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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Polar research 10 (1991), S. 0 
    ISSN: 1751-8369
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography , Geosciences
    Notes: Temperature, light and dissolved nutrients are considered the “master” abiotic properties controlling primary production in the ocean. Each of these properties, in turn, is influenced by water column stability Sustained research over the past several decades has endeavored to ascertain which of these properties is most important in regulating phytoplankton growth. In no region has this research effort been more evident than at high latitudes. For both polar regions, extremes in each of these properties is the rule in surface waters where phytoplankton grow: the lowest ocean temperatures, the greatest seasonal excursion in incident solar radiation, and the highest dissolved nutrient concentrations.Based largely on indirect evidence, early researchers speculated that polar primary production was high relative to production at lower latitudes. This was commonly attributed to the abundant surface “macronutrients” (NO3, PO4, H4SiO4) since physiological adaptations to the suboptimum temperatures and light were thought to characterise these high latitude populations. Intensification of polar research since the late 1960's has in many respects modified this view. Current perspectives are that important differences exist between the Arctic and Antarctic with regard to the availability and role nutrients play in regulating primary production. In general much less emphasis is now placed on the significance of the macronutrients in the Antarctic although there is speculation and some evidence that “micronutrients” (Fe) may be important. Macronutrient availability appears to play a more important, though secondary, role in the Arctic, that of sustaining rather than initiating phytoplankton growth.This paper reviews early, contemporary, and present research addressing the question, “What role does nutrient availability play in the distribution and magnitude of primary production in Arctic and Antarctic waters?” Emphasis is placed on new research on under-ice communities as well as on the historically studied pelagic communities.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 86 (1985), S. 75-84 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tracer exchange kinetics were consistent with the view that microplankton of waters near Hawaii produced and assimilated dissolved orthophosphate and dissolved compounds other than orthophosphate at roughly equal rates in experiments conducted in September, 1982. Using simple exchange models plus chemical measurements, we inferred that material other than orthophosphate could sometimes dominate the soluble molybdate-reactive pool (SRP), as is frequently the case in fresh waters. Where phosphorus exchange was most rapid, the tracer kinetics suggested that some fraction of the plankton community was disproportionately responsible for dissolved phophorus exchange. Comparisons against independent measurements of rapid phytoplankton turnover in these communities supported the conclusion that dissolved compounds other than orthophosphate were rapidly cycled and formed an important substrate for plankton growth.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Assimilation rates of 15N-labelled ammonium, urea, and nitrate by plankton in the upper euphotic zone were measured in 2 summer, 2 winter, and 1 spring cruise in the central North Pacific Ocean. Average rates of ammonium plus urea assimilation could not be determined precisely, but were estimated to be 7 to 25 μg-at. N m-3 day-1. Indirect evidence suggested that non-photosynthetic microorganisms contributed to these rates. Nitrate assimilation was negligible in the upper waters considered in this report (above the chlorophyll maximum and the nutricline). Potential, nitrate-saturated rates were in the range 1 to 8 μg-at. N m-3 day-1. Seasonal comparison showed lowest rates of both carbon and nitrogen assimilation rates per chlorophyll a in winter.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 40 (1977), S. 9-18 
    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
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  • 5
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen cycling in a natural planktonic food chain was followed before and after perturbation by copper (10 μg l-1). Observations were separated into effects from artificial containment of the food chain and effects from the addition of copper. An initial reduction of seston-N and subsequent recovery, uniformly high settling rates of suspended particulate-N, and general decrease in zooplankton-N were attributed to the physical limitations imposed by the enclosures (e.g. elimination of normal mixing processes). Acute inhibition of nitrate assimilation by the seston, acute elevation of seston-N settling and chronic inhibition of zooplankton feeding, along with accelerated decline in zooplankton stocks, were attributed to copper stress. Since zooplankton stocks and fluxes were most drastically affected by copper, its overall effect on N-cycling through the planktonic food chain would depend largely upon the importance of zooplankton in regulating the production of the remaining seston.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Polar biology 5 (1986), S. 153-164 
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Analyses of some 700 photosynthesis-irradiance (P-I) experiments made on natural marine phytoplankton assemblages in over six years of field work are summarized. Observed variations in P-I parameters are discussed in relation to geographical location, sample depth and temporal cycles (diel to interannual). Results suggest that P-I characteristics and therefore regional primary production are largely under physical control; temperature and light appear to be the most important environmental covariables.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Polar biology 6 (1986), S. 145-152 
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The spatial distribution and size-dependence of oxygen consumption (respiration) and production by microplankton in near surface waters of the Canadian Arctic were measured during summer, 1983. High oxygen flux rates (consumption and production) were observed near surface (upper 20–30 m) and were generally associated with high phytoplankton biomass (chlorophyll a) levels. A substantial portion of the respiration (〉50%), however, was below the euphotic zone. Integrated oxygen fluxes (0–100 m) were approximately in balance (i.e., net oxygen production ≈ 0) at most locations sampled. In general, oxygen fluxes were higher than have been observed in the Southern Ocean but in the same range as found in temperate coastal waters. Size-fractionation studies showed that most (〉60%) of the oxygen production and phytoplankton biomass (chlorophyll a) were associated with organisms greater than 35 μm. On the other hand, more than 70% of the respiration was associated with organisms less than 35 μm; on average, more than 50% of the respiration was associated with organisms less than 1 μm. These results are consistent with theoretical studies and with experimental observations from temperate waters.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Deep profiles of particulate organic matter, microplankton (phytoplankton and bacteria), zooplankton and their metabolic activities were investigated during two summer voyages to the eastern Canadian Arctic. Magnitudes and depth distributions were similar in many respects to observations from temperate and tropical waters. Strong gradients in most properties were observed in the upper 50–100 m and subsurface maxima were generally associated with the upper mixed-layer (〉50 m). In addition to the general vertical decreases in plankton biomass and metabolic activity there was evidence for both rapid transport (sinking) of organic matter and for enhanced (above background) levels of microbial metabolic activity in deep waters (〉500 m). Zooplankton depth distributions differed from the pattern generally observed at lower latitudes; in the Arctic, zooplankton abundance decreased to a lesser degree with depth than particulate organics and microplankton. The overwintering behavior of high-latitude zooplankton appeared to be the best explanation for their relatively high abundance at depth. Despite this, however, zooplankton apparently contributed little to the total column community metabolism.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During a cruise to the eastern Canadian Arctic (Northern Baffin Bay) in the summer of 1980, we took advantage of the 24-h photoperiod to conduct a 32-h time course experiment of 14C accumulation under natural solar radiation. The degree of non-linearity in the time course was judged against a time-dependent curve of radioactivity constructed by cumulatively adding the amount of 14C taken up in sequential short (2 h) incubations of plankton held in a replicate bottle but left unlabelled until removed for assay. Departure from linearity was due first to decreasing rates of 14C incorporation into polysaccharides and then into lipids. There was a close correspondence between 14C incorporation into proteins in the 32-h incubation and in the sequence of short incubations. These observations are consistent with patterns in utilization of photosynthetic end-products established from laboratory studies of unicellular algal cultures. Based on parallel or independent control experiments, it was judged that complicating factors such as diel light changes, nitrogenous nutrient exhaustion, bottle size effects or inhibitory conterminants in NaH14CO3 stock solutions would not seriously affect our interpretation that non-linearity resulted from catabolic loss of radiocarbon.
    Type of Medium: Electronic Resource
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