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Gustaaf M. Hallegraeff - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Progress in Understanding Algal Bloom- Mediated Fish Kills: The Role of Superoxide Radicals, Phycotoxins and Fatty Acids
2016Co-Authors: Juan José Dorantes-ar, Andreas Seger, Peter D Nichols, Jorge I. Mardones, Gustaaf M. HallegraeffAbstract:Quantification of the role of reactive oxygen species, phycotoxins and fatty acids in fish tox-icity by harmful marine microalgae remains inconclusive. An in vitro fish gill (from rainbow troutOncorhynchus mykiss) assay was used to simultaneously assess the effect in super-oxide dismutase, catalase and lactate dehydrogenase enzymatic activities caused by seven species of ichthyotoxic microalgae (Chattonella marina, Fibrocapsa japonica, Het-erosigma akashiwo, Karenia mikimotoi, Alexandrium catenella, Karlodinium veneficum, Prymnesium parvum). Quantification of superoxide production by these algae was also per-formed. The effect of purified phycotoxins and crude extracts was compared, and the effect of fatty acids is discussed. The Raphidophyte Chattonellawas the most ichthyotoxic (gill cell viability down to 35%) and also the major producer of superoxide radicals (14 pmol cell-1 hr-1) especially after cell lysis. The Raphidophyte Heterosigmaand dinoflagellate Alexan-driumwere the least toxic and had low superoxide production, except when A. catenella was lysed (5.6 pmol cell-1 hr-1). Catalase showed no changes in activity in all the treatments. Superoxide dismutase (SOD) and lactate dehydrogenase exhibited significant activit
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Species of marine phytoplankton used for exposure experiments to test their toxicity on fish cells RTgill-W1, and production of superoxide radicals.
2015Co-Authors: Juan José Dorantes-aranda, Peter D Nichols, Andreas Seger, Jorge I. Mardones, Gustaaf M. HallegraeffAbstract:The nontoxic species Tetraselmis suecica was used as a negative control. Two strains of the Raphidophyte Chattonella marina were used.
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Ichthyotoxicity of gymnodinioid dinoflagellates: PUFA and superoxide effects in sheepshead minnow larvae and rainbow trout gill cells
Marine Ecology, 2011Co-Authors: Ben D. Mooney, Jj Dorantes Aranda, Allen R. Place, Gustaaf M. HallegraeffAbstract:While 24 h exposure of sheepshead minnow fish larvae to purified monogalactosyl diglyceride (MGDG) lipids, containing octadecapentaenoic acid (OPA) exclusively or as a mixture of octadecatetraenoic acid, eicosapentaenoic acid, and OPA (OTA-EPA-OPA), caused sluggish swimming and gulping, it produced no mortalities even at concentrations up to 120 mg l–1. In contrast, comparable concentrations and exposure times caused significant reductions in viability of rainbow trout gill cells. Pure EPA was the most harmful to gill cells (up to 98.5% viability loss in 60 h) followed by OPA-rich MGDG (45% loss), with OTA-rich MGDG (37% loss) the least toxic. OPA-pure MGDG was non-toxic to rainbow trout gill cells; however, surprisingly, pure palmitic acid was harmful (40% viability loss), and we conclude that gill cell line toxicity of the OPA-rich MGDG fraction was caused by admixture with palmitic acid. Screening of 15 Kareniaceae dinoflagellate species demonstrated that these species are low (on average 10 times less) producers of superoxide compared to the ichthyotoxic Raphidophyte Chattonella marina. No mortality of sheepshead minnow fish larvae occurred when exposed to superoxide alone or superoxide combined with either OPA-rich MGDG or OTA-rich MGDG. Superoxide showed a slight impact on viability of rainbow trout gill cells. In conclusion, synergistic interactions between free fatty acids and reactive oxygen species as previously claimed for Raphidophytes could not be confirmed. Gill damaging effects from EPA were conclusively demonstrated, however; when these co-occurred with OTA, a higher loss of viability was observed (up to 37%), suggesting a magnified toxic effect. Contradictory literature claims as to the ichthyotoxicity of OPA (nontoxic in our work) may relate to the presence of chemical impurities.
