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  • Other Sources  (80)
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  • 1997  (80)
  • 1
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    Geophysik (1997)
    Springer
    In:  Bull., Polar Proj. OP-O3A4, Handbuch zur Erkundung des Untergrundes von Deponien und Altlasten hrsg. von der Bundesanstalt für Geowissenschaften und Rohstoffe, Heidelberg, Springer, vol. 3, no. 1, pp. 81-92, (ISBN: 3-540-23712-7)
    Details
    Publication Date: 1997
    Keywords: Applied geophysics ; environment ; waste ; disposal ; Seismics (controlled source seismology) ; Geoelectrics ; Gravimetry, Gravitation ; RADAR ; Borehole geophys. ; Physical properties of rocks ; Handbook of geophysics ; Knodel
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Guidelines for efficient wellbore stability analysis (1997)
    Elsevier
    In:  Int. J. Rock Mech. & Min Sci., Taipei, Elsevier, vol. 34, no. 3-4, pp. 155-162, pp. B09401, (ISBN: 0-12-018847-3)
    Details
    Publication Date: 1997
    Keywords: Borehole geophys. ; Stress ; Borehole breakouts ; Hydraulic fracturing ; stability ; Anisotropy ; shear ; tensile ; Strength ; Rock mechanics
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    Tides in water saturated rock (1997)
    Springer
    In:  Bull., Polar Proj. OP-O3A4, Contributions to the 6th Annual KTB-Colloquium: Geoscientific Results, Berlin, Springer, vol. 66, no. 2, pp. 277-291, (ISBN 0-87590-532-3, AGU Code: GD0305323)
    Details
    Publication Date: 1997
    Keywords: Earth tides ; poro-elasticity ; pressure ; permeability ; porosity ; Fluids ; Review article
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Constraining the full stress tensor from observations of drilling-induced tensile fractures and leak-off tests: applications to borehole stability and sand production on the Norwegian margin (1997)
    Elsevier
    In:  Int. J. Rock Mech. & Min. Sci., Hannover, Elsevier, vol. 34, no. 3-4, pp. 13021-13032, pp. L15S14, (ISSN: 1340-4202)
    Details
    Publication Date: 1997
    Keywords: Stress ; Stress measurements ; Hydraulic fracturing ; Borehole geophys. ; stability ; North ; Sea ; Norway
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    BIBLIOGRAPHY SEISMOLOGY
  • 5
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    The Sn-Cl-F-C-S-H-O-Na system: Thermodynamic properties of components within the conditions of the earth’s crust (1997)
    Springer
    In:  Geochemistry International, 35 . pp. 1016-1020.
    Details
    Publication Date: 2018-01-19
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  • 6
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    A method for deployment of externally attached sonic fish tags from a manned submersible and their effects on coelacanths (1997)
    Springer
    In:  Marine Biology, 128 (3). pp. 359-362.
    Details
    Publication Date: 2017-07-06
    Description: A method for attaching acoustic transmitters externally to deep-water fishes in situ is described. Tags, each comprising a transmitter connected to a dart, were fired at fish from a pneumatic gun held by the manipulator arm of a submersible. The method was applied successfully for tagging coelacanths and may have application for use with other species of fishes living at depths to about 1000 m. The usefulness of direct observation for monitoring the effects of tags on fish is evaluated in relation to the effects of the tagging method on coelacanths.
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  • 7
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    The impact of the Mediterranean Outflow Water (MOW) on benthic foraminiferal assemblages and surface sediments at the southern Portuguese continental margin (1997)
    Elsevier
    In:  Marine Micropaleontology, 29 (3-4). pp. 211-236.
    Details
    Publication Date: 2017-06-22
    Description: Benthic foraminifera and surface sediments were analyzed from 23 box-core and core-top samples from 250 to 3600 m depth at the southern Portuguese continental margin between 37 and 38 °N. This area is affected by the MOW which flows northwards along the slope between 600 and 1500 m waterdepth. Sediment structures, grain-size distribution and clay mineral assemblages of surface sediments indicate active winnowing in the upper part of the MOW, and deposition of the fine fraction near its lower boundary. R-mode cluster analyses of foraminiferal census data from the 〉 250 μm fraction revealed four associations. The ‘Shelf Edge Association’ occurs on glauconitic shelf and upper slope sands down to 268 m. The ‘Upper Slope Association’ is recognized between 498 and 1300 m where sand-silt-clays to clayey silts are encountered. The ‘Lower Slope Association’ is found between 1405 and 2985 m and differs markedly from assemblages below 3000 m (‘Deep Water Association’) where the near-surface sediments are soft hemipelagic clays. The ‘Boundary Layer Association’ shows no significant depth limits but abundance maxima both in the density interface above the MOW and in the interval of decreasing turbulence below it. The boundaries of the ‘Shelf Edge’ and ‘Upper Slope Association’ correspond to these hydrographic boundary layers whereas the boundary between ‘Lower Slope’ and ‘Deep Water Assemblage’ is related to threshold values of nutrient flux to the benthic community. Examination of hard-substrates reveals 27 different species of epibenthic foraminifera. Six of these, the ‘Epibenthos Group’, were found attached to elevated substrates only within the MOW. Above the MOW, elevated substrates were inhabited by different species, whilst below the MOW they were not used by any epibenthic foraminifers. Evidently, the hydrodynamic environment of the MOW current provides an ecological niche which is efficiently used by opportunistic suspension feeders. The ‘Epibenthos Group’ is more abundant in the middle part of the study area between 37 °20′ and 37 °40′N where the sand content of surface sediments is also higher. Both indicate an enhanced sediment-water interaction in this area which results from an obstruction of the MOW flow by the ‘Principes d'Avis’ basement spur.
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  • 8
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    E-MORB glasses from the Gakkel Ridge (Arctic Ocean) at 87°N: evidence for the Earth's most northerly volcanic activity (1997)
    Elsevier
    In:  Earth and Planetary Science Letters, 152 (1-4). pp. 1-9.
    Details
    Publication Date: 2016-11-14
    Description: During the ARCTIC '91 expedition aboard RV Polarstern (ARK VIII/3) to the Central Arctic Ocean, a box corer sample on the Gakkel Ridge at 87 degrees N and 60 degrees E yielded a layer of sand-sized, dark brown volcanic glass shards at the surface of the sediment core. These shards have been investigated by petrographic, mineralogical, geochemical and radiogenic isotope methods. The nearly vesicle-free and aphyric glass shards bear only minute microphenocrysts of magnesiochromite and olivine (Fo(88-89)). Most glasses are fresh, although some show signs of incipient low-temperature alteration. From their shapes and sizes, the glass shards most likely formed by spalling of glassy rinds of a nearby volcanic outcrop. Geochemically, the glasses are relatively unfractionated tholeiites with E-MORB trace element compositions. Thus, they are quite similar to the previously investigated ARK IV/3-11-370-5 basalts from 86 degrees N. The Nd and Sr isotopic ratios of PS 2167-2 glasses are significantly lower than for ARK IV/3-11-370-5 basalts and suggest an isotopically heterogeneous mantle source of Gakkel Ridge MORE between 86 degrees and 87 degrees N. The positive Delta-8/4 Pb value (similar to 16) and high Sr-87/Sr-86 ratio (0.70270), found for PS 2167-2 glasses are similar to that of ARK IV/3-11-370-5 basalts and show the influence of the DUPAL isotopic anomaly in the high Arctic mantle. These results argue against the presence of an 'anti-DUPAL anomaly' in the mantle below the North Pole region and simple models of whole-mantle convection.
