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  • 1
    Electronic Resource
    Electronic Resource
    Cycling of organic nitrogen in marine plankton communities studied in enclosed water columns (1980)
    Springer
    Marine biology 59 (1980), S. 15-21 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Concentrations of fluorescamine-positive substances (primary amines) and turnover rates of L-leucine pools were measured concurrently in seawater samples taken from 1300 m3 plastic enclosures moored in Saanich Inlet, British Columbia, Canada. Concentration and turnover rates of dissolved free amino acids were calculated and then used to determine the instantaneous flux of dissolved free amino acids, which ranged from 0.09 to 2.42 μM d-1 (i.e.,5 to 145 μgC l-1 d-1). This flux was highest in the euphotic zone, and was related to net primary production but not to the type of dominant primary producer. Comparison of the flux to changes in the concentration of ammonia in deep water suggested that amino acid degradation accounted for 60% of the flux into the ammonia pool. For a given sample, the amino acid carbon flux ranged from 17 to 210% (mean=78%) of the primary production. Such fluxes of amino acid carbon, if used exclusively by the bacterioplankton, would give growth rates ranging from 0.3 to 3.0 (mean=1.7) bacterial doublings d-1. These calculations indicate that a large fraction of the community carbon and nitrogen flux passes through the bacterioplankton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396978
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  • 2
    Electronic Resource
    Electronic Resource
    Thymidine incorporation as a measure of heterotrophic bacterioplankton production in marine surface waters: Evaluation and field results (1982)
    Springer
    Marine biology 66 (1982), S. 109-120 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To assess bacterioplankton production in the sea, we have developed a procedure for measuring growth based on incorporation of tritiated thymidine into DNA; the accuracy of this procedure was tested under a variety of laboratory and field conditions. By autoradiography, we have found that for all practical purposes our technique is specific for the nonphotosynthetic bacteria and that virtually all of the “active” bacteria (one-third or more of the total countable bacteria) take up thymidine. We also measured (1) the intracellular isotope dilution of thymidine assessed by parallel experiments with labeled phosphorus, and (2) DNA content of natural marine bacteria (0.2 to 0.6 μm size fraction); a conversion factor derived from these data permitted estimation of production from thymidine incorporation results. A very similar conversion factor was independently derived from the empirical relationship between thymidine incorporation and growth of natural bacterioplankton under controlled conditions. Combined results show that this technique, which can be performed rapidly and easily at sea, provides good estimates of production. Data from Southern California Bight waters, which contain oligotrophic as well as moderately eutrophic regions, show that average bacterioplankton doubling times, like those of the phytoplankton, are on the order of a few days, with fastest growth at depths just below those of greatest phytoplankton abundance. Offshore bacterial production is roughly 5 to 25% of the primary production; thus, at a 50% assimilation efficiency, the bacterioplankton would consume 10 to 50% of the total fixed carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397184
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  • 3
    Electronic Resource
    Electronic Resource
    Bacterioplankton in the coastal euphotic zone: Distribution, activity and possible relationships with phytoplankton (1980)
    Springer
    Marine biology 60 (1980), S. 201-207 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Bacterioplankton were studied in the euphotic zone of the Southern California Bight, USA, with special attention to biological factors affecting bacterial distribution and activity. Measurements were made of bacterial abundance, thymidine incorporation into acid insoluble material, primary production (particulate and dissolved), chlorophyll, phaeopigments, total microbial ATP, particulate organic carbon and nitrogen, dissolved organic carbon, dissolved primary amines, and glucose and thymidine turnover rates. The data were analyzed by pairwise rank correlations with significance tested at the P〈.005 level. Bacterial abundance and thymidine incorporation both declined progressively with increasing distance from shore (to 100 km); similar trends occurred for the phytoplankton, with several stations having subsurface maxima. Bacterial abundance, thymidine incorporation, and thymidine and glucose turnover rates were all significantly correlated to each other, suggesting they are comparable as relative measures of bacterial activity. Thymidine incorporation per cell, an indicator of specific growth rate, was not correlated to bacterial abundance, suggesting density independent specific growth rates. Bacterioplankton growth rate was evidently influenced more by the standing stock of phytoplankton than by the primary production of the phytoplankton. Thus, bacterial growth may possibly be stimulated by leakage of dissolved organic matter not so much from healthy photosynthesizing cells as from phytoplankton being disrupted and incompletely digested during predation by the zooplankton and nekton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389163
