| 1. |
- Algesten, Grete, 1974-, et al.
(författare)
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Seasonal variation of CO2 saturation in the Gulf of Bothnia : Indications of marine net heterotrophy
- 2004
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Ingår i: Global Biogeochemical Cycles. - Washington, D.C : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 18, s. 4021-4028
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal variation of pCO2 and primary and bacterioplankton production were measured in the Gulf of Bothnia during an annual cycle. Surface water was supersaturated with CO2 on an annual basis, indicating net heterotrophy and a source of CO2 to the atmosphere. However, the Gulf of Bothnia oscillated between being a sink and a source of CO2 over the studied period, largely decided by temporal variation in bacterial respiration (BR) and primary production (PP) in the water column above the pycnocline. The calculated annual respiration-production balance (BR-PP) was very similar to the estimated CO2 emission from the Gulf of Bothnia, which indicates that these processes were major determinants of the exchange of CO2 between water and atmosphere. The southern basin (the Bothnian Sea) had a lower net release of CO2 to the atmosphere than the northern Bothnian Bay (7.1 and 9.7 mmol C m−2 d−1, respectively), due to higher primary production, which to a larger extent balanced respiration in this basin.
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| 2. |
- Andersson, Agneta, et al.
(författare)
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Pelagisk biologi
- 2004
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Ingår i: Bottniska viken. - Hörnefors : Umeå marina forskningscentrum (UMF). ; , s. 11-13
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Bokkapitel (refereegranskat)
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| 3. |
- Andersson, Agneta, et al.
(författare)
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Vattenmassans biologi
- 2001
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Förekomsten av kiselalger och dinoflagellater visar ingen generell uppgång eller nedgång vid någon av stationerna i Bottenviken, Örefjärden eller Bottenhavet under perioden 1991–2000. Växtplanktonhalterna visar dock på stor variation mellan år, vilket kan påverka andra organismer i ekosystemet.
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| 4. |
- Kisand, Veljo, et al.
(författare)
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Combining culture-dependent and -independent methodologies for estimation of richness of estuarine bacterioplankton consuming riverine dissolved organic matter
- 2003
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Ingår i: Applied and Environmental Microbiology. - : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 69:6, s. 3607-3616
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Tidskriftsartikel (refereegranskat)abstract
- Three different methods for analyzing natural microbial community diversity were combined to maximize an estimate of the richness of bacterioplankton catabolizing riverine dissolved organic matter (RDOM). We also evaluated the ability of culture-dependent quantitative DNA-DNA hybridization, a 16S rRNA gene clone library, and denaturing gradient gel electrophoresis (DGGE) to detect bacterial taxa in the same sample. Forty-two different cultivatable strains were isolated from rich and poor solid media. In addition, 50 unique clones were obtained by cloning of the bacterial 16S rDNA gene amplified by PCR from the community DNA into an Escherichia coli vector. Twenty-three unique bands were sequenced from 12 DGGE profiles, excluding a composite fuzzy band of the Cytophaga-Flavobacterium group. The different methods gave similar distributions of taxa at the genus level and higher. However, the match at the species level among the methods was poor, and only one species was identified by all three methods. Consequently, all three methods identified unique subsets of bacterial species, amounting to a total richness of 97 operational taxonomic units in the experimental system. The confidence in the results was, however, dependent on the current precision of the phylogenetic determination and definition of the species. Bacterial consumers of RDOM in the studied estuary were primarily both cultivatable and uncultivable taxa of the Cytophaga-Flavobacterium group, a concordant result among the methods applied. Culture-independent methods also suggested several not-yet-cultivated beta-proteobacteria to be RDOM consumers.
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| 5. |
- Kisand, Veljo, et al.
(författare)
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Limited resolution of 16S rDNA DGGE caused by melting properties and closely related DNA sequences
- 2003
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Ingår i: Journal of Microbiological Methods. - 0167-7012 .- 1872-8359. ; 54:2, s. 183-191
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Tidskriftsartikel (refereegranskat)abstract
- The phylogenetic affiliation of 91 operational taxonomic units, randomly sampled from three aquatic microcosm experiments, was investigated by two PCR based and one culture dependent method. The occurrence of multiple melting domains and poor coupling between Tin and DGGE retardation was demonstrated to cause poor resolution at the species level in PCR-DGGE analysis of microbial communities. We also showed that the problem of multiple melting domains was particularly prone for brackish water bacterioplankton in the Flavobacterium genus, providing characteristic band morphology for this genus. Banding patterns from DGGE analysis may therefore be misinterpreted in terms of the species richness in natural bacterial communities, when using commonly applied universal primers. (C) 2003 Elsevier Science B.V. All rights reserved.
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| 6. |
- Kisand, Veljo, et al.
(författare)
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Phylogeny of culturable estuarine bacteria catabolizing riverine organic matter in the northern Baltic Sea
- 2002
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Ingår i: Applied and Environmental Microbiology. - : American Society of Microbiology. - 0099-2240 .- 1098-5336. ; 68:1, s. 379-388
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Tidskriftsartikel (refereegranskat)abstract
- The objective of our study was to isolate and determine the phylogenetic affiliation of culturable estuarine bacteria capable of catabolizing riverine dissolved organic matter (RDOM) under laboratory conditions. Additions of RDOM consistently promoted the growth of estuarine bacteria in carbon-limited dilution cultures, with seasonal variation in growth rates and yields. At least 42 different taxa were culturable on solid agar media and, according to quantitative DNA-DNA hybridizations, constituted 32 to 89% of the total bacterial number in the enriched treatments. Five species in the Cytophaga-Flexibacter-Bacteroides group and one in the gamma-proteobacteria phylogenetic group (Marinomonas sp.) were numerically dominant during the stationary phase of the RDOM-enriched dilution cultures but not in the control cultures. Four of the isolates in Cytophaga-Flexibacter-Bacteroides group were putatively affiliated with the genus Flavobacterium. All dominating isolates were determined to be new species based on comparison to the current databases. The same group of species dominated independently of the season investigated, suggesting a low diversity of bacteria catabolizing RDOM in the estuary. It also suggested a broad tolerance of the dominating species to seasonal variation in hydrography, chemistry, and competition with other species. Taken together, our results suggest that a limited group of bacteria, mainly in the Flavobacterium genus, played an important role in introducing new energy and carbon to the marine system in the northern Baltic Sea.
