbial community. Experiments performed using radioisotope-labeled vitamins B1 and B12 and 14C-bicarbonate indicated that plankton in the size range of A. anophagefferens (1–5 mm) were responsible for the majority of primary production and the majority of vitamin B1 uptake but shared vitamin B12 uptake with smaller picoplankton (, 1 mm). Vitamin uptake rates during the brown tide were capable of turning over standing stocks of vitamin B12 in 15 h, whereas B1 depletion was slower with maximal turnover times of 2.8 d. As the brown tide intensified and vitamin B12 levels declined, the experimental enrichment of brown tide water with vitamin B12 significantly enhanced the growth rates of A. anophagefferens. Collectively, this study demonstrates that vitamin B12 can influence the intensity of harmful algal blooms caused by A. anophagefferens.
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Emergence of brown tides caused by Aureococcus anophagefferens Hargraves et Sieburth in China
Harmful Algae, 2012Co-Authors: Qingchun Zhang, Christopher J. Gobler, Limei Qiu, Fan-zhou Kong, Yun-feng Wang, Tian Yan, Mingjiang ZhouAbstract:Large-scale blooms suspected to be "brown tides" occurred in early summer for three consecutive years from 2009 to 2011 in the coastal waters of Qinhuangdao, China, and had significant negative impacts on the shellfish mariculture industry. To identify the causative species of the blooms, phytoplankton samples were collected from regions with and without bloom in the coastal waters of Qinhuangdao in 2011, and clone libraries were built using eukaryote-specific 18S ribosomal RNA gene (18S rDNA). Altogether 50 clones, including 17 clones from bloom area and 33 clones from nearby regions without bloom were amplified. Blasted in GenBank, 17 clones amplified from the bloom area were assigned to Pelagophyceae (8 clones), Mediophyceae (2 clones), Cryptophyta (2 clones), Dinophyceae (2 clones) and unidentified eukaryotic species (3 clones). Those from the non-bloom site were assigned to Cryptophyta, Eustigmatophyceae, Prasinophyceae, Coscinodiscophyceae, Mediophyceae, Raphidophyceae and Dinophyceae, but not Pelagophyceae. All 8 pelagophyte clones from the bloom area were 99.7-100% similar to a single species, Aureococcus anophagefferens Hargraves et Sieburth, the causative species of brown tides on the east coast of USA. For nearly the entire length of the 18S rDNA, there were 0-6 base pair differences between the 8 amplicons and those of A. anophagefferens from USA. Furthermore, all of the 8 clones were clustered into the same well-supported clade with A. anophagefferens (posterior probability = 0.99) in a phylogenetic tree established for pelagophytes and other related microalgae. In our previous studies, the causative species of the bloom was tentatively identified as a pelagophyte, haptophyte or silicoflagellate, based on the pigment profile of the size-fractioned phytoplankton samples. Based on this study, we conclude that blooms in the coastal waters of Qinhuangdao of the Bohai Sea were brown tides caused by A. anophagefferens. As far as we know, this is the first report of brown tide events caused by A. anophagefferens in China, which is the third country in the world reporting A. anophagefferens blooms in addition to USA and South Africa. (c) 2012 Elsevier B.V. All rights reserved.
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ANALYSES OF THE COMPLETE CHLOROPLAST GENOME SEQUENCES OF TWO MEMBERS OF THE Pelagophyceae: AUREOCOCCUS ANOPHAGEFFERENS CCMP1984 AND AUREOUMBRA LAGUNENSIS CCMP1507
Journal of Phycology, 2010Co-Authors: Han Chuan Ong, Christopher J. Gobler, Steven W. Wilhelm, George S. Bullerjahn, Michael A. Jacobs, John Mckay, Elizabeth H. Sims, Will Gillett, Yang Zhou, Eric HaugenAbstract:Heterokont members of the Pelagophyceae form the massive brown tides that have continually plagued the coastal regions of the eastern U.S. seaboard and the Gulf of Mexico. To gain a better understanding of the photosynthetic competence that may be linked to their success in forming massive blooms, we sequenced the chloroplast genomes of two pelagophytes: Aureococcus anophagefferens Hargraves et Sieburth and Aureoumbra lagunensis D. A. Stockw., DeYoe, Hargraves et P. W. Johnson. The chloroplast genomes of A. anophagefferens (89,599 bp) and Ar. lagunensis (94,346 bp) are significantly smaller than those of six other stramenopiles sequenced to date. The structure (or configuration) is partially due to the absence of the large inverted repeats common in chloroplast genomes. Eight of 10 small and tandem repeats from the A. anophagefferens and Ar. lagunensis genomes are adjacent to genes coding for photosynthetic or energy production functions, implying that these domains may have functional constraints. High genomic synteny, a multigene phylogenetic analysis, and a synapomorphic change in the form of an attenuated psbA gene confirm that A. anophagefferens and Ar. lagunensis are closely related taxa. Finally, the presence of three light-independent chl-biosynthesis genes in the chloroplast of Ar. lagunensis, but absence in the chloroplast and nuclear genomes of A. anophagefferens, suggests the persistence of a more ancient (i.e., dark-adaptive) potential in Ar. lagunensis but not in A. anophagefferens. Whether the presence of both chl-biosynthesis pathways in Ar. lagunensis contributes to the ability of this organism to sustain prolonged bloom (continuously for ∼8 years) under reduced light conditions, but not A. anophagefferens (a few months), remains an open question.
