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- Sala, M. M., et al.
(författare)
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Contrasting effects of ocean acidification on the microbial food web under different trophic conditions
- 2016
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 73:3, s. 670-679
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the effects of an increase in dissolved CO2 on the microbial communities of the Mediterranean Sea during two mesocosm experiments in two contrasting seasons: winter, at the peak of the annual phytoplankton bloom, and summer, under low nutrient conditions. The experiments included treatments with acidification and nutrient addition, and combinations of the two. We followed the effects of ocean acidification (OA) on the abundance of the main groups of microorganisms (diatoms, dinoflagellates, nanoeukaryotes, picoeukaryotes, cyanobacteria, and heterotrophic bacteria) and on bacterial activity, leucine incorporation, and extracellular enzyme activity. Our results showed a clear stimulation effect of OA on the abundance of small phytoplankton (pico- and nanoeukaryotes), independently of the season and nutrient availability. A large number of the measured variables showed significant positive effects of acidification in summer compared with winter, when the effects were sometimes negative. Effects of OA were more conspicuous when nutrient concentrations were low. Our results therefore suggest that microbial communities in oligotrophic waters are considerably affected by OA, whereas microbes in more productive waters are less affected. The overall enhancing effect of acidification on eukaryotic pico- and nanophytoplankton, in comparison with the non-significant or even negative response to nutrient-rich conditions of larger groups and autotrophic prokaryotes, suggests a shift towards medium-sized producers in a future acidified ocean.
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| 5. |
- Villarino, Ernesto, et al.
(författare)
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Large-scale ocean connectivity and planktonic body size
- 2018
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Global patterns of planktonic diversity are mainly determined by the dispersal of propagules with ocean currents. However, the role that abundance and body size play in determining spatial patterns of diversity remains unclear. Here we analyse spatial community structure - beta-diversity - for several planktonic and nektonic organisms from prokaryotes to small mesopelagic fishes collected during the Malaspina 2010 Expedition. beta-diversity was compared to surface ocean transit times derived from a global circulation model, revealing a significant negative relationship that is stronger than environmental differences. Estimated dispersal scales for different groups show a negative correlation with body size, where less abundant large-bodied communities have significantly shorter dispersal scales and larger species spatial turnover rates than more abundant small-bodied plankton. Our results confirm that the dispersal scale of planktonic and micro-nektonic organisms is determined by local abundance, which scales with body size, ultimately setting global spatial patterns of diversity.
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| 6. |
- Baltar, Federico, et al.
(författare)
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High dissolved extracellular enzymatic activity in the deep Central Atlantic Ocean
- 2010
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 58:3, s. 287-302
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of prokaryotic abundance (PA), prokaryotic heterotrophic production (PHP), and suspended particulate organic material (POM), as well as total and dissolved (operationally defined as passing through 0.2 mu m pore size filters) potential extracellular enzymatic activities (EEA; alpha- and beta-glucosidase [AGase and BGase], leucine aminopeptidase [LAPase], and alkaline phosphatase [APase]) were determined in the meso- and bathypelagic waters of the (sub)tropical Atlantic along an eastern zonal transatlantic transect and a western N-S transect. Significant differences between both transects were found for POM concentration but not for PA, PHP (except in the subsurface and oxygen minimum layer), and dissolved and total EEA. PHP decreased by 3 orders of magnitude from the lower euphotic zone to bathypelagic waters, while PA and cell-specific PHP decreased only by 1 and 2 orders of magnitude, respectively. The proportion of the dissolved to the total EEA was high in the dark ocean for all the enzymes, ranging from 54 to 100, 56 to 100, 65 to 100 and 57 to 97 % for AGase, BGase, LAPase and APase, respectively. The kinetic parameters (V-max, and K-m) of both the dissolved and total fractions of LAPase and APase were very similar throughout the water column, suggesting a similar origin for both dissolved and particulate EEA. Significant correlations of both dissolved and total EEA were found with prokaryotic metabolism and the POM pool. Based on the previous notion that the fraction of dissolved EEA is higher in particle-attached than in free-living microbes, our results suggest that microbial activity in the dark ocean occurs mainly on colloidal and particulate material. This is in agreement with recent genomic evidence. However, these colloidal and particulate materials are prone to disruption during the sampling process. Hence, more selective sampling techniques are needed to specifically collect these deep-water aggregates that probably represent hotspots of microbial activity in the deep ocean.
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| 7. |
- Baltar, Federico, et al.
(författare)
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Prokaryotic extracellular enzymatic activity in relation to biomass production and respiration in the meso- and bathypelagic waters of the (sub)tropical Atlantic
- 2009
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 11:8, s. 1998-2014
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Tidskriftsartikel (refereegranskat)abstract
- P>Prokaryotic extracellular enzymatic activity, abundance, heterotrophic production and respiration were determined in the meso- and bathypelagic (sub)tropical North Atlantic. While prokaryotic heterotrophic production (PHP) decreased from the lower euphotic layer to the bathypelagic waters by two orders of magnitude, prokaryotic abundance and cell-specific PHP decreased only by one order of magnitude. In contrast to cell-specific PHP, cell-specific extracellular enzymatic activity (alpha- and beta-glucosidase, leucine aminopeptidase, alkaline phosphatase) increased with depth as did cell-specific respiration rates. Cell-specific alkaline phosphatase activity increased from the intermediate water masses to the deep waters up to fivefold. Phosphate concentrations, however, varied only by a factor of two between the different water masses, indicating that phosphatase activity is not related to phosphate availability in the deep waters. Generally, cell-specific extracellular enzymatic activities were inversely related to cell-specific prokaryotic leucine incorporation. Thus, it is apparent that the utilization of deep ocean organic matter is linked to higher cell-specific extracellular enzymatic activity and respiration and lower cell-specific PHP than in surface waters.
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| 10. |
- Sandaa, R.-A., et al.
(författare)
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Viral control of bacterial biodiversity – Evidence from a nutrient enriched marine mesocosm experiment
- 2009
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 11:10, s. 2585-2597
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate here results showing that bottom-up and top-down control mechanisms can operate simultaneously and in concert in marine microbial food webs, controlling prokaryote diversity by a combination of viral lysis and substrate limitation. Models in microbial ecology predict that a shift in the type of bacterial growth rate limitation is expected to have a major effect on species composition within the community of bacterial hosts, with a subsequent shift in the composition of the viral community. Only moderate effects would, however, be expected in the absolute number of coexisting virus-host pairs. We investigated these relationships in nutrient-manipulated systems, under simulated in situ conditions. There was a strong correlation in the clustering of the viral and bacterial community data supporting the existence of an important link between the bacterial and viral communities. As predicted, the total number of viral populations was the same in all treatments, while the composition of the viral community varied. Our results support the theoretical prediction that there is one control mechanism for the number of niches for coexisting virus-host pairs (top-down control), and another mechanism that controls which virus-host pairs occupy these niches (bottom-up control).
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