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  • 1
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    Cambridge University Press
    In:  Cambridge, 342 pp., Cambridge University Press, vol. 13, no. XVI:, pp. 227-235, (ISBN 3-540-43528-X)
    Publikationsdatum: 1983
    Schlagwort(e): Textbook of geophysics ; Seismology ; Seismics (controlled source seismology) ; Waves
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  • 2
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    Cambridge University Press
    In:  Cambridge, 416 pp., Cambridge University Press, vol. 271, no. ALEX(01)-FR-77-01, AFTAC Contract F08606-76-C-0025, pp. 329, (ISBN: 0-08-043649-8)
    Publikationsdatum: 1997
    Schlagwort(e): FractureT ; Chaotic behaviour ; Non-linear effects ; SOC ; Seismicity ; cracks and fractures (.NE. fracturing) ; Earthquake precursor: prediction research ; Handbook of geophysics
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  • 3
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    Cambridge University Press
    In:  New York, 475 pp., Cambridge University Press, vol. 26, no. ALEX(01)-FR-77-01, AFTAC Contract F08606-76-C-0025, pp. 329, (ISBN 0-521-62434-7 hc (0-521-62478-9 pb))
    Publikationsdatum: 1999
    Schlagwort(e): Textbook of geophysics ; Seismology ; traditional ; Udias
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  • 4
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    Cambridge University Press
    In:  Cambridge, 264 pp., Cambridge University Press, vol. 42, no. 3, pp. 275-291, (ISBN: 0-444-51422-8)
    Publikationsdatum: 1997
    Schlagwort(e): physics ; philosophy
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  • 5
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    Cambridge University Press
    In:  Cambridge, 368 pp., Cambridge University Press, vol. 159, no. 22, pp. 662-664, (ISBN 0-470-87000-1 (HB), ISBN 0-470-87001-X (PB))
    Publikationsdatum: 1997
    Schlagwort(e): Textbook of geophysics ; Seismology ; Seismics (controlled source seismology) ; Gravimetry, Gravitation ; Geoelectrics ; Geomagnetics ; Earth tides ; Earth rotation
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  • 6
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    Cambridge University Press
    In:  New York, 260 pp., Cambridge University Press, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (ISBN 0-521-66023-8 hc (0-521-66953-7 pb))
    Publikationsdatum: 1999
    Schlagwort(e): Textbook of geophysics ; Seismology ; modern
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  • 7
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    Cambridge University Press
    In:  Boston, 227 pp., Cambridge University Press, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (ISBN 0-521-66023-8 hc (0-521-66953-7 pb))
    Publikationsdatum: 1982
    Schlagwort(e): Textbook of geophysics ; Seismics (controlled source seismology)
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  • 8
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    Cambridge University Press
    In:  Cambridge, 264 pp., Cambridge University Press, vol. 42, no. 3, pp. 632 pp., (ISBN 052)
    Publikationsdatum: 2004
    Schlagwort(e): Textbook of geophysics ; Seismology ; Wave propagation ; Ray seismics ; Anisotropy ; Acoustics ; Elasticity ; Layers ; Cagniard ; Inversion ; WKBJ ; Maslov ; Born ; Kirchhoff ; Migration of earthquakes ; Inhomogeneity ; more ; advanced ; than ; Aki ; and ; Richards ; MATLAB
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  • 9
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    Cambridge University Press
    In:  Cambridge, 444 pp., Cambridge University Press, vol. 7, no. Publ. No. 12, pp. 127, (ISBN: 0 521 52046 0 (pb); ISBN: 0 521 81730 7 (hb))
    Publikationsdatum: 2003
    Beschreibung: ... Pujol's book differs from the others in its purely theoretical approach to the generation and propagation of seismic waves. The author aims to fill a gap between the advanced books and the introductory ones, providing a complete derivation of the mathematical developments. ... One does not have to look for proofs elsewhere.
    Schlagwort(e): Textbook of geophysics ; Seismology ; Elasticity ; Source ; Wave propagation ; theory
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  • 10
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    Cambridge University Press
    In:  Boston, 227 pp., Cambridge University Press, vol. Developments in Petroleum Science vol. 15B, no. Publ. No. 12, pp. 9, (ISBN 0-521-66023-8 hc (0-521-66953-7 pb))
    Publikationsdatum: 1983
    Schlagwort(e): Textbook of geophysics ; Seismics (controlled source seismology)
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  • 11
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    Cambridge University Press
    In:  New York, Cambridge University Press, vol. 4, no. 1, pp. 1-40, (ISBN 0-87071-024-9)
    Publikationsdatum: 1997
    Schlagwort(e): Earthquake ; Volcanology ; Earthquake precursor: prediction research ; Earthquake hazard ; Tsunami(s)
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  • 12
    Publikationsdatum: 2017-01-04
    Beschreibung: Tropical South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation1). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum—marked in the drill core by continuous deposition of lacustrine sediments—appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in tropical South America, suggesting a common forcing.
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  • 13
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 64 . pp. 573-579.
    Publikationsdatum: 2020-07-16
    Beschreibung: Males of Eledone cirrhosa grow to a size little over 600 g and normally have well-developed, and presumably active, reproductive organs from about 200 g upwards. Total weight of the genital bag is well correlated with total body weight (r= 0·906). Growth of the testis precedes that of the spermatophoric sac, and the size of neither of these reproductive components is predictable from body weight. The sizes of these organs and the estimated number and length of stored spermatophores are given for 100 g intervals of total body weight. No evidence was obtained for a seasonal trend in male maturity.
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  • 14
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    Cambridge University Press
    In:  Geological Magazine, 140 (3). pp. 245-252.
    Publikationsdatum: 2020-07-31
    Beschreibung: Markedly different cooling histories for the hanging- and footwall of theVari detachment on Syros and Tinos islands, Greece, are revealed by zircon and apatite fission-track data. The Vari/Akrotiri unit in the hangingwall cooled slowly at rates of 5–15 ◦CMyr−1 since Late Cretaceous times. Samples from the Cycladic blueschist unit in the footwall of the detachment on Tinos Island have a mean zircon fission-track age of 10.0±1.0 Ma, which together with a published mean apatite fission-track age of 9.4±0.5 Ma indicates rapid cooling at rates of at least ∼60 ◦CMyr−1. We derive a minimum slip rate of ∼6.5 kmMyr−1 and a displacement of 〉∼20 km and propose that the development of the detachment in the thermally softened magmatic arc aided fast displacement. Intra-arc extension accomplished the final ∼6–9 km of exhumation of the Cycladic blueschists from ∼60 km depth. The fast-slipping intra-arc detachments did not cause much exhumation, but were important for regionalscale extension and the formation of the Aegean Sea.
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  • 15
    Publikationsdatum: 2017-07-07
    Beschreibung: According to small subunit ribosomal RNA (ss rRNA) sequence comparisons all known Archaea belong to the phyla Crenarchaeota, Euryarchaeota, and—indicated only by environmental DNA sequences—to the 'Korarchaeota'1, 2. Here we report the cultivation of a new nanosized hyperthermophilic archaeon from a submarine hot vent. This archaeon cannot be attached to one of these groups and therefore must represent an unknown phylum which we name 'Nanoarchaeota' and species, which we name 'Nanoarchaeum equitans'. Cells of 'N. equitans' are spherical, and only about 400 nm in diameter. They grow attached to the surface of a specific archaeal host, a new member of the genus Ignicoccus3. The distribution of the 'Nanoarchaeota' is so far unknown. Owing to their unusual ss rRNA sequence, members remained undetectable by commonly used ecological studies based on the polymerase chain reaction4. 'N. equitans' harbours the smallest archaeal genome; it is only 0.5 megabases in size. This organism will provide insight into the evolution of thermophily, of tiny genomes and of interspecies communication.
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  • 16
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    Wiley-Blackwell
    In:  Journal of Fish Biology, 59 . pp. 332-338.
    Publikationsdatum: 2017-07-06
    Beschreibung: The living coelacanth Latimeria chalumnae has a unique position in world biodiversity which raises important questions about conservation and ethics. Some relevant details of coelacanth biology are summarized, including those obtained by direct observation from submersibles. The importance of the coelacanth for evolutionary theory and palaeontology is shown to be paralleled in cultural, literary and artistic areas of human heritage. Threats to the Comoran coelacanths from artisanal fishing are described and conservation measures discussed in relation to local customs and economies as well as the promotion of tourism to spread a new awareness and concern for coelacanths worldwide.
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  • 17
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 80 . pp. 249-257.
    Publikationsdatum: 2020-07-16
    Beschreibung: A new species of terebellid polychaete, Lanice arakani sp. nov., is described from two specimens collected in deep water at seamounts of the west Pacific by the submersible `JAGO', and comparisons are made with the established species of the genus. Special reference is given to the morphology of the worm's sediment tube and in situ observations.
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  • 18
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    Cambridge University Press
    In:  Geological Magazine, 64 (6). pp. 263-275.
    Publikationsdatum: 2020-07-31
    Beschreibung: In a recent paper I stated that the hypothesis of a continuously cooling earth had “consistently failed to lead to any adequate explanations of fissure eruptions and other volcanic and tension phenomena, mountain-building processes and their distribution in time and space, and the alternation of marine transgressions and recessions”. It seems to be desirable that I should further justify this sweeping integration of objections, for Dr. Harold Jeffreys, who has actively explored the consequences of this theory during recent years, takes exception to my discouraging view of the position, and claims that the alleged failures include the principal successes of the theory. The evidence on which my summary indictment was based will be reviewed in this paper; and attention will be directed to certain other phenomena—such as the growth of geosynclines—of which the significance has not yet been generally realized. As a preliminary it will be convenient to discuss the gradually converging evidence bearing on the thickness and substructure of the continents.
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  • 19
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    Cambridge University Press
    In:  Geological Magazine, 121 (6). pp. 563-575.