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Superoxide production by marine microalgae : I. Survey of 37 species from 6 classes
Marine Biology, 2005Co-Authors: Judith-anne Marshall, Miguel De Salas, Tatsuya Oda, Gustaaf M. HallegraeffAbstract:A survey was conducted for production of the reactive oxygen species superoxide by 37 species (65 strains) of microalgae including dinoflagellates, Raphidophytes, chlorophytes, prasinophytes, eustigmatophytes and prymnesiophytes. Ichthyotoxic Raphidophyte species of Chattonella were found to produce the highest environmental levels of superoxide (177×104 total chemiluminescence units). However, ichthyotoxic dinoflagellates (Karenia, Alexandrium) and the prymnesiophyte Prymnesium were also found to produce significant levels of superoxide (4×104, 3×104 and 5×104 chemiluminescence units, respectively), equivalent to that of other Raphidophyte species of Heterosigma and Fibrocapsa (6×104 and 2×104, respectively). A direct relationship between cell size and superoxide production was observed (r2=0.94), with larger cells producing more superoxide per cell. Chattonella produced the most superoxide per cell (expressed as cellular chemiluminescence units), followed by the dinoflagellate species Karenia, Alexandrium, Takayama and Gymnodinium. Small cells, such as the Raphidophyte Heterosigma and the prymnesiophyte Prymnesium produced very little superoxide per cell (cellular chemiluminescence units), but potentially could still produce high total levels of superoxide if present at high biomass levels. Species commonly used as aquaculture bivalve feeds such as Dunaliella, Tetraselmis, Nannochloropsis and Pavlova produced negligible levels of superoxide, even at high biomass. We speculate that superoxide, while not the sole ichthyotoxic principle, may play a wider role in algal toxicity than previously considered, and propose a broad classification of microalgae based upon superoxide production.
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Superoxide production by marine microalgae: II. Towards understanding ecological consequences and possible functions
Marine Biology, 2005Co-Authors: Judith-anne Marshall, Tom Ross, Stephen Pyecroft, Gustaaf M. HallegraeffAbstract:This study investigated the possible roles of superoxide produced by Raphidophyte and prymnesiophyte microalgae as an ichthyotoxic agent to damselfish and an allelopathic agent to bacteria. We found that the rate of superoxide production varied with algal cell density, with cell densities of the Raphidophyte Chattonella marina > 10,000 cells ml-1 producing less environmental levels of superoxide per cell (94 ± 14 chemiluminescence units) than cell densities < 10,000 cells ml-1 (390 ± 54 units per cell). Microalgal cells have the capacity to change their superoxide production rate over a period of 1 h, dependent on cell density and metabolic activity. We also examined the effect of superoxide on suppression of bioluminescence of the marine bacterium Vibrio fischeri as a model for bacterial alleopathy and found that both superoxide and free fatty acids such as eicosapentaenoic acid (EPA; 20:5ω3) present in Raphidophyte microalgal cells cause suppression of bacterial bioluminescence. The combination of superoxide in the presence of EPA further enhanced bioluminescence suppression. Superoxide was also found to enhance the toxicity of free fatty acid EPA to damselfish (Acanthochromis polycanthus) at concentrations as low as 0.2 mg l-1. In conclusion, consideration should be given to density dependent and/or metabolic variations of toxicity when publishing minimum alert levels for superoxide producing ichthyotoxic microalgal species. A secondary role of superoxide production may be to enhance the toxicity of algal exudates or serve as an allelopathic agent against bacterial fouling. © Springer-Verlag 2005.
Kathryn J. Coyne - One of the best experts on this subject based on the ideXlab platform.
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Functional trait thermal acclimation differs across three species of mid-Atlantic harmful algae.
Harmful Algae, 2020Co-Authors: Nayani K. Vidyarathna, Kathryn J. Coyne, Erin Papke, Jonathan H. Cohen, Mark E. WarnerAbstract:Abstract Characterizing the thermal niche of harmful algae is crucial for understanding and projecting the effects of future climate change on harmful algal blooms. The effects of 6 different temperatures (18–32 °C) on the growth, photophysiology, and toxicity were examined in the dinoflagellate Karlodinium veneficum, and the Raphidophytes, Heterosigma akashiwo and Chattonella subsalsa from the Delaware Inland Bays (DIB). K. veneficum and H. akashiwo had skewed unimodal growth patterns, with temperature optima (Topt) at 28.6 and 27.3 °C respectively and an upper thermal niche limit of 32 °C. In contrast, C. subsalsa growth increased linearly with temperature, suggesting Topt and upper thermal boundaries >32 °C. K. veneficum photosystem II (PSII) photochemical efficiency remained stable across all temperatures, while H. akashiwo PSII efficiency declined at higher temperature and C. subsalsa was susceptible to low temperature (~18 °C) photoinactivation. Cell toxicity thermal response was species-specific such that K. veneficum toxicity increased with temperature above Topt. Raphidophyte toxicity peaked at 25–28 °C and was in close agreement with Topt for growth in H. akashiwo but below C. subsalsa maximal growth. The mode of toxicity was markedly different between the dinoflagellate and the Raphidophytes such that K. veneficum had greater hemolytic activity while the Raphidophytes had pronounced fish gill cell toxicity. These results and patterns of natural abundance for these algae in the DIB suggest that continued ocean warming may contribute to C. subsalsa bloom formation while possibly promoting highly toxic blooms of K. veneficum.
