Erdner Deana L.

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Erdner

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Deana L.

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Development of microsatellite markers in the toxic dinoflagellate Alexandrium minutum (Dinophyceae)

( 2006-01-22) Nagai, Satoshi ; McCauley, Linda A. R. ; Yasuda, N. ; Erdner, Deana L. ; Kulis, David M. ; Matsuyama, Y. ; Itakura, S. ; Anderson, Donald M.

Outbreaks of paralytic shellfish poisoning caused by the toxic dinoflagellate Alexandrium minutum (Dinophyceae) are a worldwide concern from both the economic and human health points of view. For population genetic studies of A. minutum distribution and dispersal, highly polymorphic genetic markers are of great value. We isolated 12 polymorphic microsatellites from this cosmopolitan, toxic dinoflagellate species. These loci provide one class of highly variable genetic markers, as the number of alleles ranged from 4 to 12, and the estimate of gene diversity was from 0.560 to 0.862 across the 12 microsatellites; these loci have the potential to reveal genetic structure and gene flow among A. minutum populations.
Global transcriptional profiling of the toxic dinoflagellate Alexandrium fundyense using Massively Parallel Signature Sequencing

(BioMed Central, 2006-04-25) Erdner, Deana L. ; Anderson, Donald M.

Dinoflagellates are one of the most important classes of marine and freshwater algae, notable both for their functional diversity and ecological significance. They occur naturally as free-living cells, as endosymbionts of marine invertebrates and are well known for their involvement in "red tides". Dinoflagellates are also notable for their unusual genome content and structure, which suggests that the organization and regulation of dinoflagellate genes may be very different from that of most eukaryotes. To investigate the content and regulation of the dinoflagellate genome, we performed a global analysis of the transcriptome of the toxic dinoflagellate Alexandrium fundyense under nitrate- and phosphate-limited conditions using Massively Parallel Signature Sequencing (MPSS).
Chemical data associated with field collections from the Gulf of Maine, Nauset Marsh Estuary System, and Long Island Sound (Alexandrium isotopes project)

(Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2019-03-20) Smith, Juliette L. ; Anderson, Donald M. ; Erdner, Deana L. ; McClelland, James W.

Chemical data associated with field collections from the Gulf of Maine, Nauset Marsh Estuary System, and Long Island Sound (Alexandrium isotopes project) For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/712027
Transcriptome profiling of a toxic dinoflagellate reveals a gene-rich protist and a potential impact on gene expression due to bacterial presence

(Public Library of Science, 2010-03-12) Moustafa, Ahmed ; Evans, Andrew N. ; Kulis, David M. ; Hackett, Jeremiah D. ; Erdner, Deana L. ; Anderson, Donald M. ; Bhattacharya, Debashish

Dinoflagellates are unicellular, often photosynthetic protists that play a major role in the dynamics of the Earth's oceans and climate. Sequencing of dinoflagellate nuclear DNA is thwarted by their massive genome sizes that are often several times that in humans. However, modern transcriptomic methods offer promising approaches to tackle this challenging system. Here, we used massively parallel signature sequencing (MPSS) to understand global transcriptional regulation patterns in Alexandrium tamarense cultures that were grown under four different conditions. We generated more than 40,000 unique short expression signatures gathered from the four conditions. Of these, about 11,000 signatures did not display detectable differential expression patterns. At a p-value < 1E-10, 1,124 signatures were differentially expressed in the three treatments, xenic, nitrogen-limited, and phosphorus-limited, compared to the nutrient-replete control, with the presence of bacteria explaining the largest set of these differentially expressed signatures. Among microbial eukaryotes, dinoflagellates contain the largest number of genes in their nuclear genomes. These genes occur in complex families, many of which have evolved via recent gene duplication events. Our expression data suggest that about 73% of the Alexandrium transcriptome shows no significant change in gene expression under the experimental conditions used here and may comprise a “core” component for this species. We report a fundamental shift in expression patterns in response to the presence of bacteria, highlighting the impact of biotic interaction on gene expression in dinoflagellates.
Insights into the loss factors of phytoplankton blooms : the role of cell mortality in the decline of two inshore Alexandrium blooms

( 2017-01) Choi, Chang Jae ; Brosnahan, Michael L. ; Sehein, Taylor R. ; Anderson, Donald M. ; Erdner, Deana L.

