| 1. |
- Baltar, Federico, et al.
(författare)
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Bacterial Versus Archaeal Origin of Extracellular Enzymatic Activity in the Northeast Atlantic Deep Waters
- 2013
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Ingår i: Microbial Ecology. - Springer-Verlag : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 65:2, s. 277-288
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Tidskriftsartikel (refereegranskat)abstract
- We determined the total and dissolved extracellularenzymatic activity (EEA) of α-glucosidase and β-glucosidase(AGase and BGase), alkaline phosphatase (APase) and leucineaminopeptidase (LAPase) activities in the epi-, meso- andbathypelagic waters of the subtropical Northeast Atlantic.EEA was also determined in treatments in which bacterialEEAwas inhibited by erythromycin. Additionally, EEA decayexperiments were performed with surface and deep waters todetermine EEA lifetimes in both water masses. The proportionof dissolved to total EEA (66–89 %, 44–88 %, 57–82 % and86–100 % for AGase, BGase, APase and LAPase, respectively)was generally higher than the cell-associated (i.e.,particulate) EEA. The percentage of dissolved to total EEAwas inversely proportional to the percentage of erythromycininhibitedto total EEA. Since erythromycin-inhibited plusdissolved EEA equaled total EEA, this tentatively suggeststhat cell-associated EEA in the open oceanic water column isalmost exclusively of bacterial origin. The decay constants ofdissolved EEAwere in the range of 0.002–0.048 h−1 dependingon the type of extracellular enzyme, temperature and depthin the water column. Although dissolved EEA can have differentorigins, the major contribution of Bacteria to cellassociatedEEA and the long life-time of dissolved EEAsuggest that Bacteria—and not mesophilic Archaea—areessentially the main producers of EEA in the open subtropicalNortheast Atlantic down to bathypelagic layers.
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| 2. |
- Baltar, Federico, et al.
(författare)
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Evidence of prokaryotic metabolism on suspended particulate organic matter in the dark waters of the (sub)tropical North Atlantic
- 2009
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 54:1, s. 182-193
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of prokaryotic abundance (PA), respiratory activity (ETS), heterotrophic production (PHP), and suspended particulate (POM) and dissolved (DOM) organic matter was determined in the meso- and bathypelagic waters of the (sub) tropical North Atlantic. PA decreased by one order of magnitude from the lower euphotic zone to the bathypelagic waters, while ETS decreased by two and PHP by three orders of magnitude. On a section following the Mid-Atlantic Ridge from 35 degrees N to 5 degrees N, ETS below 1000-m depth increased southwards up to three-fold. This latitudinal gradient in the deep waters was paralleled by a six-fold increase in Particulate Organic Carbon (POC), whereas no trend was apparent in the DOM distribution. Significant correlations between POM and ETS were obtained in the water masses between 1000-m and 3000-m depth, the Antarctic Intermediate Water and the North East Atlantic Deep Water. A strong imbalance in the dark ocean was found between prokaryotic carbon demand (estimated through two different approaches) and the carbon sinking flux derived from sediment-trap records corrected with Th-230. The imbalance was greater when deeper in the water column, suggesting that the suspended carbon pool must account for most of the carbon deficit. Our results, together with other recent findings discussed in this paper, indicate that microbial life in the dark ocean is likely more dependent on slowly sinking or buoyant, laterally advected suspended particles than hitherto assumed.
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| 3. |
- 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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| 4. |
- Baltar, Federico, 1982-, et al.
(författare)
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Mesoscale eddies: hot-spots for prokaryotic diversity and function in the ocean
- 2010
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Ingår i: The ISME Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370. ; 4, s. 975-988
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Tidskriftsartikel (refereegranskat)abstract
- To investigate the effects of mesoscale eddies on prokaryotic assemblage structure and activity, we sampled two cyclonic eddies (CEs) and two anticyclonic eddies (AEs) in the permanent eddy-field downstream the Canary Islands. The eddy stations were compared with two far-field (FF) stations located also in the Canary Current, but outside the influence of the eddy field. The distribution of prokaryotic abundance (PA), bulk prokaryotic heterotrophic activity (PHA), various indicators of single-cell activity (such as nucleic acid content, proportion of live cells, and fraction of cells actively incorporating leucine), as well as bacterial and archaeal community structure were determined from the surface to 2000 m depth. In the upper epipelagic layer (0–200 m), the effect of eddies on the prokaryotic community was more apparent, as indicated by the higher PA, PHA, fraction of living cells, and percentage of active cells incorporating leucine within eddies than at FF stations. Prokaryotic community composition differed also between eddy and FF stations in the epipelagic layer. In the mesopelagic layer (200–1000 m), there were also significant differences in PA and PHA between eddy and FF stations, although in general, there were no clear differences in community composition or single-cell activity. The effects on prokaryotic activity and community structure were stronger in AE than CE, decreasing with depth in both types of eddies. Overall, both types of eddies show distinct community compositions (as compared with FF in the epipelagic), and represent oceanic ‘hotspots’ of prokaryotic activity (in the epi- and mesopelagic realms).