    Publikationsdatum: 2020-07-31
    Beschreibung: We present chemical data on magmatically heterogeneous pyroclastic deposits of late Quaternary age erupted from zoned magma systems underlying Tenerife (Canary Islands), Sao Miguel and Faial (Azores), and Vesuvius. The most fractionated magmas present at each centre are respectively Na-rich phonolite, trachyte, and K-rich phonolite. Within any one deposit, chemical variation is either accompanied by changes in the phenocryst assemblage (petrographic zonation) or is largely manifested in trace element abundances, unaccompanied by any petrographic change (occult zonation). Zoning is analogous to that in calc-alkaline systems where the most fractionated products are high-silica rhyolites. When a range of magma types are considered, a correlation emerges between roofward depletion of trace elements (especially REE) in the zoned system and compatability of those same trace elements in the accessory phenocryst phases present. Thus, allanite- or chevkinite-bearing rhyolitic systems are light-REE depleted roofwards, the sphene-bearing Tenerife system is middle-REE depleted roofwards, the melanite-bearing Vesuvius system is heavy-REE depleted roofwards, while the Azores systems, which lack these phases, display roofward REE enrichment. Therefore, the behaviour of trace elements may in each case be explained by fractionation of observed phenocryst assemblages. The resemblance between features of zoned magma systems and published work on the dynamic consequences of cooling saturated aqueous solutions prompts us to suggest that sidewall crystallization and consequent boundary-layer uprise to form a capping layer at top of the system may be a plausible mechanism for the generation of both petrographic and occult zonation. Reverse zoning occurs among the first-erupted tephra of some deposits, demonstrating that the most highly differentiated magma available is not always the first to be tapped during an eruption from a zoned system.
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  • 20
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 63 . pp. 71-83.
    Publikationsdatum: 2020-07-16
    Beschreibung: Changes in the relative size of the ovary, oviducal glands and eggs are described for Eledone cirrhosa captured from the North Sea off Aberdeen over a 3 year period (N = 488). The analysis is based only on freshly caught animals, excluding those held in aquarium conditions (〉 5 days). Ovary enlargement and egg size estimates are used as indices of sexual maturity. Between 0–15% and 18–95% of total body weight is contributed by the ovary. Maximum egg length in the ovary ranges up to 7 mm. On these criteria, sexual maturation typically occurs at body sizes between 400–1000 g although some animals of 1000–1200 g are found showing no evidence of ovary enlargement. The majority of the monthly sample is always immature but maturation can apparently occur at almost any time of the year. Increase in mean ovary index and mean values for egg size are strongly seasonal and indicate a peak incidence of sexual maturity over 2–3 months in the July-September period. Spawning is presumed to follow within 1 month. Estimates of the fecundity of the females, based on the egg sample from the ovary, range from 2·2 × 103 to 55 × 10 3 eggs with a mean of 11 × 10 3 and a mode of 7·5 × 10 3 eggs.
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  • 21
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 64 . pp. 581-585.
    Publikationsdatum: 2020-07-16
    Beschreibung: Female Eledone cirrhosa held in aquarium conditions for periods of time of five daysand over show relatively enlarged ovary sizes. Values for ovary index considerably exceed thoseof freshly caught animals and the incidence of the final stage of maturity, in which eggs pack the oviducts, is greater. A comparison of maturity indices for fresh and aquarium males was inconclusive. The range of factors associated with aquarium conditions is briefly reviewed and it is concluded that studies of cephalopod reproductive maturation must distinguish fresh and aquarium animals. Introduction External factors effective in inducing sexual maturation in cephalopods have been suggested several times. The influence of the absence of light has been implicated since the experiments of Wells & Wells (1959) showed that blinded Octopus vulgar is matured precociously. An effect of short day length in stimulating the optic glands of Sepia has been found by Defretin & Richard (1967) and Richard (1967) but this is not clearly the case for Octopus (Buckley, 1977). Octopuses kept in aquarium conditions for lengthy periods are said to have larger relative gonad sizes than those fresh from the sea (Wells & Wells, 1975). One of the factors associated with aquarium conditions is often a degree of starvation, and this circumstance alone is held to be a factor in inducing precocious sexual maturation in Eledone (Mangold & Boucher-Rodoni, 1973). In the course of recent studies on the growth and reproduction of Eledone cirrhosa from the North Sea (Boyle & Knobloch, 1982,1983,1984) animals which had remained in aquarium conditions for 5 days or over were separated from the analysis.
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  • 22
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    Nature Publishing Group
    In:  Nature, 196 (4852). pp. 351-352.
    Publikationsdatum: 2020-09-09
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  • 23
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 64 (02). pp. 285-302.
    Publikationsdatum: 2020-07-16
    Beschreibung: A new species of a monogenean Isancistrum subulatae (Gyrodactylidae) has been discovered on the arms and tentacles of the cephalopod mollusc Alloteuthis subulata at Plymouth and I. loliginis, on the gills of the same host, has been re-discovered for the first time since its original description in 1912. I. subulatae, like other gyrodactylids, is viviparous, and has been shown by experiments to transfer to new hosts by contagion. In nature such transfers probably take place during copulation of the hosts and since the parasite may occur in numbers of several thousands per host, it may thereby constitute a venereal disease.
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  • 24
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    Nature Publishing Group
    In:  Nature, 377 (6545). p. 107.
    Publikationsdatum: 2017-07-04
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  • 25
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 75 (02). pp. 373-390.
    Publikationsdatum: 2020-07-16
    Beschreibung: The genus Illex is likely to constitute a large portion of the annual world ommastrephid squid catches (Roper et al, 1984), even though specific official statistics are difficult to obtain. The broad-tail short-fin squid Illex coindetii is a widespread species ranging from the western to the eastern Atlantic (Roper et al., 1984) and east through the whole Mediterranean Sea (Mangold & Boletzky, 1987). Usually a by-catch of important fisheries, it is caught mainly by trawlers. Although its economic value is lower than that of other squid species (i.e. Loligo spp.), in the Sicilian Channel Illex coindetii may represent a valuable resource due to its abundance. In Italian waters, the available statistics (Cingolani et al., 1986) report that 2680 tonnes of ommastrephid squid were landed in 1982 (0.5% of the total landed catch). The main component of these was landed in Sicily (2183 tonnes), a consistently large part of which was no doubt Illex coindetii (Ragonese & Jereb, 1992). The catches came mainly from southern Sicilian waters (Sicilian Channel) where one of the major Mediterranean landing places is in Mazara del Vallo. Large trawlers (up to 200 gross tonnage) usually carry out long fishing trips (15–20 d), and Illex coindetii is caught mainly by those targeting Parapenaeus longirostris and Merluccius merluccius (Jereb & Ragonese, 1991).
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  • 26
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 76 (01). p. 73.
    Publikationsdatum: 2020-07-16
    Beschreibung: The natural feeding of the two most abundant ommastrephid squid (Cephalopoda: Ommastrephidae) in Galician waters was studied and compared. A sample of 334 stomach contents of Todaropsis eblanae (34–222 mm ML) and 267 stomach contents of Illex coindetii (50–379 mm ML) caught by commercial trawlers was examined. A total of 21 (T. eblanae) and 23 (I. coindetii) different prey items, belonging to three zoological groups (Teleostei, Crustacea and Cephalopoda), were taken by these cephalopods. However, 43% of the T. eblanae diet comprised only one fish species, Micromesistius poutassou. The diet of these squid species was significantly influenced by the geographical area (both species), size (T. eblanae) and maturation (I. coindetii). Feeding rate of both species decreased with size, but the percentage of stomachs with food remains increased in maturing and mature females. Weight of prey captured was dependent on available prey sizes and, in small individuals, maximum prey weight was very close to the squid weight. Both squid species are mainly neritic nekto-benthic predators, but I. coindetii seems to have a broader and more pelagic diet.
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  • 27
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    Nature Publishing Group
    In:  Nature, 407 (6801). pp. 171-174.
    Publikationsdatum: 2017-01-04
    Beschreibung: The onset of the Palaeocene/Eocene thermal maximum (about 55 Myr ago) was marked by global surface temperatures warming by 5–7 °C over approximately 30,000 yr (ref. 1), probably because of enhanced mantle outgassing2, 3 and the pulsed release of approx1,500 gigatonnes of methane carbon from decomposing gas-hydrate reservoirs4, 5, 6, 7. The aftermath of this rapid, intense and global warming event may be the best example in the geological record of the response of the Earth to high atmospheric carbon dioxide concentrations and high temperatures. This response has been suggested to include an intensified flux of organic carbon from the ocean surface to the deep ocean and its subsequent burial through biogeochemical feedback mechanisms8. Here we present firm evidence for this view from two ocean drilling cores, which record the largest accumulation rates of biogenic barium—indicative of export palaeoproductivity—at times of maximum global temperatures and peak excursion values of delta13C. The unusually rapid return of delta13C to values similar to those before the methane release7 and the apparent coupling of the accumulation rates of biogenic barium to temperature, suggests that the enhanced deposition of organic matter to the deep sea may have efficiently cooled this greenhouse climate by the rapid removal of excess carbon dioxide from the atmosphere.
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  • 28
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 62 (2). pp. 277-296.
    Publikationsdatum: 2020-07-16
    Beschreibung: The growth of the octopus Eledone cirrhosa has been studied in a population from the North Sea off Aberdeen. Data are presented for the growth of individuals isolated in aquarium conditions; the growth of size classes in thefieldpopulation; and preliminary information on the growth relationships of gonad, somatic, cardiac and brain components of the body. At 15 °C Eledone cirrhosa is capable of growing from 10 to 1000 g in 270 days. From octopuses which feed readily in captivity, weight specific growth rates of up to about 3–5 % day-1 for animals of 100 g body weight are recorded, falling to a maximum of about 1–5 % day-1 at body sizes above 500 g. Females stop growing when sexually mature, but in the sample captured they were consistently larger than males, a feature which may account for the 7:1 bias towards the incidence of females. On a wet-weight basis, the mean food incorporation into growth is 37 % of the food ingested, which is 49% of the gross weight of crabs killed. Field data for 1978/79 suggest that animals recruited to the population at the beginning of the year grew steadily until December, overwintered without growing, then grew rapidly for several months in the subsequent year before disappearing from the samples. The estimated average age of those animals and by implication, the life span, is 20 months.
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  • 29
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    Cambridge University Press
    In:  Journal of Fluid Mechanics, 18 (03). pp. 409-437.
    Publikationsdatum: 2020-07-24
    Beschreibung: In this paper we examine the steady, two-dimensional convective motion which occurs in a horizontal circular cylinder whose wall is non-uniformly heated. One observes several qualitatively different physical phenomena depending on the wall temperature distribution and the value of the Rayleigh number. The low-Rayleigh-number behaviour for the single convective cell heated from below is related to the classical Rayleigh stability problem. The critical Rayleigh number for the single circular cell is approximately five times the value for Rayleigh's multi-celluar configuration. The flow which exhibits a nearly parabolic velocity profile near the critical Rayleigh number, gradually changes to a rigidly-rotating-core behaviour as the Rayleigh number increases. The speed of core rotation is a function of the Prandtl number, whereas the boundary-layer thickness is primarily a function of the Rayleigh number. When the heating is from side to side, the solution shows that as the Rayleigh number increases the core motion is progressively arrested leaving a narrow circulating band of fluid adjacent to the wall. An oblique heating produces a hybrid phenomenon, a low-Rayleigh-number behaviour which is characteristic of the sideways heating case and a high-Rayleigh-number interior motion characteristic of the bottom heating case. To determine the core motion in the high-Rayleigh-number limit, Batchelor's work concerning the uniqueness of incompressible, exactly steady, closed streamline flows with small viscosity is extended to include flows with small thermal conductivity.