While considerable effort has been devoted to understanding the factors regulating the development of phytoplankton blooms, the mechanisms leading to bloom decline and termination have received less attention. Grazing and sedimentation have been invoked as the main routes for the loss of phytoplankton biomass, and more recently, viral lysis, parasitism and programmed cell death (PCD) have been recognized as additional removal factors. Despite the importance of bloom declines to phytoplankton dynamics, the incidence and significance of various loss factors in regulating phytoplankton populations have not been widely characterized in natural blooms. To understand mechanisms controlling bloom decline, we studied two independent, inshore blooms of Alexandrium fundyense, paying special attention to cell mortality as a loss pathway. We observed increases in the number of dead cells with PCD features after the peak of both blooms, demonstrating a role for cell mortality in their terminations. In both blooms, sexual cyst formation appears to have been the dominant process leading to bloom termination, as both blooms were dominated by small-sized gamete cells near their peaks. Cell death and parasitism became more significant as sources of cell loss several days after the onset of bloom decline. Our findings show two distinct phases of bloom decline, characterized by sexual fusion as the initial dominant cell removal processes followed by elimination of remaining cells by cell death and parasitism.
Estimating genotypic richness and proportion of identical multi-locus genotypes in aquatic microalgal populations

(Oxford University Press, 2022-07-16) Sassenhagen, Ingrid ; Erdner, Deana L. ; Lougheed, Bryan C. ; Richlen, Mindy L. ; SjÖqvist, Conny

The majority of microalgal species reproduce asexually, yet population genetic studies rarely find identical multi-locus genotypes (MLG) in microalgal blooms. Instead, population genetic studies identify large genotypic diversity in most microalgal species. This paradox of frequent asexual reproduction but low number of identical genotypes hampers interpretations of microalgal genotypic diversity. We present a computer model for estimating, for the first time, the number of distinct MLGs by simulating microalgal population composition after defined exponential growth periods. The simulations highlighted the effects of initial genotypic diversity, sample size and intraspecific differences in growth rates on the probability of isolating identical genotypes. We estimated the genotypic richness for five natural microalgal species with available high-resolution population genetic data and monitoring-based growth rates, indicating 500 000 to 2 000 000 distinct genotypes for species with few observed clonal replicates (<5%). Furthermore, our simulations indicated high variability in genotypic richness over time and among microalgal species. Genotypic richness was also strongly impacted by intraspecific variability in growth rates. The probability of finding identical MLGs and sampling a representative fraction of genotypes decreased noticeably with smaller sample sizes, challenging the detection of differences in genotypic diversity with typical isolate numbers in the field.
Fiber-optic microarray for simultaneous detection of multiple harmful algal bloom species

(American Society for Microbiology, 2006-09) Ahn, Soohyoun ; Kulis, David M. ; Erdner, Deana L. ; Anderson, Donald M. ; Walt, David R.

Harmful algal blooms (HABs) are a serious threat to coastal resources, causing a variety of impacts on public health, regional economies, and ecosystems. Plankton analysis is a valuable component of many HAB monitoring and research programs, but the diversity of plankton poses a problem in discriminating toxic from nontoxic species using conventional detection methods. Here we describe a sensitive and specific sandwich hybridization assay that combines fiber-optic microarrays with oligonucleotide probes to detect and enumerate the HAB species Alexandrium fundyense, Alexandrium ostenfeldii, and Pseudo-nitzschia australis. Microarrays were prepared by loading oligonucleotide probe-coupled microspheres (diameter, 3 μm) onto the distal ends of chemically etched imaging fiber bundles. Hybridization of target rRNA from HAB cells to immobilized probes on the microspheres was visualized using Cy3-labeled secondary probes in a sandwich-type assay format. We applied these microarrays to the detection and enumeration of HAB cells in both cultured and field samples. Our study demonstrated a detection limit of approximately 5 cells for all three target organisms within 45 min, without a separate amplification step, in both sample types. We also developed a multiplexed microarray to detect the three HAB species simultaneously, which successfully detected the target organisms, alone and in combination, without cross-reactivity. Our study suggests that fiber-optic microarrays can be used for rapid and sensitive detection and potential enumeration of HAB species in the environment.
Centers for Oceans and Human Health : a unified approach to the challenge of harmful algal blooms