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| 5. |
- Baltar, Federico, et al.
(författare)
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Mesoscale variability modulates seasonal changes in the trophic structure of nano- and picoplankton communities across the NW Africa-Canary Islands transition zone
- 2009
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Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611 .- 1873-4472. ; 83:1-4, s. 180-188
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Tidskriftsartikel (refereegranskat)abstract
- The variability of picoplankton and nanoplankton autotrophic (A) and heterotrophic (H) communities was studied along a zonal gradient extending from the NW African shelf to 500 km offshore in two contrasting seasons of the year: early spring (spring) and summer (summer). Plankton abundance was significantly higher in summer than in spring. In particular, heterotrophic prokaryotes (HP) and Prochlorococcus (Proc) were an order of magnitude more abundant in summer, presumably due to a higher loading of dissolved organic matter and higher temperatures. The average ratio of A to H biomass was lower during the summer. Over the African shelf, picoplankton was lowest during summer, while both the autotrophic and heterotrophic nanoflagellates (ANF and HNF) showed the highest abundances. In contrast, in spring, the highest abundance of Picoeukaryotes (PE) and Synechococcus (Syn) was found over or close to the shelf. The offshore sampling sections intersected a complex area of strong mesoscale variability, which affected the plankton distribution. In summer, the entrainment of an upwelling filament around a cyclonic eddy provoked the increase of HP and Syn abundances by about one order of magnitude over the surrounding waters, while PE were more abundant over the core of the eddy (probably due to nutrient pumping). In spring, HP and Syn were more abundant at the boundaries of an anticyclonic eddy and in the filament (where PE also increased). Proc abundance increased up to one order of magnitude in the core of the eddy and in the eddy-oceanic waters front. ANF and HNF showed the highest abundances in the filament and the eddy. in summary, although seasonality affects the background variability in microplankton communities, the mesoscale variability found in the Canary Islands transition zone strongly modulates the patterns of distribution, abundances and changes in community structure, altering the A to H ratio and concomitantly playing a key role modifying the carbon pathways within the food web in the region.
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| 6. |
- Baltar, Federico, et al.
(författare)
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Microbial functioning and community structure variability in the mesopelagic and epipelagic waters of the subtropical Northeast Atlantic Ocean.
- 2012
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Ingår i: Applied and Environmental Microbiology. - 0099-2240 .- 1098-5336. ; 78:9, s. 3309-3316
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Tidskriftsartikel (refereegranskat)abstract
- We analyzed the regional distribution of bulk heterotrophic prokaryotic activity (leucine incorporation) and selected single-cell parameters (cell viability and nucleic acid content) as parameters for microbial functioning, as well as bacterial and archaeal community structure in the epipelagic (0-200 m) and mesopelagic (200-1000 m) subtropical Northeast Atlantic Ocean. We selectively sampled three contrasting regions covering a wide range of surface productivity and oceanographic properties within the same basin: (i) the eddy field south of the Canary Islands, (ii) the open-ocean Subtropical Gyre and (iii) the upwelling filament off Cape Blanc. In the epipelagic waters, a high regional variation in hydrographic parameters and bacterial community structure was detected accompanied, however, by a low variability in microbial functioning. In contrast, mesopelagic microbial functioning was highly variable between the studied regions despite the homogeneous abiotic conditions found therein. More microbial functioning parameters indicated differences among the three regions within the mesopelagic (i.e., viability of cells, nucleic acid content, cell-specific heterotrophic activity, nanoflagellate abundance, prokaryotic to nanoflagellate abundance ratio) than in the epipelagic (i.e., bulk activity, nucleic acid content and nanoflagellate abundance) waters. Our results show that the mesopelagic realm in the NE Atlantic is, in terms of microbial activity, more heterogeneous than its epipelagic counterpart, probably linked to mesoscale hydrographical variations.
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| 7. |
- Baltar, Federico, et al.