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Community-Level and Species-Specific Associations between Phytoplankton and Particle-Associated Vibrio Species in Delaware's Inland Bays
Applied and Environmental Microbiology, 2015Co-Authors: Christopher R. Main, Lauren R. Salvitti, Edward B. Whereat, Kathryn J. CoyneAbstract:Vibrio species are an abundant and diverse group of bacteria that form associations with phytoplankton. Correlations between Vibrio and phytoplankton abundance have been noted, suggesting that growth is enhanced during algal blooms or that association with phytoplankton provides a refuge from predation. Here, we investigated relationships between particle-associated Vibrio spp. and phytoplankton in Delaware's inland bays (DIB). The relative abundances of particle-associated Vibrio spp. and algal classes that form blooms in DIB (dinoflagellates, diatoms, and Raphidophytes) were determined using quantitative PCR. The results demonstrated a significant correlation between particle-associated Vibrio abundance and phytoplankton, with higher correlations to diatoms and Raphidophytes than to dinoflagellates. Species-specific associations were examined during a mixed bloom of Heterosigma akashiwo and Fibrocapsa japonica (Raphidophyceae) and indicated a significant positive correlation for particle-associated Vibrio abundance with H. akashiwo but a negative correlation with F. japonica. Changes in Vibrio assemblages during the bloom were evaluated using automated ribosomal intergenic spacer analysis (ARISA), which revealed significant differences between each size fraction but no significant change in Vibrio assemblages over the course of the bloom. Microzooplankton grazing experiments showed that losses of particle-associated Vibrio spp. may be offset by increased growth in the Vibrio population. Moreover, analysis of Vibrio assemblages by ARISA also indicated an increase in the relative abundance for specific members of the Vibrio community despite higher grazing pressure on the particle-associated population as a whole. The results of this investigation demonstrate links between phytoplankton and Vibrio that may lead to predictions of potential health risks and inform future management practices in this region.
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DESCRIPTION OF VIRIDILOBUS MARINUS (GEN. ET SP. NOV.), A NEW Raphidophyte FROM DELAWARE'S INLAND BAYS
Journal of Phycology, 2012Co-Authors: Elif Demir-hilton, David A. Hutchins, Kirk J. Czymmek, Kathryn J. CoyneAbstract:Delaware's Inland Bays (DIB), USA, are subject to blooms of potentially harmful Raphidophytes, including Heterosigma akashiwo. In 2004, a dense bloom was observed in a low salinity tributary of the DIB. Light microscopy initially suggested that the species was H. akashiwo; however, the cells were smaller than anticipated. 18S rDNA sequences of isolated cultures differed substantially from all Raphidophyte sequences in GenBank. Phylogenetic analysis placed it approximately equidistant from Chattonella and Heterosigma with only ~96% sequence homology with either group. Here, we describe this marine Raphidophyte as a novel genus and species, Viridilobus marinus (gen. et sp. nov.). We also compared this species with H. akashiwo, because both species are superficially similar with respect to morphology and their ecological niches overlap. V. marinus cells are ovoid to spherical (11.4 × 9.4 μm), and the average number of chloroplasts (4 per cell) is lower than in H. akashiwo (15 per cell). Pigment analysis of V. marinus revealed the presence of fucoxanthin, violaxanthin, and zeaxanthin, which are characteristic of marine Raphidophytes within the family Chattonellaceae of the Raphidophyceae. TEM and confocal microscopy, however, revealed diagnostic microscopic and ultrastructural characteristics that distinguish it from other Raphidophytes. Chloroplasts were in close association with the nucleus and thylakoids were arranged either parallel or perpendicular to the cell surface. Putative mucocysts were identified, but trichocysts were not observed. These features, along with DNA sequence data, distinguish this species from all other Raphidophyte genera within the family Chattonellaceae of the Raphidophyceae.
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Assessment of Microzooplankton Grazing on Heterosigma akashiwo Using a Species- Specific Approach Combining Quantitative Real-Time PCR (QPCR) and Dilution Methods
Microbial Ecology, 2008Co-Authors: Elif Demir, Kathryn J. Coyne, Martina A. Doblin, Sara M. Handy, David A. HutchinsAbstract:Delaware’s Inland Bays (DIB) are subject to numerous mixed blooms of harmful Raphidophytes each year, and Heterosigma akashiwo is one of the consistently occurring species. Often, Chattonella subsalsa , C. cf. verruculosa , and Fibrocapsa japonica co-occur with H. akashiwo , indicating a dynamic consortium of Raphidophyte species. In this study, microzooplankton grazing pressure was assessed as a top–down control mechanism on H. akashiwo populations in mixed communities. Quantitative real-time polymerase chain reaction (QPCR) with species-specific primers and probes were used in conjunction with the dilution method to assess grazing pressure on H. akashiwo and other Raphidophytes. As a comparison, we measured changes in chlorophyll a (chl a ) to determine whole community growth and mortality caused by grazing. We detected grazing on H. akashiwo using QPCR in samples where chl a analyses indicated little or no grazing on the total phytoplankton community. Overall, specific microzooplankton grazing pressure on H. akashiwo ranged from 0.88 to 1.88 day^−1 at various sites. Experiments conducted on larger sympatric Raphidophytes ( C. subsalsa, C. cf. verruculosa and F. japonica ) demonstrated no significant microzooplankton grazing on these species. Grazing pressure on H. akashiwo may provide a competitive advantage to other Raphidophytes such as Chattonella spp. that are too large to be consumed at high rates by microzooplankton and help to shape the dynamics of this harmful algal bloom consortium. Our results show that QPCR can be used in conjunction with the dilution method for evaluation of microzooplankton grazing pressure on specific phytoplankton species within a mixed community.
