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Toxin-producing cyanobacterium Nodularia spumigena, potential competitors and grazers: testing mechanisms of reciprocal interactions
Stockholm University, Faculty of Science, Department of Systems Ecology.
Stockholm University, Faculty of Science, Department of Systems Ecology.
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2011 (English)In: Aquatic Microbial Ecology, ISSN 0948-3055, E-ISSN 1616-1564, Vol. 62, no 1, 39-48 p.Article in journal (Refereed) Published
Abstract [en]

Interactions among toxic cyanobacteria, sympatric algae and planktivorous grazers are key processes governing plankton dynamics and cyanobacterial blooms. We studied interactions between the cyanobacterium Nodularia spumigena and microalgae (Rhodomonas salina and Tetraselmis suecica) as well as effects of zooplankton (copepod Eurytemora affinis) grazing on these interactions. N. spumigena was incubated without algae or with algae at different concentrations and with or without copepods. Following similar to 24 h incubation, we assayed changes in N. spumigena and algae abundance, concentration of intracellular (IC) and dissolved nodularin (toxin produced by N. spumigena) and quantity of Nodularia DNA in copepod guts (as a proxy for grazing pressure on the cyanobacterium). In the presence of algae, IC nodularin levels increased in a concentration-dependent manner; however, when copepods were present in the mixtures of algae and cyanobacterium, this increase was significantly less. The presence of T. suecica negatively affected the growth rate of N. spumigena, whereas the presence of the cyanobacterium strongly impeded growth of R. salina, but not of T. suecica. The IC nodularin quota correlated negatively with growth of R. salina, implicating the toxin's involvement in the observed growth suppression of the eukaryotic alga. Copepods actively ingested N. spumigena, even when the alternative food was plentiful, and neither N. spumigena quantity nor its toxin concentrations influenced copepod feeding rates and survival. These findings suggest complex allelopathic interactions between the autotrophs, whereas mesozooplankton grazers have an indirect negative effect on the nodularin concentrations by suppressing the competitors. These findings underscore the need to study ecologically important interactions among toxic cyanobacteria, sympatric algae and grazers, if we are to understand mechanisms regulating cyanobacterial blooms.

Place, publisher, year, edition, pages
2011. Vol. 62, no 1, 39-48 p.
Keyword [en]
Algae, Allelopathy, Grazers, Molecular diet analysis, Nodularin, Toxic cyanobacteria, Trophic interactions
National Category
Ecology Oceanography, Hydrology, Water Resources
Research subject
Marine Ecology
Identifiers
URN: urn:nbn:se:su:diva-68394DOI: 10.3354/ame01456ISI: 000285935100004OAI: oai:DiVA.org:su-68394DiVA: diva2:472607
Note

authorCount :6

Available from: 2012-01-04 Created: 2012-01-03 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Summer cyanobacterial blooms in the Baltic Sea - implications for copepod recruitment
Open this publication in new window or tab >>Summer cyanobacterial blooms in the Baltic Sea - implications for copepod recruitment
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

During summer, the Baltic Sea is subjected to the world’s largest cyanobacterial blooms. These blooms are linked to eutrophication and raise many questions concerning their effects on the ecosystem. To understand their impacts on the food web dynamics, it is essential to assess growth responses of grazers to these cyanobacteria. In the northern Baltic proper, copepods are the most important herbivores providing an essential link between the primary producers and higher trophic levels. In this Thesis, Papers I & II evaluate methods to estimate copepod growth in response to feeding conditions in situ. The most conspicuous diazotrophic filamentous cyanobacterium in the Baltic Sea is Nodularia spumigena, a producer of nodularin which is highly toxic to vertebrates, yet its ecological role is largely unknown. In Paper III, reciprocal interactions between cyanobacteria, sympatric algae and copepods are studied. The results suggest that nodularin is likely involved in allelopathic interactions, but it is not an inducible defense against grazers. Furthermore, the results of Papers IV & V, indicate that natural assemblages of N. spumigena and Anabaena spp. may support copepod reproduction and that total diazotrophic filamentous cyanobacteria appear to provide a beneficial feeding environment for the feeding stages of copepod nauplii, most probably by stimulating the microbial communities that nauplii feed upon. Since cyanobacterial blooms are projected to increase due to global climate change, the combined effects of toxic cyanobacteria, ocean acidification and global warming predicted for year 2100 are further investigated on copepods in Paper IV. Taken together, these studies indicate that filamentous diazotrophic cyanobacteria contribute to sustaining secondary productivity and have potential implications of management practices with respect to combating eutrophication, global climate change and sustaining fish feeding conditions.

Place, publisher, year, edition, pages
Stockholm: Department of Systems Ecology, Stockholm University, 2012. 56 p.
Keyword
Cyanobacteria, Calanoid copepods, Food web interactions, Harmful algae blooms, Zooplankton, Nodularin, Allelopathy, Baltic Sea, Biochemical markers, RNA-based indices, Acidification, Global Climate Change
National Category
Ecology
Research subject
Marine Ecology
Identifiers
urn:nbn:se:su:diva-81680 (URN)978-91-7447-566-1 (ISBN)
Public defence
2012-12-03, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 10:00 (English)
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Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.

Available from: 2012-11-12 Created: 2012-10-30 Last updated: 2015-04-13Bibliographically approved

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