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Lisa Campbell - One of the best experts on this subject based on the ideXlab platform.
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chemical analysis of Karenia papilionacea
Toxicon, 2015Co-Authors: Nicholas Fowler, Lisa Campbell, Daniel G. Baden, Carmelo Tomas, Andrea J. BourdelaisAbstract:One of the most widely studied organisms responsible for Harmful Algal Blooms (HABs) is the marine dinoflagellate Karenia brevis. This organism produces neurotoxic compounds known as brevetoxins. A related dinoflagellate, Karenia papilionacea, has been reported to occasionally co-bloom with K. brevis but has received little attention as a possible toxin producing species. Therefore, our aim was to investigate the toxin profile for K. papilionacea. A toxic fraction was identified using a cell based cytotoxicity assay and the toxin was isolated and identified as the ladder frame polyether brevetoxin-2 (PbTx-2) using mass spectrometry (MS) and nuclear magnetic resonance (NMR). Toxin production in K. papilionacea increased in response to hypoosmotic stress, as previously observed in K. brevis.
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de novo assembly and characterization of the transcriptome of the toxic dinoflagellate Karenia brevis
BMC Genomics, 2014Co-Authors: Darcie E Ryan, Alan E Pepper, Lisa CampbellAbstract:Karenia brevis is a harmful algal species that blooms in the Gulf of Mexico and produces brevetoxins that cause neurotoxic shellfish poisoning. Elevated brevetoxin levels in K. brevis cells have been measured during laboratory hypo-osmotic stress treatments. To investigate mechanisms underlying K. brevis osmoacclimation and osmoregulation and establish a valuable resource for gene discovery, we assembled reference transcriptomes for three clones: Wilson-CCFWC268, SP3, and SP1 (a low-toxin producing variant). K. brevis transcriptomes were annotated with gene ontology terms and searched for putative transmembrane proteins that may elucidate cellular responses to hypo-osmotic stress. An analysis of single nucleotide polymorphisms among clones was used to characterize genetic divergence. K. brevis reference transcriptomes were assembled with 58.5 (Wilson), 78.0 (SP1), and 51.4 million (SP3) paired reads. Transcriptomes contained 86,580 (Wilson), 93,668 (SP1), and 84,309 (SP3) predicted transcripts. Approximately 40% of the transcripts were homologous to proteins in the BLAST nr database with an E value ≤ 1.00E-6. Greater than 80% of the highly conserved CEGMA core eukaryotic genes were identified in each transcriptome, which supports assembly completeness. Seven putative voltage-gated Na+ or Ca2+ channels, two aquaporin-like proteins, and twelve putative VATPase subunits were discovered in all clones using multiple bioinformatics approaches. Furthermore, 45% (Wilson) and 43% (SP1 and SP3) of the K. brevis putative peptides > 100 amino acids long produced significant hits to a sequence in the NCBI nr protein database. Of these, 77% (Wilson and SP1) and 73% (SP3) were successfully assigned gene ontology functional terms. The predicted single nucleotide polymorphism (SNP) frequencies between clones were 0.0028 (Wilson to SP1), 0.0030 (Wilson to SP3), and 0.0028 (SP1 to SP3). The K. brevis transcriptomes assembled here provide a foundational resource for gene discovery and future RNA-seq experiments. The identification of ion channels, VATPases, and aquaporins in all three transcriptomes indicates that K. brevis regulates cellular ion and water concentrations via transmembrane proteins. Additionally, > 40,000 unannotated loci may include potentially novel K. brevis genes. Ultimately, the SNPs identified among the three ecologically diverse clones with different toxin profiles may help to elucidate variations in K. brevis brevetoxin production.
