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  • 1
    Digitale Medien
    Digitale Medien
    Extracellular enzymatic activity and secondary production in free-living and marine-snow-associated bacteria (1992)
    Springer
    Marine biology 113 (1992), S. 341-347 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Abundance, production (measured as thymidine incorporation) and extracellular enzymatic activity in free-living and marine-snow-associated bacteria were measured in the northern Adriatic Sea. Although bacterial density and production were similar in both free-living and marine-snow-associated bacteria, hydrolytic activity (α- and β-glucosidase and l-aminopeptidase) was significantly higher in marine-snow-associated bacteria, in terms of both absolute and per-cell rates. As concentrations of dissolved total and monomeric carbohydrates and free amino acids in marine snow were very close to those in the ambient water, we suggest that the observed differences between free-living and marine-snow-associated baycteria do not simply reflect catabolic repression of enzyme expression in one of the bacterial components. Whether substrate induction is responsible for the observed higher hydrolase activity in marine-snow bacteria and/or whether there are distinct bacterial species obligatorily associated with marine snow remains unknown.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00347289
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  • 2
    Digitale Medien
    Digitale Medien
    Major role of ultraviolet-B in controlling bacterioplankton growth in the surface layer of the ocean (1993)
    [s.l.] : Nature Publishing Group
    Nature 361 (1993), S. 717-719 
    Details
    ISSN: 1476-4687
    Quelle: Nature Archives 1869 - 2009
    Thema: Biologie , Chemie und Pharmazie , Medizin , Allgemeine Naturwissenschaft , Physik
    Notizen: [Auszug] In evaluating the possible effects of natural solar radiation, we have to distinguish possible effects of short- and long-term exposure on the bacterial community. In a mixed water column, short-term exposure should predominate. We determined the influence of short-term (30 min) solar radiation on ...
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1038/361717a0
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  • 3
    Digitale Medien
    Digitale Medien
    Evidence of enhanced microbial activity in the interstitial space of branched corals: possible implications for coral metabolism (1989)
    Springer
    Coral reefs 7 (1989), S. 179-184 
    Details
    ISSN: 1432-0975
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Water samples from the interstitial space of 4 Indo-Pacific coral species (Acropora sp., Echinopora horrida, Psammocora digita and Pavona clavus) and a Mediterranean coral (Cladocora cespitosa) were analysed for NO 3 - +NO 2 - , NH 4 + , molybdate reactive phosphorus, bacterial and flagellate biomass and dissolved organic matter (DOM) and compared with ambient water concentrations. Higher values of NO 3 - +NO 2 - , bacterial and flagellate biomass were observed within the interstitial space of the corals. The lower DOM pool in the interstitium in combination with the high bacterial biomass suggests high bacterial activity and efficient substrate utilization, necessary to compensate for nanoflagellate predation. Since corals may be able to feed on bacteria, the high microbial biomass (bacterial and flagellate) may be utilized either directly as an additional heterotrophic food source, or indirectly in that microbes may act as attractants for microbe-feeding zooplankters, which in turn serve as food for the corals. The combined effect of reduced flow velocities between the coral branches and its associated fauna are probably the main factors in creating a specific environment more or less independent of the nutritive stage of the surrounding water.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00301596
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  • 4
    Digitale Medien
    Digitale Medien
    Bacterial activity along a trophic gradient (1992)
    Springer
    Microbial ecology 24 (1992), S. 243-257 
    Details
    ISSN: 1432-184X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Bacterial biomass, secondary production, and extracellular enzymatic activity [α-glucosidase and leucine-aminopeptidase, measured as cleavage of artificial fluorogenic substrates 4-methyl umbelliferyl (MVF) α-D-glucopyranoside and L-leucine 7-amido-4-methyl coumarin (MCA)] were measured along a trophic gradient in the Northern Adriatic Sea in four ecologically different situations. Bacterial parameters were compared with chlorophyll a and inorganic and organic nutrient concentrations. Bacterial secondary production and extracellular enzymatic activity markedly changed among different seasons and along the trophic gradient. Average bacterial secondary production increased from 0.61 to 2.09 µg Cl−1 hour−1 preceding a bloom, to 2.09 µg Cl−1 hour−1 during the bloom, decreasing again to 0.81 and 0.83 µg Cl−1 hour−1 in the post-bloom and summer periods, respectively (values from 0.5 m depth). Leucine-aminopeptidase activity showed more consistent trends than α-glucosidase activity. Average values of leucine-aminopeptidase activity, measured by enzymatic release of MCA, increased from a pre-bloom value of 164.0 to 1,712.0 (nM MCA) hour−1 released during a bloom, decreasing to 298.5 and 133.7 (nM MCA) hour−1 released for the post-bloom and summer situation, respectively (values from 0.5 m depth). Average growth rates decreased during the bloom, whereas average extracellular enzymatic activity levels expressed on a cell basis increased by an average factor of 2. Along the trophic gradient, a consistent increase in bacterial secondary production could be observed in all but the summer situation (values from 0.5 m depth). Leucine-aminopeptidase activity also showed positive trends along the gradient, while α-glucosidase activity did not exhibit such a clear trend. Bacterial biomass trends were less obvious considering both seasonal changes and the tropic gradient. Highly significant interrelations were detected between bacterial proteolytic activity, secondary production, chlorophyll a content, and nitrate concentrations, especially in the surface horizon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00167784
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  • 5
    Digitale Medien
    Digitale Medien
    Influence of wastewater treatment on the microbial ecology of a large, temperate river system — the Danube River (1996)
    Springer
    Hydrobiologia 321 (1996), S. 205-218 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Danube River ; large river ; bacteria ; ectoenzyme ; sewage ; wastewater
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In an attempt to assess the influence of tertiary-treated sewage influx on bacterial metabolism in the Danube River, bacterial abundance, ectoenzymatic activity, faecal coliforms, faecal streptococci, chlorophyll a (chl a), concentrations of dissolved (DOC) and total organic carbon (TOC) and inorganic nutrients were measured upstream of the sewage influx and compared with sampling sites downstream. Additional samples were taken near the outlet of the sewage treatment plant. Bacterial abundance as determined by epifluorescence microscopy was compared with plate counts of total heterotrophic bacteria. Significantly higher values were obtained at the stations downstream from the sewage influx only for faecal coliforms and faecal streptococci, for glucuronidase activity and bacterial biovolume. All the other parameters were not significantly different from values obtained at the upstream sampling site. Strong seasonal dependence was detectable for nitrate with high concentrations during the winter (≈ 250 µM) and low concentrations during summer (≈ 100 µM). A distinct spring phytoplankton bloom was noticeable in the river reaching chl a concentrations of ≈ 70 µg 1−1; during the remaining seasons chl a concentrations were 〈20 µg 1−1. Highly significant correlations were found between faecal coliform counts and glucuronidase activity. C:N:P ratios of 13.9:10.7:1 (for the upstream station) and 11.7:9.2:1 (for the downstream stations) of dissolved nutrients are rather low indicating severe carbon limitation of bacterioplankton. Based on our results we conclude that the heterotrophic bacterial community is not significantly effected by the input of treated sewage but faecal contamination is readily detectable over a comparatively long reach of 30 km.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00143751
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  • 6
    Digitale Medien
    Digitale Medien
    Microbial activity under the ice cover of the shallow Neusiedler See (Austria, Central Europe) (1997)
    Springer
    Hydrobiologia 357 (1997), S. 173-184 
    Details
    ISSN: 1573-5117
    Schlagwort(e): ice cover ; shallow lake ; bacterioplankton ; phytoplankton ; growth efficiency ; dissolved organic matter ; humic matter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In an attempt to assess bacterioplankton production and growth yieldunder low temperature conditions and to compare bacterioplankton withphytoplankton production in the ice-covered water column of the shallowNeusiedler See, outdoor measurements under near in situ conditions wereperformed during the winter of 1995/96. During the investigation period,mean chlorophyll (Chl) a concentration was 21.03 ± 14.95 µg Chla l-1. Phytoplankton primary production integrated over thewater column ranged from 1.35 to production integrated over the water columnranged from 1.35 to 4.23 mg C m-2 d-1 (mean± SD = 2.46 ± 1.06 mg C m-2d-1). Bacterial abundance varied from 20 to 40×105 ml-1 for most of the investigationperiod and increased by the end of March concomitantly with the increase intemperature from 1.3 to 6.3 °C within 5 days. Mean bacterial productionwas 15.3 ± 12.8 µg C l-1 d-1(range: 3.0 to 41.7 µg C l-1 d-1) and meanbacterial growth rate 0.23 ± 0.16 d-1 following closelythe pattern in bacterial production. DOC concentration declined linearlyfrom 20.7 mg C l-1 to 16.45 mg C l-1 over