Elizabeth M. Cosper - One of the best experts on this subject based on the ideXlab platform.
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Viral-like particles (VLPS) in the alga,Aureococcus anophagefferens (Pelagophyceae), during 1999–2000 brown tide blooms in Little Egg Harbor, New Jersey
Estuaries, 2002Co-Authors: Mary Downes Gastrich, O. Roger Anderson, Elizabeth M. CosperAbstract:We assessed the presence and quantified the intracellular virus-like particles (VLPs) in natural populations of Aureococcus anophagefferens during the 1999–2000 brown tide blooms that occurred in New Jersey coastal waters. From displayed a wide range of ultrastructural changes from apparently healthy cells to those showing late stages of production of VLPs. VLP-infected cells usually had an electron dense plasma membrane and lacked the typical exocellular polysaccharide layer (EPS). The VLPs were similar in size (c. 140 nm) and morphology to those initially reported in natural populations of A. anophagefferens and to brown tide viruses (BtVs) which were previously isolated and inoculated into laboratory cultures of A. anophagefferens . VLP-infected A. anophagefferens were found consistently throughout the brown tide blooms in both years in Little Egg Harbor. Percentages of VLP-infected cells were 8.1% at the beginning of a bloom, which decreased to less than 2% at the height of the blooms during both years, and increased at the end of the 2000 bloom to 2.5%. While these percentages appear low, the estimated VLP infection rate of A. anophagefferens cells, which ranged from 0.83%–50% of the standing population, is comparable to other studies.
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Viral-like Particles (VLPS) in the Alga, Aureococcus anophagefferens (Pelagophyceae), during 1999-2000 Brown Tide Blooms in Little Egg Harbor, New Jersey
Estuaries, 2002Co-Authors: Mary Downes Gastrich, O. Roger Anderson, Elizabeth M. CosperAbstract:We assessed the presence and quantified the intracellular virus-like particles (VLPs) in natural populations ofAureococcus anophagefferens during the 1999–2000 brown tide blooms that occurred in New Jersey coastal waters. From displayed a wide range of ultrastructural changes from apparently healthy cells to those showing late stages of production of VLPs. VLP-infected cells usually had an electron dense plasma membrane and lacked the typical exocellular polysaccharide layer (EPS). The VLPs were similar in size (c. 140 nm) and morphology to those initially reported in natural populations ofA. anophagefferens and to brown tide viruses (BtVs) which were previously isolated and inoculated into laboratory cultures ofA. anophagefferens. VLP-infectedA. anophagefferens were found consistently throughout the brown tide blooms in both years in Little Egg Harbor. Percentages of VLP-infected cells were 8.1% at the beginning of a bloom, which decreased to less than 2% at the height of the blooms during both years, and increased at the end of the 2000 bloom to 2.5%. While these percentages appear low, the estimated VLP infection rate ofA. anophagefferens cells, which ranged from 0.83%–50% of the standing population, is comparable to other studies.