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| 7. |
- Langenheder, Silke, et al.
(författare)
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Growth dynamics within bacterial communities in riverine and estuarine batch cultures
- 2004
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 37, s. 137-148
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Tidskriftsartikel (refereegranskat)abstract
- We investigated temporal changes in community composition of bacteria growing on riverine dissolved organic carbon. Batch cultures were adjusted to riverine or estuarine salinity levels and inoculated with bacteria from these 2 environments to test whether growth patterns of bacterial taxa are influenced by salinity and/or the source of the inoculum. Changes in bacterial community composition at different stages of the growth phase were studied by 16S rDNA denaturing gradient gel electrophoresis (DGGE). Furthermore, the growth dynamics of 7 bacteria previously isolated from the estuary were followed by quantitative DNA-DNA hybridization. Growth dynamics within bacterial communities were significantly influenced by the source of the inoculum but not by salinity, suggesting that slight changes in salinity, to which riverine bacteria are exposed when discharged into the Northern Baltic Sea, are not a major regulating factor of community dynamics. Additionally, our results indicated only minor differences in the appearance and growth of bacteria when examined by quantitative DNA-DNA hybridization, whereas DGGE banding patterns suggested that there were fast- and slow-growing types of bacteria.
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| 8. |
- Langenheder, Silke, et al.
(författare)
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Salinity as a structuring factor for the composition and performance of bacterioplankton degrading riverine DOC
- 2003
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Ingår i: FEMS Microbiology Ecology. - 0168-6496 .- 1574-6941. ; 45:2, s. 189-202
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Tidskriftsartikel (refereegranskat)abstract
- The impact of salinity on the composition and functional performance (biomass production, growth efficiency and growth rates) of bacterial communities was investigated using batch cultures growing on dissolved organic carbon from a river draining into the Northern Baltic Sea. The cultures were adjusted to riverine or estuarine salinity levels and inoculated with bacteria from these two environments. Bacterial growth efficiencies differed in response to salinity and the origin of the inoculum. When salinity was adjusted to correspond to the salinity at the site where the inoculum was retrieved, growth efficiency was relatively high (11.5 +/- 2.6%). However, when bacteria were confronted with a shift in salinity, growth efficiency was lower (7.5 +/- 2.0%) and more of the utilized carbon was respired. In contrast, growth rates were higher when bacteria were exposed to a change in salinity. The composition of the bacterial communities developing in the batch cultures differed, as shown by 16S rDNA DGGE, depending on the origin of the inoculum and salinity. Reverse and direct DNA-DNA hybridization revealed salinity optima in the growth of specific bacterial strains as well as broader phylogenetic groups. Strains belonging to the alpha- and beta-Proteobacteria, Actinobacteria and gamma-Proteobacteria other than the genus Pseudomonas showed higher relative abundance under freshwater conditions, whereas strains of the genus Pseudomonas and the Cytophaga-Flavobacterium-Bacteroides group were favored by estuarine conditions. Generally, our results demonstrate functional changes associated with changes in community composition. We suggest that even moderate changes in salinity affect bacterial community composition, which subsequently leads to altered growth characteristics. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
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| 9. |
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| 10. |
- Sandberg, Johannes, et al.
(författare)
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Pelagic food web structure and carbon budget in the northern Baltic Sea: Potential importance of terrigenous carbon
- 2004
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Ingår i: Marine Ecology Progress Series. - : Inter-Research. - 0171-8630 .- 1616-1599. ; 268, s. 13-29
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to quantitatively assess the relative importance of terrigenous dissolved organic material (TDOC) as a carbon source for secondary producers (e.g. bacteria) and as a structuring factor for the pelagic food web in the Gulf of Bothnia, northern Baltic Sea. The 3 study sites, situated in Bothnian Bay (BB), the Öre Estuary (ÖE) and the Bothnian Sea (BS), had markedly different freshwater loads and water-residence times. In Bothnian Bay, bacterial biomass and production were higher than expected from the levels of phytoplankton biomass and productivity there, suggesting an uncoupling of bacterial productivity from phytoplankton production. Phytoplankton size structure and size-fractionated production were, however, relatively similar among areas. A simplified carbon budget model suggested that bacterioplankton dominated organic carbon consumption in all of the food webs studied, but was most marked in BB. The model showed that the available autochthonous primary production could not alone support the heterotrophic carbon demand in BB. The most likely explanation of this discrepancy was that the total annual input of terrigenous dissolved organic carbon was bioavailable, resulting in a budget closer to balance with the heterotrophic carbon demand. BB, receiving 38% of the carbon input from land, was consequently a net heterotrophic ecosystem. A sensitivity analysis showed that the bacterial carbon demand, and growth efficiency in particular, had the greatest influence on the resulting budget. TDOC was the dominant carbon source in ÖE, but the losses of carbon through advection to offshore areas and sedimentation was high. The evidence of net heterotrophy in ÖE was therefore weaker than in BB. In BS the input of TDOC was less important, and the carbon used for secondary production originated mainly from autochthonous primary production. Our results suggest that the supply of TDOC is of great importance for the abundance of plankton and as a structuring factor for the aquatic food webs in the Gulf of Bothnia.
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