Effect of nutrient enrichment on bacterioplankton biomass and community composition in mesocosms in the Archipelago Sea, northern Baltic |
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| Authors: | Sipura Jaana; Haukka Kaisa; Helminen Harri; Lagus Annika; Suomela Janne; Sivonen Kaarina |
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| Institution: | 1 Section of Ecology, Department of Biology, University of Turku, FIN-20014 Turku, Finland, 2 Department of Applied Chemistry and Microbiology, Viikki Biocenter, PO Box 56, FIN-00014 University of Helsinki, Finland and 3 SW Finland Regional Environment Centre, PO Box 47, FIN-20801 Turku, Finland
 Present Address: National Public Health Institute, Mannerheimintie 166, 00300 Helsinki, Finland |
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| Abstract: | Effects of nutrient enrichment on the biomass and communitycomposition of heterotrophic bacteria and picocyanobacteriawere studied in large (42 m3) mesocosms in the brackish-waterArchipelago Sea (Baltic Sea) in late summer 2000 using cellcounts and denaturing gradient gel electrophoresis (DGGE) ofpolymerase chain reaction (PCR)-amplified 16S rRNA gene fragments.The identity of the major DNA bands was determined by sequencing.The obtained sequences were related to  - and  -proteobacteria,actinobacteria, verrucomicrobia and cyanobacteria. Nitrogenand phosphorus additions increased the biomasses of heterotrophicbacteria and picocyanobacteria and caused significant changesin their community composition judging from the DGGE bandingpatterns. Most verrucomicrobial bands had their highest relativeintensity in the control treatment and their lowest in the highernutrient addition treatment, whereas most Synechococcus-relatedbands had their lowest relative intensity in the lower nutrientaddition treatment. The responses of proteobacteria and actinobacteriawere more variable. The presence of both freshwater and marinesequences among the closest relatives to our sequences highlightsthe intermediate character of the Archipelago Sea between afreshwater and truly marine environment. |
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