摘要:

Reducing sediments of Lake Mendota were challenged to demonstrate evidence of anaerobic conversion of l‐14C‐hexadecane to14CO2. Low levels of14CO2were detected above formaldehyde controls in anoxic sediment and bottom waters and in surface water sparged with nitrogen. Aerobic incubation of the same sediment and water demonstrated extensive conversion of l‐14C‐hexade‐cane to14CO2. The low levels of14CO2detected in anaerobic incubation were not increased by addition of nitrate or in a pre‐reduced medium containing nitrate and sulfate. An isotope‐recovery experiment demonstrated that 13.7% of added l‐14C‐hexadecane was converted to14C‐cell carbon and14CO2after 375 h incubation.

ISSN:0149-0451    

DOI:10.1080/01490457809377720

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A radiotracer technique for measuring in situ rates of sulfate reduction in marine sediments is described. Microliter portions of labeled‐sulfate solution are injected into undisturbed sediment cores, and the amount of labeled sulfide produced is analyzed. This tracer method is experimentally compared with a method that mixes label into the sediment. Controls and methodological problems of both methods are discussed.

ISSN:0149-0451    

DOI:10.1080/01490457809377721

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

A mathematical model describing vertical sulfate gradients as a function of diffusion, bacterial reduction, and sedimentation is applied to calculate the steady‐state rates of sulfate reduction in coastal sediments. Diffusion coefficients of sulfate are determined experimentally in different sediment types and depths. The rate of sulfate reduction is also determined directly on sediment cores by a radiotracer technique. Experimentally determined rates are compared with those calculated from the model. The results of the model are shown to depend strongly on its assumptions about the kinetics of bacterial sulfate reduction.

ISSN:0149-0451    

DOI:10.1080/01490457809377722

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Rates of bacterial sulfate reduction are calculated from the accumulation of reduced sulfur compounds in coastal sediments. The method is found to underestimate the in situ metabolism 10‐fold because it neglects diffusional losses of produced sulfide. In relation to this result, the quantitative connection between the pyrite, HCl‐extractable iron, and organic carbon contents of the sediments and the intensity of sulfate reduction are disussed. A comparison is made between colony counts of sulfate‐reducing bacteria and the rate of sulfate reduction in coastal sediments. The number of bacteria is roughly proportional to their measured rate of metabolism both when different sediment types and different depths are compared. The colony counts, however, seem to underestimate the true numbers of sulfate reducers by 1000‐fold or more.

ISSN:0149-0451    

DOI:10.1080/01490457809377723

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Evidence for the utilization of reduced forms of antimony, arsenic, copper, hydrogen, manganese, and selenium as energy sources for bacteria is summarized. Each of these, except arsenic in the form of arsenite, can supply energy to appropriate organisms during growth. Arsenite oxidation may be able to provide maintenance energy. A rationale is presented to explain why prokaryotes but not eukaryotes can avail themselves of inorganic energy sources.

ISSN:0149-0451    

DOI:10.1080/01490457809377724

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

摘要:

Nitrogen isotope fractionation in the assimilation of inorganic nitrogenous compounds was studied using marine diatoms(Phaeodactylum tricornutum and Chaetocerossp.). The isotopic composition (δ15N) of the diatoms ranged from 7 to ‐18‰ relative to that of the nitrogen source, i.e., ammonium, nitrite, or nitrate. When the growth was light‐limited, the isotope fractionation in nitrate assimilation was inversely correlated with the growth rate. The highest fractionation factor of 1.016 was obtained when the growth rate was as low as 0.025 day‐1. Fractionation was negligible when the growth, rate was higher than 1 day‐1. A steady‐state kinetic model was applied to explain the isotope fractionation in nitrate assimilation. The nitrogen isotope fractionation primarily takes place at the step of N‐O bond breaking in nitrate reduction to nitrite. The extent of the isotope fractionation associated with the nitrate uptake is very small, and barely exceeds the limit of detection.

ISSN:0149-0451    

DOI:10.1080/01490457809377725

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor

ISSN:0149-0451    

DOI:10.1080/01490457809377718

出版商:Taylor & Francis Group    

年代:1978

数据来源: Taylor