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reponses of the dinoflagellate Karenia brevis to climate change pco2 and sea surface temperatures
Harmful Algae, 2014Co-Authors: Reagan M. Errera, Shari A Yvonlewis, John D Kessler, Lisa CampbellAbstract:Abstract Increasing atmospheric CO2 is promoting ocean acidification and higher global temperatures and has been suggested as a possible factor for shifts in marine phytoplankton composition to more harmful species. Karenia brevis is the major harmful algal species in the Gulf of Mexico producing potent neurotoxins known as brevetoxins. We examined how changes in ocean inorganic carbon chemistry associated with pre-industrial (250 ppm), recent (350 ppm), and predicted at 2100 (1000 ppm) pCO2 levels and increased temperature affect growth rates and brevetoxin production in K. brevis. At the predicted pCO2 levels for 2100, growth rate of K. brevis Wilson clone increased substantially by 46% at 25 °C (0.43 ± 0.01 d−1) compared to recent and pre-industrial levels (0.29 ± 0.01 d−1). Growth rates also increased for a low brevetoxin-producing clone, SP1, from 0.24 ± 0.02 d−1 at lower pCO2 levels to 0.33 ± 0.003 d−1 at a pCO2 of 1000 ppm. When grown at a higher temperature (30 °C), growth rates for the Wilson clone significantly decreased at all three pCO2 by approximately 30%. However, even at the higher temperature, K. brevis growth rate significantly increased by 30% (0.30 ± 0.01 d−1) at the 1000 ppm CO2 level when compared to recent and pre-industrial CO2 levels (0.21 ± 0.01 d−1). Although K. brevis growth rate decreased at higher temperatures, the growth rate at pCO2 level of 1000 and 30 °C was slightly higher than at current conditions (pCO2 level of 350 and 25 °C). Modification of pCO2 levels and temperatures did not have an effect on total brevetoxin production or brevetoxin profiles in either clone examined. Due to the increased growth rate, total brevetoxin production was significantly higher at the pCO2 level of 1000. Finally, from these results we conclude there is no connection between growth rate and brevetoxin per cell. Although neither pCO2 nor temperature influenced brevetoxin production per cell, we suggest that under predicted future climate conditions K. brevis blooms have the potential to produce higher cell concentrations and increased brevetoxin concentrations, which will pose an increased risk for ecosystem and human health.
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Continuous automated imaging-in-flow cytometry for detection and early warning of Karenia brevis blooms in the Gulf of Mexico
Environmental Science and Pollution Research, 2013Co-Authors: Lisa Campbell, Darren W. Henrichs, Robert J. Olson, Heidi M. SosikAbstract:Monitoring programs for harmful algal blooms (HABs) typically rely on time-consuming manual methods for identification and enumeration of phytoplankton, which make it difficult to obtain results with sufficient temporal resolution for early warning. Continuous automated imaging-in-flow by the Imaging FlowCytobot (IFCB) deployed at Port Aransas, TX has provided early warnings of six HAB events. Here we describe the progress in automating this early warning system for blooms of Karenia brevis . In 2009, manual inspection of IFCB images in mid-August 2009 provided early warning for a Karenia bloom that developed in mid-September. Images from 2009 were used to develop an automated classifier that was employed in 2011. Successful implementation of automated file downloading, processing and image classification allowed results to be available within 4 h after collection and to be sent to state agency representatives by email for early warning of HABs. No human illness (neurotoxic shellfish poisoning) has resulted from these events. In contrast to the common assumption that Karenia blooms are near monospecific, post-bloom analysis of the time series revealed that Karenia cells comprised at most 60–75 % of the total microplankton.
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Osmotic stress does trigger brevetoxin production in the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Reagan M. Errera, Lisa CampbellAbstract:Although a number of factors may influence its production, the physiological role of brevetoxin in the dinoflagellate Karenia brevis is still open to debate. Not to be left out of the discussion, Sunda et al. (1) challenge our suggestion that salinity stress may be a possible trigger for brevetoxin production. Their “repeat” of our experiment is not an actual replication (extraction protocols, analytical method, K. brevis isolates, and culturing conditions differed among their three laboratories). Moreover, a number of experimental details, including use of internal standards and preparation of toxin standards, are omitted. Internal standards are important because extraction efficiency varies among samples and could affect results. Nevertheless, both reports show that there is no long-term increase in brevetoxin production after salinity stress (1, 2) and that low-toxin cultures [SP1 (2) and “nontoxic” Wilson (1)] do not increase brevetoxin production in response to hypoosmotic stress.
Cynthia A Heil - One of the best experts on this subject based on the ideXlab platform.
