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- Fistarol, G. O., et al.
(författare)
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Allelopathy in Alexandrium spp.: effect on a natural plankton community and on algal monocultures
- 2004
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 35:1, s. 45-56
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Tidskriftsartikel (refereegranskat)abstract
- We studied allelopathy in the dinoflagellate genus Alexandrium by testing the effect of A. tamarense on a natural plankton community from Hopavagen Bay, Trondheimsfjord, Norway, and the effect of toxic and non-toxic strains of A. tamarense and a toxic strain of A. minutum on algal monocultures. Also, a possible relation between the allelopathic effect and the production of paralytic shellfish poison (PSP) toxin was investigated. A. tamarense affected the whole phytoplankton community by decreasing the growth rate and changing the community structure (relative abundance of each species, dominant species). A negative effect of A. tamarense was also observed on ciliates, but not on bacteria numbers, In the bioassay with algal monocultures, the diatom Thalassiosira weissflogii and the cryptophyte Rhodomonas sp. were exposed to the filtrate of Alexandrium spp. All tested Alexandrium strains negatively affected T weissflogii and Rhodomonas sp. cultures, independent of whether PSP toxins were produced. The compounds released by Alexandrium caused lysis of natural and cultured algal cells, suggesting that the allelopathic effect may be connected with previously described ichthyotoxic and haemolytic properties of Alexandrium. Furthermore, the observation that several components of the plankton community were affected by compounds released by A. tamarense emphasizes the importance of allelopathy for the ecology of this species.
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- Kozlowsky-Suzuki, Betina, et al.
(författare)
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Disruption of the microbial food web and inhibition of metazooplankton development in the presence of iron- and DOM-stimulated Baltic Sea cyanobacteria
- 2007
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Ingår i: Marine Ecology - Progress Series. - 1616-1599. ; 337, s. 15-26
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Tidskriftsartikel (refereegranskat)abstract
- Summer N-2-fixing cyanobacterial blooms are a common feature in the Baltic Sea, and the occurrence of Nodularia spumigena toxic blooms is of particular concern. Cyanobacterial blooms can be favoured by certain conditions including high concentrations of dissolved organic matter, which may increase the availability of iron critical for N-2 fixation. Cyanobacteria may negatively affect grazers because many species produce toxins and generally lack fatty acids essential for zooplankton reproduction. In this study we investigated the effect of riverine high-molecular weight dissolved organic matter (DOM-)/iron-stimulated cyanobacteria on the development of proto- and metazooplankton, and evaluated the role of DOM in stimulating the zooplankton part of the microbial food web. A plankton community was incubated in cylinders with either nitrate (NO3) or DOM alone or combined with iron (Fe) or zooplankton >100 mu m (G). The development of proto- and metazooplankton was followed for 10 d. Trophic relationships between metazooplankton taxa and their potential food items were assessed by ordination analysis and by feeding and reproduction bottle incubations with the calanoid copepod Acartia bifflosa. Contrary to our expectations, DOM did not stimulate the microbial food web, and proto- and metazooplankton developed similarly in all treatments until the middle of the experiment. However, by the end of the experiment, the biomass of proto- and metazooplankton as well as the biomass of diatoms and dinoflagellates was greatly depressed in all DOM and NO3Fe treatments. In these treatments, cyanobacterial and bacterial biomasses were highest leading up to phosphate depletion. Plankton development seemed to be bottom-up controlled and to be affected by extracellular compound(s) produced by the dominant cyanobacteria, possibly triggered by phosphate limitation. Diatoms, dinoflagellates, protozoans and metazooplankton were instead stimulated in the NO3 and NO(3)G treatments, where cyanobacterial biomass was low. Accordingly, A. bifilosa reproduction and survival were sustained in NO3 bottles. Deleterious effects of cyanobacteria on metazooplankton were diminished in NO3 and NO(3)G tanks where other food resources were available. Overall, the results suggest that increases in the input of DOM to the Baltic Sea can potentially stimulate cyanobacterial blooms that may disrupt the microbial food web and inhibit metazooplankton development.
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| 9. |
- Salomon, Paulo, et al.
(författare)
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Predicting the population dynamics in Amoebophrya parasitoids and their dinoflagellate hosts using a mathematical model
- 2010
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Ingår i: Marine Ecology Progress Series. - : INTER-RESEARCH. - 0171-8630 .- 1616-1599. ; 419, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Free-living, photosynthetic marine dinoflagellates are frequently infected by microparasites of the genus Amoebophrya. Attacks by Amoebophrya can contribute to the termination of dinoflagellate blooms and have been suggested to influence the geographical distribution of certain host species. Because infection terminates with the killing of the host (i.e. Amoebophrya behaves like a parasitoid), the interaction can be considered, from a modeling point of view, similar to the process of predation, with the difference that it takes a longer time for the parasitoid to kill the host as compared to typical predator-prey interactions. In the present work, we explored the population dynamics in Amoebophrya and their dinoflagellate hosts using the Rosenzweig-MacArthur modification of the traditional Lotka-Volterra predation model. The model was parameterized for 3 systems, Akashiwo sanguinea, Gymnodinium instriatum, and Karlodinium micrum, and their respective Amoebophrya parasitoids, using published experimental data. Parameter validation was possible for parasitoid search rate and mortality. The potential for host control by Amoebophrya and the probability for host extinction were studied with respect to carrying capacity, a parameter that is influenced by e. g. eutrophication. The model may be useful to predict conditions under which Amoebophrya can control populations of its dinoflagellate hosts.
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