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Simultaneous enumeration of multiple Raphidophyte species by quantitative real‐time PCR: capabilities and limitations
Limnology and Oceanography: Methods, 2006Co-Authors: Sara M. Handy, David A. Hutchins, S. Craig Cary, Kathryn J. CoyneAbstract:Quantitative real-time PCR (QPCR) is a powerful method for species-specific detection and enumeration of harmful algal bloom (HAB) algae, but can be quite time-consuming and expensive for multiple species detection when only a single species is analyzed in each reaction. Rapid enumeration methods would be valuable for the investigation of multiple HAB events such as the mixed blooms of harmful Raphidophyte species (Chattonella cf verruculosa, C. subsalsa, and Heterosigma akashiwo) that co-occur in the Delaware Inland Bays (DIB), USA. This technology uses multiple species-specific probes that fluoresce at different wavelengths and allows for the simultaneous detection and enumeration of more than one species, limited only by the detection capabilities of the instrument. The approach can cut analysis time and cost at least in half, depending on the number of species that can be accurately detected and enumerated in the mixture. Here, we compared multiprobing—or using a single primer set with species-specific probes—to multiplexing, in which species-specific primers and probes are used, targeting the 18S rDNA of 3 Raphidophyte species and an internal standard. Although both methods were effective for multispecies detection compared to simplex results, multiplexing was more accurate than multiprobing for this particular group of species. We investigated the accuracy and sensitivity of multiplex/multiprobe QPCR using plasmids, genomic DNA from cultures, or DNA extracted from environmental samples as template. Smaller amplicon size and sequence heterogeneity between amplicons increased the accuracy of the results. We found that environmental samples of Raphidophytes can be successfully multiplexed or multiprobed with only minimal losses in sensitivity. In addition, we explored probe reporter dyes and quenchers for their compatibility, robustness, and reproducibility in multitemplate detection, and we compared and evaluated the capabilities and limitations of this method for detecting and enumerating multiple phytoplankton species simultaneously.
Judith-anne Marshall - One of the best experts on this subject based on the ideXlab platform.
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Superoxide production by marine microalgae : I. Survey of 37 species from 6 classes
Marine Biology, 2005Co-Authors: Judith-anne Marshall, Miguel De Salas, Tatsuya Oda, Gustaaf M. HallegraeffAbstract:A survey was conducted for production of the reactive oxygen species superoxide by 37 species (65 strains) of microalgae including dinoflagellates, Raphidophytes, chlorophytes, prasinophytes, eustigmatophytes and prymnesiophytes. Ichthyotoxic Raphidophyte species of Chattonella were found to produce the highest environmental levels of superoxide (177×104 total chemiluminescence units). However, ichthyotoxic dinoflagellates (Karenia, Alexandrium) and the prymnesiophyte Prymnesium were also found to produce significant levels of superoxide (4×104, 3×104 and 5×104 chemiluminescence units, respectively), equivalent to that of other Raphidophyte species of Heterosigma and Fibrocapsa (6×104 and 2×104, respectively). A direct relationship between cell size and superoxide production was observed (r2=0.94), with larger cells producing more superoxide per cell. Chattonella produced the most superoxide per cell (expressed as cellular chemiluminescence units), followed by the dinoflagellate species Karenia, Alexandrium, Takayama and Gymnodinium. Small cells, such as the Raphidophyte Heterosigma and the prymnesiophyte Prymnesium produced very little superoxide per cell (cellular chemiluminescence units), but potentially could still produce high total levels of superoxide if present at high biomass levels. Species commonly used as aquaculture bivalve feeds such as Dunaliella, Tetraselmis, Nannochloropsis and Pavlova produced negligible levels of superoxide, even at high biomass. We speculate that superoxide, while not the sole ichthyotoxic principle, may play a wider role in algal toxicity than previously considered, and propose a broad classification of microalgae based upon superoxide production.
