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  • 1
    Electronic Resource
    Electronic Resource
    Direct sampling and in situ observation of a persistent copepod aggregation in the mesopelagic zone of the Santa Barbara Basin (1984)
    Springer
    Marine biology 80 (1984), S. 75-81 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Observations from a one-person submersible (“Wasp”) in fall, 1982, revealed a persistent aggregation of non-migrating, Stage V copepodites of Calanus pacificus californicus Brodsky in a band 20±3 m thick at a depth of 450 m, about 100 m above the bottom of the Santa Barbara Basin, California. Copepod abundances, calculated from nearest-neighbor distances measured directly from the submersible, yielded maximum densities of 26×106 copepodites m-3. Quiescent behavior, low laminarinase activity, low protein content, high lipid content and evidence of low excretion rate all suggest that these copepodites were in a state of diapause. Diapausing C. pacificus californicus at other locations along the eastern Pacific coast were also captured in discrete depth plankton tows. Both the submersible observations and the net collections suggest that the dense aggregation of diapausing copepods we observed in the Santa Barbara Basin was a phenomenon associated with seasonal upwelling cycles, and that such aggregations occur during non-upwelling periods when food is scarce in surface waters. Numerous predators, especially the deep sea smelt Leuroglossus stilbius, were observed feeding upon the aggregated copepods; thus, in contrast to the conventional picture of surface-dominated food distribution, deep-water aggregations of C. pacificus californicus may support the mesopelagic community during periods of low food availability in surface waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393130
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  • 2
    Electronic Resource
    Electronic Resource
    Herbivory by the myctophid fish Ceratoscopelus warmingii (1984)
    Springer
    Marine biology 84 (1984), S. 119-123 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During a study of midwater fish feeding in the oligotrophic North Pacific gyre in August 1978, nine specimens of a tropical-subtropical myctophid, Ceratoscopelus warmingii, were found to have been feeding on mats of diatoms, Rhizosolenia spp. Chemical analyses of the intestinal contents of several additional specimens showed significantly elevated levels of diatom degradation products. Therefore, C. warmingii, although known to feed on zooplankton, appears to be adapted for occasional herbivory. Such an adaptation is exceptional within a major ecological group of oceanic fishes that was previously thought to be exclusively carnivorous. Like omnivorous and herbivorous fishes in general, C. warmingii has a longer intestine than other myctophid species. As an adaptive response to competition from a diverse fish fauna in a low-productivity environment, occasional herbivory by C. warmingii runs counter to the theoretical expectation by expanding rather than narrowing the range of potential food types.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392995
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Food availability as a selective factor on the chemical compositions of midwater fishes in the eastern North Pacific (1986)
    Springer
    Marine biology 91 (1986), S. 131-141 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In September and October 1980 we examined the relationships between food availability, depth, and chemical composition among 12 midwater fish species, from three adjacent areas of the eastern North Pacific: the eastern gyre, the California Current, and the transitional region between them. By comparing trends in chemical composition across a geographical productivity gradient, the influence of food availability could be examined both with and without depth as a dependent variable. In general, caloric density, lipids, and water content showed consistent trends along both vertical and horizontal gradients of food availability. Lipids and caloric contents were lowest among bathypelagic species and among fishes from the gyre. Water content was highest in the gyre and among deeper-living species. While protein content as a percentage of the total wet weight declined with depth, there was no clear trend among mesopelagic species between stations. Protein as percent of the total organic content showed no decrease with depth, but was significantly higher in the gyre among mesopelagic species. These findings suggest that compositional trends in water, lipids, and caloric content are correlated with food availability, regardless of any depth-related factors. In contrast, protein did not vary consistently with food availability and thus may be linked to other factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397578
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Bioluminescence in the Monterey Submarine Canyon: image analysis of video recordings from a midwater submersible (1989)
    Springer
    Marine biology 100 (1989), S. 541-551 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Video images of bioluminescence were recorded in situ during a 1985 study of the midwater environment of the Monterey Canyon, using a single-person, untethered submersible. Gelatinous organisms were responsible for the most brilliant bioluminescent displays, often exhibiting elaborate kinetics in response to mechanical stimulation. Images of bioluminescent displays recorded from identified organisms are shown and display patterns are described. All bioluminescence emission spectra from captured specimens were blue, with peak emissions between 460 and 494 nm. Image-analysis of recordings of mechanically stimulated bioluminescence revealed source densities between 43 and 175 m-3 and intensities between 2.5 and 37.3 μW sr-1 m-3. The predominant display type at all depths studied (between 100 and 560 m) was luminous secretions. Despite high intensities of mechanically stimulated bioluminescence, no spontaneous light production was recorded in the absence of mechanical stimulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00394831
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of seasonal pack ice on the distribution of macrozooplankton and micronekton in the northwestern Weddell Sea (1995)
    Springer
    Marine biology 124 (1995), S. 387-397 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The presence of mesopelagic organisms in the guts of surface-foraging seabirds feeding in open areas within seasonal pack ice in the Antarctic has given rise to questions regarding the effects of pack ice on the underlying mesopelagic community. Bottom-moored free-vehicle acoustic instruments were used in concert with midwater trawls and baited traps to examine the abundance, size distribution and vertical distribution of pelagic organisms in the uppermost 100 m of the water column during the austral spring of 1992 in two areas of the northwestern Weddell Sea, one covered by seasonal pack icc and the other free of ice cover. Acoustic largets were more abundant and significantly larger at the open-water station than beneath pack ice. However, targets at the ice-covered site exhibited a pronounced diel pattern, with the largest targets detected only at night. Samples from night trawls at the icecovered site contained several species of large, vertically-migrating mesopelagic fishes, whereas these species were absent from trawls taken during the day. In addition, baited traps deployed in pack ice just beneath the ice-water interface collected large numbers of scavenging lysianassoid amphipods, while deeper traps beneath the ice and traps at the open-water station were empty, indicating the presence of a scavenging community associated with the undersurface of the ice. These results sapport the idea that mesopelagic organisms migrate closer to the surface beneath pack ice than in open water, exposing them to possible predation by surface-foraging seabirds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00363912
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    An upward transport mechanism from the benthos (1984)
    Springer
    Naturwissenschaften 71 (1984), S. 322-324 
    Details
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00396618
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Sinking rates and dissolution of midwater fish fecal matter (1981)
    Springer
    Marine biology 65 (1981), S. 135-142 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The sinking rates of fecal matter from 7 southern California midwater fish species were investigated. Feces were obtained from 162 specimens of Stenobrachius leucopsarus, Triphoturus mexicanus, Leuroglossus stilbius, Lampanyctus ritteri, Argyropelecus affinis and Parvilux ingens, which were collected in the Santa Barbara and San Clemente Basins between 1977 and 1979. In addition, feces obtained from 6 laboratory-maintained specimens of the midwater zoarcid Melanostigma pammelas were used for repeated sinking-rate measurements. The mean of the measured sinking rates for all species was 1.19 cm s-1 (1 028 m d-1), which is much higher than the known descent rates of euphausiid and copepod fecal pellets and of most other particulate organic detritus. Dissolution characteristics were also investigated for fecal matter from 4 species collected by the same series of net hauls: S. leucopsarus, T. mexicanus, A. affinis, and Sternoptyx obscura. The release of dissolved organic compounds from this material is low and does not represent a significant output during the relatively short time required to sink through the water column. These findings suggest that midwater fish fecal matter may represent a major source of organic transfer between the pelagic community and the benthos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397077
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