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  • 1
    Electronic Resource
    Electronic Resource
    Coil dimensions of polystyrenes in isorefractive viscous solvents by small-angle neutron scattering (1986)
    s.l. : American Chemical Society
    Macromolecules 19 (1986), S. 1996-2002 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00161a036
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  • 2
    Electronic Resource
    Electronic Resource
    Egg production by the subtropical copepod Undinula vulgaris (1993)
    Springer
    Marine biology 117 (1993), S. 415-421 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Egg production by Undinula vulgaris, collected off Kaneohe Bay, Hawaii, was measured under field and laboratory conditions on 16 occasions from June to December 1991. In situ rates ranged from 0 to 15.7 eggs female-1 d-1, with a mean of 6.4 eggs female-1 d-1, 2.1% female body carbon d-1. Maximum in situ production was 53 eggs female-1 d-1, 17.2% C d-1. Average egg production (Y, eggs female-1 d-1) was related to the concentration of particulate carbon (X, μg C l-1) by the Ivlev function, Y=13.9[1-e-0.0097 (x-10)], with R 2=0.96. Individuals with the same feeding history produced more eggs at lower temperatures in the laboratory. Egg production was not significantly correlated with dry weight, and no noticeable temporal trend was found. Despite the elevated habitat temperatures (26 to 27°C) of this subtropical copepod, maximum fecundity of U. vulgaris was comparable to, but average rates were lower than, egg production rates of similarly-sized, temperate and borcal species of the genus Calanus. Our results caution against broad extrapolations of the temperature-growth relationship for temperate coastal copepods to species from poorly studied, oligotrophic regions of the oceans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349317
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  • 3
    Electronic Resource
    Electronic Resource
    Estimating the grazing impact of marine micro-zooplankton (1982)
    Springer
    Marine biology 67 (1982), S. 283-288 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper describes a dilution technique for estimating the micro-zooplankton grazing impact on natural communities of marine phytoplankton. Experiments performed in coastal waters off Washington, USA (October, 1980), yield estimates of micro-zooplankton impact equivalent to 6 to 24% of phytoplankton standing biomass and 17 to 52% of production per day. Indirect evidence suggests that most of this impact is due to the feeding of copepod nauplii and tintinnids; in contrast, non-loricate ciliates, comprising 80 to 90% of numerical abundance, appeared to contribute little to phytoplankton mortality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397668
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  • 4
    Electronic Resource
    Electronic Resource
    Ingestion-independent rates of ammonium excretion by the copepod Calanus pacificus (1984)
    Springer
    Marine biology 78 (1984), S. 265-270 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between food ingested and NH + 4 excretion rate was investigated for female Calanus pacificus collected in August, 1982, from the San Juan Archipelago, Washington State, USA. The copepods were preconditioned to 6 densities of the diatom Thalassiosira weissflogii (0 to 104 cells ml−1) for 30 h before the experiment. The experiment was conducted with nutrients added in excess to maintain equal rates of NH + 4 uptake by the diatoms at all densities. Although ingestion rates of C. pacificus varied from 0 to over 20% of body N d−1 at the different food levels, excretion was a constant 6.6 nM NH + 4 copepod−1 h−1 or about 10% of body N d−1. This ingestion-excretion relationship, which is consistent with previous respiration and fecundity studies, suggests that the ecological dominance of C. pacificus only under conditions of high food abundance may be due to a dramatic increase in its growth efficiency as ingestion increases above the level supporting a constant metabolic rate. The maintenance of a constant level of metabolism during relatively short periods of low food abundance may be advantageous if it allows the copepod to exploit more effectively short-term variability in its food resulting from environmental heterogeneity or vertical migration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393012
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  • 5
    Electronic Resource
    Electronic Resource
    The structure of Marine Ecosystems: An alternative (1976)
    Springer
    Marine biology 35 (1976), S. 1-7 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In “The Structure of Marine Ecosystems” (1974), Steele developed a simulation model which suggested that the stability of planktonic communities was dependent on a threshold response allowing phytoplankton a refuge in concentration below which herbivorous zooplankton did not feed. Observations from the North Sea were presented to support this hypothesis. In order to more realistically represent the simulated herbivores, Calanus spp., several of Steele's assumptions have been modified. The results of the revised model indicate that feeding thresholds are not essential for the long-term realism and stability of the simulated system and suggest an alternative, ecosystem control through predation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00386669
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  • 6
    Electronic Resource
    Electronic Resource
    Switching between herbivory and carnivory by the planktonic marine copepod Calanus pacificus (1981)
    Springer
    Marine biology 65 (1981), S. 77-82 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adult females of the omnivorous copepod Calanus pacificus, collected from the plankton off La Jolla, California, USA (June, 1978), fed disproportionately on the prey in greatest relative abundance when given mixtures of diatoms (Thalassiosira fluviatilis) and copepod (C. pacificus) nauplii as food. This switch from herbivorous to carnivorous behavior may be significant in nature during the decline of phytoplankton blooms. More generally, the widespread omnivorous habit among pelagic animals suggests a responsive and flexible trophic organization which contributes to the resiliency of planktonic communities in a dynamic physical environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397070
