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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogen metabolism by heterotrophic bacterial assemblages in Antarctic coastal waters (1994)
    Springer
    Polar biology 14 (1994), S. 195-204 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Field studies to examine the in situ assimilation and production of ammonium (NH4 +) by bacterial assemblages were conducted in the northern Gerlache Strait region of the Antarctic Peninsula. Short term incubations of surface waters containing 15N-NH4 + as a tracer showed the bacterial population taking up 0.041–0.128 μg-atoms Nl−1d−1, which was 8–25% of total NH4 + uptake rates. The large bacterial uptake of NH4 + occurred even at low bacterial abundance during a rich phytoplankton bloom. Estimates of bacterial production using 3H-leucine and -adenine were l.0μgCl−1 d−1 before the bloom and 16.2 μg Cl−1 d−1 at the bloom peak. After converting bacterial carbon production to an estimate of nitrogen demand, NH4 + was found to supply 35–60% of bacterial nitrogen requirements. Bacterial nitrogen demand was also supported by dissolved organic nitrogen, generally in the form of amino acids. It was estimated, however, that 20–50% of the total amino acids taken up were mineralized to NH4 +. Bacterial production of NH4 + was occurring simultaneously to its uptake and contributed 27–55% of total regenerated NH4 + in surface waters. Using a variety of 15N-labelled amino acids it was found that the bacteria metabolized each amino acid differently. With their large mineralization of amino acids and their relatively low sinking rates, bacteria appear to be responsible for a large portion of organic matter recycling in the upper surface waters of the coastal Antarctic ecosystem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240524
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Remineralization Ratios in the Subtropical North Pacific Gyre (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 65-85 
    Details
    ISSN: 1573-1421
    Keywords: Mixing model ; preformed nutrients ; Redfield ratios ; Remineralization ratios
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Based on a new mixing model of two end-members, the water column remineralization ratios of P/N/Corg - O2 = 1/13 ± 1/135 ± 18/170 ± 9 are obtained for the Hawaii Ocean Time-series (HOT) data set at station ALOHA. The traditional Redfield ratios of P/N/Corg/–O2 = 1/16/106/138 have standard deviations of more than 50%, when they are based on the average composition of phytoplankton. Apparently, the remineralization processes in the water column have smoothed out the observed large variability of plankton compositions. A new molar formula for the remineralized plankton may be written as 135H280O105N13P or C25(CH2O)101(CH4)9(NH3)13(H3PO4). Oxidation of this formula results in C25(CH2O)101(CH4)9(NH3)13(H3PO4) + 170O2 → 135CO2 + 132H2O + 13NO3 - + H2PO4 - + 14H+. For comparison, remineralization using Redfield's formula gives: (CH2O)106(NH3)16(H3PO4) + 138O2 → 106CO2 + 122H2O + 16NO3 -+ H2PO4 - + 17H+
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009676300859
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  • 3
    Electronic Resource
    Electronic Resource
    The grounding of the Bahia Paraiso: Microbial ecology of the 1989 Antarctic oil spill (1992)
    Springer
    Microbial ecology 24 (1992), S. 77-89 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract On 28 January 1989 the Bahia Paraiso ran aground and sank near Palmer Station, Antarctica. At least 6.8 × 105 liters of diesel fuel arctic (DFA) were released into semi-enclosed Arthur Harbor and deposited in the nearby intertidal regions. Approximately 6 weeks later, a group of scientists was deployed to evaluate the impact of the oil spill on the surrounding coastal marine ecosystem. Microbial hydrocarbon oxidation potential (14CO2 evolved from 14C-labeled hexadecane) was detected throughout both the oil-impacted and control regions. Hexadecane was mineralized at extremely low rates (0.13–1.21 pmol g−1 sediment dry weight day−1); microbiological turnover time exceeded 2 years. The acute effects of DFA (measured over exposure periods of 3–7 days) on the metabolic activities of sedimentary microorganisms appear to be negligible even at seawater saturation concentrations of DFA. Long-term exposure (120 days) to varying concentrations of DFA resulted in significant decreases (〉90%) in total ATP, but had either no effect or a slight stimulatory effect on metabolic activity and production. In contrast to planktonic microbial communities, increasing incubation temperatures of between 0 and 30°C had a positive effect on rates of metabolism and production of sedimentary assemblages. These results may influence the overall weathering rates of hydrocarbons deposited in the intertidal and supratidal regions of Arthur Harbor and other polar regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00171972
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  • 4
    Electronic Resource
    Electronic Resource
    A Sea of Change: Biogeochemical Variability in the North Pacific Subtropical Gyre (1999)
    Springer
    Ecosystems 2 (1999), S. 181-214 
    Details
    ISSN: 1435-0629
    Keywords: Key words: oceanography; microbial ecology; nutrients; climate; biodiversity; food webs; microbiology.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT The North Pacific Subtropical Gyre (NPSG) is the largest ecosystem on our planet. However, this expansive habitat is also remote, poorly sampled, and therefore not well understood. For example, the most abundant oxygenic phototroph in the NPSG, Prochlorococcus, was described only a decade ago. Other novel Bacteria, Archaea and Eukarya, recently identified by nucleic acid sequence analysis, have not been isolated. In October 1988, an ocean time-series research program was established to study ecosystem processes in the gyre, including rates and pathways of carbon and energy flow, spatial and temporal scales of variability, and coupling of ocean physics to biogeochemical processes. After a decade of ecosystem surveillance, this sentinel observatory has produced an unprecedented data set and some new views of an old ocean. Foremost is evidence for dramatic changes in microbial community structure and in mechanisms of nutrient cycling in response to large-scale ocean–atmosphere interactions. These and other observations demand reassessment of current views of physical-biogeochemical processes in this and other open-ocean ecosystems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100219900068
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  • 5
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    Minireviews: A Sea of Change: Biogeochemical Variability in the North Pacific Subtropical Gyre (1999)
    Springer
    Details
    Publication Date: 1999-05-01
    Print ISSN: 1432-9840
    Electronic ISSN: 1435-0629
    Topics: Biology
    Published by Springer
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    PAPER CURRENT
  • 6
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    Ecosystem Structure and Dynamics in the North Pacific Subtropical Gyre: New Views of an Old Ocean (2017)
    Springer
    Details
    Publication Date: 2017-03-10
    Print ISSN: 1432-9840
    Electronic ISSN: 1435-0629
    Topics: Biology
    Published by Springer
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  • 7
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    An intercomparison of oceanic methane and nitrous oxide measurements (2018)
    Copernicus Publications (EGU)
    In:  Biogeosciences (BG), 15 (19). pp. 5891-5907.