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  • 9
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    Variability of dissolved and particulate trace metals in the Kiel and Mecklenburg Bights of the Baltic Sea, 1990-1992 (1997)
    Elsevier
    In:  Marine Pollution Bulletin, 37 (2). pp. 112-122.
    Details
    Publication Date: 2017-10-05
    Description: Water samples from surface and bottom waters of two bights of the Baltic Sea were analysed for dissolved and/or particulate concentrations of Al, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb and Zn, in addition to the main oceanographic variables, at 27 stations during six cruises between February 1990 and July 1992. The metal values show distinct regional differences, with maximum concentrations at the near-shore stations, The levels of total Hg exhibit a significant negative relationship with salinity. In surface layers, seasonal differences due to biogenic uptake of elements could not be detected for any of the dissolved metals. In bottom waters, however, summer-time concentrations of a number of metals are in clear excess of winter levels either due to diffusion of metals (Go, Fe, Mn) from the sediments under low-oxygen or anaerobic conditions, or due to mineralization processes (Cd, Zn) of recently sedimented biogenic particulates. With the exception of Fe and Pb, the particulate fractions are of minor importance, with slight variabilities between the seasons only. The K-D values (ratio between metal concentrations in the particulate and dissolved fractions) decrease by more than two orders of magnitude in the order Fe-Pb-Mn-Co-Zn-Cd-Cu-Ni. Finally, the results are discussed with regard to a trace metal monitoring programme in the area.
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  • 10
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    Porin from the halophilic species Ectothiorhodospira vacuolata: cloning, structure of the gene and comparison with other porins (1997)
    Elsevier
    In:  Gene, 191 . pp. 225-232.
    Details
    Publication Date: 2019-01-22
    Description: The gene coding for the anion-specific porin of the halophilic eubacterium Ectothiorhodospira (Ect.) vacuolata was cloned and sequenced, the first such gene so analyzed from a purple sulfur bacterium. It encodes a precursor protein consisting of 374 amino acid (aa)-residues including a signal peptide of 22-aa residues. Comparison with aa sequences of porins from several other members of the Proteobacteria revealed little homology. Only two regions showed local homology with the previously sequenced porins of Neisseria species, Comamonas acidovorans, Bordetella pertussis, Alcaligenes eutrophus, and Burkholderia cepacia. Genomic Southern blot hybridization studies were carried out with a probe derived from the 5′ end of the gene coding for the porin of Ect. vacuolata. Two related species, Ect. haloalkaliphila and Ect. shaposhnikovii, exhibited a clear signal, while the extremely halophilic bacterium Halorhodospira (Hlr.) halophila (formerly Ect. halophila) did not show any cross-hybridization even at low stringency. This result is in good accordance with a recently proposed reassignment within the family Ectothiorhodospiraceae, which included the separation of the extremely halophilic species into the new genus Halorhodospira.
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  • 11
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    Heinrich Georg Bronn: Ein Brief von 1855 zur Evolutionstheorie von Darwins Werk von 1859 (1997)
    Springer
    In:  Geologische Rundschau, 87 (2). pp. 518-521.
    Details
    Publication Date: 2018-01-25
    Description: Rubrik "Neues aus dem Geologenarchiv (1997)"
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  • 12
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    Surface water changes in the Norwegian Sea during last deglacial and Holocene times (1997)
    Elsevier
    In:  Quaternary Science Reviews, 16 (10). pp. 1115-1124.
    Details
    Publication Date: 2016-09-19
    Description: Stable carbon and oxygen isotopes of the polar planktic foraminifera Neogloboquadrina pachyderma sinistral from sediment cores of the Norwegian Sea reveal several anomalous 13C and δ18O depletions in the surface water during the last glacial to interglacial transition and during the later Holocene. The depletions that are observed between the Last Glacial Maximum (LGM) and the end of the main deglacial phase were caused by massive releases of freshwater from thawing icebergs, which consequently resulted in a stratification of the uppermost surface water layer and a non-equilibrium between the water below and the atmosphere. At ~8.5 ka (14C BP) this strong iceberg melting activity ceased as defined by the cessation of the deposition of ice-rafted detritus. After this time, the dominant polar and subpolar planktic foraminiferal species rapidly increased in numbers. However, this post-deglacial evolution towards a modern-type oceanographic environment was interupted by a hitherto undescribed isotopic event (~7–8 ka) which, on a regional scale, is only identified in eastern Norwegian Sea surface water. This event may be associated with the final pulse of glacier meltwater release from Fennoscandia, which affected the onset of intensified coastal surface water circulation off Norway during a time of regional sea-level rise. All these data indicate that surface water changes are an integral part of deglacial processes in general. Yet, the youngest observed change noted around 3 ka gives evidence that such events with similar effects occur even during the later Holocene when from a climatic point of view relativelystable conditions prevailed.
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  • 13
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    Spatial and temporal distribution patterns of benthic foraminifera in the Northeast Water Polynya, Greenland (1997)
    Elsevier
    In:  Journal of Marine Systems, 10 (1-4). pp. 445-465.
    Details
    Publication Date: 2017-06-26
    Description: Abundance, biofacies and ATP content of benthic foraminifera (〉63 μm) were studied in the Northeast Water (NEW) Polynya (77–81°N, 5–17°W) over the ice-free summer, 1993, to investigate how a polynya system might influence the underlying benthic community. In the living assemblage, distinguished by Rose Bengal staining, over 60 taxa could be identified. The biofacies identified was similar to that of other Arctic shelf habitats. Foraminifera were counted in 3 size fractions (63–125 μm, 125–250 μm and 〉250 μm), with 65% of the foraminifera occurring in the smallest size fraction (63–125 μm). Total abundances (〉63 μm) in the uppermost 1 cm averaged approximately 200 ind/10 cm3 and declined down-core, as did the number of species. Abundances and species composition correlated positively with sediment chlorophyll and ATP content, with maxima occurring in the shallower northern regions of the polynya, suggesting a general dependence on food. Foraminera biomass was estimated to be 0.1-0.3 g Corg/m2. Abundances, biomass and ATP content were comparable to ice-free, deep-sea regions in the Norwegian Sea. Temporal changes observed over a 2 month period at one location were difficult to distinguish from spatial and analytical variability. Contrary to expectations, growth was unpronounced at the community and at a species level, implying either a delayed response of the benthic foraminiferal community to food inputs from the overlying water column or the presence of biological limitations other than food, such as predation.
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  • 14
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    Bioresuspension and biodeposition: a review (1997)
    Elsevier
    In:  Journal of Marine Systems, 11 (3-4). pp. 269-278.
    Details
    Publication Date: 2016-01-29
    Description: The present literature on biologically mediated fluxes from the benthic nepheloid layer (BNL) across the sediment-water interface into the sediment and vice versa is reviewed. The processes involved are categorised according to direct bioresuspension and biodeposition, i.e. direct interception of the animal with particles, and those effects, which are indirectly created by benthic organisms, e.g., changes of physical properties in the sediments, constructions like tubes and pits and the corresponding changes in hydrodynamic conditions. It is concluded that benthic organisms significantly increase the flux of particles across the interface and that the physically created fluxes are easily modified by a factor of 2 and more.
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  • 15
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    Late Quaternary sedimentation on the Portuguese continental margin: climate-related processes and products (1997)
    Elsevier
    In:  Palaeogeography, Palaeoclimatology, Palaeoecology, 130 (1-4). pp. 1-23.