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nitrogen uptake and regeneration ammonium regeneration nitrification and photoproduction in waters of the west florida shelf prone to blooms of Karenia brevis
Harmful Algae, 2014Co-Authors: Deborah A Bronk, Cynthia A Heil, Lynn Killbergthoreson, Rachel E Sipler, Margaret R Mulholland, Quinn N Roberts, Peter W Bernhardt, Matthew Garrett, Judith M OneilAbstract:Abstract The West Florida Shelf (WFS) encompasses a range of environments from inshore estuarine to offshore oligotrophic waters, which are frequently the site of large and persistent blooms of the toxic dinoflagellate, Karenia brevis. The goals of this study were to characterize the nitrogen (N) nutrition of plankton across the range of environmental conditions on the WFS, to quantify the percentage of the plankton N demand met through in situ N regeneration, and to determine whether planktonic N nutrition changes when high concentrations of Karenia are present. In the fall of 2007, 2008, and 2009 we measured ambient nutrient concentrations and used stable isotope techniques to measure rates of primary production and uptake rates of inorganic N (ammonium, NH4+, and nitrate, NO3−), and organic N and carbon (C; urea and amino acids, AA) in estuarine, coastal, and offshore waters, as well as coastal sites with Karenia blooms present. In parallel, we also measured rates of in situ N regeneration – NH4+ regeneration, nitrification, and photoproduction of NH4+, nitrite and AA. Based on microscope observations, ancillary measurements, and previous monitoring history, Karenia blooms sampled represented three bloom stages – initiation in 2008, maintenance in 2007, and late maintenance/stationary phase in 2009. Nutrient concentrations were highest at estuarine sampling sites and lowest at offshore sites. Uptake of NH4+ and NO3− provided the largest contribution to N nutrition at all sites. At the non-Karenia sites, in situ rates of NH4+ regeneration and nitrification were generally sufficient to supply these substrates equal to the rates at which they were taken up. At Karenia sites, NO3− was the most important N substrate during the initiation phase, while NH4+ was the most important N form used during bloom maintenance and stationary phases. Rates of NH4+ regeneration were high but insufficient (85 ± 36% of uptake) to support the measured NH4+ uptake at all the Karenia sites although nitrification rates far exceeded uptake rates of NO3−. Taken together our results support the “no smoking gun” nutrient hypothesis that there is no single nutrient source or strategy that can explain Karenia's frequent dominance in the waters where it occurs. Consistent with other papers in this volume, our results indicate that Karenia can utilize an array of inorganic and organic N forms from a number of N sources.
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monitoring management and mitigation of Karenia blooms in the eastern gulf of mexico
Harmful Algae, 2009Co-Authors: Cynthia A Heil, Karen A SteidingerAbstract:Abstract Annual blooms of the toxic dinoflagellate Karenia brevis in the eastern Gulf of Mexico represent one of the most predictable global harmful algal bloom (HAB) events, yet remain amongst the most difficult HABs to effectively monitor for human and environmental health. Monitoring of Karenia blooms is necessary for a variety of precautionary, management and predictive purposes. These include the protection of public health from exposure to aerosolized brevetoxins and the consumption of toxic shellfish, the protection and management of environmental resources, the prevention of bloom associated economic losses, and the evaluation of long term ecosystem trends and for potential future bloom forecasting and prediction purposes. The multipurpose nature of Karenia monitoring, the large areas over which blooms occur, the large range of Karenia cell concentrations (from 5 × 103 cells L−1 to >1 × 106 cells L−1) over which multiple bloom impacts are possible, and limitations in resources and knowledge of bloom ecology have complicated K. brevis monitoring, mitigation and management strategies. Historically, K. brevis blooms were informally and intermittently monitored on an event response basis in Florida, usually in the later bloom stages after impacts (e.g. fish kills, marine mammal mortalities, respiratory irritation) were noted and when resources were available. Monitoring of different K. brevis bloom stages remains the most practical method for predicting human health impacts and is currently accomplished by the state of Florida via direct microscopic counts of water samples from a state coordinated volunteer HAB monitoring program. K. brevis cell concentrations are mapped weekly and disseminated to stakeholders via e-mail, web and toll-free phone numbers and provided to Florida Department of Agriculture and Consumer Services (FDACS) for management of both recreational and commercial shellfish beds in Florida and to the National Oceanic and Atmospheric Administration (NOAA) for validation of the NOAA Gulf of Mexico HAB bulletin for provision to environmental managers. Many challenges remain for effective monitoring and management of Karenia blooms, however, including incorporating impact specific monitoring for the diverse array of potential human and environmental impacts associated with blooms, timely detection of offshore bloom initiation, sampling of the large geographic extent of blooms which often covers multiple state boundaries, and the involvement of multiple Karenia species other than K. brevis (several of which have yet to be isolated and described) with unknown toxin profiles. The implementation and integration of a diverse array of optical, molecular and hybrid Karenia detection technologies currently under development into appropriate regulatory and non-regulatory monitoring formats represents a further unique challenge.