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Superoxide production by marine microalgae: II. Towards understanding ecological consequences and possible functions
Marine Biology, 2005Co-Authors: Judith-anne Marshall, Tom Ross, Stephen Pyecroft, Gustaaf M. HallegraeffAbstract:This study investigated the possible roles of superoxide produced by Raphidophyte and prymnesiophyte microalgae as an ichthyotoxic agent to damselfish and an allelopathic agent to bacteria. We found that the rate of superoxide production varied with algal cell density, with cell densities of the Raphidophyte Chattonella marina > 10,000 cells ml-1 producing less environmental levels of superoxide per cell (94 ± 14 chemiluminescence units) than cell densities < 10,000 cells ml-1 (390 ± 54 units per cell). Microalgal cells have the capacity to change their superoxide production rate over a period of 1 h, dependent on cell density and metabolic activity. We also examined the effect of superoxide on suppression of bioluminescence of the marine bacterium Vibrio fischeri as a model for bacterial alleopathy and found that both superoxide and free fatty acids such as eicosapentaenoic acid (EPA; 20:5ω3) present in Raphidophyte microalgal cells cause suppression of bacterial bioluminescence. The combination of superoxide in the presence of EPA further enhanced bioluminescence suppression. Superoxide was also found to enhance the toxicity of free fatty acid EPA to damselfish (Acanthochromis polycanthus) at concentrations as low as 0.2 mg l-1. In conclusion, consideration should be given to density dependent and/or metabolic variations of toxicity when publishing minimum alert levels for superoxide producing ichthyotoxic microalgal species. A secondary role of superoxide production may be to enhance the toxicity of algal exudates or serve as an allelopathic agent against bacterial fouling. © Springer-Verlag 2005.
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Comparative Ecophysiology, Chemotaxonomy and Ichthyotoxicity of Chattonella marina (Raphidophyceae) from Australia and Japan
2003Co-Authors: Judith-anne MarshallAbstract:The Raphidophyte flagellate Chattonella Marina from South Australia that was associated with the mortality of farmed tuna in April 1996 was successfully cultured. This study investigates ecophenotypic variation in physiology, chemotaxonomy and ichthyotoxicity of Australian and Japanese C. marina. Australian C. marina had similar temperature and salinity requirements to the Japanese strain but was adapted to higher light intensities than the Japanese strain. This differentiation was reflected in high concentrations of mycosporinelike amino acids (MAA's), especially the antioxidant MAA mycosporine-glycine, in the Australian cultures. Mycosporine-glycine was absent in the Japanese strain which instead used a violaxanthin:zeaxanthin cycle to moderate inhibition by high PAR irradiance. Ecophenotypic variations in lipid profiles were also observed between Chattonella strains from different geographic locations. Fatty acid and sterol profiles allowed for a clear discrimination between the Raphidophyte genera Chattonella, Heterosigma, Fibrocapsa and Olisthodiscus, but exhibited little differentiation between C. marina, C. antiqua and C. subsalsa. Sterol and fatty acid profiles do not support the separation of C. antiqua and C. marina as distinct species. Sterol signatures, which may be useful as chemotaxonomic markers, were identified. Lipid composition correlated more closely to recent molecular classification of Raphidophytes than classification based upon carotenoid pigments. Previous research on ichthyotoxic principles of C. marina has focused on production of high levels of reactive oxygen species (ROS), a brevetoxin-like compound and free fatty acids. This study found that Chattonella marina produces levels of the ROS superoxide 100 times higher than most algae, which is partially controlled by electrons donated through photosynthetic electron transfer. Differing superoxide production and toxic effects on zooplankton and fish are documented between different geographic strains of C. marina and light treatments. These results suggest a synergistic effect between ROS and an ichthyotoxin, and cannot be explained on the basis of these mechanisms of toxicity on their own. Our investigations into Australian C. marina demonstrate an absence or only very low concentrations of brevetoxin-like compounds by LC-MS techniques and negative mouse bioassays. All Raphidophyte species were found to have high levels of eicosapentaenoic acid (EPA), which tested positive as a potential ichthyotoxin using damselfish as a model organism. EPA produced a similar mortality and fish behavioural response to that of intact C. marina cells while superoxide alone was not sufficient to cause fish mortality. However, superoxide in combination with low concentrations of EPA accelerated fish mortality. Implications of this work for mitigating the impact of Chattonella algal blooms on finfish aquaculture are discussed.
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Ichthyotoxicity of Chattonella marina (Raphidophyceae) to damselfish (Acanthochromis polycanthus): the synergistic role of reactive oxygen species and free fatty acids
Harmful Algae, 2003Co-Authors: Judith-anne Marshall, Peter D Nichols, Brett Hamilton, Richard J. Lewis, Gustaaf M. HallegraeffAbstract:This investigation aimed to elucidate the relative roles of putative brevetoxins, reactive oxygen species and free fatty acids as the toxic principle of the Raphidophyte Chattonella marina, using damselfish as the bioassay. Our investigations on Australian C. marina demonstrated an absence or only very low concentrations of brevetoxin-like compounds by radio-receptor binding assay and liquid chromatography-mass spectroscopy techniques. Chattonella is unique in its ability to produce levels of reactive oxygen species 100 times higher than most other algal species. However, high levels of superoxide on their own were found not to cause fish mortalities. Lipid analysis revealed this Raphidophyte to contain high concentrations of the polyunsaturated fatty acid eicosapentaenoic acid (EPA; 18-23% of fatty acids), which has demonstrated toxic properties to marine organisms. Using damselfish as a model organism, we demonstrated that the free fatty acid (FFA) form of EPA produced a mortality and fish behavioural response similar to fish exposed to C. marina cells. This effect was not apparent when fish were exposed to other lipid fractions including a triglyceride containing fish oil, docosahexaenoate-enriched ethyl ester, or pure brevetoxin standards. The presence of superoxide together with low concentrations of EPA accelerated fish mortality rate threefold. We conclude that the enhancement of ichthyotoxicity of EPA in the presence of superoxide can account for the high C. marina fish killing potential. (C) 2003 Elsevier B.V All rights reserved.