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  • 7
    Electronic Resource
    Electronic Resource
    Short-term changes in feeding and digestion by the copepodCalanus pacificus (1988)
    Springer
    Marine biology 99 (1988), S. 63-74 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The planktonic marine copepodCalanus pacificus exhibits an enhanced feeding rate, or hunger response, when exposed to food following short periods of starvation. In a scries of laboratory experiments with copepods collected from the main basin of Puget Sound, Washington, during 1982 and 1984, we measured maximum ingestion rate, assimilation efficiency, and digestive enzyme activity to determine the time scales over which the feeding behavior ofC. pacificus responds to increases in food. These laboratory results were then compared to field studies of diel fluctuations in digestive enzymes and gut fluorescence ofC. pacificus in Dabod Bay, a fjord of Puget Sound, during September, 1980, and the closely relatedC. marshallae off the Washington coast, in August, 1981. Laboratory experiments demonstrated that the hunger response ofC. pacificus lasts approximately 6 h before ingestion rate returns to a steady state level of about one-half maximum. On the order of 12h of starvation were required to induce the maximum ingestion rate of the hunger response. Digestive enzyme activities did not change over these time scales. Assimilation efficiency peaked within a few hours of the onset of feeding, with low initial rates possibly related to the period of starvation prior to feeding. These results were consistent with diel patterns observed in the field. The hunger response ofC. pacificus appears to be controlled by processes within the gut, and our results are discussed in relation to recent studies of the digestive processes of calanoid copepods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644978
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  • 8
    Electronic Resource
    Electronic Resource
    Predatory feeding behavior of the marine cyclopoid copepod Corycaeus anglicus (1985)
    Springer
    Marine biology 85 (1985), S. 163-169 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Feeding rates, patterns of prey selection, and starvation tolerance were investigated for adult males and females of the cyclopoid copepod Corycaeus anglicus collected from the waters of Friday Harbor, Washington, USA. Selection by C. anglicus was determined largely by prey body-size, but was also affected by species and developmental stage. Small developmental stages of all prey species were fed upon at relatively low rates. The small calanoid species Acartia clausii was increasingly vulnerable to predation by C. anglicus as it progressed through successive developmental stages. Larger prey species, Pseudocalanus sp. and Calanus pacificus, were more vulnerable in intermediate stages, the C3 and N6 stages, respectively. Larger and smaller prey were characteristically attacked at different sites on their bodies; however, attack sites fell within a similar range of body widths, 130 to 170 μm. Males of Corycaeus anglicus killed a maximum of 1.4 prey d-1 when feeding on the optimally-sized adult females of Acartia clausii, which are approximately equivalent to its own body length. Males fed at approximately double the rates of females. Despite its small size and apparent lack of metabolic stores, this cyclopoid is highly tolerant of starvation conditions. Median survival time without food is at least 2 wk for both males and females. In its predatory behavior, C. anglicus employs an ambush-type strategy and seems to be adapted for infrequent encounters with relatively large prey.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397435
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  • 9
    Electronic Resource
    Electronic Resource
    Effects of food-level acclimation on digestive enzyme activities and feeding behavior of Calanus pacificus (1983)
    Springer
    Marine biology 75 (1983), S. 47-55 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A recent hypothesis in the zooplankton literature states that zooplankton acclimate to ambient food concentrations such that higher digestive enzyme activities and, consequently, higher maximum ingestion rates are achieved at higher food levels. To test this hypothesis, adult female Calanus pacificus, collected from the main basin of Puget Sound, Washington, USA, in August 1979 and May 1982, were conditioned for 2 wk at different concentrations of the diatom Thalassiosira weissflogii (=fluviatilis). Ingestion rates and the activity of the digestive enzymes laminarinase, maltase, and cellobiase were measured periodically during acclimation and in a block-designed feeding experiment at the end of acclimation. Consistent with the hypothesis, maximum ingestion rate and digestive enzyme activity were positively correlated. However, in contrast to the hypothesized mechanism, this result arose because both maximum ingestion rate and digestive enzyme activity were negatively correlated with food concentration during acclimation. The enhanced ingestion of copepods following long-term (12 to 14 d) acclimation to low food is similar to that previously described for short-term (e.g. 1 d) starvation. It might be energetically optimal for copepods experiencing a patchy food environment to maintain higher levels of digestive enzymes at low food concentrations in order to exploit high concentrations of food when encountered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392629
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  • 10
    Electronic Resource
    Electronic Resource
    A review of important concepts in the trophic organization of pelagic ecosystems (1977)
    Springer
    Helgoland marine research 30 (1977), S. 8-17 
    Details
    ISSN: 1438-3888
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The physical environment has an important influence on the size composition of primary producers in plankton communities. This effect is transmitted through the trophic structure by size selective feeding processes at each level. A pictorial representation of trophic organization in pelagic ecosystems is presented which illustrates the complex involvement of individual species in the food web and the dynamic nature of ecosystem development along alternate pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02207821
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