(BioMed Central, 2008-11-07) Erdner, Deana L. ; Dyble, Julianne ; Parsons, Michael L. ; Stevens, Richard C. ; Hubbard, Katherine A. ; Wrabel, Michele L. ; Moore, Stephanie K. ; Lefebvre, Kathi A. ; Anderson, Donald M. ; Bienfang, Paul ; Bidigare, Robert R. ; Parker, Micaela S. ; Moeller, Peter D. R. ; Brand, Larry E. ; Trainer, Vera L.

Harmful algal blooms (HABs) are one focus of the national research initiatives on Oceans and Human Health (OHH) at NIEHS, NOAA and NSF. All of the OHH Centers, from the east coast to Hawaii, include one or more research projects devoted to studying HAB problems and their relationship to human health. The research shares common goals for understanding, monitoring and predicting HAB events to protect and improve human health: understanding the basic biology of the organisms; identifying how chemistry, hydrography and genetic diversity influence blooms; developing analytical methods and sensors for cells and toxins; understanding health effects of toxin exposure; and developing conceptual, empirical and numerical models of bloom dynamics. In the past several years, there has been significant progress toward all of the common goals. Several studies have elucidated the effects of environmental conditions and genetic heterogeneity on bloom dynamics. New methods have been developed or implemented for the detection of HAB cells and toxins, including genetic assays for Pseudo-nitzschia and Microcystis, and a biosensor for domoic acid. There have been advances in predictive models of blooms, most notably for the toxic dinoflagellates Alexandrium and Karenia. Other work is focused on the future, studying the ways in which climate change may affect HAB incidence, and assessing the threat from emerging HABs and toxins, such as the cyanobacterial neurotoxin β-N-methylamino-L-alanine. Along the way, many challenges have been encountered that are common to the OHH Centers and also echo those of the wider HAB community. Long-term field data and basic biological information are needed to develop accurate models. Sensor development is hindered by the lack of simple and rapid assays for algal cells and especially toxins. It is also critical to adequately understand the human health effects of HAB toxins. Currently, we understand best the effects of acute toxicity, but almost nothing is known about the effects of chronic, subacute toxin exposure. The OHH initiatives have brought scientists together to work collectively on HAB issues, within and across regions. The successes that have been achieved highlight the value of collaboration and cooperation across disciplines, if we are to continue to advance our understanding of HABs and their relationship to human health.
Extensive genetic diversity and rapid population differentiation during blooms of Alexandrium fundyense (Dinophyceae) in an isolated salt pond on Cape Cod, MA, USA

(John Wiley & Sons, 2012-09-13) Richlen, Mindy L. ; Erdner, Deana L. ; McCauley, Linda A. R. ; Libera, Katie ; Anderson, Donald M.

In Massachusetts, paralytic shellfish poisoning (PSP) is annually recurrent along the coastline, including within several small embayments on Cape Cod. One such system, the Nauset Marsh System (NMS), supports extensive marshes and a thriving shellfishing industry. Over the last decade, PSP in the NMS has grown significantly worse; however, the origins and dynamics of the toxic Alexandrium fundyense (Balech) populations that bloom within the NMS are not well known. This study examined a collection of 412 strains isolated from the NMS and the Gulf of Maine (GOM) in 2006–2007 to investigate the genetic characteristics of localized blooms and assess connectivity with coastal populations. Comparisons of genetic differentiation showed that A. fundyense blooms in the NMS exhibited extensive clonal diversity and were genetically distinct from populations in the GOM. In both project years, genetic differentiation was observed among temporal samples collected from the NMS, sometimes occurring on the order of approximately 7 days. The underlying reasons for temporal differentiation are unknown, but may be due, in part, to life-cycle characteristics unique to the populations in shallow embayments, or possibly driven by selection from parasitism and zooplankton grazing; these results highlight the need to investigate the role of selective forces in the genetic dynamics of bloom populations. The small geographic scale and limited connectivity of NMS salt ponds provide a novel system for investigating regulators of blooms, as well as the influence of selective forces on population structure, all of which are otherwise difficult or impossible to study in the adjacent open-coastal waters or within larger estuaries.
Characterization of ferredoxin and flavodoxin as molecular indicators of iron limitation in marine eukaryotic phytoplankton

(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-09) Erdner, Deana L.

