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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogen fixation in the North Pacific Ocean (1974)
    Springer
    Marine biology 24 (1974), S. 109-119 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen fixation in the euphotic zone of the ocean was measured by C2H2 reduction and 15N2 incorporation associated with Trichodesmium sp. and also with Richelia intracellularis occurring within the cells of Rhizosolenia styliformis var. longispina, and R. cylindrus. The vertical distribution of N2 fixation activity, N2-fixing species, particulate matter and dissolved nutrients was measured. The effects of light intensity, sample concentration, length of incubation, and nutrient enrichment on the rates of C2H2 reduction were determined. Estimates of the importance of N2 fixation in adding previously uncycled nitrogen to the euphotic zone are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389344
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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    High-affinity uptake of an ammonium analogue by two marine microflagellates from the oligotrophic Pacific (1983)
    Springer
    Marine biology 74 (1983), S. 161-168 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two marine microflagellates, isolated from the North Pacific Central Gyre, and tentatively identified as Platymonas sp. and Mantoniella sp., were examined for uptake of 14C-methylamine, a non-metabolizable analogue of ammonium. Half-saturation constants (K m) for ammonium transport, estimated from competitive inhibition of methylamine transport by ammonium, were 50 nM for Platymonas sp. and 2.9 nM for Mantoniella sp. These values are the lowest so far reported, indicating that the transport systems are well adapted to extremely low ammonium environments. The ratio of the K m for methylamine to the K m for ammonium was 17 for Platymonas sp. and 41 for Mantoniella sp. The observed ratios fell within the relatively narrow range reported for various organisms, including bacteria, fungi and phytoplankton (25.0±15.5, $$\bar x$$ ± SD, n=9), although the reported K mvalues for both ammonium and methylamine vary over a thousand-fold range. The use of 14C-methylamine may therefore be a promising technique for studying the kinetics of ammonium transport by marine microorganisms, particularly those in oligotrophic environments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00413919
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  • 5
    Electronic Resource
    Electronic Resource
    A ciliate red tide at Barrow, Alaska (1970)
    Springer
    Marine biology 7 (1970), S. 37-46 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In September 1968 the first occurrence of extensive red water in the Arctic Ocean in the vicinity of Point Barrow, Alaska, was recorded. The organism causing this water discoloration was a fairly large (100 to 150 μ) ciliated protozoan, with chlorophyll-containing endosymbionts. This ciliate, which is not identical to the commonly reported Mesodinium or Cyclotrichium species, is described in this paper, but cannot be identified with any organism described in the literature. Concentrations of dissolved inorganic nutrients and trace metals were determined on water samples obtained from the red water and also in the clear water adjacent to it. These data are discussed relative to the hydrographic conditions in the Chuckchi Sea around Point Barrow. A direct species' analysis by microscopic methods indicated that the plankton were quite similar in all the water samples except for the aforementioned red ciliate, which accounted for over 90% of the total cellular organic carbon in the samples from the red water. Chemical analyses indicated that the red tide ciliate contained approximately 51% protein, 33% lipid, 8% carbohydrate, 0.2% chlorophyll a, and 1.2% DNA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346806
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  • 6
    Electronic Resource
    Electronic Resource
    Spatial and temporal variability of phytoplankton biomass and taxonomic composition around Elephant Island, Antarctica, during the summers of 1990–1993 (1995)
    Springer
    Marine biology 123 (1995), S. 677-686 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the austral summers of 1990–1993, phytoplankton studies were conducted in the vicinity of Elephant Island, Antarctica, to investigate the spatial and temporal variability of phytoplankton biomass and taxonomic composition. There was much intraannual variability, with a trend for increasing biomass from January–February (Leg I) to February–March (Leg II), except in the 1993 studies. There was also a change in phytoplankton composition between the two legs. During 1990–1991 the increase was due mostly to diatoms, during 1992 mostly to an increase of flagellates; during 1993 there was a decrease in total biomass between the two legs, with diatoms decreasing, so that dinoflagellates, which increased slightly in numbers, dominated the biomass during the second leg. There was also much inter-annual variability, with the summers of 1990–1991 having greater biomass and higher proportions of microplanktonic diatoms than that of 1992–1993, which had a higher proportion of flagellates. Cluster analyses revealed the presence of four major phytoplankton assemblages, with varying geographical distributions. The northwestern portion of the grid (Drake Passage waters), was characterized by nanoplanktonic diatoms during 1990–1991 and 1993, but by nanoplanktonic flagellates during 1992. The central area (Drake-Bransfield confluence) was characterized by microplanktonic diatoms in 1990–1991, but by cryptophytes or flagellates in 1992–1993. The south and southeastern portion of the area (Bransfield Strait waters) was characterized mainly by either cryptophytes or other flagellates during all 4 yr. The spatial and temporal variability of phytoplankton could not be ascribed specifically to the geographical extent of the different water masses found in the study area, but appears to be due to changing growth conditions in the upper water column as influenced by physical mixing and meteorological conditions, as well as to effects of differential grazing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349110