(författare)
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Prokaryotic carbon utilization in the dark ocean: : growth efficiency, leucine-to-carbon conversion factors, and their relation
- 2010
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 60:3, s. 227-232
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were conducted in the mesopelagic subtropical northeast Atlantic Ocean to determine the range of variability in the prokaryotic leucine-to-carbon conversion factor (CF), and prokaryotic growth efficiency (PGE). The way prokaryotic heterotrophic production (PHP) is calcu- lated directly influences PGE (variations of PGE between 1 and 31% were found for a single sample). The empirically obtained deep-water CFs showed a 7-fold variability (0.13 to 0.85 kg C mol–1 Leu), but were always lower than the theoretical CF of 1.55 kg C mol–1 Leu assuming no isotope dilution. Empirically determined CFs were highly correlated to PGE, suggesting that both parameters are rep- resentations of the same basic metabolic processes. Overall, the PGEs obtained in this study suggest that mesopelagic prokaryotic assemblages can sometimes be as important in carbon processing as their epipelagic counterparts.
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| 8. |
- 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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| 9. |
- Baltar, Federico, et al.
(författare)
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Significance of non-sinking particulate organic carbon and dark CO2 fixation to heterotrophic carbon demand in the mesopelagic Atlantic
- 2010
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 37, s. L09602-
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Tidskriftsartikel (refereegranskat)abstract
- It is generally assumed that sinking particulate organic carbon (POC) constitutes the main source of organic carbon supply to the deep ocean's food webs. However, a major discrepancy between the rates of sinking POC supply (collected with sediment traps) and the prokaryotic organic carbon demand (the total amount of carbon required to sustain the heterotrophic metabolism of the prokaryotes; i.e., production plus respiration, PCD) of deep-water communities has been consistently reported for the dark realm of the global ocean. While the amount of sinking POC flux declines exponentially with depth, the concentration of suspended, buoyant non-sinking POC (nsPOC; obtained with oceanographic bottles) exhibits only small variations with depth in the (sub) tropical Northeast Atlantic. Based on available data for the North Atlantic we show here that the sinking POC flux would contribute only 4-12% of the PCD in the mesopelagic realm (depending on the primary production rate in surface waters). The amount of nsPOC potentially available to heterotrophic prokaryotes in the mesopelagic realm can be partly replenished by dark dissolved inorganic carbon fixation contributing between 12% to 72% to the PCD daily. Taken together, there is evidence that the mesopelagic microheterotrophic biota is more dependent on the nsPOC pool than on the sinking POC supply. Hence, the enigmatic major mismatch between the organic carbon demand of the deep-water heterotrophic microbiota and the POC supply rates might be substantially smaller by including the potentially available nsPOC and its autochthonous production in oceanic carbon cycling models. Citation: Baltar, F., J. Aristegui, E. Sintes, J. M. Gasol, T. Reinthaler, and G. J. Herndl (2010), Significance of non-sinking particulate organic carbon and dark CO2 fixation to heterotrophic carbon demand in the mesopelagic northeast Atlantic.
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| 10. |
- Baltar, Federico, et al.
(författare)
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Strong coast-ocean and surface-depth gradients in prokaryotic assemblage structure and activity in a coastal transition zone region
- 2007
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 50:1, s. 63-74
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Tidskriftsartikel (refereegranskat)abstract
- The distribution of marine Crenarchaeota Group 1, marine Euryarchaeota Group II and some major groups of Bacteria (SAR 11, Roseobacter, Gammaproteobacteria and Bacteroidetes) was investigated in the North Atlantic water column (surface to 2000 m depth) along a transect from the coastal waters of the NW African upwelling to the offshore waters of the Canary Coastal Transition Zone (CTZ). Catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) was used to describe the prokaryotic assemblages. Bulk picoplankton abundance and leucine incorporation were determined. Pronounced changes in prokaryotic assemblage composition were observed from the coast to the open ocean and at the deep chlorophyll maximum (DCM) with decreasing bulk heterotrophic activity. All bacterial groups decreased in absolute abundances from the coast to the open ocean; both archaeal groups increased towards the open ocean. Prokaryotic abundance and activity decreased 2 and 3 orders of magnitude, respectively, from the surface to 2000 m. Prokaryotic growth rates were high in the mesopelagic zone (similar to 0.13 d(-)1), compared to other reports from the central North Atlantic. SARI 1 in total picoplankton abundance decreased from 42 % in the DCM to 4 % at 2000 m, while marine Crenarchaeota Group I increased from 1 % in the DCM to 39 % in the oxygen minimum layer. A clear influence of the different intermediate water masses was observed on the bulk heterotrophic picoplankton activity, with lower leucine incorporation rates corresponding to layers where patches of Antarctic Intermediate Water were detected. Coast-ocean and surface-depth gradients in bulk prokaryotic abundance and production and assemblage composition were comparable to changes observed in basin-scale studies, pinpointing the CTZs as regions of strong variability in microbial diversity and metabolism.
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