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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 72 (1982), S. 183-191 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Predatory feeding of the marine mysids Mysidopsis bigelowi and Neomysis americana on several species of co-occurring copepods was examined in laboratory experiments. M. bigelowi exhibited a curvilinear functional response; there was a negative logarithmic relationship between prey density and clearance rates. N. americana also exhibited higher clearance rates at lower prey densities. Increased clearance rates at lower prey densities were probably due to increased swimming speed or reaction distance as hunger increased. This response occurred only when mysids could visually locate prey; in complete darkness clearance rates were significantly lower and independent of prey density. Feeding rates on different prey species were only partially dependent on prey size; prey movement patterns and escape behavior also strongly affected feeding rates. M. bigelowi showed active prey selection when offered a choice of different prey species. Estimates of predation rates of estuarine mysid populations indicate that they could have a significant effect on co-occurring copepod populations.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 87 (1985), S. 47-54 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In 1982–1983 nauplii and adults of several co-occurring copepods and Artemia sp. nauplii (Lake Grassmere, New Zealand strain) were fed to the hydromedusae Obelia geniculata (L.) and Phialella quadrata (Forbes), two species which are very abundant in Wellington Harbour, New Zealand. Clearance rates of both hydromedusae were significantly correlated with predator diameter, but independent of water temperature and prey density. P. quadrata consumed all developmental stages of some copepod species, but O. geniculata consumed only nauplii. Clearance rates of O. geniculata were most strongly related with the strength of the prey escape response, and showed little relation with prey size or movement rates. Clearance rates of P. quadrata were equally influenced by the prey escape response and prey size, but a large amount of the variability in clearance rates could not be explained by any of the prey characteristics, or by a linear combination of the prey characteristics. Clearance rates of the hydromedusae are combined with measures of hydromedusa abundance in Wellington Harbour to calculate daily per capita death rates of the prey.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 62 (1984), S. 97-101 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effects of predation by the chaetognath Sagitta hispida and nutrient enrichment on estuarine copepod community structure were studied by experimental manipulations in large enclosures. Chaetognath abundance and nutrient addition rates were manipulated in a factorial design. Predation by chaetognaths resulted in a significant decline in the relative abundance of Acartia tonsa and an increase in the relative abundance of Oithona colcarva. However, these effects were evident only at chaetognath densities far higher than observed in natural populations. Nutrient enrichment resulted in a decline in relative abundance of Paracalanus crassirostris, and, in the absence of chaetognath predation, an apparent increase in the relative abundance of A. tonsa. The effects of chaetognath predation were independent of enrichment level, apparently because of the absence of effects of enrichment on total copepod and chaetognath densities.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 76 (1988), S. 383-389 
    ISSN: 1432-1939
    Keywords: Microcystis aeruginosa ; Blue-green algae ; Zooplankton ; Rotifers ; Cladocerans ; Copepods ; Competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Field distribution patterns and laboratory feeding experiments have suggested that blooms of colonial blue-green algae strongly inhibit relatively large-bodied daphnid cladocerans. We conducted laboratory experiments to test the hypothesis that blooms of the colonial blue-green alga Microcystis aeruginosa would shift competitive dominance away from large-bodied daphnid cladocerans toward smaller-bodied cladocerans, copepods, and rotifers. In laboratory competition experiments, increasing the proportion of M. aeruginosa in the algal food supply resulted in a shift from dominance by the relatively largebodied cladoceran Daphnia ambigua to dominace by the copepod Diaptomus reighardi. The small-bodied cladoceran Bosmina longirostris was always numerically heavily dominant over D. ambigua, but its estimated population biomasses were only slightly higher than those of D. ambigua. Daphnia ambigua consistently outcompeted the rotifer Brachionus calyciflorus. Our results demonstrate that blooms of M. aeruginosa can alter zooplankton competitive relations in laboratory experiments, favoring small-bodied cladocerans and copepods at the expense of large-bodied cladocerans. However, contrary to predictions, blooms of M. aeruginosa did not improve the competitive ability of rotifers.
    Type of Medium: Electronic Resource
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