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  • 30
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 35 (01). p. 63.
    Publikationsdatum: 2020-09-10
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  • 31
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 75 (03). p. 743.
    Publikationsdatum: 2020-07-16
    Beschreibung: This communication presents the first records of mated female Loligo gahi in Falkland Island waters. In October 1993 fully mature mated female L. gahi were identified in samples taken from the commercial fishery in waters east of Lively Island, East Falkland, at depths of 145–174 m. Spermatophores were found in both the mantle cavity and buccal sites of deposition. These records, combined with past records of spent females, suggest spawning periods in late October/early November and April/May. These concur with two of the three periods of spawning suggested from previous studies of juvenile and adult L. gahi.
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  • 32
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 75 (03). p. 593.
    Publikationsdatum: 2020-07-16
    Beschreibung: Age, growth and maturation of Loligo vulgaris were studied by examination of growth increments within statoliths of 294 specimens (mantle length, ML, ranging from 31 to 498 mm) caught on the west Saharan shelf between 1985 and 1988. Maximum age was 335 d (290 mm ML) for females, and 396 d (498 mm ML) for males. Growth rates varied considerably among individuals with a greater range in males. Sexual dimorphism in length was apparent after about 210 d. Males and females diverged considerably in weight, with males reaching a greater weight after about 180 d. Growth in length between 124 and 396 d was best described by a power function, while growth in weight was best described by the Gompertz function. Males started maturing at 180–210 d and mature males ranged in age between 250 and 396 d; while females started maturing at 240–270 d and mature females ranged between 285 and 335 d. Loligo vulgaris hatched throughout the year with two distinct peaks; in winter (December - early March) and summer (June-July). The life cycle of L. vulgaris populations on the west Saharan shelf lasts ~1 y, with large males (〉450 mm ML) living slightly longer.
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  • 33
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 75 (03). pp. 621-634.
    Publikationsdatum: 2020-07-16
    Beschreibung: The reproductive strategies of male and female Loligo forbesi Steenstrup, 1856 were investigated from samples obtained from commercial catches and research cruises in Irish waters. In females maturity increased with size, but in males two modes in the size at maturity were identified, with approximately 40% mature at small size (180–200 mm mantle length), and the remainder mature at 〉250 mm mantle length. The difference in estimated age of the two modes of mature males was small, so size differences were probably due to different growth rates. Growth and maturation proceeded together in both sexes over much of the life-cycle. The effect of maturation on relative growth of somatic tissues was examined using analysis of covariance and multivariate regressions. In males there was a significant decline in total mass, and in mass of mantle, head and viscera, relative to mantle length with maturation. In females total mass was not significantly affected by maturation, but relative masses of head, mantle and viscera declined with maturation, indicating that energy was diverted from somatic growth to gonad production. Potential fecundity estimates were obtained by counting eggs and ova in the oviduct and ovary of mature females and were in the range 2500 to 10,500 (mean 5800). Fecundity was positively related to mantle length. The ovaries of mature females contained a range of egg sizes and developmental stages, indicating that spawning probably occurs intermittently.
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  • 34
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    Nature Publishing Group
    In:  Nature, 403 (6765). p. 38.
    Publikationsdatum: 2017-07-06
    Beschreibung: Living coelacanths (Latimeria chalumnae) are normally found only in the western Indian Ocean, where they inhabit submarine caves in the Comores Islands. Two specimens have since been caught off the island of Manado Tua, north Sulawesi, Indonesia, some 10,000 kilometres away. We sought to determine the ecological and geographic distribution of Indonesian coelacanth populations with a view to drawing up conservation measures for this extremely rare fish. During our explorations, we discovered two living Indonesian coelacanths 360 km southwest of Manado Tua.
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  • 35
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    Nature Publishing Group
    In:  Nature, 374 (6520). p. 314.
    Publikationsdatum: 2017-07-06
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  • 36
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    Nature Publishing Group
    In:  Nature, 421 (6922). pp. 520-523.
    Publikationsdatum: 2016-05-10
    Beschreibung: Breaking waves markedly increase the rates of air–sea transfer of momentum, energy and mass. In light to moderate wind conditions, spilling breakers with short wavelengths are observed frequently. Theory and laboratory experiments have shown that, as these waves approach breaking in clean water, a ripple pattern that is dominated by surface tension forms at the crest. Under laboratory conditions and in theory, the transition to turbulent flow is triggered by flow separation under the ripples, typically without leading to overturning of the free surface15. Water surfaces in nature, however, are typically contaminated by surfactant films that alter the surface tension and produce surface elasticity and viscosity16, 17. Here we present the results of laboratory experiments in which spilling breaking waves were generated mechanically in water with a range of surfactant concentrations. We find significant changes in the breaking process owing to surfactants. At the highest concentration of surfactants, a small plunging jet issues from the front face of the wave at a point below the wave crest and entraps a pocket of air on impact with the front face of the wave. The bubbles and turbulence created during this process are likely to increase air–sea transfer.
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  • 37
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    Nature Publishing Group
    In:  Nature, 289 (5794). pp. 164-167.
    Publikationsdatum: 2016-04-11
    Beschreibung: There has been concern about recent temperature trends and the future effects of CO2 concentrations in the atmosphere1,2; but instrumental records only cover a few decades to a few centuries and it is essential that proxy data sources, such as pollen spectra from peats and lake sediments, be carefully interpreted as climate records. Several workers have shown statistically significant associations between the modern pollen rain and climatic parameters, an approach that by-passes the recognition of pollen/vegetation units. Statistically defined equations that associate abiotic and biotic elements are called transfer functions. We report here on the application of transfer function equations to nine middle and late Holocene peat and lake sediment sequences from northern Canada (Fig. 1).
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  • 38
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    Nature Publishing Group
    In:  Nature, 288 (5788). pp. 260-263.
    Publikationsdatum: 2016-03-01
    Beschreibung: Organic detritus passing from the sea surface through the water column to the sea floor controls nutrient regeneration, fuels benthic life and affects burial of organic carbon in the sediment record. Particle trap systems have enabled the first quantification of this important process. The results suggest that the dominant mechanism of vertical transport is by rapid settling of rare large particles, most likely of faecal pellets or marine snow of the order of 〉200 μm in diameter, whereas the more frequent small particles have an insignificant role in vertical mass flux4–6. The ultimate source of organic detritus is biological production in surface waters of the oceans. I determine here an empirical relationship that predicts organic carbon flux at any depth in the oceans below the base of the euphotic zone as a function of the mean net primary production rate at the surface and depth-dependent consumption. Such a relationship aids in estimating rates of decay of organic matter in the water column, benthic and water column respiration of oxygen in the deep sea and burial of organic carbon in the sediment record.
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  • 39
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom UK, 62 . pp. 435-451.
    Publikationsdatum: 2020-07-27
    Beschreibung: The planktonic foraminifer Globigerinoides sacculifer (Brady) was cultured under two different light intensities and in continuous darkness. High light intensity (HLI = 4oo-soo einsteins/m2/s) resulted in a longer lifespan, a greater number of chambers formed, and a larger final shell size compared with individuals cultured under low light intensity (LLI = 20-50 einsteins/m2/s) or in continuous darkness. Shell growth rates were unaffected by increasing light intensity, but gametogenesis was delayed. Continuous darkness induced a rapid onset of gametogenesis in organisms with shell lengths larger than 250 m. Feeding frequency had a greater effect on growth and reproduction than light intensity under conditions of LLI and HLI, but continuous darkness had an overriding effect on growth and reproduction owing to the rapid onset of gametogenesis which terminated the life of the mother cell. Our previous data indicated that the longevity of G. sacculifer was dependent on feeding frequency, and that G. sacculifer cultured under LLI had a lifespan of approximately 2-4 weeks. Present results suggest that the lifespan can vary from a minimum of 8 days for organisms fed daily in continuous darkness to a maximum of 54 days for organisms fed once every 7 days and maintained in HLI. It is concluded that individual G. sacculifer attain a shell size greater than 6oo ,urn only if they maintain their position in the euphotic zone. Prolonged existence below the euphotic zone would result in premature death or gametogenesis following stunted shell growth.
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  • 40
    Publikationsdatum: 2017-02-27
    Beschreibung: The ability to monitor the heat content of oceans over long distances is becoming increasingly important for understanding the role of oceans in climate change, for determining the variability of the state of the oceans, for operational ocean observing systems, and for studying large-scale ocean processes such as water-mass formation. Although the properties of the upper layers of the ocean can be routinely measured on large scales by satellite remote sensing (providing altimetric and infrared data) and with expendable probes dropped from commercial vessels, the deep interior of the ocean is more difficult to monitor. Ocean acoustic tomography1 is a promising technique for such applications, as it has the potential to provide systematic, instantaneous and repeated measurements of the ocean interior over large parts of an ocean basin. Here we demonstrate the capability of this technique for measuring the heat content across an entire (albeit small) ocean basin—the western Mediterranean Sea.
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  • 41
    Publikationsdatum: 2017-01-31
    Beschreibung: Destructive macroalgal mass blooms threaten estuarine and coastal ecosystems worldwide. We asked which factors regulate macroalgal bloom intensity, distribution and species composition. In field experiments in the Baltic Sea, we analyzed the relative effects of nutrients, herbivores and algal propagule banks on population development and dominance patterns in two co-occurring bloom-forming macroalgae, Enteromorpha intestinalis and Pilayella littoralis. Both species were highly affected by the combined effects of a propagule bank, herbivory and nutrients. The magnitude of effects varied with season. The propagule bank was an important overwintering mechanism for both algae, and allowed for recruitment two months earlier than recruitment via freshly dispersed propagules. This provided a seasonal escape from intense herbivory and nutrient limitation later in the year. Favored by massive recruitment from the propagule bank, Enteromorpha was the superior space occupier in early spring, thereby reducing recruitment of Pilayella. Elimination of the propagule bank and recruitment via freshly dispersed propagules favored Pilayella. Strong and selective herbivory on Enteromorpha supported Pilayella in the presence, but not in the absence of the propagule bank. Nutrient enrichment in summer counteracted herbivore pressure on Enteromorpha, thereby negatively affecting Pilayella. Herbivore and nutrient effects were more pronounced for early life stages than adult algae. These results show that recruitment processes and forces affecting early life stages at the beginning of the vegetation period determine development and dominance patterns of macroalgal blooms. Herbivores naturally suppress blooms but increasing nutrient enrichment can override this important control mechanism. The propagule bank plays a previously unrecognized role for population and community dynamics.