the 4months period of ice cover. The contribution of humic substances to thetotal DOC pool declined from 43.6% at the end of November to37.3% at the end of March. Calculated on an area basis, phytoplanktonproduction amounted to only 16% of bacterial production which makesit unlikely that phytoplankton supply substrate for bacterioplankton growthin significant quantities when the lake is ice covered. From the observeddecline in DOC over the investigation period and assuming only negligibleinput of DOC from other sources we calculated an average DOC uptake by thebacterioplankton community of 47.5 µg C l-1d-1 resulting in a bacterial growth efficiency of 15.9%for the ice covered conditions. Based on the growth efficiency we estimatethat pelagic primary production amounts to 2.8% of the bacterialcarbon demand. This might indicate that the bacterioplankton in NeusiedlerSee sustain their high growth rates at low temperatures (〈2°C formost of the investigation period) by using probably the DOC originating fromthe previous season. This DOM stems most likely from the decay of the reedPhragmites australis and its epiphytes and, probably of minor importance,from phytoplankton leachates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003151323756
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  • 7
    Digitale Medien
    Digitale Medien
    Role of ultraviolet-B radiation on bacterioplankton and the availability of dissolved organic matter (1997)
    Springer
    Plant ecology 128 (1997), S. 43-51 
    Details
    ISSN: 1573-5052
    Schlagwort(e): Bacterial utilization ; Bacterioplankton ; Dissolved organic matter (DOM) ; Radiation ; Ultraviolet-B (UV-B)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Attenuation of ultraviolet (UV)-radiation into the water column is highly correlated with the concentration of the dissolved organic matter (DOM). Thus UV penetrates deeper into marine waters than into freshwater systems. DOM is efficiently cleaved by solar surface radiation levels consuming more oxygen than bacterial metabolism. This photolytically cleaved DOM exhibits higher absorbance ratios (250/365 nm) than untreated DOM. Natural bacterioplankton reach higher abundance if inoculated in previously solar-exposed DOM than in untreated DOM; during bacterial growth the absorbance ratio declines steadily indicating the utilization of the photolytically cleaved DOM. On the other hand, bacterioplankton are greatly reduced in their activity if exposed to surface solar radiation levels. Photoenzymatic repair of DNA induced by UV-A radiation, however, leads to an efficient recovery of bacterial activity once the UV-B stress is released. Turbulent mixing of the upper layers of the water column leads to a continuous alteration of the UV exposure regime. Close to the surface, bacteria and DOM are exposed to high levels of UV-B leading to a reduction in bacterial activity and to photolysis of DOM. Once mixed into deeper layers where UV-B is attenuated, but sufficient UV-A is remaining to allow photoenzymatic repair, the photolytically cleaved DOM is efficiently taken up by bacterioplankton leading to even higher bacterial activity than prior to the exposure. Thus, the overall effect of UV on bacterioplankton is actually an enhancement of bacterial activity despite their lack of protective pigments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009742508284
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  • 8
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    Unbekannt
    Deep carbon export from a Southern Ocean iron-fertilized diatom bloom (2012)
    Nature Publishing Group
    In:  Nature, 487 (7407). pp. 313-319.
    Details
    Publikationsdatum: 2019-09-23
    Beschreibung: Fertilization of the ocean by adding iron compounds has induced diatom-dominated phytoplankton blooms accompanied by considerable carbon dioxide drawdown in the ocean surface layer. However, because the fate of bloom biomass could not be adequately resolved in these experiments, the timescales of carbon sequestration from the atmosphere are uncertain. Here we report the results of a five-week experiment carried out in the closed core of a vertically coherent, mesoscale eddy of the Antarctic Circumpolar Current, during which we tracked sinking particles from the surface to the deep-sea floor. A large diatom bloom peaked in the fourth week after fertilization. This was followed by mass mortality of several diatom species that formed rapidly sinking, mucilaginous aggregates of entangled cells and chains. Taken together, multiple lines of evidence—although each with important uncertainties—lead us to conclude that at least half the bloom biomass sank far below a depth of 1,000 metres and that a substantial portion is likely to have reached the sea floor. Thus, iron-fertilized diatom blooms may sequester carbon for timescales of centuries in ocean bottom water and for longer in the sediments.
    Materialart: Article , PeerReviewed
    Format: text
    Format: text
    Format: text
    DOI: 10.1038/nature11229
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