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nutrient availability in support of Karenia brevis blooms on the central west florida shelf what keeps Karenia blooming
Continental Shelf Research, 2008Co-Authors: Gabriel A Vargo, Cynthia A Heil, Kent A Fanning, Kellie L Dixon, Merrie Beth Neely, Kristen M Lester, Danylle Ault, Susan Murasko, Julie Havens, John WalshAbstract:Abstract Identifying nutrient sources, primarily nitrogen (N) and phosphorus (P), sufficient to support high biomass blooms of the red tide dinoflagellate, Karenia brevis, has remained problematic. The West Florida Shelf is oligotrophic, yet populations >106 cells L−1 frequently occur and blooms can persist for months. Here we examine the magnitude and variety of sources for N and P that are available to support blooms. Annual average in situ or background concentrations of inorganic N in the region where blooms occur range 0.02–0.2 μM while inorganic P ranges 0.025–0.24 μM. Such concentrations would be sufficient to support the growth of populations up to ∼3×104 cells L−1 with at least a 1 d turnover rate. Organic N concentrations average 1–2 orders of magnitude greater than inorganic N, 8–14 μM while organic P concentrations average 0.2–0.5 μM. Concentrations of organic N are sufficient to support blooms >105 cells L−1 but the extent to which this complex mixture of N species is utilizable is unknown. Other sources of nutrients included in our analysis are aerial deposition, estuarine flux, benthic flux, zooplankton excretion, N2-fixation, and subsequent release of organic and inorganic N by Trichodesmium spp., and release of N and P from dead and decaying fish killed by the blooms. Inputs based on atmospheric deposition, benthic flux, and N2-fixation, were minor contributors to the flux required to support growth of populations >2.6×104 cells L−1. N and P from decaying fish could theoretically maintain populations at moderate concentrations but insufficient data on the flux and subsequent mixing rates does not allow us to calculate average values. Zooplankton excretion rates, based on measured zooplankton population estimates and excretion rates could also supply all of the N and P required to support populations of 105 and 106 cells L−1, respectively, but excretion is considered as “regenerated” nutrient input and can only maintain biomass rather than contribute to “new” biomass. The combined estuarine flux from Tampa Bay, Charlotte Harbor, and the Caloosahatchee River can supply a varying, but at times significant level of N and P to meet growth and photosynthesis requirements for populations of approximately 105 cells L−1 or below. Estimates of remineralization of dead fish could supply a significant proportion of bloom maintenance requirements but the rate of supply must still be determined. Overall, a combination of sources is required to maintain populations >106 cells L−1.
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On the remote monitoring of Karenia brevis blooms of the west Florida shelf
Continental Shelf Research, 2008Co-Authors: Remy Luerssen, Frank E. Muller-karger, Kendall L. Carder, Cynthia A HeilAbstract:Abstract In situ surveys (1997–2002) of Karenia brevis distribution on the west Florida shelf were used to explain spectral remote sensing reflectance, chlorophyll- a concentration, and backscattering coefficient estimates derived using SeaWiFS satellite data. Two existing approaches were tested in an attempt to differentiate K. brevis blooms from other blooms or plumes. A chlorophyll-anomaly method used operationally by the National Oceanic and Atmospheric Administration (NOAA) sometimes correctly identified K. brevis blooms but also generated false positives and false negatives. The method identified approximately 1000 km 2 of high chlorophyll-anomalies (>1 mg m −3 ) off southwest Florida between the 10 and 50-m isobaths nearly every day from summer to late fall. Whether these patches were K. brevis blooms or not is unknown. A second method used a backscattering:chlorophyll- a ratio to identify K. brevis patches. This method separated K. brevis from other blooms using in situ optical data, but it yielded less satisfactory results with SeaWiFS data. Spectral reflectance ( R rs ) estimates for K. brevis blooms, diatom blooms, and coastal river plumes are statistically similar for many cases. Large pixel size, shallow water, and imperfect algorithms distort satellite retrievals of bio-optical parameters in patchy blooms. At present, a combination of chlorophyll- a , chlorophyll-anomaly, backscattering:chlorophyll- a ratio, RGB composites, MODIS fluorescence data, as well as time-series analysis and ancillary data such as winds, currents, and sea surface temperature can improve K. brevis bloom assessments. Progress in atmospheric correction and bio-optical inversion algorithms is required to help improve capabilities to monitor K. brevis blooms from space. Further, satellite sensors with improved radiometric capabilities and temporal/spatial resolutions are also required.