    Details
    Publication Date: 2017-01-23
    Description: The late Quaternary sedimentary history of the continental margin off Portugal was reconstructed from sediment gravity cores. Hemipelagic sedimentation (lithofacies A) was dominant during glacial times. It was interrupted periodically by deposition of shelf- and upper-slope-derived silty and sandy terrigenous material by dilute turbidity currents (lithofacies B and C), ice-rafted debris during distinct periods of breakdown of North Atlantic ice sheets (Heinrich events, lithofacies D) and large amounts of pteropods (lithofacies F). Settling of biogenic particulate material (lithofacies E) prevailed during the Holocene, when sea level and sea surface temperatures were high and terrigenous shelf-input was low. Downslope transport was dominant on the northern part of the Portuguese margin, culminating in frequent turbidity current transport between 35 and 70 ka. This may be due to a humid climate and a high fluvial input. Pteropod muds are confined to cores south of 41°N. Prominent peaks in pteropod concentration were radiocarbon dated at 17.8 and 24.6 ka. Layers rich in ice-rafted debris (IRD) were found along the entire margin. The base of these layers have been dated at 13.6–15.9 14C ka, 21.0–22.0 14C ka, 33.8 14C ka and ±64.5 ka, which correspond well with the ages of Heinrich events 1, 2, 4 and 6 in the central North Atlantic. Heinrich events 0 (10.5 ka), 3 (27 ka) and 5 (50 ka) rarely influenced sedimentation on the Portuguese slope. A mineralogical study of the IRD within Heinrich layers suggests that most icebergs were derived from the Laurentide Ice Sheet in the Hudson Strait and Hudson Bay area through the Labrador Current and the Canary Current and flowed in a southward direction along the margin. IRD from European ice sheets may have been mixed in during Heinrich event 6. On their way along the margin the icebergs lost much of their sediment load due to melting of the ice in a progressively warmer climate. The southernmost latitude studied (37°N) may be close to the southeastern extension of iceberg transport during Heinrich events.
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  • 16
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    Boron concentrations and isotopic composition of the Icelandic mantle: evidence from glass inclusions in olivine (1997)
    Elsevier
    In:  Chemical Geology, 135 (1-2). pp. 21-34.
    Details
    Publication Date: 2017-12-08
    Description: Quenched tholeiitic glasses and glassy rims of tholeiitic lava flows and pillow lavas from the neovolcanic rift zone on Iceland (Reykjanes and Hengill fissure swarms) contain olivine phenocrysts (Fo87–91) with abundant primary glass inclusions. These inclusions and host glasses were analyzed by ion microprobe for boron concentrations and isotopic compositions. Inclusions are believed to represent primary or near-primary mantle melts that have not been modified at shallow levels. Boron concentrations and B/K ratios in these melt inclusions are highly variable (0.18–1.35 ppm B, B/K = 2.8 × 10−4−6.1 × 10−3), whereas their δ11B values are nearly constant (−11.3, Full-size image (〈1 K)). This indicates that the Icelandic mantle is likely to have a constant boron isotope composition similar to that previously proposed for the primitive mantle (Full-size image (〈1 K)). The Hengill host glasses are characterized by low concentrations of B (0.26–0.42 ppm) and δ11B values similar to melt inclusions (−11.3, Full-size image (〈1 K)). In contrast, the Reykjanes host glasses have higher δ11B values (∼ −3‰) at the same relatively low concentrations of B (0.43–0.44 ppm), which are likely to be due to interactions of the ascending magmas with the crustal rocks hydrothermally altered at low temperatures by seawater-derived fluids. Boron concentrations and B/K ratios in melt inclusions and matrix glasses correlate with TiO2, K2O and P2O5 contents, and La/Sm)n ratios. Boron contents recalculated on the basis of melt inclusion compositions for the Icelandic mantle are slightly different for the Reykjanes and Hengill areas (0.21, 1σn ± 0.05 and 0.13, 1σn ± 0.03 ppm B, respectively). This is likely to reflect the presence of zones within the Icelandic mantle variously enriched and/or depleted in boron of similar isotopic composition.
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  • 17
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    Climate: Is the past the key to the future? (1997)
    Springer
    In:  Geologische Rundschau, 86 (2). pp. 471-491.
    Details
    Publication Date: 2019-01-22
    Description: The climate of the Holocene is not well suited to be the baseline for the climate of the planet. It is an interglacial, a state typical of only 10% of the past few million years. It is a time of relative sea-level stability after a rapid 130-m rise from the lowstand during the last glacial maximum. Physical geologic processes are operating at unusual rates and much of the geochemical system is not in a steady state. During most of the Phanerozoic there have been no continental ice sheets on the earth, and the planet’s meridional temperature gradient has been much less than it is presently. Major factors influencing climate are insolation, greenhouse gases, paleogeography, and vegetation; the first two are discussed in this paper. Changes in the earth’s orbital parameters affect the amount of radiation received from the sun at different latitudes over the course of the year. During the last climate cycle, the waxing and waning of the northern hemisphere continental ice sheets closely followed the changes in summer insolation at the latitude of the northern hemisphere polar circle. The overall intensity of insolation in the northern hemisphere is governed by the precession of the earth’s axis of rotation, and the precession and ellipticity of the earth’s orbit. At the polar circle a meridional minimum of summer insolation becomes alternately more and less pronounced as the obliquity of the earth’s axis of rotation changes. Feedback processes amplify the insolation signal. Greenhouse gases (H2O, CO2, CH4, CFCs) modulate the insolation-driven climate. The atmospheric content of CO2 during the last glacial maximum was approximately 30% less than during the present interglacial. A variety of possible causes for this change have been postulated. The present burning of fossil fuels, deforestation, and cement manufacture since the beginning of the industrial revolution have added CO2 to the atmosphere when its content due to glacial-interglacial variation was already at a maximum. Anthropogenic activity has increased the CO2 content of the atmosphere to 130% of its previous Holocene level, probably higher than at any time during the past few million years. During the Late Cretaceous the atmospheric CO2 content was probably about four times that of the present, the level to which it may rise at the end of the next century. The results of a Campanian (80 Ma) climate simulation suggest that the positive feedback between CO2 and another important greenhouse gas, H2O, raised the earth’s temperature to a level where latent heat transport became much more significant than it is presently, and operated efficiently at all latitudes. Atmospheric high- and low-pressure systems were as much the result of variations in the vapor content of the air as of temperature differences. In our present state of knowledge, future climate change is unpredictable because by adding CO2 to the atmosphere we are forcing the climate toward a “greenhouse” mode when it is accustomed to moving between the glacial–interglacial “icehouse” states that reflect the waxing and waning of ice sheets. At the same time we are replacing freely transpiring C3 plants with water-conserving C4 plants, producing a global vegetation complex that has no past analog. The past climates of the earth cannot be used as a direct guide to what may occur in the future. To understand what may happen in the future we must learn about the first principles of physics and chemistry related to the earth’s system. The fundamental mechanisms of the climate system are best explored in simulations of the earth’s ancient extreme climates.
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  • 18
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    Iron species determination to investigate early diagenetic reactivity in marine sediments (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 (1). pp. 63-72.
    Details
    Publication Date: 2017-09-26
    Description: Iron speciation was determined in hemiplegic sediments from a high productivity area to investigate systematically the early diagenetic reactivity of Fe. A combination of various leaching agents (1 M HCI, dithionite buffered in citrate/acetic acid, HF/H2SO4, acetic Cr(II)) was applied to sediment and extracted more than 80% of total Fe. Subsequent Fe species determination defined specific mineral fractions that are available for Fe reduction and fractions formed as products of Fe diagenesis. To determine the Fe speciation of (sheet) silicates we explored an extraction procedure (HF/H2SO4) and verified the procedure by application to standard rocks. Variations of Fe speciation of (sheet) silicates reflect the possible formation of Fe-bearing silicates in near surface sediments. The same fraction indicates a change in the primary input at greater depth, which is supported by other parameters. The Fe(II)/ Fe(III) -ratio of total sediment determined by extractions was compared with Mössbauer-spectroscopy ] at room temperature and showed agreement within 10%. M6ssbauer-spectroscopy indicates the occurrence of siderite in the presence of free sulfide and pyrite, supporting the importance of microenvironments during mineral formation. The occurrence of other Fe(II) bearing minerals such as ankerite (Ca-, Fe-, Mg-carbonate) can be presumed but remains speculative.
