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

Abstract

In order to assess the effects of Fe-enrichment on the growth and domoic acid (DA) production of the toxigenic diatom Pseudo-nitzschia multiseries, static cultures that received the addition of different iron (Fe) concentrations were maintained for 30 days. Intra- and extracellular DA concentrations were evaluated over time, and growth and chain-formation were compared to those of non-toxic diatoms, Bacillaria sp. Growth rates of P. multiseries (μ = 0.45–0.73 d−1) were similar among cultures containing different Fe concentrations. Likewise, the similar incidence and length of P. multiseries stepped cell chains (usually 2–4; up to 8-cell long) among the treatments reinforces that the cultures were not growth-inhibited under any condition tested, suggesting an efficient Fe acquisition mechanism. Moreover, DA concentrations were significantly higher under the highest Fe concentration, indicating that Fe is required for toxin synthesis. Bacillaria sp. reached comparable growth rates under the same Fe concentrations, except when the dissolved cell contents from a P. multiseries culture was added. The 50–70% reduction in cell density and 70–90% decrease in total chlorophyll-a content of Bacillaria sp. at early stationary growth phase indicates, for the first time, an allelopathic effect of undetermined compounds released by Pseudo-nitzschia to another diatom species.

Pseudo-nitzschia sp. diversity and seasonality in the southern North Sea, domoic acid levels and associated phytoplankton communities

“…Other studies suggest that DA synthesis requires available Fe (e.g. Sobrinho et al 2017). In both cases, accumulated iron in the polysaccharidic matrix of P.…”

Dissolved Domoic Acid Does Not Improve Growth Rates and Iron Content in Iron-Stressed Pseudo-Nitzschia subcurvata

“…They are, however, consistent with observations for DA producing Pseudo-nitzschia species. Even though an increased release of dDA in iron limited treatments was observed, exponential phase growth rates remained lower for these treatments than for iron sufficient treatments (Maldonado et al, 2002;Sobrinho et al, 2017).…”

“…Since Pseudo-nitzschia spp. generally adapt well to low iron concentrations (Marchetti et al, 2006;Sobrinho et al, 2017), the limiting effect of iron might be relatively low in this experiment, resulting in changes less prominent. With regard to DA addition, elevated Fe:C was observable in the +DA treatment but not in the +FeDA treatment, which showed equally low values as in the Control treatment.…”

“…Pseudo-nitzschia spp. are known to adapt better to low iron concentrations compared to other oceanic diatoms (Marchetti et al, 2006;Hoppe et al, 2013;Russo et al, 2015;Sobrinho et al, 2017). It was suggested, that Pseudo-nitzschia may cope with low iron conditions by using an efficient iron uptake system (Wells et al, 2005) and storing excess iron (Marchetti et al, 2006).…”

Differential Influence of Life Cycle on Growth and Toxin Production of three Pseudo‐nitzschia Species (Bacillariophyceae)

“…In addition, cells may be more vulnerable during sexual reproduction, so domoic acid could act as a grazer deterrent: its production has been shown to increase in the presence of copepods (Harðard ottir et al 2015. Finally, different studies also showed an allelopathic effect of Pseudo-nitzschia or DA addition on different phytoplankton species (Lundholm et al 2005, Smeti et al 2015, Sobrinho et al 2017, Van Meerssche et al 2018). Higher DA production may therefore also represent an ecological advantage that could offset the growth arrest/decrease during sexual events in Pseudo-nitzschia blooms.…”