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Chemotaxonomic survey of sterols and fatty acids in six marine Raphidophyte algae
Journal of Applied Phycology, 2002Co-Authors: Judith-anne Marshall, Peter D Nichols, Gustaaf M. HallegraeffAbstract:Fatty acid and sterol profiles allowed for clear discrimination betweentheRaphidophyte genera Chattonella , Heterosigma , Fibrocapsa and Olisthodiscus , but exhibited little differentiation forindividual Chattonella species( C.marina , C. antiqua and C.subsalsa ). Sterol and fatty acid profiles do not support theseparation of Chattonella antiqua and C.marina as distinct species. Ecophenotypic variations in lipidprofiles were also observed between Chattonella strainsfromdifferent geographic locations. Sterol signatures which may be useful aschemotaxonomic markers were: the absence of C_27 sterols (cholesteroland 24-dihydrozymosterol) in Heterosigma akashiwo ; thepresence of isofucosterol in Chattonella ; and theoccurrence of brassicasterol, poriferasterol and fucosterol in Olisthodiscus luteus . High levels of eicosapentaenoic acid(EPA; 17-27% of fatty acids) were present in all Raphidophyte species. Lipidcomposition correlated more closely to recent molecular classification ofRaphidophytes than carotenoid pigments.
Roman Stocker - One of the best experts on this subject based on the ideXlab platform.
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phytoplankton can actively diversify their migration strategy in response to turbulent cues
Nature, 2017Co-Authors: Anupam Sengupta, Francesco Carrara, Roman StockerAbstract:Here, marine phytoplankton are shown to diversify their migratory strategy in response to turbulent cues through a rapid change in shape, thus challenging a fundamental paradigm in oceanography that phytoplankton are passively at the mercy of ocean turbulence. Until now, phytoplankton have been considered as passive subjects to ocean turbulence, which can change as suddenly as nutrient and light availability in the dynamic underwater environment. Roman Stocker and colleagues now show that several species of phytoplankton actively respond to turbulent cues by altering their migration routes to avoid layers of strong turbulence. They report that phytoplankton split into two groups, one swimming upward and another downward. This migratory behaviour could affect which species will survive in a changing ocean and will contribute to understanding of how communities respond to a warming climate. Marine phytoplankton inhabit a dynamic environment where turbulence, together with nutrient and light availability, shapes species fitness, succession and selection1,2. Many species of phytoplankton are motile and undertake diel vertical migrations to gain access to nutrient-rich deeper layers at night and well-lit surface waters during the day3,4. Disruption of this migratory strategy by turbulence is considered to be an important cause of the succession between motile and non-motile species when conditions turn turbulent1,5,6. However, this classical view neglects the possibility that motile species may actively respond to turbulent cues to avoid layers of strong turbulence7. Here we report that phytoplankton, including Raphidophytes and dinoflagellates, can actively diversify their migratory strategy in response to hydrodynamic cues characteristic of overturning by Kolmogorov-scale eddies. Upon experiencing repeated overturning with timescales and statistics representative of ocean turbulence, an upward-swimming population rapidly (5–60 min) splits into two subpopulations, one swimming upward and one swimming downward. Quantitative morphological analysis of the harmful-algal-bloom-forming Raphidophyte Heterosigma akashiwo together with a model of cell mechanics revealed that this behaviour was accompanied by a modulation of the cells’ fore–aft asymmetry. The minute magnitude of the required modulation, sufficient to invert the preferential swimming direction of the cells, highlights the advanced level of control that phytoplankton can exert on their migratory behaviour. Together with observations of enhanced cellular stress after overturning and the typically deleterious effects of strong turbulence on motile phytoplankton5,8, these results point to an active adaptation of H. akashiwo to increase the chance of evading turbulent layers by diversifying the direction of migration within the population, in a manner suggestive of evolutionary bet-hedging. This migratory behaviour relaxes the boundaries between the fluid dynamic niches of motile and non-motile phytoplankton, and highlights that rapid responses to hydrodynamic cues are important survival strategies for phytoplankton in the ocean.
David A. Hutchins - One of the best experts on this subject based on the ideXlab platform.