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  • 19
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    Oxygen isotopes in marine diatoms: a comparative study of analytical techniques and new results on the isotope fractionation during phytoplankton growth (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 . pp. 2275-2280.
    Details
    Publication Date: 2017-08-09
    Description: Oxygen isotope analyses of marine diatoms were performed in two independent ways. Stepwise fluorination of hydrous opal-A results in plateau δ180 values representing the isotopic composition of the silica frame oxygen. A method of controlled isotope exchange before silica dehydration also produces reliable results, although the exchangeability of the silica was variable. Consequently, a calibration of the isotope exchange method using the results from stepwise fluorination experiments is very useful (and sometimes essential) in order to select a water vapor of an appropriate isotopic composition to be used for equilibration. Sediment diatom samples Ethmodiscus rex and Thalassiothrix longissima from the Antarctic and the North Atlantic Ocean, respectively, show strong 180 enrichments of 46.8 and 44.1‰, which are caused by large isotope fractionation occurring at the low temperature prevailing during silica-water isotope exchange reactions. However, phytoplankton samples from surface waters of the Norwegian-Greenland Sea and the Bellingshausen Sea (Antarctica) have δ180 values between 30.4 and 35.0‰. Thus, the true silica-water isotopic fractionation is approximately 3 to 10‰ lower than the temperature-dependent silica-water equilibrium published in the literature for sedimentary diatoms. Our results indicate that successive isotope exchange reactions of diatomaceous silica with ambient seawater and/or pore water determine the isotope values of diatoms in sediments.
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  • 20
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    Quantifying fluid flow, solute mixing and biogeochemical turnover at cold vents of the eastern Aleutian subduction zone (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 (24). pp. 5209-5219.
    Details
    Publication Date: 2017-08-03
    Description: In situ oxygen fluxes were measured at vent sites in the Aleutian trench at a water depth of almost 5000 m using a TV-guided benthic flux chamber. The flux was 2 orders of magnitude greater than benthic oxygen fluxes in areas unaffected by venting on the continental margin off Alaska. Porewater profiles taken from the surface sediment below a vent site showed high concentrations of sulfide, methane, and ammonia. The reduced carbon and nitrogen compounds are transported to the vent site by fluids expelled from deeper anoxic sediment layers by the forces of plate convergence. The tectonically driven fluid flow was determined from the biochemical turnover in vent communities and was found to be 3.4 ± 0.5 m yr−1. A model was used to quantify the transport of silica, Ca2+, and sulfate via diffusion, advection, and bioirrigation through the surface sediments of a vent site. A nonlocal mixing coefficient of 20–30 yr−1 was determined by fitting the model curves to the measured porewater profiles showing that the transport of solutes within the near-surface sediments and across the sediment-water interface is dominated by the activity of the vent fauna. Sulfate-containing oceanic bottom water and methane-rich vent fluids were mixed below the clam colony to produce sulfide and a CaCO3 precipitate. The vent biota shape their immediate environment and control the sediment-water exchange and the benthic fluxes at vent sites. The oxygen consumption at vent sites is a major sink for oxygen at the study area.
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  • 21
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    Modelling the cod larvae drift in the Bornholm Basin in summer 1994 (1997)
    Elsevier
    In:  Continental Shelf Research, 17 (14). pp. 1765-1784.
    Details
    Publication Date: 2019-09-23
    Description: A combined 3-D physical oceanographic model and a field sampling program was performed in July and August 1994 to investigate the potential drift of larval Baltic cod from the center of spawning effort in the Bornholm Basin, Baltic Sea. The goal of this exercise was to predict the drift trajectories of cod larvae in the Bornholm Basin, thereby aiding in the development of future sampling programs as well as the identification of processes influencing larval retention/dispersion in the Bornholm Basin. Distributions of variables (T, S and larval distribution) were obtained utilizing a three-dimensional eddy-resolving baroclinic model of the Baltic Sea based on the Bryan-Cox-Semtner code. Larval drift was simulated by the incorporation of a passive tracer into the model utilized to represent individual cod larvae. Additionally, simulated Lagrangian drift trajectories are presented. For model purposes, initial fields of temperature, salinity and cod larvae concentration for the Bornholm Basin were constructed by objective analysis using observations taken during a research survey in early July, 1994. Outside the Bornholm Basin generalized hydrographic features of the Baltic Sea were utilized with the baroclinic model forced by wind data for the whole Baltic taken from the Europa-Modell (EM) of the German weather service, Offenbach. Verification of simulations was performed by comparison with field measurements of hydrographic variables and ADCP derived current measurements taken during the surveys. In general, most of the hydrographic features observed during the second research cruise are correctly simulated, with variations mainly attributed to the prescribed initial conditions outside the Bornholm Basin. Results from larval sampling during the second cruise could not entirely confirm the modeled larval distributions due to the low numbers of larvae captured. However, the modeled results based on the agreement of the flow fields and hydrographic properties with observed features suggest that predictions of larval distributions can be made with a high degree of confidence if appropriate larval behaviours are included in the simulations.
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  • 22
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    U-Pb single zircon dating under cathodoluminescence control (CLC-method): application to polymetamorphic orthogneisses (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 139 (1-4). pp. 287-297.
    Details
    Publication Date: 2017-08-25
    Description: The dating of polymetamorphic rocks with the U-Pb zircon method often results in discordant data. Thus a new technique combining cathodoluminescence imaging (CL) and thermal ion mass spectrometry (TIMS) measurements was developed. Cathodoluntinescence-controlled UPb dating (CLC-method) works with bisected zircons and was successfully applied to the multistage S-type granitoids of the Swiss Silvretta nappe. CLC-method enables the resolution of the different anatectic events and later major overprints (Cambrian, Ordovician, Silurian) and gives information about the protolith (Archaean) of the investigated gneisses. This is achieved by conventional UPb dating of selected grains, recovered from the SEM (scanning electron microscope) mounts after cathodoluminescence (CL) imaging. Applying this new combination of two established techniques yields geologically meaningful UPb zircon ages even for complex polymetamorphic rocks.
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  • 23
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    Particle flux in deep seas: regional characteristics and temporal variability. (1997)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 44 (8). pp. 1377-1403.
