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The effect of grazing and nutrient supply on periphyton associated bacteria
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
2006 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 52, no 1, 31-41 p.Article in journal (Refereed) Published
Abstract [en]

The effects of nutrient additions and grazing by macro-invertebrates on periphyton-associated algae and bacteria were studied by performing an enclosure experiment on three occasions from early spring to summer at mesotrophic Lake Erken and Väddö, at the Swedish Baltic coast. There were significant interactions between nutrient additions and grazing on bacterial biomass and specific activity in Lake Erken. Thus, the importance of either bottom-up or top-down effects could not be singled out. Bacterial biomass increased with enrichment only in the absence of grazers. Grazer presence tended to increase bacterial biomass in ambient nutrient conditions, but to decrease bacterial biomass under enrichment. For specific activity the positive response to enrichment was restricted to grazer presence. Hence, grazing by macro-invertebrates may have an indirect positive effect on bacterial activity by enhancing nutrient conditions through their feeding activities and/or fecal pellets production. In addition, we found a significant relationship between bacterial production and chlorophyll a at both sites. This relationship weakened in the presence of macro-invertebrates. Thus, the importance of internal nutrient regeneration by bacteria and algae decreased, possibly due to increased nutrient availability, in the presence of macro-invertebrate grazers.

Place, publisher, year, edition, pages
2006. Vol. 52, no 1, 31-41 p.
Keyword [en]
Periphyton, Bacterium, Nutrient regeneration, Grazing, Metabolically active bacterium, Cell-specific activity
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-92276DOI: 10.1016/j.femsec.2004.10.003PubMedID: 16329890OAI: oai:DiVA.org:uu-92276DiVA: diva2:165290
Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Attached Bacterial Communities in Lakes – Habitat-Specific Differences
Open this publication in new window or tab >>Attached Bacterial Communities in Lakes – Habitat-Specific Differences
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For many years, the importance of microorganisms attached to surfaces in littoral zones and wetlands has been disregarded when describing aquatic ecosystem dynamics. Supporting evidence is scarce but convincing that these microbial communities are not only very productive but can often serve as major regulators of nutrient and carbon dynamics in many freshwaters. In order to determine the quantitative importance of epiphytic bacteria for the overall carbon turnover, I compared the relative contribution of epiphytic bacteria on the submerged macrophyte Ranunculus circinatus, sediment and free-living bacteria to the total bacterial production. Sediment bacteria generally dominated total bacterial biomass in the littoral zone. Although the epiphytic biomass on R. circinatus was ten times lower than the biomass of sediment bacteria, it often contributed at least equally to the total bacterial production. Thus, the results presented in this thesis confirm that most bacterial biomass and production in shallow lakes is associated with surfaces, and that in littoral zones with dense macrophyte stands, epiphytic bacteria can contribute significantly to the overall carbon turnover.

There is increasing evidence that not all cells in natural bacterial communities are metabolically active. In Lake Erken, there were large differences in the fraction of active bacteria between different habitats, while the within-habitat differences were small. The sediments had the largest bacterial fraction, followed by epiphytic bacteria, while in the water column only a few percent of the bacteria were active. In this thesis the fraction of active bacteria is connected to environmental fluctuations. I hypothesize that smaller fluctuations in chemical, biological or physical factors result in large active bacterial fractions. Thus, small environmental fluctuations within a habitat allow large active bacterial fractions, while the active fraction is constrained when the environmental fluctuations are large.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2004. 35 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1029
Keyword
Ecology, bacteria, freshwater, sediment, epiphyton, bacterioplankton, metabolically active, Ekologi
National Category
Ecology
Identifiers
urn:nbn:se:uu:diva-4627 (URN)91-554-6067-4 (ISBN)
Public defence
2004-11-19, Lecture Hall, Department of Limnology, Norbyvägen 20, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2009-03-31Bibliographically approved

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