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Nitrogen Isotope Fractionation and Toxin Production During the Uptake of Micromolar Concentrations of Nitrate, Ammonium, and Urea by a Marine Dinoflagellate.

Record Type:	Language materials, manuscript : Monograph/item
Title/Author:	Nitrogen Isotope Fractionation and Toxin Production During the Uptake of Micromolar Concentrations of Nitrate, Ammonium, and Urea by a Marine Dinoflagellate./
Author:	Armstrong, C. Taylor.
Description:	1 online resource (93 pages)
Notes:	Source: Masters Abstracts International, Volume: 56-04.
Subject:	Aquatic sciences. -
Online resource:	click for full text (PQDT)
ISBN:	9781369702309

Nitrogen Isotope Fractionation and Toxin Production During the Uptake of Micromolar Concentrations of Nitrate, Ammonium, and Urea by a Marine Dinoflagellate.
Armstrong, C. Taylor.

Nitrogen Isotope Fractionation and Toxin Production During the Uptake of Micromolar Concentrations of Nitrate, Ammonium, and Urea by a Marine Dinoflagellate. - 1 online resource (93 pages)

Source: Masters Abstracts International, Volume: 56-04.

Thesis (M.S.)--The College of William and Mary, 2017.

Includes bibliographical references

Despite an increased global interest in harmful algal bloom (HAB) species and eutrophication, the relationship between nutrient sources and changes in species composition or toxicity remains unclear. Stable isotopes are routinely used to identify and track nitrogen (N) sources to water bodies, as sources can be differentiated based on stable isotope values. While literature is available describing N fractionation by diatoms and coccolithophores, data are greatly lacking regarding isotope fractionation by dinoflagellates. Here we investigate the fractionation of nitrogen isotopes by saxitoxin-producing Alexandrium fundyense, to validate the use of the delta 15N of particulate organic matter and identify the nitrogen source fueling a dinoflagellate bloom and its toxicity. The effects of N chemical form on isotope fractionation, toxin content, and toxicity, were investigated using isolates in single-N and mixed-N experiments. Growth on NO3 -, NH4+, or urea, resulted in isotope fractionation of 2.761.48‰, 29.019.32‰, or 0.340.19‰, respectively, with the lowest cellular toxicity and toxin quotas reported during urea utilization. Toxin composition and growth rates, however, remained constant across all N treatments, showing no effects of NO3-, NH 4+, or urea utilization. Alexandrium fundyense was then preconditioned to either NO3-, NH4 +, or urea, and abruptly inoculated into mixed-N medium containing all three chemical forms. All treatments initially utilized NH4 + and urea upon inoculation into mixed medium, suggesting no effect of preconditioning. Cells only began utilizing NO3- after NH4+ decreased below 2-4 microM in the medium. During the inhibition of NO3- uptake by NH 4+ utilization, the cellular delta15N was at its lowest (-5‰), and through the course of the experiment, the delta15N continuously changed to mimic the isotope value of the most recent N source(s) being utilized. When utilizing multiple sources, the isotope signature of the cells fell between the signal of the two N sources. Together this suggests that in NO3- and urea rich environments, the delta15NPOM would reliably look like the source or sources of nitrogen utilized, but that caution should be taken in NH4+ rich environments where the large value could lead to misinterpretation of the signal. Nutrients are only one factor influencing bloom dynamics, but information about the relative importance of natural or anthropogenic nutrients in the development and toxicity of bloom events is necessary to predict future shifts in phytoplankton species composition, density, and toxicity.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2018

Mode of access: World Wide Web

ISBN: 9781369702309Subjects--Topical Terms:

1178821
Aquatic sciences.
Index Terms--Genre/Form:

554714
Electronic books.

Nitrogen Isotope Fractionation and Toxin Production During the Uptake of Micromolar Concentrations of Nitrate, Ammonium, and Urea by a Marine Dinoflagellate.
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500 $a Source: Masters Abstracts International, Volume: 56-04.
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504 $a Includes bibliographical references
520 $a Despite an increased global interest in harmful algal bloom (HAB) species and eutrophication, the relationship between nutrient sources and changes in species composition or toxicity remains unclear. Stable isotopes are routinely used to identify and track nitrogen (N) sources to water bodies, as sources can be differentiated based on stable isotope values. While literature is available describing N fractionation by diatoms and coccolithophores, data are greatly lacking regarding isotope fractionation by dinoflagellates. Here we investigate the fractionation of nitrogen isotopes by saxitoxin-producing Alexandrium fundyense, to validate the use of the delta 15N of particulate organic matter and identify the nitrogen source fueling a dinoflagellate bloom and its toxicity. The effects of N chemical form on isotope fractionation, toxin content, and toxicity, were investigated using isolates in single-N and mixed-N experiments. Growth on NO3 -, NH4+, or urea, resulted in isotope fractionation of 2.761.48‰, 29.019.32‰, or 0.340.19‰, respectively, with the lowest cellular toxicity and toxin quotas reported during urea utilization. Toxin composition and growth rates, however, remained constant across all N treatments, showing no effects of NO3-, NH 4+, or urea utilization. Alexandrium fundyense was then preconditioned to either NO3-, NH4 +, or urea, and abruptly inoculated into mixed-N medium containing all three chemical forms. All treatments initially utilized NH4 + and urea upon inoculation into mixed medium, suggesting no effect of preconditioning. Cells only began utilizing NO3- after NH4+ decreased below 2-4 microM in the medium. During the inhibition of NO3- uptake by NH 4+ utilization, the cellular delta15N was at its lowest (-5‰), and through the course of the experiment, the delta15N continuously changed to mimic the isotope value of the most recent N source(s) being utilized. When utilizing multiple sources, the isotope signature of the cells fell between the signal of the two N sources. Together this suggests that in NO3- and urea rich environments, the delta15NPOM would reliably look like the source or sources of nitrogen utilized, but that caution should be taken in NH4+ rich environments where the large value could lead to misinterpretation of the signal. Nutrients are only one factor influencing bloom dynamics, but information about the relative importance of natural or anthropogenic nutrients in the development and toxicity of bloom events is necessary to predict future shifts in phytoplankton species composition, density, and toxicity.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2018
538 $a Mode of access: World Wide Web
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650 4 $a Toxicology. $3 580973
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710 2 $a The College of William and Mary. $b School of Marine Science. $3 1185898
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