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Growth, Toxin Production and Allelopathic Effects of Pseudo-nitzschia multiseries under Iron-Enriched Conditions

Bruna Fernanda Sobrinho1, Luana Mocelin de Camargo2, Leonardo Sandrini-Neto3

  • 1Centro de Estudos do Mar, Universidade Federal do Paraná, P.O. Box 1, Pontal do Paraná 83255-976, PR, Brazil. brunafernanda.sob@gmail.com.

Marine Drugs
|October 25, 2017
PubMed

Insights

Iron enrichment boosts domoic acid (DA) production in the toxic diatom Pseudo-nitzschia multiseries, but does not affect its growth. Pseudo-nitzschia also releases compounds that inhibit the growth of non-toxic diatoms.

Area of Science:

  • Marine biology
  • Phycology
  • Ecotoxicology

Background:

  • The toxic diatom Pseudo-nitzschia multiseries produces domoic acid (DA), a harmful algal bloom (HAB) toxin.
  • Iron (Fe) is a key nutrient in marine ecosystems, influencing phytoplankton growth and toxin production.

Purpose of the Study:

  • To investigate the impact of iron enrichment on the growth and DA production of P. multiseries.
  • To compare the growth of P. multiseries and a non-toxic diatom, Bacillaria sp., under varying iron conditions.
  • To identify potential allelopathic interactions between P. multiseries and other diatom species.

Main Methods:

  • Static cultures of P. multiseries and Bacillaria sp. were maintained for 30 days with varying iron concentrations.
  • Intra- and extracellular DA concentrations were measured over time.
  • Growth rates, cell chain formation, and chlorophyll-a content were assessed.
  • Allelopathic effects were evaluated by co-culturing or adding dissolved cell contents.

Main Results:

  • P. multiseries exhibited consistent growth rates (0.45-0.73 d⁻¹) and chain formation across all tested iron concentrations, indicating efficient iron uptake.
  • Higher iron concentrations significantly increased DA concentrations in P. multiseries, suggesting iron's role in toxin synthesis.
  • Bacillaria sp. showed reduced growth and chlorophyll-a content when exposed to dissolved cell contents from P. multiseries, indicating an allelopathic effect.

Conclusions:

  • Iron availability is a critical factor regulating domoic acid production in Pseudo-nitzschia multiseries.
  • Pseudo-nitzschia multiseries possesses an efficient iron acquisition mechanism, allowing for sustained growth under various iron conditions.
  • This study provides the first evidence of an allelopathic effect of P. multiseries on other diatom species, mediated by undetermined compounds.
Keywords:
allelopathydomoic acidharmful algaeiron fertilizationphycotoxinstoxic diatoms

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