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Attached Bacterial Communities in Lakes – Habitat-Specific Differences
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Evolution, Limnology.
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. , p. 35
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 1029
Keywords [en]
Ecology, bacteria, freshwater, sediment, epiphyton, bacterioplankton, metabolically active
Keywords [sv]
Ekologi
National Category
Ecology
Identifiers
URN: urn:nbn:se:uu:diva-4627ISBN: 91-554-6067-4 (print)OAI: oai:DiVA.org:uu-4627DiVA, id: diva2:165291
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
List of papers
1. Quantitative importance of epiphytic versus sediment and planktonic bacteria for the overall carbon turnover in littoral zones
Open this publication in new window or tab >>Quantitative importance of epiphytic versus sediment and planktonic bacteria for the overall carbon turnover in littoral zones
(English)Article in journal (Refereed) Submitted
Identifiers
urn:nbn:se:uu:diva-92273 (URN)
Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2009-03-30Bibliographically approved
2. Large differences in the fraction of active bacteria in plankton, sediments, and biofilm
Open this publication in new window or tab >>Large differences in the fraction of active bacteria in plankton, sediments, and biofilm
2002 (English)In: Microbial Ecology, ISSN 0095-3628, Vol. 43, p. 232-241Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-92274 (URN)
Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2017-11-30Bibliographically approved
3. Depth distribution of active bacteria and bacterial activity in lake sediment
Open this publication in new window or tab >>Depth distribution of active bacteria and bacterial activity in lake sediment
2003 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, Vol. 46, p. 31-38Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-92275 (URN)
Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2017-11-30Bibliographically approved
4. The effect of grazing and nutrient supply on periphyton associated bacteria
Open this publication in new window or tab >>The effect of grazing and nutrient supply on periphyton associated bacteria
2006 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 52, no 1, p. 31-41Article 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.

Keywords
Periphyton, Bacterium, Nutrient regeneration, Grazing, Metabolically active bacterium, Cell-specific activity
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-92276 (URN)10.1016/j.femsec.2004.10.003 (DOI)16329890 (PubMedID)
Available from: 2004-10-28 Created: 2004-10-28 Last updated: 2017-12-14Bibliographically approved

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