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  • 1
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    Future marine zooplankton research - a perspective (2001)
    In:  EPIC3Marine ecology-progress series, 222, pp. 297-308
    Details
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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    PAPER (OA)
  • 2
    Electronic Resource
    Electronic Resource
    Gut pigment accumulation and destruction by arctic copepods in vitro and in situ (1992)
    Springer
    Marine biology 112 (1992), S. 583-592 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The results presented here were obtained at six locations during three cruises in 1985 (off the coast of Labrador), 1986 (at the eastern end of Viscount Melbourne Sound) and 1988 (off the coast of Labrador). In situ chlorophyll maximum concentrations were 〉7 μgl-1 at depths of between 0 and 30 m in all sampling areas. In feeding experiments copepods attained higher gut pigment concentrations the longer they had been previously starved and higher concentrations when fed in the dark than when fed in the light. Community ingestion rates calculated from changes in particulate chlorophyll were higher than estimates derived from gut pigment data except when copepods had been starved for 24 h. Differences between estimates by the two methods suggested pigment destruction. In feeding experiments pigment: biogenic silica ratios in food and faecal pellets suggested that the length of starvation period affected the degree of pigment destruction differently at different stations and that feeding in the light greatly increased pigment destruction. A comparison of pigment: silica ratios in the water column, and in faecal pellets collected from copepods which had fed there, suggested that pigment destruction may occur in situ sometimes and that the degree to which it occurs may be affected by feeding history, light, diel feeding behaviour and species composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346176
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  • 3
    Electronic Resource
    Electronic Resource
    Comparison of the chemical composition of particulate material and copepod faecal pellets at stations off the coast of Labrador and in the Gulf of St. Lawrence (1992)
    Springer
    Marine biology 112 (1992), S. 593-600 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Faecal pellets were collected in 1988 from copepods which had fed in situ or in laboratory experiments, using screened natural seawater as food, at two stations off the coast of Labrador and one in the Gulf of St. Lawrence. The chemical composition of the pellets and of particulate material in profiles and in laboratory food were measured in terms of particulate carbon, carbohydrate (soluble and insoluble), protein and lipid. Faecal pellet composition was somewhat similar in all experiments at the first two stations, where the compositions of particulate material in situ and copepod species assemblages were also similar. At the third station the compositions of faecal pellets and particulate material were slightly different from those at the other stations and the copepod species composition varied between sampling times. Faecal pellets at the first two stations had very low levels of soluble carbohydrate, while concentrations in the food were generally high, suggesting that it was efficiently metabolized by copepods, although it might have been absent because of ‘sloppy feeding’ or release, after passage through the gut, in soluble form or from faecal pellets. Comparisons of POC: biogenic silica ratios in food and faecal pellets, calculated using data presented elsewhere (Head 1992; Mar. Biol. 112: 583–592), suggested that at these stations, where food concentrations were high (chlorophyll concentrations〉8 μgl-1), copepods may have been assimilating carbon rather inefficiently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346177
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  • 4
    Electronic Resource
    Electronic Resource
    Estimation of Arctic copepod grazing rates in vivo and comparison with in-vitro methods (1986)
    Springer
    Marine biology 92 (1986), S. 371-379 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gut evacuation rates were measured in Calanus hyperboreus and C. glacialis from two stations in Jones Sound, Northwest Territory (NWT) and one station in an Ellesmere Island Fjord during late summer of 1984. Gut content decreased exponentially with a rate constant, that, for Stage V C. glacialis at least, was independent of food type and time of day. Gut filling rates were measured in Stage V C. glacialis in the light and in the dark, at noon and midnight. Nighttime gut filling rates were very similar for both light intensities, and also similar to the daytime rate in the dark, whereas the daytime rate in the light was much lower. Ingestion rates were calculated for these latter experiments, including a rate term for defecation, and these results were compared to the values obtained from the observations of gut filling rates in vivo as reported in Head et al. (1985) and from long-term (2–3 d) bottle incubations as reported in Head et al. (in press). The following points were made: (1) in-vivo and in-vitro ingestion rates were very close if appropriate in-vitro experimental conditions were used with respect to light intensity and time of day; (2) copepods could fill their guts at a rate apparently higher than their normal nocturnal ingestion rate; and (3) the calculated rations were dependent on the shape of the observed diurnal feeding patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392678
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  • 5
    Electronic Resource
    Electronic Resource
    A rapid method for the purification of octopine dehydrogenase for the determination of cell metabolites (1979)
    Springer
    Cellular and molecular life sciences 35 (1979), S. 304-305 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Unlike other NAD+-dependent dehydrogenases, octopine dehydrogenase was not bound by blue Sepharose. A rapid 2-step purification procedure (gel filtration on Sephadex G-100 followed by affinity chromatography on blue Sepharose) resulted in a final preparation of octopine dehydrogenase which had a sp. act. of 65 units/mg protein and was free of contaminating NAD+-oxidoreductases. This preparation has been used successfully for the estimation of phospho-L-arginine, L-arginine and octopine in perchloric acid extracts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01964314
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  • 6
    Electronic Resource
    Electronic Resource
    Grazing, defecation and excretion rates of copepods from inter-island channels of the Canadian Arctic archipelago (1988)
    Springer