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characterization of a lytic virus infectious to the bloom forming microalga aureococcus anophagefferens Pelagophyceae
Journal of Phycology, 1998Co-Authors: Ronald T. Garry, Patrick Hearing, Elizabeth M. CosperAbstract:Aureococcus anophagefferens Hargraves and Sieburth has caused recurring monospecific blooms in Long Island embayments since it was first described in 1985. It was termed the “brown tide,” due to the resulting water color, and has had a devastating effect on Long Island’s (New York) marine ecosystem. In 1992, a virus that was capable of causing lysis of A. anophagefferens was isolated and maintained in culture. We report on the further characterization of this virus, Aureococcus anophagefferens virus-1 (AaV-1), indicated by a buoyant density of 1.2776 g·mL−1 in a CsCl equilibrium gradient. Electron microscopy revealed a phage with a hexagonal head and tail similar to previously described phages. By using adenovirus for calibration, the virus was found to have a head 50—55 nm wide and a tail 70–75 nm long. The viral band was infectious to A. anophagefferens after dialysis. The virus was composed of at least 16 distinct polypeptides ranging in molecular weight from 20 to 230 kDa. The adsorption coefficient for the virus was 7.2 × 10−9 mL·min−1, and the burst size was calculated to be 9.4 viruses per A. anophagefferens cell at 20° C. Complete lysis of A. anophagefferens occurred with a titer as low as 893 viruses·mL−1, and the lower limit of infectivity was 93 viruses·mL−1. The virus lost its infectivity between 30° and 40° C. These results suggest that AaV-1 is highly infectious and that the role of the virus in preventing or ending A. anophagefferens blooms needs further investigation.
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Ultrastructural analysis of viral infection in the brown-tide alga, Aureococcus anophagefferens (Pelagophyceae)
Phycologia, 1998Co-Authors: Mary Downes Gastrich, O. Roger Anderson, Sharon S. Benmayor, Elizabeth M. CosperAbstract:Abstract The DNA-containing virus (BtV) is known to lyse laboratory cultures of Aureococcus anophagefferens Hargraves et Sieburth, an alga known to cause blooms devastating to shellfish and eelgrass beds. Ultrastructural study of the infection of A. anophagefferens by this virus shows a progressive degradation of host algal cells. Healthy uninfected algal cells (c. 2.0 μm) exhibit organelles typical of the Pelagophyceae and are surrounded by a prominent fibrous glycocalyx. All laboratory cultures of A. anophagefferens inoculated with the BtV virus were lysed within 24–48 h, leaving no living cells. Infected brown-tide cells had an unusually electron-dense, crenated plasma membrane and lacked a glycocalyx. During early stages of infection, the vacuole disappeared, and the nucleus was disrupted by the formation of viroplasm. The organelles disappeared, with the chloroplast being the last to degrade. A few intracellular viral capsids (c. 140–160 nm) were observed during the degeneration of the organelles. In...
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CHARACTERIZATION OF A LYTIC VIRUS INFECTIOUS TO THE BLOOM‐FORMING MICROALGA AUREOCOCCUS ANOPHAGEFFERENS (Pelagophyceae)
Journal of Phycology, 1998Co-Authors: Ronald T. Garry, Patrick Hearing, Elizabeth M. CosperAbstract:Aureococcus anophagefferens Hargraves and Sieburth has caused recurring monospecific blooms in Long Island embayments since it was first described in 1985. It was termed the “brown tide,” due to the resulting water color, and has had a devastating effect on Long Island’s (New York) marine ecosystem. In 1992, a virus that was capable of causing lysis of A. anophagefferens was isolated and maintained in culture. We report on the further characterization of this virus, Aureococcus anophagefferens virus-1 (AaV-1), indicated by a buoyant density of 1.2776 g·mL−1 in a CsCl equilibrium gradient. Electron microscopy revealed a phage with a hexagonal head and tail similar to previously described phages. By using adenovirus for calibration, the virus was found to have a head 50—55 nm wide and a tail 70–75 nm long. The viral band was infectious to A. anophagefferens after dialysis. The virus was composed of at least 16 distinct polypeptides ranging in molecular weight from 20 to 230 kDa. The adsorption coefficient for the virus was 7.2 × 10−9 mL·min−1, and the burst size was calculated to be 9.4 viruses per A. anophagefferens cell at 20° C. Complete lysis of A. anophagefferens occurred with a titer as low as 893 viruses·mL−1, and the lower limit of infectivity was 93 viruses·mL−1. The virus lost its infectivity between 30° and 40° C. These results suggest that AaV-1 is highly infectious and that the role of the virus in preventing or ending A. anophagefferens blooms needs further investigation.
Tracy A. Villareal - One of the best experts on this subject based on the ideXlab platform.