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  • 42
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    Nature Publishing Group
    In:  Nature, 382 (6589). pp. 344-346.
    Publikationsdatum: 2017-02-27
    Beschreibung: The conventional model whereby plume volcanism forms linear age-progressive volcanic chains, with the youngest activity occurring nearest a spreading axis (at a 'hotspot'), has been challenged for the Easter seamount chain1–4. Whereas early work suggested the existence of a linear melting anomaly (a 'hotline')1,2, more recent studies3,4 have proposed a hotspot near Salas y Gomez island, connected with the Easter microplate spreading system by an ~800-km-long, volcanically active plume channel. Here we use geochemical, geological and geochronological data to argue that the hotspot lies close to Easter Island. Moreover, new isotopic data for lavas from the seamount chain provide evidence for bidirectional flow between the spreading axis and the plume, thus supporting geophysical and fluid-dynamical models of mantle flow in a plume/spreading axis system5–7. Material balance and flux considerations show the Easter plume to be weak and cool compared with those beneath larger features such as Iceland, Hawaii and the Galápagos islands.
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  • 43
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    Wiley-Blackwell
    In:  Oikos, 37 (2). p. 173.
    Publikationsdatum: 2015-10-06
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  • 44
    Publikationsdatum: 2015-11-24
    Beschreibung: Noble-gas geochemistry is an important tool for understanding planetary processes from accretion to mantle dynamics and atmospheric formation. Central to much of the modelling of such processes is the crystal–melt partitioning of noble gases during mantle melting, magma ascent and near-surface degassing5. Geochemists have traditionally considered the 'inert' noble gases to be extremely incompatible elements, with almost 100 per cent extraction efficiency from the solid phase during melting processes. Previously published experimental data on partitioning between crystalline silicates and melts has, however, suggested that noble gases approach compatible behaviour, and a significant proportion should therefore remain in the mantle during melt extraction. Here we present experimental data to show that noble gases are more incompatible than previously demonstrated, but not necessarily to the extent assumed or required by geochemical models. Independent atomistic computer simulations indicate that noble gases can be considered as species of 'zero charge' incorporated at crystal lattice sites. Together with the lattice strain model9, 10, this provides a theoretical framework with which to model noble-gas geochemistry as a function of residual mantle mineralogy.
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  • 45
    Publikationsdatum: 2020-07-31
    Beschreibung: Single grains of detrital white mica from two different synorogenic sediments in the Southern Urals were analysed using the in situ ultraviolet laser ablation Ar–Ar dating technique to discriminate between age signatures associated with a high-pressure signal (phengites) from those related to muscovite only. Two disparately aged sandstone formations of Neoproterozoic (Upper Vendian) and Upper Devonian (Famennian) age were formed by the erosion of high-relief source areas with contemporaneously exhumed high-pressure rocks. A bimodal distribution of ages and chemical compositions can be detected in the two detrital populations. There is no age overlap between the two populations, reflecting completely different source areas containing high-pressure rocks of different ages.Within the Upper Vendian sandstones, detrital white mica from a 571–609 Ma age group is phengitic in composition (Si 3.3–3.41 per formula unit), while an older 645–732 Ma age group is comprised of muscovite composition grains only. The first group is compatible with the time of late exhumation and emplacement of a source area containing high-pressure rocks, the Neoproterozoic Beloretzk terrane. The older age range is compatible with a long history of cooling and the allochthonous nature of this terrane. Detrital white mica from the Famennian sandstones(Zilair Formation) comprises one age group (342–421 Ma) containing phengite (Si 3.21–3.39 per formula unit) and muscovite, and a second group (446–496 Ma) containing muscovite only. While the derivation of the second group cannot be correlated with any as yet known regional data, the first age group indicates the earliest arrival of high-pressure rocks at the surface along the suture zone after Late Devonian arc–continent collision.
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  • 46
    Publikationsdatum: 2020-07-31
    Beschreibung: A mineralogical and 4OAr/39Ar study of 13 amphibole samples in the Kamila Amphibolite Belt and Kamila Shear Zone in northern Pakistan has found a correlation between the degree of greenschist facies alteration and quantity of excess 40Ar. Additionally, there is a north–south divide with amphibole samples from the northern region showing larger degrees of gree schist facies alteration, brittle deformation, and excess 40Ar incorporation compared to the predominantly plastically deformed, less altered, amphibole samples from the Kamila Shear Zone in the south. Acid leaching of two amphiboles from the Kamila Amphibolite Belt indicates that a large proportion of the excess 40Ar is correlated with later greenschist facies alteration hases, and can be easily removed by acid etching, thus revealing acceptable regional 40Ar/39Ar plateau ages.
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  • 47
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    Nature Publishing Group
    In:  Nature, 397 (6718). pp. 389-391.
    Publikationsdatum: 2015-07-16
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  • 48
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    Nature Publishing Group
    In:  Nature Reviews Microbiology, 2 (5). pp. 414-424.
    Publikationsdatum: 2020-06-23
    Beschreibung: Horizontal gene transfer is an important mechanism for the evolution of microbial genomes. Pathogenicity islands — mobile genetic elements that contribute to rapid changes in virulence potential — are known to have contributed to genome evolution by horizontal gene transfer in many bacterial pathogens. Increasing evidence indicates that equivalent elements in non-pathogenic species — genomic islands — are important in the evolution of these bacteria, influencing traits such as antibiotic resistance, symbiosis and fitness, and adaptation in general. This review discusses the recent lessons that have been learned from pathogenicity islands in pathogenic microorganisms and how they apply to the role of genomic islands in commensal, symbiotic and environmental bacteria.
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  • 49
    Publikationsdatum: 2020-04-28
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  • 50
    Publikationsdatum: 2020-04-28
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  • 51
    Publikationsdatum: 2017-02-27
    Beschreibung: A knowledge of past changes in the biological productivity of the oceans is important for understanding the interactions between carbon cycling and climate. Phytoplankton productivity in today's oceans can be estimated from the concentrations of chlorophyll in sea water1, but chlorophyll is not preserved in the sediments. Existing proxies for past algal productivity do not represent total productivity; for example, biogenic opal2 reflects the contribution of only part of the phytoplankton community, and the organic carbon record can be subject to contamination from terrestrial inputs2,3. Although chlorins, the pigment-transformation products of chlorophyll, are widespread in Quaternary marine sediments, their potential as proxy measures of past variations in primary productivity has not been convincingly demonstrated. Here we report a high-resolution molecular stratigraphic record of chlorin concentrations over the past 350,000 years in a sediment core from the subtropical Atlantic continental margin. Maxima in the chlorin accumulation rate coincide with significant peaks in the accumulation rates of biogenic opal (at the end of glacial terminations) and organic carbon (between terminations). These results suggest that chlorins, unlike other proxies, can serve as a measure of total primary productivity variations.
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  • 52
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    Wiley-Blackwell
    In:  Oikos, 84 (3). p. 398.
    Publikationsdatum: 2015-02-09
    Beschreibung: In both terrestrial and aquatic environments introductions of non-indigenous species are continuing and represent one important component of global change. Negative biotic interactions by resident species may prevent successful invaders from becoming pests. Few experimental data are available on the presence and significance of such biotic resistance other than predation or competition. This study addresses the role of habitat structure provided by a native eelgrass (Zostera marina) canopy on growth and survival of the non-indigenous mussel Musculista senhousia, a habitat-modifying gregarious suspension feeder with strong effects on native infauna and eelgrass. In 2 southern California bays, a series of transplantation experiments using tagged mussels revealed that inside an eelgrass canopy, Musculista growth rates were reduced by more than half in 3 of 4 experiments compared to adjacent unvegetated areas. Musculista survival also decreased inside the vegetation in a 4-mo experiment. As one element of habitat structure, we tested the effects of eelgrass patch size, using natural (1 site) and planted (1 site) eelgrass patches of defined sizes. Growth rates of Musculista were highest outside the vegetation and decreased as eelgrass patch size increased. As a potential mechanism for the canopy effects, we suggest that Musculista receives less food inside the vegetation. In the experimental plots, the presence and spatial extent of the macrophyte canopy strongly affected near bottom (10 cm) horizontal water flow assessed with a direct dye tracking method. Reduced mussel growth rates were linearly associated with lower water flow, and presumably, food flux. Over a period of 7 mo, food resources (particulate chlorophyll a) were consistently lower 1 and 5 cm above the sea floor inside eelgrass patches compared to the sand flat. The reduction in food availability matched the growth reduction of Musculista. Also, mussel condition (dry flesh mass/shell mass) was worse in individuals growing in eelgrass than in the sand flat. Previous experiments revealed that dense beds of Musculista impede the rhizome growth and vegetative propagation of eelgrass, yet mussels attain abundances sufficient for interference only if eelgrass beds are patchy. Thus, anthropogenic disturbances on eelgrass beds, which often result in meadow fragmentation, and the proliferation of Musculista may have synergistic negative effects on the persistence of eelgrass beds.
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  • 53
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    Wiley-Blackwell
    In:  The Journal of Wildlife Management, 62 (1). pp. 380-388.
    Publikationsdatum: 2020-05-11
    Beschreibung: The use of stable isotope analysis in ecological and wildlife studies is rapidly increasing. Studies include evaluating flow of nutrients in ecosystems and studying dietary composition of individual animals. Several mixing models have been developed to evaluate the relative contribution of different foods to the diet of consumers. All these mixing models require that all prey types will be significantly different in bivariate space. This requirement usually poses a problem in analyzing data of stable isotope ratios because sample sizes in most studies are small and seldom normally distributed. We propose a randomization test that we based on the K nearest-neighbor approach. Results from our simulations of power revealed that the K nearest-neighbor test appears to have high power even with small sample sizes and comparatively low displacement. The K nearest-neighbor test described here provides the preliminary statistical analysis necessary for the use of the mixing models, and therefore is a new, powerful tool for analyzing stable isotope data. In evaluating the test performance on data collected from American martens (Martes americana) and their prey on Chichagof Island, Southeast Alaska, we were able to reject our null hypothesis that all samples of prey were drawn from identical populations (P = 0.05). A program written in Pascal or S-Plus is available from the authors to evaluate the K nearest-neighbor statistic for several groups.