    Marine biology 99 (1988), S. 333-340 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zooplankton (〉800 μm) and water samples were collected at night at eleven stations in Parry Channel and adjacent waters, between 28 August and 14 September 1986. Chlorophyll concentrations varied between ≈17 μg l-1 at the surface at one station in Wellington Channel, Canada, and ≈1.5 μg l-1 throughout the top 30 m at one station in Byam Martin Channel, Canada. In tows from 0 to 50 m the zooplankton community at all stations was dominated by varying proportions of three species,Calanus hyperboreus, C. glacialis andMetridia longa. Levels of chlorophyllderived pigments inC. hyperboreus Stages V, IV and III were correlated with the concentration of chlorophyll at the chlorophyll maximum. Defecation rate constants, measured for the different stages where present, were variable but not correlated with ambient chlorophyll concentrations. Ammonia excretion was measured simultaneously for the communities in which defecation was being measured in the invividual species and stages. In these experiments the rate of ammonia accumulation decreased significantly over the period during which the copepods were actively defecating (usually the first 3 h) and then tended to a constant level (over the next 18 to 20 h). The time courses of ammonia accumulation could be described by a model comprised of the sum of a straight line and a saturating curve. For seven experiments the ammonia release given by the asymptote of the saturating component was correlated with the estimate of community defecation, obtained by summing the individual defecations, suggesting that the two processes were closely associated. Weight specific defecation and weight specific “defecation-associated” ammonia excretion were both correlated with ambient chlorophyll concentration. The ratio of initial to basal ammonia excretion rate varied between 2 and 20, so that “defecation-associated” ammonia release may be important in the estimation of in vivo nitrogen excretion or regeneration rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02112125
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  • 7
    Electronic Resource
    Electronic Resource
    Physiological and biochemical changes in Calanus hyperboreus from Jones Sound NWT during the transition from summer feeding to overwintering condition (1985)
    Springer
    Polar biology 4 (1985), S. 99-106 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Several biochemical and physiological characteristics of stage V and female adult Calanus hyperboreus from two different depth ranges (0–50 m and 200–500 m) were compared at a time near the peak of the summer pelagic algal bloom in Jones Sound, and again one month later, when the near surface chlorophyll levels were low and most copepods had migrated to their overwintering dephts. For a given stage deep water animals were larger and had higher total lipid levels than did surface animals. Feeding activities, as evidenced by gut pigment contents, may be lower in animals at depth, although potential digestive activities, as expressed in the levels of three digestive enzymes, were not very different either in different stages or at different depths. Respiration rates in animals that had migrated down for the winter were not much lower than in those at the surface although energetic considerations suggest that they may decrease later. Ammonia excretion rates however, changed dramatically. Surface, feeding animals had the highest rates and deep water animals in September had undetectably (〈1 ng atom ammonia nitrogen animal-1 · day-1) low rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442907
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  • 8
    Electronic Resource
    Electronic Resource
    Depth profiles of plankton, particulate organic matter and microbial activity in the eastern Canadian Arctic during summer (1987)
    Springer
    Polar biology 7 (1987), S. 207-224 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00287417
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  • 9
    Electronic Resource
    Electronic Resource
    Physiological adaptations of an under-ice population of Pseudocalanus in Barrow Strait (N.W.T) to increasing food supply in spring (1990)
    Springer
    Polar biology 10 (1990), S. 561-570 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Zooplankton and water samples were collected at weekly intervals between April 25 and May 30, 1986 in Barrow Strait, N.W.T. (Canadian Arctic Archipelago). In tows from 0–30 m, the zooplankton community (〉202 μm) was dominated by Pseudocalanus. The population was apparently growing and developing as shown by an increase in the proportion of adults (stage VI) and decreases in the proportion of stages III, IV, and V as the season progressed. Respiration and excretion rates of the Pseudocalanus populations were probably linked, there being an immediate increase in excretion rate, accompanying an increase in feeding rate when chlorophyll concentrations increased, which was followed by a smaller increase in respiration rate after a time lag. Hence, there was a large decrease in the O∶N ratio. Increased metabolism coincided with changes in the population structure, as did protease and bodily protein, but could not be clearly linked to dietary acclimation. Only laminarinase activity could be statistically related to an identifiable fraction of potential nutritional value in the water, particulate soluble carbohydrate, but neither showed overall seasonal change.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239367
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  • 10
    Electronic Resource
    Electronic Resource
    Copepod feeding behavior and the measurement of grazing rates in vivo and in vitro (1988)
    Springer
    Hydrobiologia 167-168 (1988), S. 31-41 
    Details
    ISSN: 1573-5117
    Keywords: gut pigment ; turnover time ; pigment destruction ; copepods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper some aspects of the use of the gut fluorescence method for estimating ingestion rates have been, examined. One assumption is that gut turnover time in feeding copepods is equal to the gut clearance time in filtered seawater. When arctic Pseudocalanus were pre-fed on Thalassiosira weisflogii, and then given a trace addition of the same C14-labelled culture, or were transferred to filtered seawater, results suggested that this assumption was probably justified. In another experiment in which Pseudocalanus were fed at the same concentration of either melted ice algae, or pelagic under ice algae, there were significant differences in both gut clearance times and gut pigment levels in the two cases. Pigment: biogenic silica ratios in epontic algae were higher than those in faecal pellets produced by Pseudocalanus feeding on the algae, suggesting that pigment destruction was occurring during grazing. In a 28 hr time course experiment ingestion rates determined by rate of disappearance of particulate chlorophyll were higher than those simultaneously determined by the gut fluorescence method, which also supports the idea of pigment destruction in copepods guts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00026292
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