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organic and inorganic nutrient effects on growth rate irradiance relationships in the texas brown tide alga aureoumbra lagunensis Pelagophyceae
Journal of Phycology, 2007Co-Authors: Harris I. Muhlstein, Tracy A. VillarealAbstract:Pelagophyte species in the genera Aureococcus and Auroumbra form brown tides in coastal bays that cause food-web disruption and extensive shading of benthic primary producers. Organic nutrients have been suggested as key factors in the origination and persistence of the East Coast (USA) brown-tide alga Aureococcus anophagefferens Hargraves et Sieburth. To evaluate this finding for the Texas brown-tide alga Aureoumbra lagunensis D. A. Stockw., DeYoe, Hargraves et P. W. Johnson, we grew strain TBA-2 with dissolved inorganic nitrogen (DIN; or ) or dissolved organic nitrogen (DON; urea or glutamate) as the nitrogen (N) source under eight light intensities. Maximum growth rates decreased with N source from (1.0 div · d−1) to (0.48 div · d−1). Neither growth rate efficiency (α) nor Ik varied significantly between N treatments. Both inorganic phosphorus (P) and β-glycerophosphate supported growth. Aureoumbra lagunensis can utilize at least some forms of organic N and P and can use them to persist or grow when inorganic forms become limiting. We found no evidence to support the hypothesis that organic utilization enhances or supplements growth at low light levels.
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Organic and inorganic nutrient effects on growth rate–irradiance relationships in the Texas brown‐tide alga Aureoumbra lagunensis (Pelagophyceae)
Journal of Phycology, 2007Co-Authors: Harris I. Muhlstein, Tracy A. VillarealAbstract:Pelagophyte species in the genera Aureococcus and Auroumbra form brown tides in coastal bays that cause food-web disruption and extensive shading of benthic primary producers. Organic nutrients have been suggested as key factors in the origination and persistence of the East Coast (USA) brown-tide alga Aureococcus anophagefferens Hargraves et Sieburth. To evaluate this finding for the Texas brown-tide alga Aureoumbra lagunensis D. A. Stockw., DeYoe, Hargraves et P. W. Johnson, we grew strain TBA-2 with dissolved inorganic nitrogen (DIN; or ) or dissolved organic nitrogen (DON; urea or glutamate) as the nitrogen (N) source under eight light intensities. Maximum growth rates decreased with N source from (1.0 div · d−1) to (0.48 div · d−1). Neither growth rate efficiency (α) nor Ik varied significantly between N treatments. Both inorganic phosphorus (P) and β-glycerophosphate supported growth. Aureoumbra lagunensis can utilize at least some forms of organic N and P and can use them to persist or grow when inorganic forms become limiting. We found no evidence to support the hypothesis that organic utilization enhances or supplements growth at low light levels.
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NUTRIENT‐LIMITED GROWTH OF AUREOUMBRA LAGUNENSIS (Pelagophyceae), WITH IMPLICATIONS FOR ITS CAPABILITY TO OUTGROW OTHER PHYTOPLANKTON SPECIES IN PHOSPHATE‐LIMITED ENVIRONMENTS
Journal of Phycology, 2001Co-Authors: Hongbin Liu, Tracy A. Villareal, Edward A. Laws, Edward J BuskeyAbstract:Growth and chemical compositional characteristics of the brown tide-forming alga, Aureoumbra lagunensis Stockwell, DeYoe, Hargraves et Johnson, were studied through a series of nitrogen-limited and phosphate-limited continuous cultures over a range of growth rates. The specific growth rate of A. lagunensis was hyperbolically related to the cell quota of the limiting nutrient in ammonium-limited cultures. In phosphate-limited cultures, the relationship was best described by a straight line. The N cell quota of A. lagunensis ranges from about 20 fmol at zero growth rate under N-limited conditions to a high of roughly 85 fmol under N-replete conditions. Similarly, the P cell quota of A. lagunensis ranges from about 0.15 fmol at zero growth rate under P-limited conditions to a high of 2 fmol under P-replete conditions. Aureoumbra lagunensis has a very high N:P critical ratio (>100). The high N:P critical ratio, as well as the organism's apparent ability to use forms of phosphorus other than phosphate under severe phosphate deficiency, may partially explain its success in P-limited environments, such as the Laguna Madre. In addition, a uniqe quadratic relationship between the productivity index (PI) and growth rate was discovered. Such a relationship supports an earlier argument that PI may not be a good indicator of nutritional status.
