| 1. |
- Selander, Erik, 1973, et al.
(författare)
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Copepods induce paralytic shellfish toxin production in marine dinoflagellates
- 2006
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Ingår i: Proceedings of the Royal Society B-Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954. ; 273:1594, s. 1673-1680
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Tidskriftsartikel (refereegranskat)abstract
- Among the thousands of unicellular phytoplankton species described in the sea, some frequently occurring and bloom-forming marine dinoflagellates are known to produce the potent neurotoxins causing paralytic shellfish poisoning. The natural function of these toxins is not clear, although they have been hypothesized to act as a chemical defence towards grazers. Here, we show that waterborne cues from the copepod Acartia tonsa induce paralytic shellfish toxin (PST) production in the harmful algal bloom-forming dinoflagellate Alexandrium minutum. Induced A. minutum contained up to 2.5 times more toxins than controls and was more resistant to further copepod grazing. Ingestion of non-toxic alternative prey was not affected by the presence of induced A. minutum. The ability of A. minutum to sense and respond to the presence of grazers by increased PST production and increased resistance to grazing may facilitate the formation of harmful algal blooms in the sea.
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| 2. |
- Bergkvist, Johanna, 1980, et al.
(författare)
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Induction of toxin production in dinoflagellates: the grazer makes a difference
- 2008
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 156:1, s. 147-154
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Tidskriftsartikel (refereegranskat)abstract
- The dinoflagellate Alexandrium minutum has previously been shown to produce paralytic shellfish toxins (PST) in response to waterborne cues from the copepod Acartia tonsa. In order to investigate if grazer-induced toxin production is a general or grazer-specific response of A. minutum to calanoid copepods, we exposed two strains of A. minutum to waterborne cues from three other species of calanoid copepods, Acartia clausi, Centropages typicus and Pseudocalanus sp. Both A. minutum strains responded to waterborne cues from Centropages and Acartia with significantly increased cell-specific toxicity. Waterborne cues from Centropages caused the strongest response in the A. minutum cells, with 5 to > 20 times higher toxin concentrations compared to controls. In contrast, neither of the A. minutum strains responded with significantly increased toxicity to waterborne cues from Pseudocalanus. The absolute increase in PST content was proportional to the intrinsic toxicity of the different A. minutum strains that were used. The results show that grazer-induced PST production is a grazer-specific response in A. minutum, and its potential ecological importance will thus depend on the composition of the zooplankton community, as well as the intrinsic toxin-producing properties of the A. minutum population.
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| 3. |
- Juul-Pedersen, T., et al.
(författare)
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Sedimentation following the spring bloom in Disko Bay, West Greenland, with special emphasis on the role of copepods
- 2006
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 314, s. 239-255
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Tidskriftsartikel (refereegranskat)abstract
- The sedimentation of particulate organic material was investigated in Disko Bay, West Greenland, during June 2001. Post spring-bloom conditions were encountered, with seasonally decreasing phytoplankton biomass associated with the pycnocline. Calanus finmarchicus, C. glacialis, and C. hyperboreus dominated the zooplankton community, comprising up to 88% of the copepod biomass. Faecal pellet production by C. finmarchicus and C. glacialis was positively correlated to the available food (chlorophyll a > 10 mu m). Results from short-term sediment trap deployments (6 h) showed that particulate organic carbon (POC) sedimentation from the euphotic zone was, on average, 628 mg C m(-2) d(-1), with copepod faecal pellets contributing, on average, 29% of this amount. The faecal pellet contribution to the vertical sinking export of POC was equivalent to that of phytoplankton and amorphous detritus. Yet, on average, 35% of the copepod faecal pellet production was retained within the euphotic zone. The POC: PON (particulate organic nitrogen) ratio of the suspended material in the euphotic zone (8.1 +/- 0.4) was comparable to that of the material collected in the sediment traps just below the euphotic zone (8.0 +/- 0.9). In addition, the daily loss rates of POC and PON within each sampling depth were similar, and the carbon to nitrogen ratio in the sediment traps did not change with depth. These results indicate that the pelagic system had a low retention efficiency of nitrogen just after the spring bloom.
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| 4. |
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| 5. |
- Selander, Erik, 1973, et al.
(författare)
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Effects of nitrate and phosphate on grazer-induced toxin production in Alexandrium minutum
- 2008
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Ingår i: Limnology & Oceanography. ; 53:2, s. 423-530
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Tidskriftsartikel (refereegranskat)abstract
- Two strains of Alexandrium minutum were exposed to waterborne cues from copepod grazers in factorial combinations of nitrate and phosphate concentrations to evaluate the importance of grazer-induced paralytic shellfish toxin (PST) production under different nutrient regimes. In nitrate-rich treatments, the presence of waterborne cues from grazers resulted in significantly increased cell-specific PST content. In low nitrate treatments, however, waterborne cues from grazers did not result in any detectable increase in cell-specific PST content. The grazer-induced increase in cell-specific PST content in nitrate-rich treatments was comparable in size to the effects of nitrate in the absence of grazers. Effects of phosphate limitation were less consistent, resulting in increased PST content in nitrate-rich treatments in one of the A. minutum strains, but had no significant effect in the other. The ability of dinoflagellates to sense and respond to the presence of grazers by increased PST production may be one of the most important factors affecting cell-specific PST content under nitrogen replete conditions.
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| 6. |
- Thor, Peter, 1965, et al.
(författare)
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Post-spring bloom community structure of pelagic copepods in the Disko Bay, Western Greenland
- 2005
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Ingår i: Journal of Plankton Research. - : Oxford University Press (OUP). - 0142-7873 .- 1464-3774. ; 27:4, s. 341-356
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Tidskriftsartikel (refereegranskat)abstract
- Community structure of pelagic copepods was investigated in the upper 200 m in the Disko Bay, Western Greenland, during the post-spring bloom period in June, 2001. This was the first study of the copepod community in West Greenland coastal waters sampled using smaller mesh sizes (50 mu m as opposed to 200 mu m). The mesozooplankton was dominated by copepods who constituted 82% of the total abundance and 95% of the total mesozooplankton biomass (> 50 mu m). Nauplii of Calanus, Pseudocalanus and Oithona dominated by number and the copepodites and adults were dominated by Oithona spp., Oncaea sp., Pseudocalanus sp., harpacticoids, Calanus finmarchicus, C. glacialis, and C. hyperboreus. Multivariate tests showed that the species/stage abundance composition of copepods changed significantly with depth. With one exception, all depth intervals showed unique significantly different compositions. Accordingly, the copepod community structure was influenced primarily by depth rather than by chlorophyll a concentration. Factors other than herbivorous grazing, such as omnivory, predator avoidance or association to marine snow aggregates of specific species, may have influenced the depth distribution of the total copepod community in the Disko Bay. Nevertheless, subsequent Pearson product moment correlations showed positive significant correlations between the vertical distribution of the three Calanus spp. and Pseudocalanus spp. and chlorophyll a concentrations, which points towards these species as prime components in the classic diatom-copepod food chain.
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