The influence of nitrogen speciation on growth and toxicity of Pseudo-nitzschia multiseries and P. pungens in batch and continuous cultures (original) (raw)
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Harmful Algae, 2020
In spring 2016, two silos containing liquid nitrogen-containing fertilizer collapsed on a harbor in Fredericia, Denmark. More than 2,750 tons of fertilizer spilled into inner Danish waters. A bloom of Pseudo-nitzschia occurred approximately one month after the incident. The bloom caused a 5-week quarantine of numerous musselharvesting areas along the eastern coast of Jutland. The levels of domoic acid measured up to 49 mg kg −1 in mussel meat after the bloom. In the months following the event, the species diversity of phytoplankton was low, while the abundance was high comprising few dominant species including Pseudo-nitzschia. The main part of the liquid nitrogen-containing compound was urea, chemically produced for agricultural use. To investigate the potential impact of urea on Pseudo-nitzschia, four strains, including one strain of P. delicatissima, two of P. seriata and one of P. obtusa, were exposed each to three concentrations of urea in a batch culture experiment: 10 μM, 20 μM and 100 μM N urea, and for comparison one concentration of nitrate (10 μM). Nitrate, ammonium, and urea were metabolized at different rates. Pseudo-nitzschia obtusa produced domoic acid and grew best at low urea concentrations. Both P. seriata strains had a positive correlation between urea concentration and growth rate, and the highest growth rate in the nitrate treatment. One strain of P. seriata produced domoic acid peaking at low N loads (10 µM N urea and 10 µM N nitrate). In conclusion, the ability to adapt to the available nitrogen source and retain a high growth rate was exceedingly varying and not only species-specific but also strain specific.
Marine Ecology Progress Series, 2004
The effect of elevated pH on growth and on production of the neurotoxin domoic acid was studied in selected diatoms belonging to the genera Pseudo-nitzschia and Nitzschia. Growth of most of the 11 species studied stopped at pH values of 8.7 to 9.1. However, for P. delicatissima and N. navis-varingica the pH limit for growth was higher, 9.3 and 9.7 to 9.8, respectively. A compilation of all available data on the pH limits for growth of marine planktonic diatoms suggests that species from ponds and rock pools all have higher limits than coastal and oceanic species. Taking only coastal and oceanic species into account, the data suggest that smaller species have a higher upper pH limit for growth than larger species. Elevated pH induced production of domoic acid in P. multiseries in amounts comparable to those detected previously under silicate and phosphate limitation. As Pseudo-nitzschia species are found in high concentrations in nutrient-enriched areas, high pH and hence induction of the production of domoic acid would be expected during blooms. These results may help to understand when and why Pseudo-nitzschia species produce domoic acid in the field.
Nitrogenous nutrition of the potentially toxic diatom Pseudonitzschia pungens f. multiseries Hasle
Journal of Plankton Research, 1996
The potentially toxic diatom Pseudoniizschia pungens f. multiseries was grown on different sources of nitrogen in batch cultures. Ammonium did not support growth at concentrations >200 u.M, and even lowered the growth rate, when it was supplied in addition to growth-saturating nitrate concentrations. This seemed to be a combined effect of inhibition of nitrate uptake and direct ammonia toxicity. Urea, glutamine and nitrite were used readily by P.pungens.
Lack of allelopathic effects of the domoic acid-producing marine diatom Pseudo-nitzschia multiseries
Marine Ecology Progress Series, 2005
Many Pseudo-nitzschia species produce the toxin domoic acid, which accumulates in the food web during blooms, sometimes causing amnesic shellfish poisoning (ASP) in higher trophic levels, including humans. In addition, Pseudo-nitzschia species have been reported to form longlasting monospecific blooms, and a possible explanation for this could be allelopathic effects of the toxin, since domoic acid has been detected in high amounts in the surrounding medium in stationary growth phase. We therefore examined the potential allelopathic effects of P. multiseries and its toxin domoic acid. In mixed-batch culture studies of domoic acid-producing P. multiseries and the algal test species Chrysochromulina ericina, Heterocapsa triquetra, Eutreptiella gymnastica and Rhodomonas marina, no allelopathic effects of P. multiseries were found. Different growth results using 2 different strains of P. multiseries grown with C. ericina were explained by minor differences in pH. Bioassays testing the effect of domoic acid itself on 9 different phytoplankton species, namely C. ericina, E. gymnastica, Karenia mikimotoi, H. triquetra, Heterosigma akashiwo, Prorocentrum minimum, P. micans, Pyramimonas propulsa and R. marina confirmed a lack of allelopathic effects of the toxin. This lack of allelopathic effect of the shellfish-poisoning toxin domoic acid seems to correspond with the results of phytoplankton species causing DSP (diarrheic shellfish poisoning) and PSP (paralytic shellfish poisoning), where it appears that these shellfish-poisoning toxins do not cause allelopathic effects either.
Journal of Plankton Research, 2011
ABSTRACT Here we compare cell physiology and domoic acid (DA) production for two strains of the diatom Pseudo-nitzschia multiseries originating from two opposite latitudes: Canada (CA) and Brazil (BR). The algae were grown as chemostat cultures at 0.2, 0.3 and 0.4 day(-1) under nitrogen (N)- and phosphorus (P)-deficient conditions. The level of deficiency significantly affected the atomic C:N, C:P, C:Si and N:P ratios in both strains. In both strains, P per cell was 2-4 x higher in the N- than in the P-deficient cultures. The opposite was not found for N in the P-deficient cultures) as shown by the N:P ratios and C:N ratios. The C:N and C:P ratios were significantly lower in the CA strain, and this did not change due to the level of deficiency The concentration and production of DA per cell per day were significantly higher for both strains under P deficiency as expected since the toxin is rich in N. However, DA was also produced by both strains during continuous cell division under N deficiency High or low bacterial densities associated with P multiseries did not increase or decrease DA production. Our data imply that more attention needs to be given to the N:P ratios and concentrations in the waters where these algae occur, as both N and P deficiencies affect DA production and cellular DA concentrations.
Journal of Science …, 2010
Amnesic shellfish poisoning (ASP) is a type of shellfish poisoning due to the consumption of shellfish mollusks contaminated with domoic acid (DA). The toxin was first reported in the chain-forming pennate diatom, Pseudo-nitzschia and subsequently in other diatom species. In this study, clonal cultures of Pseudo-nitzschia were established from plankton samples collected from Sarawak and Sabah coastal waters. Clonal cultures were maintained in SWII medium with the addition of silicate at 25°C, 30 PSU and under 12:12 light-dark photoperiod. Fifteen milliliters of late exponential phase cultures were collected for toxin analysis and subsamples were taken for cell count. Cellular toxin was extracted by boiling in medium at 100°C for 5 minutes. The extracts were filtered to remove cell debris before being analyzed with HPLC using standard domoic acid, isodomoic A and B as reference toxins. All the 32 strains of Pseudo-nitzschia sp. analyzed in this study showed the absence of peaks corresponding to the three ASP toxins. This implies that non-toxic strains of Pseudo-nitzschia sp. are common in Malaysian waters. Further study will be carried out to include more strains along the coastal waters of Borneo as well as selected sites with shellfish farming activities in Peninsula Malaysia.