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nutrient limited growth of aureoumbra lagunensis Pelagophyceae with implications for its capability to outgrow other phytoplankton species in phosphate limited environments
Journal of Phycology, 2001Co-Authors: Hongbin Liu, Tracy A. Villareal, Edward A. Laws, Edward J BuskeyAbstract:Growth and chemical compositional characteristics of the brown tide-forming alga, Aureoumbra lagunensis Stockwell, DeYoe, Hargraves et Johnson, were studied through a series of nitrogen-limited and phosphate-limited continuous cultures over a range of growth rates. The specific growth rate of A. lagunensis was hyperbolically related to the cell quota of the limiting nutrient in ammonium-limited cultures. In phosphate-limited cultures, the relationship was best described by a straight line. The N cell quota of A. lagunensis ranges from about 20 fmol at zero growth rate under N-limited conditions to a high of roughly 85 fmol under N-replete conditions. Similarly, the P cell quota of A. lagunensis ranges from about 0.15 fmol at zero growth rate under P-limited conditions to a high of 2 fmol under P-replete conditions. Aureoumbra lagunensis has a very high N:P critical ratio (>100). The high N:P critical ratio, as well as the organism's apparent ability to use forms of phosphorus other than phosphate under severe phosphate deficiency, may partially explain its success in P-limited environments, such as the Laguna Madre. In addition, a uniqe quadratic relationship between the productivity index (PI) and growth rate was discovered. Such a relationship supports an earlier argument that PI may not be a good indicator of nutritional status.
Sarah Caronni - One of the best experts on this subject based on the ideXlab platform.
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The interactive effect of herbivory, nutrient enrichment and mucilage on shallow rocky macroalgal communities
PeerJ, 2019Co-Authors: Sarah Caronni, Augusto Navone, Maria Anna Delaria, Pieraugusto Panzalis, Chiara Calabretti, Sandra Citterio, Rodolfo Gentili, Giovanni Macri, Chiara Montagnani, Giulia PiazzaAbstract:This paper focuses on the interactive short and long-term effect of three different stressors on a macroalgal assemblage. Three stressors are considered: herbivory, nutrients and mucilage. The experiment was conducted in Tavolara Punta Coda Cavallo Marine Protected Area (Mediterranean Sea) during a bloom of the benthic mucilage-producing microalga Chrysophaeum taylorii (Pelagophyceae); this microalga is recently spreading in the Mediterranean Sea. On a rocky substratum, 36 plots 20 × 20 cm in size were prepared. Factorial combinations of three experimental treatments were applied in triplicate, including three grazing levels crossed with two nutrient enrichment and two mucilage removal treatments. Significant differences were observed among treatments 8 weeks later, at the end of summer. In particular, dark filamentous algae were more abundant in all enriched plots, especially where mucilage and macroalgae had been removed; a higher percent cover of crustose coralline algae was instead observed where nutrients had been increased and no grazing pressure acted. Furthermore, the abundance of Dictyota spp. and Laurencia spp. was significantly higher in enriched mucilage-free plots where the grazing pressure was null or low. However, the effects of the treatments on the overall assemblage of the macroalgal community were not long persistent (36 weeks later). These results illustrate the capacity of a shallow-water macroalgal community to quickly recover from the simultaneous impacts of herbivory, nutrient enrichment, and mucilage.
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The interactive effect of herbivory, nutrient enrichment and mucilage on shallow rocky macroalgal communities
2018Co-Authors: Sarah Caronni, Giulia Ceccherelli, Augusto Navone, Maria Anna Delaria, Chiara Calabretti, Sandra Citterio, Rodolfo Gentili, Giovanni Macri, Chiara Montagnani, Pieraugusto PanzalisAbstract:In this paper the results of a manipulative experiment aimed to evaluate the interactive short- and long-term effect of three different stressors, herbivory, nutrient and mucilage, on a macroalgal assemblage are presented. The experiment was conducted in Tavolara Punta Coda Cavallo Marine Protected Area during a bloom of the benthic mucilage-producing microalga Chrysophaeum taylorii Lewis and Bryan (Pelagophyceae), recently spreading in the Mediterranean Sea. On a rocky substratum, 18 plots 20x20 cm in size were prepared and, according to different treatments, nutrients were added in some of them to simulate eutrophication, macroalgae were removed to simulate clearings produced by grazers and mucilage was manually removed to simulate mucilage-free conditions. Differences in the composition of macroalgal assemblages were found when considering the short term effect of the considered stressors, and also the response of the most abundant taxa (DFA, ECA, Dictyotales, Laurencia spp. and Padina pavonica) varied among treatments, proving that a combined effect of such stressors on the recovery of macroalgae was present. On the contrary, the effect of treatments was neither highlighted on the most abundant algae nor on the whole structure of the macroalgal assemblage.