Karen A Steidinger - One of the best experts on this subject based on the ideXlab platform.
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historical perspective on Karenia brevis red tide research in the gulf of mexico
Harmful Algae, 2009Co-Authors: Karen A SteidingerAbstract:Abstract Research on Karenia brevis blooms in the Gulf of Mexico started with the 1946–1947 red tide along the Florida west coast. Early research was on the organism itself, its tolerances and requirements, and the environment in which it lived and grew. Control of blooms, as a management option, was pursued in the 1950s with little success. However, in the 1960s–1970s, new regulation of shellfish growing areas was a public health management success. Research on K. brevis blooms followed funding cycles and was sporadic until the late 1990s when the National Oceanic and Atmospheric Administration (NOAA) and the Environmental Protection Agency (EPA) funded the Ecology and Oceanography of Harmful Algal Blooms (ECOHAB) and NOAA Monitoring and Event Response of Harmful Algal Blooms (MERHAB) programs. These particular funding programs, augmented by State of Florida appropriations, provided the opportunity to study K. brevis blooms on different temporal-spatial scales and consequently advanced the science. This review looks at historical research results in the light of today's advances.
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monitoring management and mitigation of Karenia blooms in the eastern gulf of mexico
Harmful Algae, 2009Co-Authors: Cynthia A Heil, Karen A SteidingerAbstract:Abstract Annual blooms of the toxic dinoflagellate Karenia brevis in the eastern Gulf of Mexico represent one of the most predictable global harmful algal bloom (HAB) events, yet remain amongst the most difficult HABs to effectively monitor for human and environmental health. Monitoring of Karenia blooms is necessary for a variety of precautionary, management and predictive purposes. These include the protection of public health from exposure to aerosolized brevetoxins and the consumption of toxic shellfish, the protection and management of environmental resources, the prevention of bloom associated economic losses, and the evaluation of long term ecosystem trends and for potential future bloom forecasting and prediction purposes. The multipurpose nature of Karenia monitoring, the large areas over which blooms occur, the large range of Karenia cell concentrations (from 5 × 103 cells L−1 to >1 × 106 cells L−1) over which multiple bloom impacts are possible, and limitations in resources and knowledge of bloom ecology have complicated K. brevis monitoring, mitigation and management strategies. Historically, K. brevis blooms were informally and intermittently monitored on an event response basis in Florida, usually in the later bloom stages after impacts (e.g. fish kills, marine mammal mortalities, respiratory irritation) were noted and when resources were available. Monitoring of different K. brevis bloom stages remains the most practical method for predicting human health impacts and is currently accomplished by the state of Florida via direct microscopic counts of water samples from a state coordinated volunteer HAB monitoring program. K. brevis cell concentrations are mapped weekly and disseminated to stakeholders via e-mail, web and toll-free phone numbers and provided to Florida Department of Agriculture and Consumer Services (FDACS) for management of both recreational and commercial shellfish beds in Florida and to the National Oceanic and Atmospheric Administration (NOAA) for validation of the NOAA Gulf of Mexico HAB bulletin for provision to environmental managers. Many challenges remain for effective monitoring and management of Karenia blooms, however, including incorporating impact specific monitoring for the diverse array of potential human and environmental impacts associated with blooms, timely detection of offshore bloom initiation, sampling of the large geographic extent of blooms which often covers multiple state boundaries, and the involvement of multiple Karenia species other than K. brevis (several of which have yet to be isolated and described) with unknown toxin profiles. The implementation and integration of a diverse array of optical, molecular and hybrid Karenia detection technologies currently under development into appropriate regulatory and non-regulatory monitoring formats represents a further unique challenge.