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  • 4
    Electronic Resource
    Electronic Resource
    Microbial uptake of dissolved organic matter in Mcmurdo Sound, Antarctica (1981)
    Springer
    Marine biology 61 (1981), S. 89-94 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution and activity of bacterioplankton, and the turnover of dissolved organic matter (DOM) were examined in McMurdo Sound, Antarctica. On the eastern side of the Sound, bacteria averaged 6.5×108 l-1, and turnover rates of dissolved adenosine triphosphate, D-glucose and l-leucine averaged 16, 116 and 124 h, respecitvely. These molecules as well as thymidine were taken up maximally from 0° to 5°C and near-maximally from -1.5° to 0°C, indicating bacterial adaptation to rapid turnover of dissolved organic matter at the ambient temperature. On the west side of the Sound, bacteria averaged only 0.65×108 l-1, and turnover times for adenosine triphosphate, D-glucose and lleucine averaged 59, 20454, and 3070 h, respectively. Total microbial adenosine triphosphate (an indicator of total microbial biomass) and chlorophyll a were also much lower at the western than at the eastern side stations. Moreover, no primary production could be detected at one western side station (New Harbor). Thus, in McMurdo Sound, the western side is highly oligotrophic, but the eastern side has an abundant active bacterioplankton, comparable to that of temperate coastal waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386648
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  • 5
    Electronic Resource
    Electronic Resource
    Use of tritiated substrates in the study of heterotrophy in seawater (1973)
    Springer
    Marine biology 23 (1973), S. 191-196 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An improved method is described for the study of heterotrophic utilization of dissolved organic substances by marine microorganisms. The method is based on the use of 3H-labelled organic substrates of very high specific activity, rather than the conventionally used 14C-labelled substrates. Direct measurement of the rate of tracer uptake at near ambient concentration can thus be made instead of extrapolation using the Michaelis-Menten equation. The method also permits comparison between the rates of tracer uptake in sub-samples exposed to different physico-chemical conditions (temperature, light, pollutants, etc.) without the necessity of determining the ambient substrate concentration. The method was applied to the determination of D-glucose uptake by nearshore and pelagic natural microbial populations, and was found to be sensitive and convenient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389484
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  • 6
    Electronic Resource
    Electronic Resource
    Some experiments on phosphate assimilation by coastal marine plankton (1977)
    Springer
    Marine biology 40 (1977), S. 9-18 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study of phosphate assimilation by coastal marine plankton revealed that both phytoplankton and microheterotrophs incorporated radioactive phosphorus (33P). Size fractionation of the particulate matter (using 1 μm pore diameter Nucleopore® membrane filters), antibiotic treatment (using garamycin), and independent estimaties of photoautotrophic (14CO2 uptake) and heterotrophic (3H-glucose uptake) activities were employed to separate phyto- and bacterioplankton phosphate uptake. Results indicated that phytoplankton 33P-uptake was best estimated by the fraction of particulate matter retained on the 1 μm membrane filters. Usually, less than 10% of the phytoplankton (based on chlorophyll a measurements) passed the 1 μm pore-diameter filters, whereas about 90% of the heterotrophic activity passed. At least 50% of the 33P-uptake was associated with the 〈1 μm fraction. It may be possible to resolve the phytoplankton and bacterial contributions to 33P-uptake by comparing the percent of total 33P-uptake with the percent of total 3H-glucose uptake associated with the 〉1 μm fraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390622
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  • 7
    Electronic Resource
    Electronic Resource
    Improved methodology for ATP determination in marine environments (1976)
    Springer
    Marine biology 34 (1976), S. 143-149 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A simple technique is described for de-salting and concentrating adenosine triphosphate (ATP) extracted from seawater or marine sediment samples prior to assays with the standard luciferin-luciferase procedure. The technique involves chromatography of H2SO4 extracts on columns of activated carbon. The efficiency of ATP recovery from marine sediments using this pre-treatment was superior to that attained with either boiling “Tris” extraction or with H2SO4 extraction without subsequent purification. All ions which interfere with the luciferase reaction or precipitate ATP upon neutralization of acid extracts are removed with this procedure, thus eliminating the 50- to 100-fold dilutions required with other acid-extraction procedures. In addition, the purified ATP extracts may be concentrated up to 100-fold, thus greatly improving the sensitivity of ATP measurement in samples containing very low biomass. This procedure has been applied to ATP determination in marine sediments in the upwelling area off northwest Africa. The average ATP concentrations in the upper 6 cm of sediment from 1000 and 200 m were 195 and 545 ng per ml wet sediment, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390756
