<div><p>Refer to the Methods section of Griffin, et al. (2019).</p>
<p><strong>Culture and culturing condition:</strong><br />
All assays were run with the dinoflagellate <em>Alexandrium catenella </em>strain BF-5, a highly toxigenic strain isolated from the Bay of Fundy, Canada. Cells were cultured in F/2 medium (Guillard, 1975) without silicate. Batch cultures were kept under exponential-phase growth at a temperature of 18 °C, with a photoperiod of 12 h of light and 12 h of darkness. Fluorescent lights were used at an intensity of ~50 µM m⁻² s⁻¹.</p>
<p><strong>Nitrogen sources:</strong><br />
These assays simulated potential bias due to N-sources (ammonium and urea) excreted by the copepod grazer <em>Acartia hudsonica</em>. Treatments consisted of daily additions of either 0.083 μmol L⁻¹ ammonium, 50 μmol L⁻¹ ammonium, or 50 μmol L⁻¹ urea over a 3 day period. The lower ammonium concentration (0.083 μmol L⁻¹) is an estimate of the nitrogen excreted per day from the 15 copepods in a bottle. The higher concentration of ammonium (50 μmol L⁻¹) represents the ammonium concentration in K-medium (Keller et al., 1987). The F/2 medium in nutrient-replete conditions contains nitrate as its N-source. Urea was used at a concentration of 50 μmol L⁻¹, which is far higher than could result from copepod excretion. The controls consisted of cells grown in F/2 medium (880 µmol L⁻¹ nitrate and 36.3 µmol L⁻¹ phosphate) or 0.22 μm filtered seawater (FSW) collected from Long Island Sound (~3 µmol L⁻¹ nitrate and ~1 µmol L⁻¹ phosphate).</p>
<p><strong>Alarm cues:</strong><br />
Crushed cells of the highly toxigenic <em>Alexandrium catenella </em>(strain BF-5), the low toxigenic <em>A. catenella </em>(strain GTCN-16), <em>Tetraselmis </em>sp<em>.,</em> and <em>Thalassisosira weissflogii </em>were added to separate experimental bottles. Added cells were crushed via sonic dismembrator on ice. Complete lysis of cells was confirmed by microscopic examination. 140 μgC of crushed cells for each species tested were added daily to bottles during the three-day period incubations. Cell-to-carbon conversion factors used were 2.7 x 10<sup>-3</sup> μgC per <em>Alexandrium</em> cell, 8.0 x 10<sup>-5</sup> μgC per <em>T. weissflogii </em>cell, and 5.1 x 10<sup>-5</sup> μgC per <em>Tetraselmis </em>sp. cell desired quantity of carbon.</p>
<p><strong>Grazer exposure:</strong><br />
Grazer assays measured the combined effects of copepod kairomone and other feeding-related cues on cell toxin production. Treatments consisted of additions of 15 adult female copepods (<em>Acartia hudsonica)</em> collected from Maine, USA, which have a history of exposure to <em>A. catenella</em> blooms. Copepods had been kept in culture conditions similar to the experimental algae, and grown on a mixed diet of nontoxigenic phytoplankton. At the conclusion of the grazing assays, contents of the bottles were first passed through a 63 μm mesh to separate grazers, eggs and fecal pellets from the <em>Alexandrium catenella </em>cells<em>.</em> The filtrate was then passed through a 10 μm mesh, which collected the washed <em>A. catenella </em>cells, which were then checked to ensure the absence of cells and resuspended in 0.22 µm-FSW in 50 mL centrifuge tubes.</p>
<p><strong>Cell concentration and toxin analysis:</strong><br />
In the nitrogen source and alarm cue assays, which did not involve use of copepods, there was no need to pass cells through the 63 μm mesh before cells were collected on the 10 μm mesh. A fraction of the contents of each centrifuge tube was preserved using Lugol’s solution, and two subsamples were counted under an inverted microscope for cell abundance. In the remaining fraction, cells were centrifuged at 4000 × g for 20 minutes. The supernatant was carefully discarded and the cell pellet was resuspended in 0.1 M acetic acid. Cells were then lysed using a sonic dismembrator on ice. The solution was centrifuged and the extract was filtered through a 0.45 μm ultracentrifuge cartridge to remove the cell particles. The supernatant was stored at -80°C to prevent chemical reactions from occurring during the period before processing. After toxin extraction, toxin analysis by High Performance Liquid Chromatography (HPLC) with fluorescent detection was used to determine the total toxin content.</p></div>
Chemical Defenses-4: Griffin et al. 2019
Chemical Defenses-4: Griffin et al. 2019
<div><p><strong>Data Processing:</strong><br />
A multiple comparison analysis of variance (ANOVA) with the Student–Newman–Keul's (SNK) post-hoc test was performed for each assay, to test for the treatment effect and differences within treatments, using the statistical program R version 3.3.1. The program R and SPSS version 26 were also used to create box and whisker plots to represent toxin production for each assay.</p></div>
853877
Chemical Defenses-4: Griffin et al. 2019
2021-06-16T10:49:44-04:00
2021-06-16T10:49:44-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:853877
Toxin content of Alexandrium catenella in response of nitrogen sources, algal alarm cues, and grazer exposure
Data include Paralytic Shellfish Toxin production of the marine dinoflagellate Alexandrium catenella. PST production of A. catenella was measured as a function of varying concentrations of added nitrogen sources
(ammonium and urea), alarm cues from lysed conspecific (A. catenella Group I strains) and interspecific (the diatom, Thalassiosira weissflogii, and the green flagellate, Tetraselmis sp.) algae, and the presence of a grazer (the copepod Acartia hudsonica).
Independent variable: treatment type such as nitrogen sources (mol per liter), algal alarm cues (carbon content per cell), and grazer exposure in either the F/2 or FSW assays (control)
Dependent variables: cell density (cells per liter), cell toxin content (mol per cell), cell diameter (μm per cell)
Data were published in:
Griffin, J. E., Park, G., & Dam, H. G. (2019). Relative importance of nitrogen sources, algal alarm cues and grazer exposure to toxin production of the marine dinoflagellate Alexandrium catenella. Harmful algae, 84, 181-187. https://doi.org/10.1016/j.hal.2019.04.006
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Dam, H. G. (2021) Toxin content of Alexandrium catenella in response of nitrogen sources, algal alarm cues, and grazer exposure. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2021-06-16 [if applicable, indicate subset used]. doi:10.26008/1912/bco-dmo.853877.1 [access date]
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10.26008/1912/bco-dmo.853877.1
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2021-06-16
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