    Details
    Publication Date: 2021-02-08
    Description: Large-scale climatic forcing is impacting oceanic biogeochemical cycles and is expected to influence the water-column distribution of trace gases, including methane and nitrous oxide. Our ability as a scientific community to evaluate changes in the water-column inventories of methane and nitrous oxide depends largely on our capacity to obtain robust and accurate concentration measurements that can be validated across different laboratory groups. This study represents the first formal international intercomparison of oceanic methane and nitrous oxide measurements whereby participating laboratories received batches of seawater samples from the subtropical Pacific Ocean and the Baltic Sea. Additionally, compressed gas standards from the same calibration scale were distributed to the majority of participating laboratories to improve the analytical accuracy of the gas measurements. The computations used by each laboratory to derive the dissolved gas concentrations were also evaluated for inconsistencies (e.g., pressure and temperature corrections, solubility constants). The results from the intercomparison and intercalibration provided invaluable insights into methane and nitrous oxide measurements. It was observed that analyses of seawater samples with the lowest concentrations of methane and nitrous oxide had the lowest precisions. In comparison, while the analytical precision for samples with the highest concentrations of trace gases was better, the variability between the different laboratories was higher: 36% for methane and 27% for nitrous oxide. In addition, the comparison of different batches of seawater samples with methane and nitrous oxide concentrations that ranged over an order of magnitude revealed the ramifications of different calibration procedures for each trace gas. Finally, this study builds upon the intercomparison results to develop recommendations for improving oceanic methane and nitrous oxide measurements, with the aim of precluding future analytical discrepancies between laboratories.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: archive
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  • 8
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    Global oceanic diazotroph database version 2 and elevated estimate of global oceanic N2 fixation (2023)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2024-02-07
    Description: Marine diazotrophs convert dinitrogen (N-2) gas into bioavailable nitrogen (N), supporting life in the global ocean. In 2012, the first version of the global oceanic diazotroph database (version 1) was published. Here, we present an updated version of the database (version 2), significantly increasing the number of in situ diazotrophic measurements from 13 565 to 55 286. Data points for N-2 fixation rates, diazotrophic cell abundance, and nifH gene copy abundance have increased by 184 %, 86 %, and 809 %, respectively. Version 2 includes two new data sheets for the nifH gene copy abundance of non-cyanobacterial diazotrophs and cell-specific N2 fixation rates. The measurements of N-2 fixation rates approximately follow a log-normal distribution in both version 1 and version 2. However, version 2 considerably extends both the left and right tails of the distribution. Consequently, when estimating global oceanic N-2 fixation rates using the geometric means of different ocean basins, version 1 and version 2 yield similar rates (43-57 versus 45-63 TgNyr (-1); ranges based on one geometric standard error). In contrast, when using arithmetic means, version 2 suggests a significantly higher rate of 223 +/- 30 TgNyr (-1) (mean +/- standard error; same hereafter) compared to version 1 (74 +/- 7 TgNyr (-1)). Specifically, substantial rate increases are estimated for the South Pacific Ocean (88 +/- 23 versus 20 +/- 2 TgNyr 1), primarily driven by measurements in the southwestern subtropics, and for the North Atlantic Ocean (40 +/- 9 versus 10 +/- 2 TgNyr (-1)). Moreover, version 2 estimates the N-2 fixation rate in the Indian Ocean to be 35 +/- 14 TgNyr (-1), which could not be estimated using version 1 due to limited data availability. Furthermore, a comparison of N-2 fixation rates obtained through different measurement methods at the same months, locations, and depths reveals that the conventional N-15(2) bubble method yields lower rates in 69% cases compared to the new N-15(2) dissolution method. This updated version of the database can facilitate future studies in marine ecology and biogeochemistry. The database is stored at the Figshare repository (https://doi.org/10.6084/m9.figshare.21677687; Shao et al., 2022).
    Type: Article , PeerReviewed
    Format: text
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