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effect of salinity on the distribution growth and toxicity of Karenia spp
Harmful Algae, 2006Co-Authors: Alisa Maier F Brown, Frances M. Van Dolah, Karen A Steidinger, Bill Richardson, Quay Dortch, Tod A Leighfield, Wendy Morrison, Anne E Thessen, Cynthia A Moncreiff, Jonathan PennockAbstract:Abstract The first recorded bloom of Karenia spp., resulting in brevetoxin in oysters, in the low salinity waters of the Northern Gulf of Mexico (NGOMEX) occurred in November 1996. It raised questions about the salinity tolerance of Karenia spp., previously considered unlikely to occur at salinities
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comparative morphology and molecular phylogenetic analysis of three new species of the genus Karenia dinophyceae from new zealand
Journal of Phycology, 2004Co-Authors: Allison J Haywood, Karen A Steidinger, Earnest W Truby, Patricia R Bergquist, Peter L Bergquist, Janet Adamson, Lincoln MackenzieAbstract:Three new dinoflagellate species, Karenia papilionacea sp. nov., Karenia selliformis sp. nov., and Karenia bidigitata sp. nov., were compared with the toxic species Karenia mikimotoi (Miyake & Kominami ex Oda) G. Hansen & Moestrup, Karenia brevis (Davis) G. Hansen & Moestrup, and Karenia brevisulcata (Chang) G. Hansen & Moestrup using the same fixative. Distinguishing morphological characters for the genus Karenia included a smooth theca and a linear apical groove. The new species can be distinguished on the basis of morphological characters of vegetative cells that include the location and shape of the nucleus; the relative excavation of the hypotheca; the characteristics of apical and sulcal groove extensions on the epitheca; the cellular shape, size, and symmetry; the degree of dorsoventral compression; and the presence of an apical protrusion or carina. Species with pronounced dorsoventral compression swim in a distinctive fluttering motion. An intercingular tubular structure traversing the proximal and distal ends of the cingulum is common to the species of Karenia, Karlodinium micrum (Leadbeater & Dodge) J. Larsen, Gymnodinium pulchellum J. Larsen, and Gyrodinium corsicum Paulmier. Molecular phylogenetic analyses of rDNA sequence alignments show that the new species are phylogenetically distinct but closely related to K. mikimotoi and K. brevis.
William G Sunda - One of the best experts on this subject based on the ideXlab platform.
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Increased Toxicity of Karenia brevis during Phosphate Limited Growth: Ecological and Evolutionary Implications
2016Co-Authors: Rance Hardison, William G Sunda, See Profile, Damian Shea, Richard Wayne Litaker, Donnie Ransom HardisonAbstract:Karenia brevis is the dominant toxic red tide algal species in the Gulf of Mexico. It produces potent neurotoxins (brevetoxins [PbTxs]), which negatively impact human and animal health, local economies, and ecosystem function. Field measurements have shown that cellular brevetoxin contents vary from 1–68 pg/cell but the source of this variability is uncertain. Increases in cellular toxicity caused by nutrient-limitation and inter-strain differences have been observed in many algal species. This study examined the effect of P-limitation of growth rate on cellular toxin concentrations in five Karenia brevis strains from different geographic locations. Phosphorous was selected because of evidence for regional P-limitation of algal growth in the Gulf of Mexico. Depending on the isolate, P-limited cells had 2.3- to 7.3-fold higher PbTx per cell than P-replete cells. The percent of cellular carbon associated with brevetoxins (%C-PbTx) was, 0.7 to 2.1 % in P-replete cells, but increased to 1.6– 5 % under P-limitation. Because PbTxs are potent anti-grazing compounds, this increased investment in PbTxs shoul
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osmotic stress does not trigger brevetoxin production in the dinoflagellate Karenia brevis
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: William G Sunda, Leanne J Flewelling, Alina A. Corcoran, Jennifer L. Wolny, Cheska Burleson, Ransom D Hardison, Jeanine S Morey, Zhihong Wang, Frances M Van DolahAbstract:With the global proliferation of toxic harmful algal bloom species, there is a need to identify the environmental and biological factors that regulate toxin production. One such species, Karenia brevis, forms nearly annual blooms that threaten coastal regions throughout the Gulf of Mexico. This dinoflagellate produces brevetoxins, which are potent neurotoxins that cause neurotoxic shellfish poisoning and respiratory illness in humans, as well as massive fish kills. A recent publication reported that a rapid decrease in salinity increased cellular toxin quotas in K. brevis and hypothesized that brevetoxins serve a role in osmoregulation. This finding implied that salinity shifts could significantly alter the toxic effects of blooms. We repeated the original experiments separately in three different laboratories and found no evidence for increased brevetoxin production in response to low-salinity stress in any of the eight K. brevis strains we tested, including three used in the original study. Thus, we find no support for an osmoregulatory function of brevetoxins. The original publication also stated that there was no known cellular function for brevetoxins. However, there is increasing evidence that brevetoxins promote survival of the dinoflagellates by deterring grazing by zooplankton. Whether they have other as-yet-unidentified cellular functions is currently unknown.