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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
    Amino acid uptake and respiration by marine heterotrophs (1976)
    Springer
    Marine biology 35 (1976), S. 41-47 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The concentration and turnover of dissolved free amino acids were measured in samples from 25 and 100 m on three occasions at a station 6 miles off the California (USA) coast. Individual amino acid concentrations varied from undetectable (〈0.05 μg/l) to 3 μg/l, the total amino acid concentration from 1.8 to 8.5 μg/l. The greater concentration of total amino acids was always found at 25 m. The predominant amino acids were serine, lysine, aspartate, glutamate and alanine; reliable analyses could not be made for glycine because of a high blank. For the 10 individual amino acids studied, the rate of heterotrophic turnover ranged from undetectable to 1.2 μg/l day-1; serine, aspartate, alanine and glutamate showed the highest rates. In samples from 25 m, the rates were 15 to 20 times higher than those taken from 100 m. The total calculated flux of the amino acids studied varied from 0.015 to 3.2 μg/l day-1 and amounted to 1–10% of photosynthetic carbon dioxide fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386673
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  • 9
    Electronic Resource
    Electronic Resource
    Physiology and chemical composition of nitrogen-fixing phytoplankton in the central North Pacific Ocean (1977)
    Springer
    Marine biology 41 (1977), S. 213-227 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The magnitude and physiological characteristics of biological nitrogen fixation have been studied in the oligotrophic waters of the North pacific gyre. The filamentous blue-green algae Trichodesmium spp. and Richelia intracellularis were the important nitrogen-fixing phytoplankton. Most of the nitrogen fixation occurs in the upper 40 m of the water column, with detectable fixation as deep as 90 m, which corresponds to about the 1 % light depth. There was no evidence of photoinhibition of nitrogen fixation, although CO2 reduction was depressed slightly at the highest light levels. The rate of nitrogen fixation in the water column varied throughout the day, being highest in mid-morning and in late afternoon. Relatively high fixation rates were also found during periods of darkness. Elevated oxygen concentrations had a marked inhibitory effect on rates of nitrogen fixation, a pO2 of 0.4 atm causing a 75% inhibition. Data from studies of nitrogen fixation and assimilation rates of 15N-labelled nitrate, ammonium, and urea indicate that nitrogen fixation furnished about 3% of the total daily fixed nitrogen requirement for phytoplankton growth. Studies with isolated colonies of Trichodesmium spp. indicated that 100% of their nitrogen requirement was met by nitrogen fixation. Chemical composition of the Trichodesmium colonies showed that the C:N ratio was 4.1 and that their phosphorus content relative to carbon or nitrogen was much lower than that of the total particulate material in the water column. Elevated ratios of carbon: adenosine triphosphate (ATP) also suggest that phosphorus deficiency may be limiting the growth of Trichodesmium. The magnitude of nitrogen fixation in the gyre is seasonally dependent, with high rates in late summer and autumn. At these times the water column is stratified, with phosphate and nitrate barely detectable in the upper 100 m. Our data suggest that during these months of stratification, biological fixation of nitrogen amounts to about 33 μg-at N/m2/day.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394908
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  • 10
    Electronic Resource
    Electronic Resource
    Release of photoassimilated carbon as dissolved organic matter by marine phytoplankton (1974)
    Springer
    Marine biology 28 (1974), S. 305-310 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The release of photoassimilated carbon as dissolved organic matter was studied in situ in oligotrophic and eutrophic marine waters and in axenic laboratory cultures. Percentage extracellular release (PER), integrated for the trophogenic zone, ranged from 6 to 12% in eutrophic waters and from 17 to 27% in oligotrophic seas. Most of the algal cultures released low amounts of dissolved organic matter (∼5%) during exponential growth. The highest levels of PER were observed in surface and deep samples, possibly as a result of elevated photorespiration and senescent cells. The generally lower values for extracellular release reported in this work as compared to other studies may be partly due to improved experimental techniques which minimized previously encountered artifacts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388498
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