Expression and regulation of the ferredoxin and flavodoxin proteins in marine phytoplankton were investigated to assess their utility as biomarkers of iron limitation. A phylogenetic survey of seventeen microalgal species showed flavodoxin induction, with accompanying ferredoxin repression, to be a common response to iron stress. A minority of organisms examined never expressed flavodoxin, a condition associated with, but not characteristic of, neritic habitats. Antibodies raised against ferredoxin and flavodoxin from Thalassiosira weissflogii proved to be mono- and diatom-specific, respectively. Flavodoxin induction responded specifically to iron limitation and not to nitrogen, phosphorus, silicate, zinc or light deficiency. In iron-limited T. weissflogii, relative cellular ferredoxin and flavodoxin content (Fd index) varied with growth rates above ~50%μmax and was not affected by growth on either nitrate or ammonium as a sole nitrogen source. Below ~50%μmax, ferredoxin was absent. This variation with severity of stress and specificity to iron limitation make the Fd index an excellent choice as an indicator of iron limitation. HPLC measurement of ferredoxin and flavodoxin during the IronExII mesoscale enrichment experiment detected a strong flavodoxin signal but no significant ferredoxin synthesis, despite increases in chlorophyll and photosynthetic efficiency (Fv/Fm) observed by others. The absence of ferredoxin and the persistence of flavodoxin suggested that iron addition released the phytoplankton from iron starvation but was insufficient to completely relieve physiological iron limitation. Laboratory experiments demonstrated that a pennate diatom clone isolated from the IronExII bloom expressed both flavodoxin and ferredoxin and could alter its protein expression in about one day, further supporting the conclusion of continued iron limitation during IronExII. During IronExII, Fd index was uniformly zero while Fv/Fm increased from 0.26 to 0.56. In contrast, a laboratory iron addition experiment showed little change in Fv/Fm when the Fd index increased from 0.5-0.9. A conceptual model of the covariation of Fv/Fm and Fd index describes a complementary relationship between the two measures. Model results suggest that photochemical systems are affected by iron limitation only after cellular adaptive capacity, in the form of ferredoxin, is exhausted.
Diversity and dynamics of a widespread bloom of the toxic dinoflagellate Alexandrium fundyense

(Public Library of Science, 2011-07-29) Erdner, Deana L. ; Richlen, Mindy L. ; McCauley, Linda A. R. ; Anderson, Donald M.

Historically, cosmopolitan phytoplankton species were presumed to represent largely unstructured populations. However, the recent development of molecular tools to examine genetic diversity have revealed differences in phytoplankton taxa across geographic scales and provided insight into the physiology and ecology of blooms. Here we describe the genetic analysis of an extensive bloom of the toxic dinoflagellate Alexandrium fundyense that occurred in the Gulf of Maine in 2005. This bloom was notable for its intensity and duration, covering hundreds of kilometers and persisting for almost two months. Genotypic analyses based on microsatellite marker data indicate that the open waters of the northeastern U.S. harbor a single regional population of A. fundyense comprising two genetically distinct sub-populations. These subpopulations were characteristic of early- and late-bloom samples and were derived from the northern and southern areas of the bloom, respectively. The temporal changes observed during this study provide clear evidence of succession during a continuous bloom and show that selection can act on the timescale of weeks to significantly alter the representation of genotypes within a population. The effects of selection on population composition and turnover would be magnified if sexual reproduction were likewise influenced by environmental conditions. We hypothesize that the combined effects of differential growth and reproduction rates serves to reduce gene flow between the sub-populations, reinforcing population structure while maintaining the diversity of the overall regional population.

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