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Dangerous Relations in the Arctic Marine Food Web: Interactions between Toxin Producing Pseudo-nitzschia Diatoms and Calanus Copepodites.

Harðardóttir S, Pančić M, Tammilehto A, Krock B, Møller EF, Nielsen TG, Lundholm N - Mar Drugs (2015)

Bottom Line: When P. seriata was exposed to the copepodites, either through physical contact with the grazers or separated by a membrane, the toxicity of P. seriata increased (up to 3300%) suggesting the response to be chemically mediated.The induced response was also triggered when copepodites grazed on another diatom, supporting the hypothesis that the cues originate from the copepodite.Neither pH nor nutrient concentrations explained the induced DA production.

View Article: PubMed Central - PubMed

Affiliation: Natural History Museum of Denmark, University of Copenhagen, Sølvgade 83S, 1307 Copenhagen, Denmark. Sara.Hardardottir@snm.ku.dk.

ABSTRACT
Diatoms of the genus Pseudo-nitzschia produce domoic acid (DA), a toxin that is vectored in the marine food web, thus causing serious problems for marine organisms and humans. In spite of this, knowledge of interactions between grazing zooplankton and diatoms is restricted. In this study, we examined the interactions between Calanus copepodites and toxin producing Pseudo-nitzschia. The copepodites were fed with different concentrations of toxic P. seriata and a strain of P. obtusa that previously was tested to be non-toxic. The ingestion rates did not differ among the diets (P. seriata, P. obtusa, a mixture of both species), and they accumulated 6%-16% of ingested DA (up to 420 µg per dry weight copepodite). When P. seriata was exposed to the copepodites, either through physical contact with the grazers or separated by a membrane, the toxicity of P. seriata increased (up to 3300%) suggesting the response to be chemically mediated. The induced response was also triggered when copepodites grazed on another diatom, supporting the hypothesis that the cues originate from the copepodite. Neither pH nor nutrient concentrations explained the induced DA production. Unexpectedly, P. obtusa also produced DA when exposed to grazing copepodites, thus representing the second reported toxic polar diatom.

No MeSH data available.


Related in: MedlinePlus

(a) Cell concentrations (ln cells mL−1, mean ± SD) in the induction experiment. (a) The two controls (both n = 3); (b) Cell concentrations in flask A with 12 copepodites and flask B with only P. seriata cells separated from flask A by a 2 µm membrane (n = 4). (c) Cell concentrations in flask A with 20 copepodites and flask B with only cells separated from flask A by a 2 µm membrane (n = 4). The cross and arrows indicate the time and the amount for P. seriata cells or 1/10 L medium addition.
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marinedrugs-13-03809-f005: (a) Cell concentrations (ln cells mL−1, mean ± SD) in the induction experiment. (a) The two controls (both n = 3); (b) Cell concentrations in flask A with 12 copepodites and flask B with only P. seriata cells separated from flask A by a 2 µm membrane (n = 4). (c) Cell concentrations in flask A with 20 copepodites and flask B with only cells separated from flask A by a 2 µm membrane (n = 4). The cross and arrows indicate the time and the amount for P. seriata cells or 1/10 L medium addition.

Mentions: The initial cell concentrations were the same in all treatments and in the controls at the start of the experiment (one-way ANOVA, F2,11 = 3.7, P = 0.05). Mean growth rates (eight days) in all incubators containing only P. seriata cells, i.e., flasks B and controls, were the same (Kruskal-Wallis test, P = 0.7), indicating similar growth conditions (Figure 4). The growth rates were slightly lower during the first two days, 0.1 ± 0.9 d−1 and stabilized thereafter around 0.3 ± 0.1 day−1. The cell density was significantly lower in flask A than in flask B on day 2 in both treatments (12 and 20 copepodites) (Figure 5b) (t-test, P < 0.001 and Mann-Whitney Rank Sum Test, P = 0.029) illustrating that the copepodites grazed on the toxic cells. Despite the addition of cells in flask A on day 3, the cell numbers were significantly lower in flask A than in flask B on day 8 in both treatments (Figure 5) (t-test, P = 0.018, and Mann-Whitney Rank Sum Test, P = 0.029).