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The invasive microalga Chrysophaeum taylorii: Interactive stressors regulate cell density and mucilage production.
Marine environmental research, 2017Co-Authors: Sarah Caronni, Giulia Ceccherelli, Augusto Navone, Maria Anna Delaria, Chiara Calabretti, Giovanni Macri, Gianluca Cavagna, Pieraugusto PanzalisAbstract:Abstract The benthic mucilage producing microalga Chrysophaeum taylorii Lewis and Bryan ( Pelagophyceae ) has recently received attention for its rapid spread in the Mediterranean Sea, where its blooms have remarkable detrimental effects. So far no information on C. taylorii response to multiple stressors, especially in terms of mucilage hyperproduction, is available in the literature yet, and a manipulative field experiment in this topic was designed in Tavolara Punta Coda Cavallo Marine Protected Area. The aim of the study was to test the effects of nutrient enrichment (addition of nutrients), mechanical disturbance (partial and total benthic organisms removal) and hydrodynamics (increased water turbulence) on C. taylorii cell density and mucilage abundance. To the purpose, the three above mentioned stressors were simulated and the three treatments were assigned to 20 × 20 cm plots following a full-factorial design (n = 3). Interactive effects of the three stressors affected significantly both benthic C. taylorii cell density and mucilage cover although differently. Mechanical disturbance and high hydrodynamics produced consistent effects on cell density and mucilage production (i.e. the former factor enhancing and the latter decreasing). Nutrient enrichment on the contrary led to contrasting effects, promoting cell abundance and inhibiting mucilage production. Therefore, important mucilage blooms are expected in oligotrophic sheltered coastal locations where barren areas are present.
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Ecology of the benthic mucilage-forming microalga Chrysophaeum taylorii in the W Mediterranean Sea: Substratum and depth preferences
Estuarine Coastal and Shelf Science, 2015Co-Authors: Sarah Caronni, Kirsten Heimann, Augusto Navone, Alessia Bresciani, Maria Anna Delaria, Federico Meloni, Pieraugusto Panzalis, Giulia CeccherelliAbstract:Chrysophaeum taylorii Lewis and Bryan (Pelagophyceae) is an allochthonous benthic microalga recently recorded in the Mediterranean Sea where it is spreading quickly. Although this species secretes mucilage which is seriously affecting marine communities, it has been scarcely studied and no information on its ecologyisavailableyet.Wepresenttheresultsofa fiveyearstudyaimedtoincreaseknowledgeonsubstratum and depth preferences of this bloom-forming microalga with special emphasis on its colonisation efficiency. Three separate field experiments established that cell abundances of Chrysophaeum taylorii were significantly lower on macroalgae, mollusc shells and sand than on hard granitic substrata, where the microalga settled efficiently and proliferated immediately independently of the colonisation level of the substratum (bare vs colonised) and the substratum stability (mobility) (cobbles vs rocks). Furthermore, C. taylorii abundance (density) decreased with depth >2 m, showing it prefers shallow waters in which it is able to resist to high light intensities. These results offer some important insights into the ecology of this bloom-forming microalga that will contribute to the planning of future research and strategies for management of bloom events.
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Relevant scales of variability of the benthic allochthonous microalga Chrysophaeum taylorii
Marine Biology, 2014Co-Authors: Sarah Caronni, Nicola Sechi, Augusto Navone, Maria Anna Delaria, Pier Panzalis, Giulia CeccherelliAbstract:Chrysophaeum taylorii (Pelagophyceae) is an allochthonous benthic microalga recently recorded in the Mediterranean Sea. During summer, the occurrence of C. taylorii is usually visible to the naked eye due to the large amount of mucilage this species produces. Information on the spatio-temporal variability of this species and on the predictability of massive mucilage events is still scarce and requires to define ad hoc managing strategies of major bloom events. The aim of this work was to identify the relevant scales of variation in the abundance of C. taylorii abundance and to estimate the relative recurrence of its blooms, testing the hypothesis that mucilage was depend- ent on the cell density. The first approach was the identi- fication of the most appropriate sampling procedure to estimate benthic cell abundance of C. taylorii. The second one was the estimation of the magnitude of variation in C. taylorii cell abundance attributable to each of several spa- tial (areas, sites, zones and replicates) and temporal scales (fortnights and years) in the Marine Protected area of Tavolara Punta Coda Cavallo (Western Mediterranean Sea). The results indicate fortnight and year as the most relevant scales of variability in the cell abundance of C. taylorii and