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  • 8
    Electronic Resource
    Electronic Resource
    Predator-prey interactions between the larvacean Oikopleura dioica and bacterioplankton in enclosed water columns (1980)
    Springer
    Marine biology 56 (1980), S. 49-57 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The larvacean Oikopleura dioica Fol was fed 3H-labeled natural assemblages of marine bacterioplankton. Grazing rates ranged from 〈1 to 〉100 ml day-1 individual-1 and were highly dependent onlarvacean body size. These rates were combined with estimates of abundance of O. dioica in large floating enclosures with semi-natural populations (Controlled Ecosystems Populations Experiment, CEPEX) to determine the impact of the larvacean on the bacterial populations and to estimate the amount of bacteria ingested by the larvaceans. Apparently, O. dioica has minimal influence on the population dynamics of the free-living bacteria, although bacteria may form a substantial portion of the larvacean's diet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390593
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  • 9
    Electronic Resource
    Electronic Resource
    Availability of soil and fertilizer nitrogen to wheat (Triticum aestivum L.) following rice-straw amendment (1990)
    Springer
    Biology and fertility of soils 10 (1990), S. 134-138 
    Details
    ISSN: 1432-0789
    Keywords: 15N ; N immobilization ; N loss ; N uptake ; Rice straw ; Soil N ; Wheat ; Triticum aestivum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A pot experiment was conducted to study the N availability to wheat and the loss of 15N-labelled fertilizer N as affected by the rate of rice-straw applied. The availability of soil N was also studied. The straw was incorporated in the soil 2 or 4 weeks before a sowing of wheat and allowed to decompose at a moisture content of 60% or 200% of the water-holding capacity. The wheat plants were harvested at maturity and the roots, straw, and grains were analysed for total N and 15N. The soil was analysed for total N and 15N after the harvest to determine the recovery of fertilizer N in the soil-plant system and assess its loss. The dry matter and N yields of wheat were significantly retarded in the soil amended with rice straw. The availability of soil N to wheat was significantly reduced due to the straw application, particularly at high moisture levels during pre-incubation, and was assumed to cause a reduction in the dry matter and N yields of wheat. A significant correlation (r=0.89) was observed between the uptake of soil N and the dry matter yield of wheat with different treatments. In unamended soil 31.44% of the fertilizer N was taken up by the wheat plants while 41.08% of fertilizer N was lost. The plant recovery of fertilizer N from the amended soil averaged 30.78% and the losses averaged 45.55%
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336249
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  • 10
    Electronic Resource
    Electronic Resource
    Microbial biomass and mineralization-immobilization of nitrogen in some agricultural soils (1986)
    Springer
    Biology and fertility of soils 2 (1986), S. 157-163 
    Details
    ISSN: 1432-0789
    Keywords: Available N ; Fumigation method ; N immobilization-remineralization ; Microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The chloroform fumigation-incubation method (CFIM) was used to measure the microbial biomass of 17 agricultural soils from Punjab Pakistan which represented different agricultural soil series. The biomass C was used to calculate biomass N and the changes occurring in NH4 +-N and NO3 −-N content of soils were studied during the turnover of microbial biomass or added C source. Mineral N released in fumigated-incubated soils and biomass N calculated from biomass C was correlated with some N availability indexes. The soils contained 427–1240 kg C as biomass which represented 1.2%–6.9% of the total organic C in the soils studied. Calculations based on biomass C showed that the soils contained 64–186 kg N ha−1 as microbial biomass. Immobilization of NCO3 −-N was observed in different soils during the turnover of microbial biomass and any net increase in mineral N content of fumigated incubated soils was attributed entirely to NH4 +-N. Biomass N calculated from biomass C showed non-significant correlation with different N availability indexes whereas mineral N accumulated in fumigated-incubated soils showed highly significant correlations with other indexes including N uptake by plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00257595
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