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DESCRIPTION OF VIRIDILOBUS MARINUS (GEN. ET SP. NOV.), A NEW Raphidophyte FROM DELAWARE'S INLAND BAYS
Journal of Phycology, 2012Co-Authors: Elif Demir-hilton, David A. Hutchins, Kirk J. Czymmek, Kathryn J. CoyneAbstract:Delaware's Inland Bays (DIB), USA, are subject to blooms of potentially harmful Raphidophytes, including Heterosigma akashiwo. In 2004, a dense bloom was observed in a low salinity tributary of the DIB. Light microscopy initially suggested that the species was H. akashiwo; however, the cells were smaller than anticipated. 18S rDNA sequences of isolated cultures differed substantially from all Raphidophyte sequences in GenBank. Phylogenetic analysis placed it approximately equidistant from Chattonella and Heterosigma with only ~96% sequence homology with either group. Here, we describe this marine Raphidophyte as a novel genus and species, Viridilobus marinus (gen. et sp. nov.). We also compared this species with H. akashiwo, because both species are superficially similar with respect to morphology and their ecological niches overlap. V. marinus cells are ovoid to spherical (11.4 × 9.4 μm), and the average number of chloroplasts (4 per cell) is lower than in H. akashiwo (15 per cell). Pigment analysis of V. marinus revealed the presence of fucoxanthin, violaxanthin, and zeaxanthin, which are characteristic of marine Raphidophytes within the family Chattonellaceae of the Raphidophyceae. TEM and confocal microscopy, however, revealed diagnostic microscopic and ultrastructural characteristics that distinguish it from other Raphidophytes. Chloroplasts were in close association with the nucleus and thylakoids were arranged either parallel or perpendicular to the cell surface. Putative mucocysts were identified, but trichocysts were not observed. These features, along with DNA sequence data, distinguish this species from all other Raphidophyte genera within the family Chattonellaceae of the Raphidophyceae.
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Assessment of Microzooplankton Grazing on Heterosigma akashiwo Using a Species- Specific Approach Combining Quantitative Real-Time PCR (QPCR) and Dilution Methods
Microbial Ecology, 2008Co-Authors: Elif Demir, Kathryn J. Coyne, Martina A. Doblin, Sara M. Handy, David A. HutchinsAbstract:Delaware’s Inland Bays (DIB) are subject to numerous mixed blooms of harmful Raphidophytes each year, and Heterosigma akashiwo is one of the consistently occurring species. Often, Chattonella subsalsa , C. cf. verruculosa , and Fibrocapsa japonica co-occur with H. akashiwo , indicating a dynamic consortium of Raphidophyte species. In this study, microzooplankton grazing pressure was assessed as a top–down control mechanism on H. akashiwo populations in mixed communities. Quantitative real-time polymerase chain reaction (QPCR) with species-specific primers and probes were used in conjunction with the dilution method to assess grazing pressure on H. akashiwo and other Raphidophytes. As a comparison, we measured changes in chlorophyll a (chl a ) to determine whole community growth and mortality caused by grazing. We detected grazing on H. akashiwo using QPCR in samples where chl a analyses indicated little or no grazing on the total phytoplankton community. Overall, specific microzooplankton grazing pressure on H. akashiwo ranged from 0.88 to 1.88 day^−1 at various sites. Experiments conducted on larger sympatric Raphidophytes ( C. subsalsa, C. cf. verruculosa and F. japonica ) demonstrated no significant microzooplankton grazing on these species. Grazing pressure on H. akashiwo may provide a competitive advantage to other Raphidophytes such as Chattonella spp. that are too large to be consumed at high rates by microzooplankton and help to shape the dynamics of this harmful algal bloom consortium. Our results show that QPCR can be used in conjunction with the dilution method for evaluation of microzooplankton grazing pressure on specific phytoplankton species within a mixed community.
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Simultaneous enumeration of multiple Raphidophyte species by quantitative real‐time PCR: capabilities and limitations
Limnology and Oceanography: Methods, 2006Co-Authors: Sara M. Handy, David A. Hutchins, S. Craig Cary, Kathryn J. CoyneAbstract:Quantitative real-time PCR (QPCR) is a powerful method for species-specific detection and enumeration of harmful algal bloom (HAB) algae, but can be quite time-consuming and expensive for multiple species detection when only a single species is analyzed in each reaction. Rapid enumeration methods would be valuable for the investigation of multiple HAB events such as the mixed blooms of harmful Raphidophyte species (Chattonella cf verruculosa, C. subsalsa, and Heterosigma akashiwo) that co-occur in the Delaware Inland Bays (DIB), USA. This technology uses multiple species-specific probes that fluoresce at different wavelengths and allows for the simultaneous detection and enumeration of more than one species, limited only by the detection capabilities of the instrument. The approach can cut analysis time and cost at least in half, depending on the number of species that can be accurately detected and enumerated in the mixture. Here, we compared multiprobing—or using a single primer set with species-specific probes—to multiplexing, in which species-specific primers and probes are used, targeting the 18S rDNA of 3 Raphidophyte species and an internal standard. Although both methods were effective for multispecies detection compared to simplex results, multiplexing was more accurate than multiprobing for this particular group of species. We investigated the accuracy and sensitivity of multiplex/multiprobe QPCR using plasmids, genomic DNA from cultures, or DNA extracted from environmental samples as template. Smaller amplicon size and sequence heterogeneity between amplicons increased the accuracy of the results. We found that environmental samples of Raphidophytes can be successfully multiplexed or multiprobed with only minimal losses in sensitivity. In addition, we explored probe reporter dyes and quenchers for their compatibility, robustness, and reproducibility in multitemplate detection, and we compared and evaluated the capabilities and limitations of this method for detecting and enumerating multiple phytoplankton species simultaneously.