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Increased Toxicity of Karenia brevis during Phosphate Limited Growth: Ecological and Evolutionary Implications
PloS one, 2013Co-Authors: Donnie Ransom Hardison, William G Sunda, Damian Shea, Richard Wayne LitakerAbstract:Karenia brevis is the dominant toxic red tide algal species in the Gulf of Mexico. It produces potent neurotoxins (brevetoxins [PbTxs]), which negatively impact human and animal health, local economies, and ecosystem function. Field measurements have shown that cellular brevetoxin contents vary from 1–68 pg/cell but the source of this variability is uncertain. Increases in cellular toxicity caused by nutrient-limitation and inter-strain differences have been observed in many algal species. This study examined the effect of P-limitation of growth rate on cellular toxin concentrations in five Karenia brevis strains from different geographic locations. Phosphorous was selected because of evidence for regional P-limitation of algal growth in the Gulf of Mexico. Depending on the isolate, P-limited cells had 2.3- to 7.3-fold higher PbTx per cell than P-replete cells. The percent of cellular carbon associated with brevetoxins (%C-PbTx) was ∼ 0.7 to 2.1% in P-replete cells, but increased to 1.6–5% under P-limitation. Because PbTxs are potent anti-grazing compounds, this increased investment in PbTxs should enhance cellular survival during periods of nutrient-limited growth. The %C-PbTx was inversely related to the specific growth rate in both the nutrient-replete and P-limited cultures of all strains. This inverse relationship is consistent with an evolutionary tradeoff between carbon investment in PbTxs and other grazing defenses, and C investment in growth and reproduction. In aquatic environments where nutrient supply and grazing pressure often vary on different temporal and spatial scales, this tradeoff would be selectively advantageous as it would result in increased net population growth rates. The variation in PbTx/cell values observed in this study can account for the range of values observed in the field, including the highest values, which are not observed under N-limitation. These results suggest P-limitation is an important factor regulating cellular toxicity and adverse impacts during at least some K. brevis blooms.
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nitrogen limitation increases brevetoxins in Karenia brevis dinophyceae implications for bloom toxicity 1
Journal of Phycology, 2012Co-Authors: Ransom D Hardison, William G Sunda, Damian Shea, Wayne R Litaker, Patricia A. TesterAbstract:Laboratory and field measurements of the toxin content in Karenia brevis cells vary by >4-fold. These differences have been largely attributed to genotypic variations in toxin production among strains. We hypothesized that nutrient limitation of growth rate is equally or more important in controlling the toxicity of K. brevis, as has been documented for other toxic algae. To test this hypothesis, we measured cellular growth rate, chlorophyll a, cellular carbon and nitrogen, cell volume, and brevetoxins in four strains of K. brevis grown in nutrient-replete and nitrogen (N)-limited semi-continuous cultures. N-limitation resulted in reductions of chlorophyll a, growth rate, volume per cell and nirtogen:carbon (N:C) ratios as well as a two-fold increase (1%-4% to 5%-9%) in the percentage of cellular carbon present as brevetoxins. The increase in cellular brevetoxin concentrations was consistent among genetically distinct strains. Normalizing brevetoxins to cellular volume instead of per cell eliminated much of the commonly reported toxin variability among strains. These results suggest that genetically linked differences in cellular volume may affect the toxin content of K. brevis cells as much or more than innate genotypic differences in cellular toxin content per unit of biomass. Our data suggest at least some of the >4-fold difference in toxicity per cell reported from field studies can be explained by limitation by nitrogen or other nutrients and by differences in cell size. The observed increase in brevetoxins in nitrogen limited cells is consistent with the carbon:nutrient balance hypothesis for increases in toxins and other plant defenses under nutrient limitation.
Patricia A. Tester - One of the best experts on this subject based on the ideXlab platform.
