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  • 1
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    Limited carbon cycling due to high-pressure effects on the deep-sea microbiome (2022)
    Nature Research
    Details
    Publication Date: 2024-02-07
    Description: Deep-sea microbial communities are exposed to high-pressure conditions, which has a variable impact on prokaryotes depending on whether they are piezophilic (that is, pressure-loving), piezotolerant or piezosensitive. While it has been suggested that elevated pressures lead to higher community-level metabolic rates, the response of these deep-sea microbial communities to the high-pressure conditions of the deep sea is poorly understood. Based on microbial activity measurements in the major oceanic basins using an in situ microbial incubator, we show that the bulk heterotrophic activity of prokaryotic communities becomes increasingly inhibited at higher hydrostatic pressure. At 4,000 m depth, the bulk heterotrophic prokaryotic activity under in situ hydrostatic pressure was about one-third of that measured in the same community at atmospheric pressure conditions. In the bathypelagic zone—between 1,000 and 4,000 m depth—~85% of the prokaryotic community was piezotolerant and ~5% of the prokaryotic community was piezophilic. Despite piezosensitive-like prokaryotes comprising only ~10% (mainly members of Bacteroidetes, Alteromonas) of the deep-sea prokaryotic community, the more than 100-fold metabolic activity increase of these piezosensitive prokaryotes upon depressurization leads to high apparent bulk metabolic activity. Overall, the heterotrophic prokaryotic activity in the deep sea is likely to be substantially lower than hitherto assumed, with major impacts on the oceanic carbon cycling.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    A device for assessing microbial activity under ambient hydrostatic pressure: The in situ microbial incubator (ISMI) (2023)
    ASLO (Association for the Sciences of Limnology and Oceanography)
    Details
    Publication Date: 2024-02-07
    Description: Microbes in the dark ocean are exposed to hydrostatic pressure increasing with depth. Activity rate measurements and biomass production of dark ocean microbes are, however, almost exclusively performed under atmospheric pressure conditions due to technical constraints of sampling equipment maintaining in situ pressure conditions. To evaluate the microbial activity under in situ hydrostatic pressure, we designed and thoroughly tested an in situ microbial incubator (ISMI). The ISMI allows autonomously collecting and incubating seawater at depth, injection of substrate and fixation of the samples after a preprogramed incubation time. The performance of the ISMI was tested in a high-pressure tank and in several field campaigns under ambient hydrostatic pressure by measuring prokaryotic bulk H-3-leucine incorporation rates. Overall, prokaryotic leucine incorporation rates were lower at in situ pressure conditions than under to depressurized conditions reaching only about 50% of the heterotrophic microbial activity measured under depressurized conditions in bathypelagic waters in the North Atlantic Ocean off the northwestern Iberian Peninsula. Our results show that the ISMI is a valuable tool to reliably determine the metabolic activity of deep-sea microbes at in situ hydrostatic pressure conditions. Hence, we advocate that deep-sea biogeochemical and microbial rate measurements should be performed under in situ pressure conditions to obtain a more realistic view on deep-sea biotic processes.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
    Electronic Resource
    Electronic Resource
    Assessment for the complicated occurrence of nuisance odours from phytoplankton and environmental factors in a eutrophic lake (2004)
    Oxford, UK : Blackwell Science, Ltd
    Lakes & reservoirs 9 (2004), S. 0 
    Details
    ISSN: 1440-1770
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography
    Notes: Odours in waters used for various purposes, especially musty odours, is a worldwide problem. To establish an early warning system, the nuisance odour in an aquatic environment, the causative microorganisms and compounds, and the mechanism of odour in Lake Kasumigaura, the second biggest lake in Japan, were examined using in situ studies. In this study, the mechanism for the occurrence of musty odours was determined, and the level of musty odour was discriminated, based on 32 months of phytoplankton data from three sampling stations. The results indicate that the cell numbers of Phormidium tenue, Synedra and Ankistrodesmus were significantly related to the occurrence of 2-methlisoborneol (MIB) and geosmin. Furthermore, the odour occurrence for both MIB and geosmin was effectively predicted and validated using environmental factors as explanatory variables, using multiple linear regression and artificial neural network technology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1770.2004.00246.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    UV spectrometry for measuring particulate organic matter in natural water (1996)
    Springer
    Aquatic sciences 58 (1996), S. 91-102 
    Details
    ISSN: 1420-9055
    Keywords: POM ; POC ; UV-spectra ; nitrogen/carbon ratio ; organic carbon cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ultraviolet (UV) spectra were measured to characterize the dissolved and particulate organic matter in a bog and to investigate the seasonal fluctuation of this organic matter. The optical density spectra in the UV region of dissolved organic matter (DOM) were proportional toλ −4, whereλ is the wavelength of incident light. There was also small absorption on theλ −4 spectra. The optical density at a wavelength of 280 nm was proportional to the concentration of dissolved organic carbon (DOC). The spectra and the dependency of optical density on DOC did not vary throughout the investigation period. The UV spectra of acid extractions of particulate organic matter (POM) showed two absorption peaks at the wavelengths of 220 nm and 335 nm. These peaks are well represented by the sum of two Lorentz functions. The ratio of the absorbances,A 280/A 335, was dependent on the nitrogen/carbon ratio of POM and the chlorophyll fraction in particulate organic carbon (POC), and not dependent on POC itself. The dependency of POC absorption at 280 nm varied with this ratio which fluctuated seasonally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877109
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Trophodynamic structure of a swampy bog at the climax stage of limnological succession II. Bacterioplankton dynamics (1994)
    Springer
    Water, air & soil pollution 76 (1994), S. 481-489 
    Details
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Matsumi-ike Bog is a swampy bog that has attained the climax stage of limnological succession. The dynamics of bacterioplankton were studied in relation to the influence of environment factors. The water temperature was shown primarily affect bacterial dynamics as a limiting factor throughout the year. The second most profound factor on the dynamics was the concentration of dissolved organic carbon (DOC) when dead phytoplankton were the major DOC source in the bog, whereas phosphate concentration was most important in the periods when the dead emergent plants were responsible for the DOC supply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00482720
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Biomass and production of bacterioplankton at the hydrothermal vent areas in the rift system of the North Fiji Basin (1994)
    Springer
    Journal of oceanography 50 (1994), S. 635-642 
    Details
    ISSN: 1573-868X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Mesoscale distribution of the density and productivity of bacterioplankton at representative geological locations in the rift ecosystem of the North Fiji Basin were clarified by sampling using a mannedShinkai 6500 submersible. The bacterioplankton density inside the hot and warm fluids of hydrothermal vents was one order magnitude greater than that in the deep water outside the vent plume. The bacterial production was highest inside the hot and warm vent fluids, and was higher just outside the hot and warm vent fluids than further outside in the deep water surrounding the vent plume, respectively. Productivity from outside to inside the vent fluid varied from 0.01 to 0.71 gC m−3 day−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02270496
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    Paper (German National Licenses)
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