    Details
    Publication Date: 2016-09-30
    Description: Particle flux data have been collated from the literature representing most areas of the open ocean to determine regional trends in deep water flux and its seasonal variability. Organic carbon flux data normalised to a depth of 2000 m exhibits a range of an order of magnitude in areas outside the polar domains (0.38 to 4.2 g/m2/y). In polar regions the range is wider (0.01–5.9 g/m2/y). Latitudinal trends are not apparent for most components of the flux although calcite flux exhibits a poleward decrease. Limited data from polar regions show fluxes of opaline silica not significantly higher than elsewhere. The variability of flux over annual cycles was calculated and expressed as a Flux Stability Index (FSI) and the relationship between this and vertical flux of material examined. Somewhat surprisingly there is no significant relationship between FSI and fluxes of dry mass, organic carbon, inorganic carbon or opaline silica. At each site, net annual primary production was determined using published satellite derived estimates. There is a negative but weak relationship between FSI and the proportion of primary production exported to 2000 m (e2000 ratio). The most variable of the non-polar environments export to 2000 m about twice as much of the primary production as the most stable ones. Polar environments have very low e2000 ratios with no apparent relationship to FSI. At primary production levels below 200 g C/m2/y there is a positive correlation between production and organic carbon flux at 2000 m but above this level, flux remains constant at about 3.5g C/m2/y. A curve derived to describe this relationship was applied to estimates of annual primary production in each of 34 of the open ocean biogeochemical provinces proposed by Longhurst et al. (1995). Globally, open ocean flux of organic carbon at 2000 m is 0.34 Gt/yr which is 1% of the total net primary production in these regions. This flux is nearly equally divided between the Atlantic, Pacific and Southern Oceans. The Indian and Arctic oceans between them only contribute 5% to the total. The eight planktonic climatological categories proposed by Longhurst (1995) provide a most useful means of examining the data on flux and its variability. A characteristic level of FSI was found in each category with highest levels in the tropics and lowest levels in the Antarctic. There is also a characteristic level of export ratio in each category with the highest in monsoonal environments (1.7%) and the lowest in Antarctica (0.1%)
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  • 24
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    Asymmetry parameters of the phase function for isolated and densely packed spherical particles with multiple internal inclusions in the geometrics optics limit (1997)
    Elsevier
    In:  Journal of Quantitative Spectroscopy and Radiative Transfer, 57 . pp. 767-794.
    Details
    Publication Date: 2017-10-05
    Description: Since large, homogeneous dielectric particles have positive asymmetry parameters even when they are densely packed, it has been hypothesized that negative asymmetry parameters retrieved with Hapke's phenomenological model of bidirectional reflectance result from a complicated internal structure of planetary regolith particles. This paper tests that hypothesis by theoretically computing asymmetry parameters for isolated and densely packed composite spherical particles with size typical of regolith grains. It is assumed that the wavelength of the scattered light is much smaller than the particle size, and that particles are filled with large numbers of small inclusions. The computations show that it is essentially impossible to make asymmetry parameters of planetary regolith particles even slightly negative by filling the particles with large numbers of internal inclusions in the form of voids and/or grains with a refractive index substantially different from that of the host medium. Asymmetry parameters are positive even for densely packed composite particles with no internal absorption and extreme values of the internal scattering coefficient. Furthermore, they are sharply increased by even modest absorption inside composite particles, by reducing the refractive index contrast between the inclusions and the host particles, and/or by decreasing the packing density. Thus, the negative asymmetry parameters retrieved with Hapke's model need another explanation rather than assuming that they are real and are the result of a complicated internal structure of regolith particles. Besides the opposition-effect term, Hapke's model is nothing more than an approximate solution of the radiative transfer equation which inherently violates the energy conservation law. Therefore, the negative asymmetry parameters are likely to be numerical artefacts resulting from the approximations made in the model.
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  • 25
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    Secular changes of lead and neodymium in central Pacific seawater recorded by a Fe-Mn crust (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta (61). pp. 3957-2974.
    Details
    Publication Date: 2016-05-25
    Description: Oceanic and atmospheric circulation patterns varied considerably during the Tertiary and Quaternary and influenced the geochemical cycles of elements in seawater. We report the first resolution lead and neodymium isotopic record of such changes at a high time resolution in two depths profiles from a hydrogenous FeMn crust. The crust, Va13-2, is located in the central Pacific (146°W, 9°25′N, 4830 m) and has previously been dated by 230Th and 10Be. The first profile was drilled with a sample time resolution of ∼3 kyr and allows evaluation of short-term changes to lead and neodymium sources to central Pacific seawater over the last 400 kyr (marine δ18O stages 2 to 11). Longer-term changes were monitored at lower time resolution in a second profile to an age of 10 Ma. Short-term variations in lead and neodymium isotope ratios are resolved in the high resolution profile (0 to 400 kyr). Superimposed on the short-term variations is a secular decrease in Full-size image (〈1 K) ratios beginning at ∼130 kyr in marine δ18O stage 5, implying a change in the lead sources to the central Pacific. Lead and neodymium isotopic compositions indicate an increased influence from Central American eolian sources to Pacific seawater at this time. Lead isotopes are found to be statistically more variable during interglacial than glacial periods. These observations are supported by the greater eolian dust fluxes found in sediment cores from the equatorial Pacific during interglacial stages. The most important paleoceanographic event of the last 10 Ma to affect Pacific seawater was the closure of the Panama gateway. Changes in lead and neodymium isotopes in Val3-2 during the last 10 Ma occurred along with gradual closure of the Panama straits. However, these changes did not occur in tandem: while neodymium isotope ratios increase between 10 and 8 Ma, lead isotope ratios remain constant. In contrast, the period 7 to 1 Ma is marked by a secular increase in lead isotope ratios but nearly constant neodymium. These changes are consistent with a source of radiogenic lead and neodymium conveyed by the Circumpolar Current into the Pacific, rather than by the Panama gateway, and involve 20 to 40% Southern Component Water (SCW) input of lead and neodymium. Modelling of lead and neodymium isotopic mixing between the different water masses involved in generating Pacific deep waters lead us to the following conclusions: (1) Small variations in the strength and composition of North Atlantic Deep Water (NADW) have a relatively minor effect on the amounts of lead and neodymium from SCW contributing to the Pacific and (2) an enhanced SCW flow with an open isthmus of Panama, as suggested by General Circulation Models (GCM), requires a corresponding reduction in NADW Pb and Nd contributions to SCW. The general agreement between the isotopic compositions of surface layers of Mn nodules, integrated over such long time intervals, and those of present-day bottom waters at their respective locations show that the present-day ocean circulation pattern has dominated through the Pleistocene. Our study of Mn crust Va13-2 shows that shorter-term changes in lead and neodymium isotope ratios can be resolved, provided that such crusts are sampled at an appropriate time resolution.
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  • 26
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    Strontium isotopic, chemical, and sedimentological evidence for the evolution of Lake Lisan and the Dead Sea (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 . pp. 3975-3992.
    Details
    Publication Date: 2017-09-26
    Description: Precise strontium isotope ratios, combined with chemical analyses and sedimentological information, are used to monitor the water sources and the evolution of the Dead Sea and its late Pleistocene precursor, Lake Lisan (70-18 kyr B.P.). The materials analyzed include bulk aragonite, water-leached soluble salts, and residual aragonite and gypsum from the Lisan Formation in the Perazim Valley (near the SW shore of the Dead Sea). The residual aragonite and the associated soluble salts display systematic fluctuations in 17Sr86Sr ratios between 0.70803 and 0.70806 and from 0.70805 to 0.70807, respectively. In individual soluble salt-residual aragonite pairs, the soluble salt displays a higher 87Sr86Sr ratio. Gypsum samples yield 17Sr86Sr ratios similar to the soluble salts from adjacent layers in the section. This shows that, in individual samples, the source of Sr in aragonite was distinct from that in soluble salts and the gypsum. The sterility of the Lisan sediments, their strictly nonbioturbated fine lamination, and their high content of chloride salts indicate that Lake Lisan was a saline, or even hypersaline water body. In the absence of alternative sources of HCO3− and S042− the abundance of primary aragonite and gypsum in the Lisan column reflects an import of very large volumes of freshwater into the otherwise saline lake, resulting in a density stratification of this water body. The history of the upper water layer and that of the lower brine is reflected in the chemical and strontium isotope composition of the aragonite and in that of the associated soluble salts and in the gypsum samples, respectively. Whereas the bicarbonate and much of the Ca2+ required for aragonite crystallization were supplied by the freshwater, the complementary Ca2+ (and Sr 2+) were added by the lower brine. The upper water layer of Lake Lisan acted as a SO42− capacitor during the lake's rise periods. It was removed therefrom, as prominent gypsum beds, upon climatic-induced (drier period) mixing or even complete overturn of the lake. The evolution of Lake Lisan took place between two distinct modes. The first was characterized by an extensive supply of freshwater and resulted in a rise of the lake's level, a (density) layered structure, and precipitation of aragonite. The second mode was marked by a diminishing freshwater input, resulting in mixing or complete overturn of its water, and precipitation of gypsum. These two modes reflect the climatic evolution of the region in the late Pleistocene which fluctuated between drier and wetter periods. The transition to the Holocene is accompanied by the dry up of Lake Lisan and its contraction to the present Dead Sea.