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nitrogen limitation increases brevetoxins in Karenia brevis dinophyceae implications for bloom toxicity 1
Journal of Phycology, 2012Co-Authors: Ransom D Hardison, William G Sunda, Damian Shea, Wayne R Litaker, Patricia A. TesterAbstract:Laboratory and field measurements of the toxin content in Karenia brevis cells vary by >4-fold. These differences have been largely attributed to genotypic variations in toxin production among strains. We hypothesized that nutrient limitation of growth rate is equally or more important in controlling the toxicity of K. brevis, as has been documented for other toxic algae. To test this hypothesis, we measured cellular growth rate, chlorophyll a, cellular carbon and nitrogen, cell volume, and brevetoxins in four strains of K. brevis grown in nutrient-replete and nitrogen (N)-limited semi-continuous cultures. N-limitation resulted in reductions of chlorophyll a, growth rate, volume per cell and nirtogen:carbon (N:C) ratios as well as a two-fold increase (1%-4% to 5%-9%) in the percentage of cellular carbon present as brevetoxins. The increase in cellular brevetoxin concentrations was consistent among genetically distinct strains. Normalizing brevetoxins to cellular volume instead of per cell eliminated much of the commonly reported toxin variability among strains. These results suggest that genetically linked differences in cellular volume may affect the toxin content of K. brevis cells as much or more than innate genotypic differences in cellular toxin content per unit of biomass. Our data suggest at least some of the >4-fold difference in toxicity per cell reported from field studies can be explained by limitation by nitrogen or other nutrients and by differences in cell size. The observed increase in brevetoxins in nitrogen limited cells is consistent with the carbon:nutrient balance hypothesis for increases in toxins and other plant defenses under nutrient limitation.
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hydrodynamic accumulation of Karenia off the west coast of florida
Continental Shelf Research, 2008Co-Authors: Richard P. Stumpf, Wayne R Litaker, Lyon W J Lanerolle, Patricia A. TesterAbstract:Abstract Blooms of the toxic dinoflagellates, Karenia spp. occur nearly annually in the eastern Gulf of Mexico with cell abundances typically >10 5 cells L −1 . Thermal and ocean color satellite imagery shows sea surface temperature patterns indicative of upwelling events and the concentration of chlorophyll at fronts along the west Florida continental shelf. Daily cell counts of Karenia show greater increases in cell concentrations at fronts than can be explained by Karenia 's maximum specific growth rate. This is observed in satellite images as up to a 10-fold greater increase in chlorophyll biomass over 1–2 d periods than can be explained by in situ growth. In this study, we propose a model that explains why surface blooms of Karenia may develop even when nutrients on the west Florida shelf are low. In the summer, northward winds produce a net flow east and southeast bringing water and nutrients from the Mississippi River plume onto the west Florida shelf at depths of 20–50 m. This water mass supplies utilizable inorganic and organic forms of nitrogen that promote the growth of Karenia to pre-bloom concentrations in sub-surface waters in the mid-shelf region. In the fall, a change to upwelling favorable winds produces onshore transport. This transport, coupled with the swimming behavior of Karenia , leads to physical accumulation at frontal regions near the coast, resulting in fall blooms. Strong thermal fronts during the winter provide a mechanism for re-intensification of the blooms, if Karenia cells are located north of the fronts. This conceptual model leads to testable hypotheses on bloom development throughout the Gulf of Mexico.
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Sublethal effects of the toxic dinoflagellate Karenia brevis on marine copepod behavior
Journal of Plankton Research, 2007Co-Authors: Jonathan H. Cohen, Patricia A. Tester, Richard B. ForwardAbstract:Apart from grazing interactions, little is known regarding the sublethal effects of Karenia brevis cells on copepod behavior. We conducted grazing and mortality experiments with K. brevis cells and brevetoxins (PbTx-2), establishing routes of toxicity for the copepods Acartia tonsa, Temora turbinata and Centropages typicus. Subsequent behavioral experiments determined whether copepod swimming and photobehavior, both behaviors involved in predator avoidance, were impaired at sublethal K. brevis and PbTx-2 levels. Copepods variably grazed toxic K. brevis and non-toxic Prorocentrum minimum at bloom concentrations. Although copepods accumulated brevetoxins, significant mortality was only observed in T turbinata at the highest test concentration (1 x 10 7 K. brevis cells L -1 ). Acartia tonsa exhibited minimal sublethal behavioral effects. However, there were significant effects on the swimming and photobehavior of T. turbinata and C. typicus at the lowest sublethal concentrations tested (0.15 μg PbTx-2 L -1 , 1 x 10 5 K. brevis cells L -1 ). Although physiological incapacitation may have altered copepod behavior, starvation likely played a major role as well. These data suggest that sublethal effects of K. brevis and brevetoxin on copepod behavior occur and predicting the role of zooplankton grazers in trophic transfer of algal toxins requires knowledge of species-specific sublethal effects.