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  • 54
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    Cambridge University Press
    In:  Geological Magazine, 99 (02). pp. 164-172.
    Publikationsdatum: 2020-07-31
    Beschreibung: The results of an examination of one quarry within the gneisses of the Bartica Assemblage are described and the validity of these results throughout the whole of the Bartica Assemblage is discussed. The foliation and banding of the gneisses at Kereti Quarry are mainly the results of tectonism; concomitant metamorphism within the Amphibolite Facies was succeeded by a two-phase metasomatism involving successive additions of Na and K. These results appear valid throughout the Bartica Assemblage and it is further suggested that the main rock type distribution in the Bartica Assemblage is also controlled by tectonism.
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  • 55
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    Cambridge University Press
    In:  Geological Magazine, 101 (6). pp. 541-547.
    Publikationsdatum: 2020-07-31
    Beschreibung: Textural differences in the occurrence of microcline define augen gneisses, subhedral porphyroblastic gneisses and euhedral porphyroblastic gneisses within the Bartica Assemblage, British Guiana. The introduction of microcline is metasomatic and the nature of the porphyroblasts appears to be a reflection of tectonic control during their development.
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  • 56
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    Cambridge University Press
    In:  Mineralogical Magazine, 59 (394). pp. 121-127.
    Publikationsdatum: 2020-06-30
    Beschreibung: PEEM allows ‘real-time’ observations to be made of solid-state transformations and other high-temperature processes taking place during vacuum-heating up to c. 2000°C The solid state transformations of an amphibole-rich hornblendite specimen have been observed in the temperature range of 750–1000°C (± 50°C Between c. 970–990°C a rapid change in orientation contrast was observed, indicating a structural rearrangement from an oxyhornblende crystal lattice to a clinopyroxene structure. This phase retains the original amphibole shape and texture (including two 120°C intersecting cleavage traces), but possesses a clinopyroxene crystal structure. At higher temperatures this phase is seen to decompose, forming iron oxides and other fine-grained products. PEEM has provided useful information on both the nature and rates of transformation of natural amphiboles which has proved invaluable in our understanding of the mineralogically-controlled mechanisms of argon release during 40Ar/39Ar dating of amphibole samples.
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  • 57
    Publikationsdatum: 2020-04-28
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  • 58
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    Nature Publishing Group
    In:  Nature Geoscience, 417 . pp. 848-851.
    Publikationsdatum: 2017-02-28
    Beschreibung: A key question in ecology is which factors control species diversity in a community1, 2, 3. Two largely separate groups of ecologists have emphasized the importance of productivity or resource supply, and consumers or physical disturbance, respectively. These variables show unimodal relationships with diversity when manipulated in isolation4, 5, 6, 7, 8. Recent multivariate models9, 10, however, predict that these factors interact, such that the disturbance–diversity relationship depends on productivity, and vice versa. We tested these models in marine food webs, using field manipulations of nutrient resources and consumer pressure on rocky shores of contrasting productivity. Here we show that the effects of consumers and nutrients on diversity consistently depend on each other, and that the direction of their effects and peak diversity shift between sites of low and high productivity. Factorial meta-analysis of published experiments confirms these results across widely varying aquatic communities. Furthermore, our experiments demonstrate that these patterns extend to important ecosystem functions such as carbon storage and nitrogen retention. This suggests that human impacts on nutrient supply11 and food-web structure12, 13 have strong and interdependent effects on species diversity and ecosystem functioning, and must therefore be managed together.
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  • 59
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    Nature Publishing Group
    In:  Nature, 417 . pp. 487-488.
    Publikationsdatum: 2017-03-07
    Beschreibung: BOOK REVIEWED: Plate Tectonics: An Insider's History of the Modern Theory of the Earth / edited by Naomi Oreskes Westview Press: 2001. 448 pp.
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  • 60
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    Unbekannt
    Wiley-Blackwell
    In:  Oikos (100). pp. 592-600.
    Publikationsdatum: 2017-01-31
    Beschreibung: Conceptual models predict counteractive effects of herbivores and nutrient enrichment on plant diversity and reversed effects of grazers under different nutrient regimes. I tested these hypotheses in 11 field experiments with periphyton communities in three different aquatic habitats (a highly eutrophic lake, an meso-eutrophic lake, and an meso-eutrophic part of the Baltic Sea coast) and in different seasons. Grazer access and nutrient supply were manipulated in a factorial design. Species richness and evenness were chosen as response variables. Both manipulated factors had significant and contrasting effects on diversity, with variable effect strength between sites and seasons. From the two aspects of diversity, evenness well reflected the changes in community composition. Fertilization tended to increase the dominance of few species and thus to decrease evenness, whereas grazers counteracted these effects by removing dominant life forms. The response of species richness was not as expected, since grazers decreased richness throughout, whereas nutrients had weaker effects but tended to increase richness. Species richness rather reflected changes in periphyton architecture. Grazers reduced algal richness presumably by co-consumption of rare species in the tightly connected periphyton assemblages, whereas enrichment may increase richness by providing more structure via increased dominance of filamentous species. Although grazer and nutrient effects on richness and evenness were opposing, there was no change in the effect of one factor by manipulation of the other.
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  • 61
    Publikationsdatum: 2017-03-09
    Beschreibung: The existence in the ocean of deep western boundary currents, which connect the high-latitude regions where deep water is formed with upwelling regions as part of the global ocean circulation, was postulated more than 40 years ago1. These ocean currents have been found adjacent to the continental slopes of all ocean basins, and have core depths between 1,500 and 4,000 m. In the Atlantic Ocean, the deep western boundary current is estimated to carry (10–40) times 106 m3 s-1 of water2, 3, 4, 5, transporting North Atlantic Deep Water—from the overflow regions between Greenland and Scotland and from the Labrador Sea—into the South Atlantic and the Antarctic circumpolar current. Here we present direct velocity and water mass observations obtained in the period 2000 to 2003, as well as results from a numerical ocean circulation model, showing that the Atlantic deep western boundary current breaks up at 8° S. Southward of this latitude, the transport of North Atlantic Deep Water into the South Atlantic Ocean is accomplished by migrating eddies, rather than by a continuous flow. Our model simulation indicates that the deep western boundary current breaks up into eddies at the present intensity of meridional overturning circulation. For weaker overturning, continuation as a stable, laminar boundary flow seems possible.
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  • 62
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    Cambridge University Press
    In:  In: The Changing Ocean Carbon Cycle: a midterm synthesis of the Joint Global Ocean Flux Study. , ed. by Hanson, R. B., Ducklow, H. W. and Field, J. G. Cambridge University Press, Cambridge, UK, pp. 375-391.
    Publikationsdatum: 2020-03-26
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  • 63
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    Unbekannt
    Cambridge University Press
    In:  Journal of The Marine Biological Association of The United Kingdom, 76 . pp. 327-344.
    Publikationsdatum: 2019-07-01
    Beschreibung: The size distribution of benthic nematodes was investigated along different gradients of food availability in various regions of the north-eastern Atlantic: I, across the continental margin and II, with increasing distance from the continental rise. An overall trend for miniaturization with increasing distance from the food source was found. Moreover, our results indicate that seasonally varying food supply or a periodically pulsed input of organic matter to the sea floor affects nematode size spectra. The hypothesis is proposed that the life cycle of deep-sea nematode species and hence the size structure of their populations are related to seasonal energy availability. This dependence might result in one year life spans of deep-sea nematodes and probably other meiofauna.
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  • 64
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    Unbekannt
    Wiley-Blackwell
    In:  Journal of Fish Biology, 59 . pp. 1638-1652.
    Publikationsdatum: 2017-09-08
    Beschreibung: Phylogenetic analyses, using 482 bp of the mitochondrial 16S rDNA and 461 bp of the control region of 16 Diplodus species and Oblada melanura, Pagellus bogaraveo and Pagellus acarne, all close relatives of Diplodus, identified the two representatives of Pagellus as the sister group of Diplodus. Oblada melanura was confirmed as the sister taxon of D. puntazzo, despite its different dental morphology and ecology. Within the genus Diplodus, three clades were identified, the first containing D. annularis and D. bellottii, the second D. vulgaris and D. prayensis, and the third comprising three subclades. These were formed by O. melanura clustering with D. puntazzo, D. fasciatus with D. cervinus, and by the Diplodus sargus sub-species assemblage which also included the West Atlantic taxa D. argenteus, D. bermudensis, D. holbrooki, and the Red Sea endemic D. noct. All members of the D. sargus assemblage were genetically closely related. Among them, D. sargus lineatus from the Cape Verde islands was resolved as most ancestral branch, pointing to the possibility that the diversification and spread of the D. sargus assemblage originated in this region. The hypothesis of stepwise speciation following colonization events within the D. sargus complex is fully supported by phylogenetic reconstruction.
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  • 65
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    Wiley-Blackwell
    In:  Marine Ecology, 20 (1). pp. 35-47.
    Publikationsdatum: 2020-07-14
    Beschreibung: In situ experiments were run with the seastar Asterias rubens to investigate the influence of epibiosis on predation preferences. Mussels (Mytilus edulis) monospecifically fouled by different epibiont species (the barnacle Balanus improvisus, the red filamentous alga Ceramium strictum, the sponge Halichondria panicea and the hydrozoan Laomedea flexuosa) and macroscopically clean mussels were exposed and seastar predation was monitored by SCUBA. Asterias rubens preferred macroscopical unfouled mussels as prey. Fouling generally reduced predation pressure on the mussel hosts (associational resistance). Barnacles protected mussels less efficiently than hydrozoans or algae. We hypothesize that in top-down controlled communities this influence of epibiosis on predation pressure should affect mussel community patterns. A survey of natural mussel-epibiont distribution in the presence or absence of A. rubens showed that the prevalence of differently fouled mussels differed between predation-exposed and predation-protected habitats. Natural mussel-epibiont associations reflected the preferential predation of the major local predators. Additionally, higher epibiotic diversity and evenness could be observed at locations accessible to benthic predators as compared with habitats protected from predation. As blue mussels and seastars are important structuring and controlling elements in the shallow water community of Kiel Fjord, major consequences of epibiosis on the entire system are discussed.
