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  • 1
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    MedFlux: Investigations of particle flux in the Twilight Zone. (2009)
    In:  EPIC3Deep-Sea Research II, 56., 1363
    Details
    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
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  • 2
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    PARTICLE EXPORT FROM OCEAN SURFACE WATERS BY MEANS OF 234Th/238U AND 210Po/210Pb DISEQUILIBRIA: A COMPARISON OF TWO RADIOTRACER PAIRS (2005)
    In:  EPIC3ASLO Summer Meeting, 19-24. June 2005, Santiago de Compostela, Spain.
    Details
    Publikationsdatum: 2019-07-17
    Beschreibung: 234Th (T1/2 = 24.1 d), 210Pb and 210Po (T1/2 = 138.4 d) are particle reactive radioisotopes that have been frequently used as tracers for particle cycling in the upper ocean. Particle export has usually been estimated using 234Th/238U disequilibrium, as 234Th is often deficient from its conservative parent 238U in the euphotic zone. Lately, however, some researchers are paying attention to the use of 210Po/210Pb disequilibrium as an additional tool to complement the knowledge about particle cycling, scavenging rates and the nature of the material settling out of the euphotic zone. In this work, we present a comparison of the use of both radiotracer pairs in an attempt to quantify the particle export from surface waters. To that end, we present data compiled from previous studies together with our own results from the Mediterranean. We test the advantages of integrating particle flux estimates over different time scales based on the different half-lives and scavenging affinities of these radioisotopes.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Conference , notRev
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  • 3
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    What determines the fate of materials within ocean margins? (1991)
    In:  EPIC3Ocean margin processes in global change (R F C Mantoura, J -M Martin, R Wollast, eds ) Dahlem workshop reports 9, Wiley & Sons, Chichester, pp. 211-234
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    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Book , peerRev
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  • 4
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    An assessment of particulate organic carbon to thorium-234 ratios in the ocean and their impact on the application of 234Th as a POC flux proxy (2006)
    In:  EPIC3Marine chemistry. 100, pp. 213-233
    Details
    Publikationsdatum: 2019-07-17
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Format: application/pdf
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  • 5
    Digitale Medien
    Digitale Medien
    Flux of cadmium through euphausiids (1974)
    Springer
    Marine biology 27 (1974), S. 205-212 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Flux of the heavy metal cadmium through the euphausiid Meganyctiphanes norvegica was examined. Radiotracer experiments showed that cadmium can be accumulated either directly from water or through the food chain. When comparing equilibrium cadmium concentration factors based on stable element measurements with those obtained from radiotracer experiments, it is evident that exchange between cadmium in the water and that in euphausiid tissue is a relatively slow process, indicating that, in the long term, ingestion of cadmium will probably be the more important route for the accumulation of this metal. Approximately 10% of cadmium ingested by euphausiids was incorporated into internal tissues when the food source was radioactive Artemia. After 1 month cadmium, accumulated directly from water, was found to be most concentrated in the viscera with lesser amounts in eyes, exoskeleton and muscle, respectively. Use of a simple model, based on the assumption that cadmium taken in by the organism must equal cadmium released plus that accumulated in tissue, allowed assessment of the relative importance of various metabolic parameters in controlling the cadmium flux through euphausiids. Fecal pellets, due to their relatively high rate of production and high cadmium content, accounted for 84% of the total cadmium flux through M. norvegica. Comparisons of stable cadmium concentrations in natural euphausiid food and the organism's resultant fecal pellets indicate that the cadmium concentration in ingested material was increased nearly 5-fold during its passage through the euphausiid. From comparisons of all routes by which cadmium can be released from M. norvegica to the water column, it is concluded that fecal pellet deposition represents the principal mechanism effecting the downward vertical transport of cadmium by this species.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00391945
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  • 6
    Digitale Medien
    Digitale Medien
    Long-Term observations on the moulting frequency of the shrimp Lysmata seticaudata (1980)
    Springer
    Marine biology 59 (1980), S. 219-223 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of body-size and temperature on moulting frequency of the shrimp Lysmata seticaudata Risso were examined under controlled laboratory conditions. Shrimp ranging in weight from approximately 0.4 to 1.14 g and maintained at 17°C exhibited intermoult periods of similar duration (≈20 d). On the other hand, small individuals (0.23 g) held at the same temperature moulted on the average every 14.5 d. Over a temperature range from 8° to 20°C mean intermoult periods were inversely and linearly related to temperature; an increase of 1 C0 resulted in a decrease in the intermoult period of approximately 1.5 d. Although temperature acted to regulate the intermoult period of each shrimp in increments of whole days, it had little effect on the time of moulting within any 24 h period, since moulting occurred more than 93% of the time between 18.00 and 08.00 hrs. The night-time moulting pattern also tended to be most pronounced at lower temperatures (8° and 13°C) and in larger individuals. Possible factors controlling this phenomenon and its occurrence in other crustacean species are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00404744
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  • 7