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  • 27
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    Slow sedimentation and Ir Anomalies at the Cretaceous-Tertiary Boundary (1997)
    Springer
    In:  Geologische Rundschau, 86 . pp. 168-177.
    Details
    Publication Date: 2018-03-21
    Description: Iridium enrichments, at or close to the K/T boundary, are often cited as evidence for impacts of cosmic bodies or volcanic events, or both, that resulted in mass extinctions. A third possible explanation for the high Ir concentrations, that the enrichments were caused by the cosmic micrometeorite flux during times of slow Sediment accumulation, has generally been rejected. In this study we examine the Ir/Au ratios and conclude that they may indicate enrichment of siderophile elements by slow sedimentation. In addition, the concept of slow sedimentation at the K/T boundary is consistent with many aspects of the K/T boundary research such as the gradual decline of the species before the major extinction level and recent reports of faunal transitions from Cretaceous to Tertiary without sudden extinctions, hiatuses or Ir anomalies.
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  • 28
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    Elemental distribution and neodymium isotopic composition of Silurian metasediments, western Maine, USA: Redistribution of the rare earth elements (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 (9). pp. 1847-1861.
    Details
    Publication Date: 2017-09-26
    Description: Pelitic schists from the lower garnet to lower staurolite zones from the Rangeley, Perry Mountain, and Smalls Falls formations of western Maine were analyzed for major elements, trace elements, and neodymium isotopes. These formations were derived from highlands created during the Taconian orogeny, deposited into a trough, and metamorphosed during subsequent orogenic events. Most major and trace element abundances relative to Al2O3 were statistically identical between zones of the same formation, as well as between formations. Although the average major element composition of these formations are the same, there are systematic variations in some elements. Notably, plots of SiO2 vs. Al2O3 and K2O vs. Al2O3 suggest that most of the variation could be produced by mixing of a fairly constant ratio of clay minerals and feldspar with varied amounts of quartz due to sorting in the sedimentary system. Different amounts of these minerals should not influence the shape of the REE patterns of the metapelites, but higher amounts of quartz and feldspar may dilute the REEs and most elemental abundances of the clay minerals and lead to lower elemental abundances. The major difference between the samples within the Perry Mountain Formation are different LREE and MREE abundances relative to Al2O3 which are not correlated to differences in major element or other trace element abundances relative to Al2O3. The samples in the Perry Mountain with higher LREE and MREE abundances have, for example, 42.3 ± 8.3 ppm, and those with low abundances have 5.6 ± 3.6 ppm. The samples with the high REE abundances of the Perry Mountain Formation are similar in abundances and REE patterns to those of the Rangeley and Smalls Falls formations typical of mudstones derived from granitoids. Another difference between the low and high REE abundance samples are the calculated Tdm model ages. The high REE abundance samples of the Perry Mountain Formation show Tdm similar to the samples of the Rangeley Formation, with ages of about 1.7–1.8 Ga. The Perry Mountain samples with low REE abundances, however, give unrealistically old Tdms between 2.5 and 5.3 Ga. These unrealistically old Tdms are due to the relatively high Sm/Nd ratios (compared to crustal values) which are characteristic of samples of the Perry Mountain Formation with lower REE abundances. We therefore suggest that these samples may be indicators for open system behavior of the neodymium isotopic system. The timing of this disturbance of the neodymium isotope system is difficult to determine and cannot be tied to weathering or a definite postdepositional event. The complexities of the data suggest more than one resetting event. The most likely event that could have produced much of the movement of the LREEs and MREEs could have been due to small scale migration between anoxic hemipelagites and turbidite mudstones during diagenesis, but some migration may have continued during metamorphism in order to reconcile the neodymium isotopic data.
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  • 29
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    Rhodospira trueperi, gen. nov. and spec. nov., a new phototrophic Proteobacterium of the alpha group (1997)
    Springer
    In:  Archives of Microbiology, 168 (1). pp. 39-45.
    Details
    Publication Date: 2016-05-26
    Description: A new phototrophic purple bacterium was isolated from a flat, laminated microbial mat in a salt marsh near Woods Hole, Mass., USA. The spiral-shaped bacterium was highly motile and had bipolar tufts of flagella and intracytoplasmic membranes of the vesicular type. The major photosynthetic pigments were identified as the carotenoid tetrahydrospirilloxanthin and bacteriochlorophyll b. The long wavelength in vivo absorption maximum of the bacteriochlorophyll was at 986 nm. The marine bacterium showed optimal growth in the presence of 2% NaCl. It utilized a number of organic substrates as carbon and energy sources and required vitamins and sulfide as a reduced sulfur source for growth. In the presence of sulfide, elemental sulfur globules were formed outside the cells. Elemental sulfur was not further oxidized to sulfate. The new isolate had a unique lipid and fatty acid composition, and according to the 16S rRNA gene sequence, it is most similar to Rhodospirillum rubrum. It is described as a new species and assigned to a new genus with the proposed name Rhodospira trueperi.
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  • 30
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    Chromatium glycolicum sp. nov., a moderately halophilic purple sulfur bacterium that uses glycolate as substrate (1997)
    Springer
    In:  Archives of Microbiology, 167 (1). pp. 11-18.
    Details
    Publication Date: 2016-05-26
    Description: From the microbial mats that develop in Solar Lake, a new purple sulfur bacterium was isolated. This strain (Chromatium strain SL 3201) was morphologically similar to Chromatium gracile and Chromatium minutissimum. Chromatium SL 3201 was found to be a moderate halophile with a growth range between 2 and 20% NaCl (optimum 4-5% NaCl) and was able to grow photo-organotrophically using glycolate and glycerol. It is the first described phototrophic sulfur bacterium able to use glycolate. According to NaCl requirements and utilization of organic compounds, the strain is not related to any known species of the genus Chromatium. On the basis of its 16S rRNA gene sequence, it clusters with other Chromatium species and is most similar to Chromatium salexigens and Chr. gracile, but it is sufficiently separated to be considered as a new species of the genus. It is, therefore, described as Chromatium glycolicum sp. nov.
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  • 31
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    Biogeochemical dynamics and the silicon cycle in the Atlantic sector of the Southern Ocean during austral spring 1992 (1997)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 44 (1/2). pp. 69-90.