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  • 66
    Publikationsdatum: 2017-03-07
    Beschreibung: More than 50% of the Earth' s surface is sea floor below 3,000 m of water. Most of this major reservoir in the global carbon cycle and final repository for anthropogenic wastes is characterized by severe food limitation. Phytodetritus is the major food source for abyssal benthic communities, and a large fraction of the annual food load can arrive in pulses within a few days1, 2. Owing to logistical constraints, the available data concerning the fate of such a pulse are scattered3, 4 and often contradictory5, 6, 7, 8, 9, 10, hampering global carbon modelling and anthropogenic impact assessments. We quantified (over a period of 2.5 to 23 days) the response of an abyssal benthic community to a phytodetritus pulse, on the basis of 11 in situ experiments. Here we report that, in contrast to previous hypotheses5, 6, 7, 8, 9, 10, 11, the sediment community oxygen consumption doubled immediately, and that macrofauna were very important for initial carbon degradation. The retarded response of bacteria and Foraminifera, the restriction of microbial carbon degradation to the sediment surface, and the low total carbon turnover distinguish abyssal from continental-slope ‘deep-sea’ sediments.
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  • 67
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 78 (02). pp. 561-575.
    Publikationsdatum: 2020-07-16
    Beschreibung: A total of 57 comparative hauls using a rectangular midwater trawl with a fishing mouth area of 50 m2 (RMT 50) were carried out along the sides of an imaginary triangle south of Madeira in 1986. A total of 1258 cephalopods were caught, giving a mean of 22 per haul with a range from 0 to 67. The nets were used with a diver's light on the top bar which was either switched off or was operated with a 20, 70 or 150 W bulb, powered by a car battery. A significantly greater number of individuals per haul was caught with lights on than without lights, increasing from a mean of 13·5–25·1, a factor of 1·8. Similarly, the number of species caught was increased from a mean of 7 to 10·4, a factor of 1·5 and the volume of cephalopods was increased from a mean of 41·1–162·3ml, a factor of 3·9. Similar comparisons made for catches during day or night separately and on the three courses separately also showed marked increases with the lights. Samples show that increase in power of the lights increased the total number of cephalopod individuals caught. In the 12 species with more than ten individuals, in 33 of the 36 comparisons (of number of individuals, species and volumes) there is an increase with the light. The most influenced species was Taonius pavo which increased in numbers by a mean factor of 3·9 times with 20W, 4·0 times with 70W and 6·1 times with 150W when compared with the numbers caught with no light.
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  • 68
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    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 32 (6). pp. 641-644.
    Publikationsdatum: 2020-07-16
    Beschreibung: Tables for the speed of sound in sea water are presented. These tables have been prepared from an empirical formula which was derived to fit measured sound‐speed data obtained over the temperature range −3°C to 30°C, the pressure range 1.033 kg/cm2 to 1000 kg/cm2, and the salinity range 33‰ to 37‰. The discrepancy of −3.0 m/sec found by Del Grosso at 1 atm., as compared to the tables of Kuwahara, is substantiated. In addition, the pressure coefficient of sound speed observed in the present work differs from that predicted by Kuwahara.
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  • 69
    Publikationsdatum: 2017-03-07
    Beschreibung: The shells of the planktonic foraminifer Neogloboquadrina pachyderma have become a classical tool for reconstructing glacial–interglacial climate conditions in the North Atlantic Ocean1, 2, 3. Palaeoceanographers utilize its left- and right-coiling variants, which exhibit a distinctive reciprocal temperature and water mass related shift in faunal abundance both at present and in late Quaternary sediments1, 2, 4, 5. Recently discovered cryptic genetic diversity in planktonic foraminifers6, 7, 8 now poses significant questions for these studies. Here we report genetic evidence demonstrating that the apparent ‘single species’ shell-based records of right-coiling N. pachyderma used in palaeoceanographic reconstructions contain an alternation in species as environmental factors change. This is reflected in a species-dependent incremental shift in right-coiling N. pachyderma shell calcite δ18O between the Last Glacial Maximum and full Holocene conditions. Guided by the percentage dextral coiling ratio, our findings enhance the use of δ18O records of right-coiling N. pachyderma for future study. They also highlight the need to genetically investigate other important morphospecies to refine their accuracy and reliability as palaeoceanographic proxies.
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  • 70
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    Cambridge University Press
    In:  Journal of The Marine Biological Association of The United Kingdom, 82 . pp. 913-916.
    Publikationsdatum: 2021-07-05
    Beschreibung: Possible effects of ‘El Niño’ Southern Oscillation (ENSO) components ‘El Niño’ and ‘La Niña’ on populations of southern elephant seals, Mirounga leonina, were analysed. Changes in the cephalopod diet composition of moulting females at King George Island, Antarctic Peninsula were considered. The diet of female elephant seals sampled in 1991–1992 and 1992–1993 (El Niño years) were compared with those taken in 1995–1996 (La Niña year) at the same site and employing the same methodology. The squid Psychroteuthis glacialis constituted the main cephalopod prey of the seals. A reduction in the ‘Index of Biomass Ingested’ by female elephant seals (IBIF) of this prey species was observed in ‘El Niño’ years (1992, 1993) compared with the ‘La Niña’ year (1996). This reduction in biomass applied to all squid species in the seals' prey with the exception of Galiteuthis glacialis, which occurred in low numbers, but was more abundant during El Niño years than in the La Niña year.
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  • 71
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    Wiley-Blackwell
    In:  Journal of Fish Biology, 51 (Suppl. A.). pp. 352-369.
    Publikationsdatum: 2017-09-08
    Beschreibung: Newly hatched Baltic cod Gadus morhua larvae are typically found at depths 〉60 m. This is a region of low light and prey availability, hence generating the hypothesis that larvae have to migrate from hatching depth to the surface layer to avoid starvation and improve their nutritional condition. To test this hypothesis, Baltic cod larvae were sampled during the spawning seasons of 1994 and 1995 with depth-resolving multiple opening/closing nets. Each larva was aged by otolith readings and its RNA/DNA ratio was determined as a measure of nutritional condition. The RNA/DNA ratios of these larvae aged 2-25 days (median 10 days) ranged from 0.4 to 6.2, corresponding to levels exhibited by starving and fast-growing larvae in laboratory calibration studies (starvation, protein growth rate, Gpi= -12.2% day−1; fastgrowing larvae, Gpi=14.1%day−1) respectively. Seventy per cent of the field caught larvae had RNA/DNA ratios between the mean values found for starving and fed laboratory larvae. Only larvae aged 8-11 days had higher mean RNA/DNA ratios above 45 m than below (t-test, P〈0.05). However, the instantaneous protein growth rates were significantly higher for all larval age groups in the surface layers (t-test, P〈0.05). Starving larvae were found in all depths sampled (10-85 m), whereas growing larvae (positive Gpi) were restricted to samples taken shallower than 45 m. These superior growth rates above 45 m corroborate the hypothesis and imply that migration to the shallow water layers is a prerequisite for good nutritional condition, growth and survival of Baltic cod larvae. The frequent occurrence of cod larvae older than 8 days in the deep water in poor condition suggests that a proportion of the larvae will die from Starvation in the deep layers of the Baltic Sea.
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  • 72
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    Unbekannt
    Wiley-Blackwell
    In:  Journal of Fish Biology, 62 . pp. 253-276.
    Publikationsdatum: 2017-09-08
    Beschreibung: A set of histological characteristics to judge ovarian development was established and used to elaborate morphological criteria of 10 maturity stages of Baltic cod Gadus morhua sampled throughout the annual cycle to represent different macroscopic maturity stages. The applied characteristics confirmed most stages of the macroscopic scale, but the separation of late immature and resting mature females remained imprecise. Atretic vitellogenic oocytes or encapsulated residual eggs identified the resting condition morphologically, but not all ovaries with visible signs of previous spawning showed such features. One ovarian stage that was previously classified as ‘ripening’ was changed to ‘spawning’, owing to the prevalence of hydrated eggs and empty follicles. Ovaries with malfunctions were defined by a separate stage. Macroscopic criteria were revised by comparing the gross anatomy of ovaries with their histology. Female length and gonado-somatic index supported stage definitions, but substantial variation in Fulton's condition factor and the hepato-somatic index rendered these of little use for this purpose. The time of sampling influenced staging accuracy. A female spawner probability function based on the proportion of ripening and ripe specimens in early spring seems to be the most appropriate method to estimate spawner biomass and reproductive potential.
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  • 73
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    Cambridge University Press
    In:  In: Hydrogeology of Oceanic Lithosphere. , ed. by Davis, E. E. and Elderfield, H. Cambridge University Press, Cambridge, pp. 128-150. 1 ISBN 0521819296
    Publikationsdatum: 2012-02-23
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  • 74
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    Unbekannt
    Wiley-Blackwell
    In:  Journal of Fish Biology, 63 . pp. 280-299.
    Publikationsdatum: 2017-09-13
    Beschreibung: During peak spawning of sprat Sprattus sprattus in the Baltic Sea in May–June egg specific gravity averaged ±s.d. 1·00858 ± 0·00116 g cm−3 but was significantly higher in the beginning and significantly lower towards the end of the spawning season. A close relationship was found between egg diameter and egg specific gravity (r2 = 0·71). This relationship, however, changed during the spawning season indicating that some other factor was involved causing the decrease in specific gravity during the spawning period. The vertical egg distribution changed during the spawning season: eggs were distributed mainly in the deep layers early in the season, occurred in and above the permanent halocline during peak spawning, and above the halocline towards the end of the spawning season. Consequently, poor oxygen conditions in the deep layers and low temperatures in layers between the halocline and the developing thermocline may affect egg development. Thus, opportunities for egg development vary over the spawning season and among spawning areas, and depending on frequency of saline water inflows into the Baltic Sea and severity of winters, between years
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  • 75
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    Nature Publishing Group
    In:  Nature, 412 . pp. 605-606.
    Publikationsdatum: 2017-02-28
    Beschreibung: One way of accounting for lowered atmospheric carbon dioxide concentrations during Pleistocene glacial periods is by invoking the Antarctic stratification hypothesis, which links the reduction in CO2 to greater stratification of ocean surface waters around Antarctica1, 2. As discussed by Sigman and Boyle3, this hypothesis assumes that increased stratification in the Antarctic zone (Fig. 1) was associated with reduced upwelling of deep waters around Antarctica, thereby allowing CO2 outgassing to be suppressed by biological production while also allowing biological production to decline, which is consistent with Antarctic sediment records4. We point out here, however, that the response of ocean eddies to increased Antarctic stratification can be expected to increase, rather than reduce, the upwelling rate of deep waters around Antarctica. The stratification hypothesis may have difficulty in accommodating eddy feedbacks on upwelling within the constraints imposed by reconstructions of winds and Antarctic-zone productivity in glacial periods.
