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Impact of Alexandrium tamarense allelochemicals on DOM dynamics in an estuarine microbial community
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences. (Marine Ecology)
French research Institute for the exploitation of the sea (Ifremer), L`Houmeau, France. (Ressources and Environment Laboratory)
French research Institute for the exploitation of the sea (Ifremer), L`Houmeau, France. (Ressources and Environment Laboratory)
Linnaeus University, Faculty of Science and Engineering, School of Natural Sciences.
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2012 (English)In: Harmful Algae, ISSN 1568-9883, E-ISSN 1878-1470, Vol. 13, 58-64 p.Article in journal (Refereed) Published
Abstract [en]

Plankton and dissolved organic carbon (DOC) dynamics in fractionated estuarine microbial communities (<150 μm, <60 μm and <20 μm), incubated with allelopathic (lytic) or non allelopathic (non-lytic) Alexandrium tamarense filtrates were investigated over a period of 48 h. Additionally, the amount of dissolved organic matter (DOM) available for bacterial growth in the treatments was measured via bacterial seawater culture experiments immediately and 6 h after addition of A. tamarense filtrates. The lack of effect on DOC concentrations and plankton community composition in lytic treatments indicated that allelochemicals did not inhibit the growth of the microbial community. Nevertheless, bacterial seawater culture experiments provided evidence that lytic filtrate addition provoked the release of bioavailable DOM from the microbial community. Since DOM was only released from the largest seawater fraction, microorganisms >60 μm were probably most sensitive towards allelochemicals.

Place, publisher, year, edition, pages
2012. Vol. 13, 58-64 p.
Keyword [en]
alexandrium, marine ecology, phytoplankton, bacteria, dissolved organic carbon, allelopathy, microbial food webs
National Category
Ecology
Research subject
Natural Science, Aquatic Ecology; Natural Science, Microbiology
Identifiers
URN: urn:nbn:se:lnu:diva-11370DOI: 10.1016/j.hal.2011.10.003OAI: oai:DiVA.org:lnu-11370DiVA: diva2:410041
Projects
ALGBACT
Available from: 2011-04-12 Created: 2011-04-12 Last updated: 2015-12-17Bibliographically approved
In thesis
1. The role of allelopathy in microbial food webs
Open this publication in new window or tab >>The role of allelopathy in microbial food webs
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Phytoplankton produce allelochemicals; excreted chemical substances that are affecting other microorganisms in their direct environment.

In my thesis, I investigated strain specific variability in the expression of allelochemicals of the harmful flagellate Prymnesium parvum, that is euryhaline but mainly bloom forming in brackish water. I found a large variation among strains, but further showed that all strains of P. parvum were more allelopathic in brackish water compared to marine water.

In a marine microbial community, allelochemicals can affect prey, competitors and grazers both, directly and indirectly. For instance, in a food web where grazing controls prey abundance, the negative direct effect of allelochemicals on grazers will positive affect their prey. During my thesis, I investigated how marine microbial communities respond to the addition of allelochemicals. I performed field experiments with microbial communities from seawater collected from different places over Europe, and tested how this communities respond to the addition of allelochemicals from the dinoflagellate Alexandrium tamarense. Before I incubated the microbial communities for several days with A. tamarense algal filtrate, I evaluated the allelopathic efficiency of the algal filtrates with an algal monoculture of Rhodomonas spp. This allowed me to compare the effect of A. tamarense filtrate between the different microbial communities.

In general, bacteria reached higher abundances when allelochemicals were present. As allelochemicals also inhibited nanoflagellates and ciliates, we concluded, that allelochemicals indirectly benefit bacteria by reducing grazing pressure. In microbial food webs with many heterotrophic grazers, allelochemicals further benefitted other phytoplankton by inhibiting grazers.

It was also shown that bioavailable DOM is released from a microbial community when allelochemicals are present. As most DOM was released from the seawater fraction > 60 μm, we concluded, that larger microorganisms are more affected by allelochemicals than smaller microorganisms. The results can be explained by the surface to volume ratio of microorganisms: Larger organisms provide more contact surface for allelochemicals, and therefore, are probably more vulnerable towards allelochemicals.

In conclusion, the effect of allelochemicals on a microbial community depends among others on the structure of the microbial food web, the amount of available DOM, the particle density in the seawater and the composition of the phytoplankton community.

Place, publisher, year, edition, pages
Växjö, Kalmar: Linnaeus University Press, 2011
Series
Linnaeus University Dissertations, 33/2011
Keyword
Microbial food web, Allelopathy, Alexandrium tamarense, Prymnesium parvum, Infochemicals, marine plankton community
National Category
Ecology
Research subject
Natural Science, Aquatic Ecology
Identifiers
urn:nbn:se:lnu:diva-11375 (URN)978-91-86491-62-8 (ISBN)
Public defence
2011-03-04, Fullrigarren, Barlastgatan 11, Kalmar, 09:15 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Available from: 2011-04-13 Created: 2011-04-12 Last updated: 2014-05-12Bibliographically approved

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