    Details
    Publication Date: 2016-10-10
    Description: High biogenic silica (BSi) concentrations (maximum: 11.7μmoll−1) were recorded during late November at the southern border of the Polar Frontal region (PFr). Position of the BSi maximum at depth suggested the occurrence of a sinking diatom population. By contrast, siliceous biomass was low (BSi 〈0.6 μmol l−1) in the Marginal Ice Zone (MIZ) despite a sea-ice retreat of 200 km during the study period. Diatoms released from the receding ice were not actively growing. The Permanently Open Ocean Zone also showed very low BSi biomass (〈0.5μmol l−1) and appeared as an area where phytoplankton are not dominated by siliceous organisms, especially in its middle part where BSi/POC (particulate organic carbon) molar ratios ranged between 0.04 and 0.06 at 53°S, from surface to 200 m depth. At the southern border of the PFZ, the bloom coincided with an area of high lithogenic silica concentrations probably of aeolian origin. In addition, BSi/POC molar ratios measured in the PFZ were the highest ever recorded in the surface waters of the Southern Ocean (maximum: 1.75). This could be due to the presence of heavily silicified diatoms such as Fragilariopsis kerguelensis or also could reflect the more rapid recycling of POC as compared to BSi. Within the bloom area BSi concentrations were positively correlated to pyrophaeophytin pigments, possibly indicating the occurrence of a senescent diatom population. High concentrations of BSi (〉 1.5 μmol Si 1−1) extended to 200 m between 49°S and 51°S. Numerous empty frustules also were observed, suggesting significant sedimentation of siliceous particles between 49°S and 51°S. Estimates of the BSi production of the Polar Frontal region are derived from 14C primary production and appropriate BSi/POC ratios, and implications for the total annual production of BSi for the Southern Ocean are discussed.
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  • 32
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    Mössbauer spectroscopic studies on the iron forms of deep-sea sediments (1997)
    Springer
    In:  Physics and Chemistry of Minerals, 24 . pp. 281-293.
    Details
    Publication Date: 2017-01-03
    Description: Mössbauer spectroscopy was applied to characterize the valence states Fe(II) and Fe(III) in sedimentary minerals from a core of the Peru Basin. The procedure in unraveling this information includes temperature-dependent measurements from 275 K to very low temperature (300 mK) in zero–field and also at 4.2 K in an applied field (up to 6.2 T) and by mathematical procedures (least-squares fits and spectral simulations) in order to resolve individual spectral components. The depth distribution of the amount of Fe(II) is about 11% of the total Fe to a depth of 19 cm with a subsequent steep increase (within 3 cm) to about 37%, after which it remains constant to the lower end of the sediment core (at about 40 cm). The steep increase of the amount of Fe(II) defines a redox boundary which coincides with the position where the tan/green color transition of the sediment occurs. The isomer shifts and quadrupole splittings of Fe(II) and Fe(III) in the sediment are consistent with hexacoordination by oxygen or hydroxide ligands as in oxide and silicate minerals. Goethite and traces of hematite are observed only above the redox boundary, with a linear gradient extending from about 20% of the total Fe close to the sediment surface to about zero at the redox boundary. The superparamagnetic relaxation behavior allows to estimate the order of magnitude for the size of the largest goethite and hematite particles within the particle-site distribution, e.g. ∼170 Å and ∼50 Å, respectively. The composition of the sediment spectra recorded at 300 mK in zero-field, apart from the contributions due to goethite and hematite, resembles that of the sheet silicates smectite, illite and chlorite, which have been identified as major constituents of the sediment in the 〈2 μm fraction by X-ray diffraction. The specific “ferromagnetic” type of magnetic ordering in the sediment, as detected at 4.2 K in an applied field, also resembles that observed in sheet silicates and indicates that both Fe(II) and Fe(III) are involved in magnetic ordering. This “ferromagnetic” behavior is probably due to the double-exchange mechanism known from other mixed-valence Fe(II)–Fe(III) systems. A significant part of the clay-mineral iron is redox sensitive. It is proposed that the color change of the sediment at the redox boundary from tan to green is related to the increase of Fe(II)–Fe(III) pairs in the layer silicates, because of the intervalence electron transfer bands which are caused by such pairs.
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  • 33
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    Physical anatomy of fronts and surface waters in the ACC near the 6°W meridian during austral spring 1992 (1997)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 44 (1/2). pp. 23-50.
    Details
    Publication Date: 2016-10-10
    Description: Small-scale features of the Antarctic Circumpolar Current (ACC) along a meridional section at 6°W between the Polar Front and the ACC-Weddell Gyre Boundary Front are discussed using data collected during the austral spring cruise ANT X/6 of R. V. Polarstern organized within the framework of the European IGBP-JGOFS (Southern Ocean). The section covered three distinct fronts, namely the Polar Front, the Southern Polar Front (also Southern ACC Front), and the ACC-Weddell Gyre Boundary Front. Physical measurements during repeated transects over a period of 6 weeks in October/November revealed a large variability in the Polar Frontal region, indicating meandering and eddy shedding. The positions of the Southern Polar Front and the ACC-Weddell Gyre Boundary Front were observed to be far more stable than that of the Polar Front. A possible reconstruction of the meandering flow field near the Polar Front, based upon the physical observations, is presented. Details in the flow field coincide with the spatial distribution of a number of biological parameters such as phytoplankton biomass and species, and photosynthetic pigments. Although a causal relationship between them is likely, biomass enhancement cannot be understood simply in terms of macronutrients from deeper layers entering the euphotic zone, as substantiated for other oceanic frontal regions, because macronutrients do not limit phytoplankton blooms. This process, however, can be important for the micronutrient iron. Evidence is presented that the Antarctic Zone of the ACC can be subdivided into a number of spheres of influence related to the fronts. Interleaving of water is apparent between positions within such a region, but not between the regions.
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  • 34
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    The Foundation Seamount chain: a first survey and sampling (1997)
    Elsevier
    In:  Marine Geology, 137 (3-4). pp. 191-200.
    Details
    Publication Date: 2017-06-23
    Description: The Foundation Seamounts form a 1400 km-long chain on the Pacific plate from 32 °S, 127 °W to the Pacific-Antarctic spreading axis at 38 °S, 111 °W. Previously only known from sparse single-beam echosoundings and satellite altimetry, we present here the first multibeam bathymetric survey and geological sampling results. We confirm that the submarine topography correlates with the altimetry, and that the chain is volcanic rather than tectonic or microcontinental in origin. The chain can be divided up morphologically and geochemically into three section: (1) west of 125 °W large flat-topped volcanoes composed of incompatible-element depleted lavas ( ≈ 1) of a near-ridge origin with little or no plume influence, (2) between 125 and 115 °W true intraplate volcanoes with incompatible element enrichment ( 〉 1.9) generated over the Foundation plume, (3) east of 115 °W E-W-trending volcanic ridges with compositions ( 2.0-0.3) suggestive of interaction between the plume and the Pacific-Antarctic spreading axis. On the spreading axis moderate incompatible element enrichments ( ≈0.8, cf. ≈ 0.3 outside the Foundation area) also suggest plume influence. It appears that the activity of the Foundation plume in the last few million years has (1) significantly waned and (2) become wholly channeled towards the spreading axis. The Foundation plume may be in the process of “dying”.
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  • 35
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    High benthic fertility and taphonomy of foraminifera: a case study of the Skagerrak, North Sea (1997)
    Elsevier
    In:  Marine Micropaleontology, 31 (3-4). pp. 157-175.