Dangerous Relations in the Arctic Marine Food Web: Interactions between Toxin Producing Pseudo-nitzschia Diatoms and Calanus Copepodites.

Harðardóttir S, Pančić M, Tammilehto A, Krock B, Møller EF, Nielsen TG, Lundholm N - Mar Drugs (2015)

(a) Cell concentrations (ln cells mL−1, mean ± SD) in the induction experiment. (a) The two controls (both n = 3); (b) Cell concentrations in flask A with 12 copepodites and flask B with only P. seriata cells separated from flask A by a 2 µm membrane (n = 4). (c) Cell concentrations in flask A with 20 copepodites and flask B with only cells separated from flask A by a 2 µm membrane (n = 4). The cross and arrows indicate the time and the amount for P. seriata cells or 1/10 L medium addition.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4483658&req=5

marinedrugs-13-03809-f005: (a) Cell concentrations (ln cells mL−1, mean ± SD) in the induction experiment. (a) The two controls (both n = 3); (b) Cell concentrations in flask A with 12 copepodites and flask B with only P. seriata cells separated from flask A by a 2 µm membrane (n = 4). (c) Cell concentrations in flask A with 20 copepodites and flask B with only cells separated from flask A by a 2 µm membrane (n = 4). The cross and arrows indicate the time and the amount for P. seriata cells or 1/10 L medium addition.
Mentions: The initial cell concentrations were the same in all treatments and in the controls at the start of the experiment (one-way ANOVA, F2,11 = 3.7, P = 0.05). Mean growth rates (eight days) in all incubators containing only P. seriata cells, i.e., flasks B and controls, were the same (Kruskal-Wallis test, P = 0.7), indicating similar growth conditions (Figure 4). The growth rates were slightly lower during the first two days, 0.1 ± 0.9 d−1 and stabilized thereafter around 0.3 ± 0.1 day−1. The cell density was significantly lower in flask A than in flask B on day 2 in both treatments (12 and 20 copepodites) (Figure 5b) (t-test, P < 0.001 and Mann-Whitney Rank Sum Test, P = 0.029) illustrating that the copepodites grazed on the toxic cells. Despite the addition of cells in flask A on day 3, the cell numbers were significantly lower in flask A than in flask B on day 8 in both treatments (Figure 5) (t-test, P = 0.018, and Mann-Whitney Rank Sum Test, P = 0.029).

Bottom Line: When P. seriata was exposed to the copepodites, either through physical contact with the grazers or separated by a membrane, the toxicity of P. seriata increased (up to 3300%) suggesting the response to be chemically mediated.The induced response was also triggered when copepodites grazed on another diatom, supporting the hypothesis that the cues originate from the copepodite.Neither pH nor nutrient concentrations explained the induced DA production.

View Article: PubMed Central - PubMed

Affiliation: Natural History Museum of Denmark, University of Copenhagen, Sølvgade 83S, 1307 Copenhagen, Denmark. Sara.Hardardottir@snm.ku.dk.

ABSTRACT
Diatoms of the genus Pseudo-nitzschia produce domoic acid (DA), a toxin that is vectored in the marine food web, thus causing serious problems for marine organisms and humans. In spite of this, knowledge of interactions between grazing zooplankton and diatoms is restricted. In this study, we examined the interactions between Calanus copepodites and toxin producing Pseudo-nitzschia. The copepodites were fed with different concentrations of toxic P. seriata and a strain of P. obtusa that previously was tested to be non-toxic. The ingestion rates did not differ among the diets (P. seriata, P. obtusa, a mixture of both species), and they accumulated 6%-16% of ingested DA (up to 420 µg per dry weight copepodite). When P. seriata was exposed to the copepodites, either through physical contact with the grazers or separated by a membrane, the toxicity of P. seriata increased (up to 3300%) suggesting the response to be chemically mediated. The induced response was also triggered when copepodites grazed on another diatom, supporting the hypothesis that the cues originate from the copepodite. Neither pH nor nutrient concentrations explained the induced DA production. Unexpectedly, P. obtusa also produced DA when exposed to grazing copepodites, thus representing the second reported toxic polar diatom.

No MeSH data available.


Related in: MedlinePlus