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  • 76
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    Nature Publishing Group
    In:  Nature, 385 . pp. 618-621.
    Publikationsdatum: 2017-02-27
    Beschreibung: The ocean stores and transports vast quantities of heat, fresh water, carbon and other materials, and its circulation plays an important role in determining both the Earth's climate and fundamental processes in the biosphere. Understanding the development of climate and important biological cycles therefore requires detailed knowledge of ocean circulation and its transport properties. This cannot be achieved solely through modelling, but must involve accurate observations of the spatio-temporal evolution of the global oceanic flow field. Estimates of oceanic flow are currently made on the basis of space-borne measurements of the sea surface, and monitoring of the ocean interior. Satellite altimetry and acoustic tomography are complementary for this purpose1, as the former provides detailed horizontal coverage of the surface, and the latter the requisite vertical sampling of the interior. High-quality acoustic-tomographic2 and altimetric3 data are now available to test the combined power of these technologies for estimating oceanic flows. Here we demonstrate that, with the aid of state-of-the-art numerical models, it is possible to recover from these data a detailed spatio-temporal record of flow over basin-scale volumes of fluid. Our present results are restricted to the Mediterranean Sea, but the method described here provides a powerful tool for studying oceanic circulation worldwide.
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  • 77
    Publikationsdatum: 2017-03-07
    Beschreibung: The climate of the last glacial period was extremely variable, characterized by abrupt warming events in the Northern Hemisphere, accompanied by slower temperature changes in Antarctica and variations of global sea level. It is generally accepted that this millennial-scale climate variability was caused by abrupt changes in the ocean thermohaline circulation. Here we use a coupled ocean–atmosphere–sea ice model to show that freshwater discharge into the North Atlantic Ocean, in addition to a reduction of the thermohaline circulation, has a direct effect on Southern Ocean temperature. The related anomalous oceanic southward heat transport arises from a zonal density gradient in the subtropical North Atlantic caused by a fast wave-adjustment process. We present an extended and quantitative bipolar seesaw concept that explains the timing and amplitude of Greenland and Antarctic temperature changes, the slow changes in Antarctic temperature and its similarity to sea level, as well as a possible time lag of sea level with respect to Antarctic temperature during Marine Isotope Stage 3.
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  • 78
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    Nature Publishing Group
    In:  Nature, 406 . pp. 955-956.
    Publikationsdatum: 2021-07-01
    Beschreibung: Birds taking time off from breeding head for their favourite long-haul destinations. What oceanic seabirds do outside their breeding periods is something of a mystery, although altogether these "sabbaticals' add up to more than half of their lifetime and are probably a key feature of their life history. Here we use geolocation systems based on light-intensity measurements to show that during these periods wandering albatrosses (Diomedea exulans) leave the foraging grounds that they frequent while breeding for specific, individual oceanic sectors and spend the rest of the year there — each bird probably returns to the same area throughout its life. This discovery of individual home-range preferences outside the breeding season has important implications for the conservation of albatrosses threatened by the development of longline fisheries.
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  • 79
    Publikationsdatum: 2017-03-10
    Beschreibung: The role of iron in enhancing phytoplankton productivity in high nutrient, low chlorophyll oceanic regions was demonstrated first through iron-addition bioassay experiments1 and subsequently confirmed by large-scale iron fertilization experiments2. Iron supply has been hypothesized to limit nitrogen fixation and hence oceanic primary productivity on geological timescales3, providing an alternative to phosphorus as the ultimate limiting nutrient4. Oceanographic observations have been interpreted both to confirm and refute this hypothesis5, 6, but direct experimental evidence is lacking7. We conducted experiments to test this hypothesis during the Meteor 55 cruise to the tropical North Atlantic. This region is rich in diazotrophs8 and strongly impacted by Saharan dust input9. Here we show that community primary productivity was nitrogen-limited, and that nitrogen fixation was co-limited by iron and phosphorus. Saharan dust addition stimulated nitrogen fixation, presumably by supplying both iron and phosphorus10, 11. Our results support the hypothesis that aeolian mineral dust deposition promotes nitrogen fixation in the eastern tropical North Atlantic.
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  • 80
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    Nature Publishing Group
    In:  Nature, 422 . pp. 602-606.
    Publikationsdatum: 2019-09-23
    Beschreibung: The Messinian salinity crisis—the desiccation of the Mediterranean Sea between 5.96 and 5.33 million years (Myr) ago1—was one of the most dramatic events on Earth during the Cenozoic era2. It resulted from the closure of marine gateways between the Atlantic Ocean and the Mediterranean Sea, the causes of which remain enigmatic. Here we use the age and composition of volcanic rocks to reconstruct the geodynamic evolution of the westernmost Mediterranean from the Middle Miocene epoch to the Pleistocene epoch (about 12.1–0.65 Myr ago). Our data show that a marked shift in the geochemistry of mantle-derived volcanic rocks, reflecting a change from subduction-related to intraplate-type volcanism, occurred between 6.3 and 4.8 Myr ago, largely synchronous with the Messinian salinity crisis. Using a thermomechanical model, we show that westward roll back of subducted Tethys oceanic lithosphere and associated asthenospheric upwelling provides a plausible mechanism for producing the shift in magma chemistry and the necessary uplift (approx1 km) along the African and Iberian continental margins to close the Miocene marine gateways, thereby causing the Messinian salinity crisis.
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  • 81
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    Nature Publishing Group
    In:  Nature, 429 .
    Publikationsdatum: 2017-03-10
    Beschreibung: No need to wait for more information: industrialized fishing is already wiping out stocks.
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  • 82
    Publikationsdatum: 2019-09-23
    Beschreibung: The formation and sinking of biogenic particles mediate vertical mass fluxes and drive elemental cycling in the ocean1. Whereas marine sciences have focused primarily on particle production by phytoplankton growth, particle formation by the assembly of organic macromolecules has almost been neglected2, 3. Here we show, by means of a combined experimental and modelling study, that the formation of polysaccharide particles is an important pathway to convert dissolved into particulate organic carbon during phytoplankton blooms, and can be described in terms of aggregation kinetics. Our findings suggest that aggregation processes in the ocean cascade from the molecular scale up to the size of fast-settling particles, and give new insights into the cycling and export of biogeochemical key elements such as carbon, iron and thorium.
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  • 83
    Publikationsdatum: 2019-09-23
    Beschreibung: The deposition of atmospheric dust into the ocean has varied considerably over geological time1, 2. Because some of the trace metals contained in dust are essential plant nutrients which can limit phytoplankton growth in parts of the ocean, it has been suggested that variations in dust supply to the surface ocean might influence primary production3, 4. Whereas the role of trace metal availability in photosynthetic carbon fixation has received considerable attention, its effect on biogenic calcification is virtually unknown. The production of both particulate organic carbon and calcium carbonate (CaCO3) drives the ocean's biological carbon pump. The ratio of particulate organic carbon to CaCO3 export, the so-called rain ratio, is one of the factors determining CO2 sequestration in the deep ocean. Here we investigate the influence of the essential trace metals iron and zinc on the prominent CaCO3-producing microalga Emiliania huxleyi. We show that whereas at low iron concentrations growth and calcification are equally reduced, low zinc concentrations result in a de-coupling of the two processes. Despite the reduced growth rate of zinc-limited cells, CaCO3 production rates per cell remain unaffected, thus leading to highly calcified cells. These results suggest that changes in dust deposition can affect biogenic calcification in oceanic regions characterized by trace metal limitation, with possible consequences for CO2 partitioning between the atmosphere and the ocean.
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  • 84
    Publikationsdatum: 2019-01-22
    Beschreibung: This contribution aims to report the reflections we had with the scientific community during two international workshops on reference materials for stable isotopes in Davos (2002) and Nice (2003). After evaluating the isotopic homogeneity of some existing reference materials, based on either certificates, literature data or specific inter-laboratory rounds, we confirm these as primary reference materials or propose new ones relative to which stable isotope compositions should be reported. We propose DSM-3 for Mg, NIST SRM 915a for Ca, L-SVEC for Li and NBS28 for Si. Cadmium does not yet have a well identified delta zero material, although three commercial mono-elemental Cd solutions have yielded the same isotopic composition relative to one another. In order to scale the linearity of any mass spectrometer, some secondary reference materials are also proposed: Cambridge-1 solution for Mg, the “Münster-Cd” and JEPPIM Cd solutions for Cd and the “Big Batch” silicate for Si. The team from Nancy propose to prepare a mixed spike solution for Li isotopes. Well-characterised natural samples such as ocean or continental waters, diatoms, sponges, rocks and minerals are needed to validate the entire analytical procedure, particularly to take into account the effect of sample mineralisation and of chemical manipulations for elemental separation prior to analysis.
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  • 85
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    Nature Publishing Group
    In:  Nature, 387 . pp. 31-32.
    Publikationsdatum: 2017-02-28
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  • 86
    Publikationsdatum: 2017-03-07
    Beschreibung: The circulation of water masses in the northeastern North Atlantic Ocean has a strong influence on global climate owing to the northward transport of warm subtropical water to high latitudes1. But the ocean circulation at depths below the reach of satellite observations is difficult to measure, and only recently have comprehensive, direct observations of whole ocean basins been possible2, 3, 4. Here we present quantitative maps of the absolute velocities at two levels in the northeastern North Atlantic as obtained from acoustically tracked floats. We find that most of the mean flow transported northward by the Gulf Stream system at the thermocline level (about 600 m depth) remains within the subpolar region, and only relatively little enters the Rockall trough or the Nordic seas. Contrary to previous work5, 6, our data indicate that warm, saline water from the Mediterranean Sea reaches the high latitudes through a combination of narrow slope currents and mixing processes. At both depths under investigation, currents cross the Mid-Atlantic Ridge preferentially over deep gaps in the ridge, demonstrating that sea-floor topography can constrain even upper-ocean circulation patterns.
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  • 87
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    Wiley-Blackwell
    In:  Oikos, 106 . pp. 93-104.