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simultaneous enumeration of multiple Raphidophyte species by quantitative real time pcr capabilities and limitations
Limnology and Oceanography-methods, 2006Co-Authors: Sara M. Handy, David A. Hutchins, Craig S Cary, Kathryn J. CoyneAbstract:Quantitative real-time PCR (QPCR) is a powerful method for species-specific detection and enumeration of harmful algal bloom (HAB) algae, but can be quite time-consuming and expensive for multiple species detection when only a single species is analyzed in each reaction. Rapid enumeration methods would be valuable for the investigation of multiple HAB events such as the mixed blooms of harmful Raphidophyte species (Chattonella cf verruculosa, C. subsalsa, and Heterosigma akashiwo) that co-occur in the Delaware Inland Bays (DIB), USA. This technology uses multiple species-specific probes that fluoresce at different wavelengths and allows for the simultaneous detection and enumeration of more than one species, limited only by the detection capabilities of the instrument. The approach can cut analysis time and cost at least in half, depending on the number of species that can be accurately detected and enumerated in the mixture. Here, we compared multiprobing—or using a single primer set with species-specific probes—to multiplexing, in which species-specific primers and probes are used, targeting the 18S rDNA of 3 Raphidophyte species and an internal standard. Although both methods were effective for multispecies detection compared to simplex results, multiplexing was more accurate than multiprobing for this particular group of species. We investigated the accuracy and sensitivity of multiplex/multiprobe QPCR using plasmids, genomic DNA from cultures, or DNA extracted from environmental samples as template. Smaller amplicon size and sequence heterogeneity between amplicons increased the accuracy of the results. We found that environmental samples of Raphidophytes can be successfully multiplexed or multiprobed with only minimal losses in sensitivity. In addition, we explored probe reporter dyes and quenchers for their compatibility, robustness, and reproducibility in multitemplate detection, and we compared and evaluated the capabilities and limitations of this method for detecting and enumerating multiple phytoplankton species simultaneously.
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Evaluating vertical migration behavior of harmful Raphidophytes in the Delaware Inland Bays utilizing quantitative real-time PCR
Aquatic Microbial Ecology, 2005Co-Authors: Sara M. Handy, Kathryn J. Coyne, Elif Demir, Martina A. Doblin, Kevin J. Portune, Clinton E. Hare, Stephen C. Cary, David A. HutchinsAbstract:Mixed blooms of 4 species of harmful Raphidophytes (Chattonella cf. verruculosa, Chat- tonella subsalsa, Heterosigma akashiwo, and Fibrocapsa japonica) occur in the shallow (1 to 2 m) Delaware Inland Bays (DIB), USA. Raphidophytes vertically migrate in other deeper water ecosys- tems to utilize deep nutrient stocks at night, and thus obtain an advantage over non-migrating algae. Anoxic DIB sediments release high levels of bioavailable phosphate, which could potentially be used by vertically migrating flagellates. This study aimed to characterize and understand the migration patterns of DIB Raphidophytes, and determine whether benthic phosphate fluxes could provide the cells with P. We demonstrated vertical migration of isolated DIB Raphidophyte cultures in the labora- tory, where differences in the response of C. subsalsa and H. akashiwo to light:dark period manipu- lations suggested possible differences in external versus endogenous regulation of migration behav- ior in the 2 species. Natural blooms in the field (enclosed in a mesocosm system) also exhibited patterns of diel vertical migration, as determined by quantitative real-time PCR (QPCR) used to enumerate the diel vertical distributions of each species. Our data suggested that these 2 photoauto- trophic species spend daylight hours near the surface and are found directly on the sediment surface at night. However, diel changes in particulate C:P ratios did not support the hypothesis that there is preferential uptake of sedimentary phosphate at night. Our results also suggested that the migration behavior may have important implications for designing sampling strategies for monitoring pro- grams. QPCR has a number of decisive advantages over traditional microscopic counting methods, making this a powerful tool for fine spatial and temporal scale detection and enumeration of vertically migrating harmful algal species.