    Digitale Medien
    Digitale Medien
    Flux of 141Ce through a euphausiid crustacean (1973)
    Springer
    Marine biology 21 (1973), S. 317-325 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The role of the Mediterranean euphausiid Meganyctiphanes norvegica in the cycling of radiocerium (141Ce) was examined. When uptake of 141Ce occurs directly from the water, a “dynamic” population equilibrium is reached at a concentration factor of about 250. Molting was responsible for up to 99% loss of total body burden at first molt, and about 45% of the remaining activity at second molt, thus denying true longterm equilibrium to individual animals. Fecal pellets did not contain measureable 141Ce activity when the euphausiids accumulated the isotope from water, thus proving that surface adsorption was the key accumulating process from water. When radiocerium was taken in through ingestion of labelled Artemia, about 99% of the body burden was voided as fecal pellets. Excretion by this route was accelerated when euphausiids were fed non-radioactive Artemia during loss phase. Radioactive counts of the pellets confirmed that all ingested 141Ce was lost through defecation. When 141Ce was ingested as labelled phytoplankton, a substantial fraction of the total body burden occurred in the molts, which indicated that the phytoplankton lost 141Ce to the water and the radioactivity was subsequently adsorbed to outer surfaces of the euphausiids. Molts, fecal pellets, and freshly-killed euphausiids lost 141Ce to the water exponentially, the rates being similar to the exponential portions of the loss curves for live, non-molting individuals. It is suggested that M. norvegica, and probably other pelagic zooplankters, can greatly accelerate radiocerium transport to the ocean floor by packaging the isotope as fecal pellets. In coastal areas subject to low-level radioactive waste disposal, 141Ce might be ionic (or at least soluble) to a great extent, in which case euphausiids could take up the isotope rapidly and accelerate its vertical transport via molting.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00381088
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  • 8
    Digitale Medien
    Digitale Medien
    Plutonium and Americium: Uptake from contaminated sediments by the polychaete Nereis diversicolor (1976)
    Springer
    Marine biology 38 (1976), S. 95-100 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The polychaete Nereis diversicolor O.F. Müller was exposed to marine sediments which had been contaminated with plutonium and americium either through the testing of nuclear devices or by the release of liquid waste effluent from a nuclear fuel reprocessing plant. The uptake of both plutonium and americium was small, about 0.5% of the concentration of these transuranics in the sediments. The degree of relative uptake of plutonium from both sediments was comparable; relative uptake of americium from sediments contaminated by waste effluent was greater than that from nuclear sediment and those previously determined from water-uptake experiments to environmentally determined plutonium concentrations in sediments and overlying waters leads to the tentative conclusion that water may be the predominant pathway for plutonium accumulation by deposit-feeding worms like N. diversicolor.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00390762
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  • 9
    Digitale Medien
    Digitale Medien
    Factors affecting the flux of arsenic through the mussel Mytilus galloprovincialis (1979)
    Springer
    Marine biology 51 (1979), S. 209-219 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Radiotracer experiments were designed to study the effects of certain environmental and biological factors on arsenic accumulation and elimination processes in the Mediterranean mussel Mytilus galloprovincialis. Arsenic (as arsenate) uptake increased with increasing arsenic concentration in the water; however, the response was not proportional, indicating that accumulation was partially suppressed at higher external arsenic concentrations. In general, approximately 80% of the 74As taken up was associated with the soft parts, with small mussels concentrating 74As to a greater degree than larger individuals. The highest 74As concentrations were recorded in the byssus and the digestive gland. Increased temperature enhanced both arsenic uptake and loss. Mussels in sea water at 19‰ S accumulated approximately three times more 74As than those held at 38‰ S. Arsenic loss was much less affected by salinity, with only a tendency for greater arsenic retention noted at lower salinities. Studies carried out in the laboratory and in situ revealed that arsenic turnover was significantly more rapid in actively growing individuals living under natural conditions. Arsenic-74 loss from the in situ group was essentially biphasic, with biological half-times of approximately 3 and 32 days for the fast and slow compartments, respectively. The active secretion of arsenic in the byssal threads contributed to the total elimination of the element from the mussels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00386800
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  • 10
    Digitale Medien
    Digitale Medien
    Uptake of 55Fe from contaminated sediments by the polychaete Nereis diversicolor (1980)
    Springer
    Marine biology 56 (1980), S. 277-280 
    Details
    ISSN: 1432-1793
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The polychaete Nereis diversicolor O. F. Müller was exposed to marine sediments which had been contaminated with 55Fe either through the testing of nuclear devices or by the release of liquid waste effluent from a nuclear fuel reprocessing plant. The amount of 55Fe taken up reached a concentration in the worms about 6% of the concentration in both types of sediment. Bioavailability of 55Fe was shown to depend on its concentration in sediment and not on sediment type, stable iron concentration, or the source of contamination. N. diversicolor may not extract from sediment the same fraction of 55Fe as does 0.1N HCl and caution should be exercised in using such measurements to represent the bioavailable fraction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00386865
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