    Publikationsdatum: 2016-05-26
    Beschreibung: Ecological stoichiometry describes the biochemical constraints of trophic interactions emerging from the different nutrient content and nutrient demand of producers and consumers, respectively. Most research on this topic originates from well-mixed pelagic food webs, whereas the idea has received far less attention in spatially structured habitats. Here, we test how light as well as grazing and nutrient regeneration by consumers affects growth and biomass of benthic primary producers. In the first laboratory experiment, we manipulated grazer presence (two different snail species plus ungrazed control), in the second experiment we factorially combined manipulation of grazer presence and light intensity. We monitored snail and periphyton biomass as well as dissolved and particulate nutrients (nitrogen and phosphorus) over time. Grazers significantly reduced algal biomass in both experiments. Grazers affected periphyton nutrient content depending on the prevailing nutrient limitation and their own body stoichiometry. In the nitrogen (N-) limited first experiment, grazers increased N both in the periphyton and in the water column. The effect was stronger for grazers with lower N-content. In the phosphorus (P-) limited second experiment, grazers increased the P-content of the periphyton, but the grazer with lower N-content had additionally positive effects on algal N. Light reduction did not affect periphyton biomass, but increased chlorophyll-, N- and P-content of the periphyton. These experiments revealed that the indirect effects of grazers on periphyton were bound by stoichiometric constraints of nutrient incorporation and excretion.
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  • 88
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    Nature Publishing Group
    In:  Nature, 300 (5889). pp. 245-246.
    Publikationsdatum: 2018-03-08
    Beschreibung: A subtropical front was observed in the area south and southeast of the Azores during cruises of FS Meteor and FS Poseidon in early 1982. The front has a basically west–east extension, with considerable meandering observed. Meso-scale eddies are found on both sides. The overall flow pattern corresponds to earlier results on geopotential differences in the upper northeast Atlantic, but the baroclinic transport of the order of 107 m3 s−1 is found to be concentrated in a 60-km wide jet. We suggest here that the current band is part of the gyre circulation, resulting from a branching of the North Atlantic Current.
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  • 89
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    Unbekannt
    American Institute of Physics
    In:  The Leading Edge, 18 (1). pp. 74-80.
    Publikationsdatum: 2018-01-18
    Materialart: Article , NonPeerReviewed
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  • 90
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    Nature Publishing Group
    In:  Nature, 398 (6729). pp. 694-697.
    Publikationsdatum: 2021-02-25
    Beschreibung: The El Niño/Southern Oscillation (ENSO) phenomenon is the strongest natural interannual climate fluctuation1. ENSO originates in the tropical Pacific Ocean and has large effects on the ecology of the region, but it also influences the entire global climate system and affects the societies and economies of manycountries2. ENSO can be understood as an irregular low-frequency oscillation between a warm (El Niño) and a cold (La Niña) state. The strong El Niños of 1982/1983 and 1997/1998, along with the more frequent occurrences of El Niños during the past few decades, raise the question of whether human-induced 'greenhouse' warming affects, or will affect, ENSO3. Several global climate models have been applied to transient greenhouse-gas-induced warming simulations to address this question4, 6, but the results have been debated owing to the inability of the models to fully simulate ENSO (because of their coarse equatorial resolution)7. Here we present results from a global climate model with sufficient resolution in the tropics to adequately represent the narrow equatorial upwelling and low-frequency waves. When the model is forced by a realistic future scenario of increasing greenhouse-gas concentrations, more frequent El-Niño-like conditions and stronger cold events in the tropical Pacific Ocean result
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  • 91
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    Cambridge University Press
    In:  Journal of Fluid Mechanics, 476 . pp. 335-343.
    Publikationsdatum: 2019-01-15
    Beschreibung: The effect of boundary conditions on the ‘critical dynamics’ at the onset of Taylor vortices is investigated in a combined numerical and experimental study. Numerical calculations of Navier–Stokes equations with ‘stress-free’ boundary conditions show that the Landau amplitude equation provides a good model of the transient dynamics. However, this rapidly breaks down when the ‘no-slip’ condition is approached. Apparent ‘critical’ behaviour observed in experiments is shown to have a surprising dependence on the length of the system.
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  • 92
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    Nature Publishing Group
    In:  Nature, 394 . pp. 266-269.
    Publikationsdatum: 2019-02-27
    Beschreibung: In steady state, the export of photosynthetically fixed organic matter to the deep ocean has to be balanced by an upward flux of nutrients into the euphotic zone1. Indirect geochemical estimates2 of the nutrient supply to surface waters have been substantially higher than direct biological and physical measurements3, particularly in subtropical regions. A possible explanation for the apparent discrepancy is that the sampling strategy of the direct measurements has under-represented episodic nutrient injections forced by mesoscale eddy dynamics, whereas geochemical tracer budgets integrate fluxes over longer time and space scales. Here we investigate the eddy-induced nutrient supply by combining two methods potentially capable of delivering synoptic descriptions of the ocean's state on a basin scale. Remotely sensed sea-surface height data from the simultaneous TOPEX/Poseidon and ERS-1 satellite missions are assimilated into a numerical eddy-resolving coupled ecosystem–circulation model of the North Atlantic Ocean. Our results indicate that mesoscale eddy activity accounts for about one-third of the total flux of nitrate into the euphotic zone (taken to represent new production) in the subtropics and at mid-latitudes. This contribution is not sufficient to maintain the observed primary production in parts of the subtropical gyre, where alternative routes of nitrogen supply will have to be considered.
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  • 93
    Publikationsdatum: 2019-01-21
    Beschreibung: Circumpolar surface waters dominate the circulation of the Southern Ocean and sustain one of the ocean's largest standing stocks of biomass thereby producing a significant output of biogenic components, mainly diatoms, to the bottom sediments. Generally transit of biogenic matter from the sea surface to the sea floor affects nutrient regeneration fuels benthic life and transfers signals to the sediment record1–5. Reliable quantification of the relationship between biological production, fractionation of skeletal and tissue components and bottom sediment accumulation depends on direct vertical flux measurements from sediment trap deployments6–9, which have proved to be most scientifically productive10–13. We now present data on vertical mass fluxes from the Southern Ocean and evidence for strong biogeochemical fractionation between organic carbon-, nitrogen- and phosphorus-containing compounds, siliceous and calcareous skeletal remains, and refractory aluminosilicates.
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  • 94
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    Cambridge University Press
    In:  Journal of Fluid Mechanics, 12 (04). p. 481.
    Publikationsdatum: 2020-07-24
    Beschreibung: The energy flux in a finite-depth gravity-wave spectrum resulting from weak non-linear couplings between the spectral components is evaluated by means of a perturbation method. The fifth-order analysis yields a fourth-order effect comparable in magnitude to the generating and dissipating processes in wind-generated seas. The energy flux favours equidistribution of energy and vanishes in the limiting case of a white, isotropic spectrum. The influence on the equilibrium structure of fully developed wave spectra and on other phenomena in random seas is discussed briefly.
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  • 95
    Publikationsdatum: 2016-09-02
    Beschreibung: Analysis of aeolo-marine dust deposits in the subtropical eastern Atlantic enables the strength of the major wind patterns during the late Quaternary to be evaluated and gives an insight into the climate of North Africa.
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  • 96
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    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 62 (04). p. 799.
    Publikationsdatum: 2020-07-16
    Beschreibung: Five hundred and twenty-eight specimens of Loligo forbesi Steenstrup, from landings in Horta, Faial, Azores, during the year 1 March 1980 to 28 February 1981, were tudied; 59·3 % were males, 40·7 % females. Of the males 80·2 % were sexually mature, of the females 91·6 %, both sexes showing the highest degree of maturity in spring and he lowest in autumn. The mean dorsal mantle length of the mature males was 56·5 cm, or females 33·5 cm. A weight-length relationship was calculated. he stomachs of 622 specimens were sampled, of which 306 contained food. The prey omponents were studied qualitatively. The main prey was fish (82·0%), of which 0·5 % were horse mackerel, Trachurus picturatus, this being the most important food rganism. Preliminary results of statolith readings are given.
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  • 97
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    American Institute of Physics
    In:  The Leading Edge, 14 (10). pp. 1053-1058.
    Publikationsdatum: 2016-07-26
    Beschreibung: Seismic data are usually acquired and processed for imaging reflections. This paper describes a method of processing seismic data for imaging discontinuities (e.g., faults and stratigraphic features). One application of this nontraditional process is a 3-D volume, or cube, of coherence coefficients within which faults are revealed as numerically separated surfaces. Figure 1 compares a traditional 3-D reflection amplitude time slice with the results of the new method. To our knowledge, this is the first published method of revealing fault surfaces within a 3-D volume for which no fault reflections have been recorded.
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  • 98
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    Nature Publishing Group
    In:  Nature, 421 (6921). pp. 324-325.
    Publikationsdatum: 2016-07-19
    Beschreibung: An excellent sediment record from the Arabian Sea traces recent patterns in the activity of the Asian monsoon. It reveals both variability in monsoon strength and links with climatic events elsewhere. The monsoon is the main determinant of environmental conditions over much of Asia, and so affects the most densely populated region on Earth. Differential heating of the north Indian Ocean and the northwest Pacific, and of the Asian land-mass, cause the seasonal reversal of monsoon winds. In summer, these winds blow northwards over the northern Indian Ocean, carrying huge amounts of moisture over the neighbouring land. The ensuing heavy rainfall can have devastating consequences for human life and livelihood. Conversely, agriculture in Asia depends on monsoon rains; and the seasonal upwelling of nutrient-laden subsurface waters, driven by monsoon winds, is essential to the success of coastal fisheries.
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  • 99
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    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 103 (3). pp. 1346-1352.
    Publikationsdatum: 2020-07-16
    Beschreibung: Two sets of equations, covering all world oceans and seas, are presented to calculate pressure from depth for the computation of sound speed, and depth from pressure for use in ocean engineering. They are based on the algorithm of UNESCO 1983 [N. P. Fofonoff and R. C. Millard, Jr., Unesco Tech. Papers in Mar. Sci. No. 44 (1983)], and on calculations from temperature and salinity profiles. The pressure to depth conversion is presented first. The equations can be used in those cases where the desired accuracy is reduced to ±0.8 m. The equations to convert depth to pressure provide an overall accuracy between ±8000 Pa and ±1000 Pa. This leads to errors in sound speed consistently smaller than ±0.02 m/s. The discussion, and comparisons with results and other formulas, suggest that the new equations are a substantial improvement on the previous simplified ones, which should now be abandoned.
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  • 100
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    Nature Publishing Group
    In:  Nature, 376 (6537). pp. 212-213.
    Publikationsdatum: 2016-06-16
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