    Details
    Publication Date: 2016-06-15
    Description: The Skagerrak basin is a deep water extension of the North Sea. It is of particular interest as an analogue for past epicontintal shelf basins because it presents environmental contrasts with the adjacent shelf seas. In this study the distribution patterns of benthic foraminifera have been used to infer taphonomic and oceanographic processes. Only by separating living from dead assemblages is it possible to interpret taphonomic changes. The transport of foraminiferal tests to the Danish slope is inferred from the presence there of dead exotic tests whose provenance is considered to be from the south. The abundance of detrital organic matter on the Danish slope is likewise inferred to be sourced from the same direction. Thus, the Danish slope is interpreted to be a depositional sink. Apart from transport, another taphonomic process is the dissolution of calcareous tests. This is clearly demonstrated both by the fragility of some tests as viewed under the microscope and by the disparity between the composition of the living and dead factor associations. In the deep basin in particular, the two predominantly calcareous living associations are replaced by a single predominantly agglutinated dead association due to carbonate dissolution. The Danish slope of the Skagerrak Basin is demonstrated to be an area of high benthic fertility. This is based on the high density of living (stained) benthic foraminifera (comparable with that of the Mississippi delta), particularly the abundance of Stainforthia fusiformis, an opportunistic species, and tubular agglutinated forms. The fertility is linked with the high abundance of particulate organic matter here. Previous regional studies have focused on total (living plus dead) distributions of 〉 100 or 〉 125 μm sized foraminifera. These factor assemblages are distinct from the 〉63 μm living and dead associations described here.
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  • 36
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    Oxygen isotope composition of living Neogloboquadrina pachyderma (sin.) in the Arctic Ocean (1997)
    Elsevier
    In:  Earth and Planetary Science Letters, 146 (1-2). pp. 47-58.
    Details
    Publication Date: 2016-11-14
    Description: Data from the Nansen Basin of the Arctic Ocean are used to investigate the habitat and conditions under which the polar planktic foraminifer Neogloboquadrina pachyderma (sin.) calcifies. The vertical distribution of δ18O values of net-sampled speciments, together with their abundances and proportion of calcification, are compared with δ18O values from both water samples and foraminiferal tests from core-top sediments. Within the Nansen Basin the average depth of habitat of N. pachyderma (sin.) changes from about 150 m in the southern part to about 80 m in the northern. The average depth of calcification, however, in both regimes varies between 100 and 200 m water depth. δ18O data from net sampled N. pachyderma (sin.) are directly reflected in the core-top sediment data, but compared to equilibrium calcite δ18O values derived from measurements of the ambient water, a consistent offset of about 1‰ over all depth intervals is observed. While in the southern part of the Nansen Basin advection through Fram Strait of planktic foraminifers from further south may play a role, the data from the northern part of the Nansen Basin give clear evidence that the observed offset in δ18O values is caused by a vital effect of N. pachyderma (sin.).
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  • 37
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    Thiorhodococcus minus, gen. nov., sp. nov., a new purple sulfur bacterium isolated from coastal lagoon sediments (1997)
    Springer
    In:  Archives of Microbiology, 168 (1). pp. 16-23.
    Details
    Publication Date: 2016-05-26
    Description: A new marine phototrophic purple sulfur bacterium (strain CE2203) was isolated in pure culture from a man-made coastal lagoon located on the Atlantic coast (Arcachon Bay, France). Single cells were coccus-shaped, did not contain gas vesicles, and were highly motile. Intracellular photosynthetic membranes were of the vesicular type. Bacteriochlorophyll a and carotenoids of the normal spirilloxanthin series were present as photosynthetic pigments. Hydrogen sulfide, thiosulfate, elemental sulfur, and molecular hydrogen were used as electron donors during photolithotrophic growth under anoxic conditions, while carbon dioxide was utilized as carbon source. Acetate, propionate, lactate, glycolate, pyruvate, fumarate, succinate, fructose, sucrose, ethanol, and propanol were photoassimilated in the presence of hydrogen sulfide. During growth on sulfide, elemental sulfur globules were stored inside the cells. Chemotrophic growth under microoxic conditions in the dark was possible. The DNA base composition was 66.9 mol% G+C. Comparative sequence analysis of the 16S rRNA gene confirmed the membership of strain CE2203 in the family Chromatiaceae. Morphological characteristics of strain CE2203 indicated a close affiliation to the genera Thiocystis and Thiocapsa. However, the phylogenetic treeing revealed no closer relationship to Thiocystis spp. than to Thiocapsa roseopersicina or other known members of the Chromatiaceae. Consequently, strain CE2203 is proposed as the type strain of a new genus and species, Thiorhodococcus minus gen. nov., sp. n
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  • 38
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    Speciation and cycling of trace metals in Esthwaite Water: A productive English lake with seasonal deep-water anoxia (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 (24). pp. 5233-5253.
    Details
    Publication Date: 2014-02-04
    Description: The chemical speciation of Cu, Ni, and Cr and the dissolved and unfiltered concentrations of Mo, Ti, Co, Fe, Mn, and Zn were determined in the water column of a lake with a seasonally anoxic hypolimnion (Esthwaite Water, Cumbria, UK) during three surveys in the summer of 1991. Cathodic stripping voltammetry (CSV) with ligand competition was used for this speciation study. The metal data, in conjunction with physical and nutrient data, were used to assess the biogeochemical processes controlling the distribution and speciation of the trace metals in the lake and their seasonal variation. Thermodynamic calculations were used to assess the dissolved trace metal speciation and the saturation state of metal-sulphide phases. The development of anoxia in the lake had an important influence on the redox speciation of dissolved Cr, with Cr(III) forming the major Cr species under anoxic conditions. Cobalt showed enhanced concentrations in the hypolimnion during anoxia, coinciding with enhanced Fe and Mn levels. Dissolved Cu, Ni, and Zn concentrations in the hypolimnion decreased during anoxia, which could possibly be explained by particle scavenging (iron sulphides) and a decline in hypolimnetic supply as the season develops. Regeneration processes of sunken organic detritus on the sediment-water interface were the most likely causes for enhanced hypolimnetic concentrations of Ni, Cu, and Zn, during periods when the lake was completely oxic. Substantial organic Ni and Cu complexation was observed in Esthwaite Water, which was attributed to the eutrophic character of the lake. Between 25 and 80 of the dissolved Ni in Esthwaite Water was strongly complexed by natural ligands. The highest proportions of Ni complexation were observed in the epilimnion and hypolimnion, with a minimum in the thermocline. Strong Cu complexing ligands were observed in the lake, with dissolved ligand concentrations between 6.8 and 29.4 nM and conditional stability constants between 10 11.1 and 10 14.4. More than 94 of the dissolved Cu in Esthwaite Water was complexed by the natural ligands. Copyright © 1997 Elsevier Science Ltd.
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  • 39
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    Chemical specification of chromium and nickel in the western Mediterranean (1997)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 44 (3-4). pp. 693-720.
    Details
    Publication Date: 2014-02-04
    Description: The chemical speciation of dissolved Cr and Ni was measured onboard ship in the western Mediterranean Sea using cathodic stripping voltammetry (CSV) during the winter of 1992 and summer of 1993. Vertical profiles for dissolved Cr(III) in the water column showed concentrations between 0 and 1.4 nM, with highest concentrations in the surface layer, possibly caused by photochemical conversion of Cr(VI) to Cr(III) during summer periods and by atmospheric inputs during winter periods. Enhanced Cr(III) levels also were encountered in the deeper Mediterranean waters and were attributed to mineralisation of sinking biological material and diffusion from sediments. Dissolved Cr(VI) concentrations ranged between 2 and 3 nM, and total dissolved Cr concentrations between 2 and 3.5 nM. Lowest concentrations of total Cr and Cr(VI) occurred in the surface Atlantic waters and highest levels in the deeper Mediterranean waters. Total dissolved Ni concentrations ranged between 1.5 and 5 nM. Between 10 and 20 of the total dissolved Ni in the western Mediterranean appeared to be strongly organically complexed. Both labile and total dissolved Ni concentrations were lower in the surface Atlantic waters than in the Mediterranean deeper waters Little difference was observed between the data sets for winter and summer, indicating that the influence of seasonal changes on the speciation of Ni was small. A clear nutrient-like behaviour was not apparent for Ni and Cr, and their vertical and horizontal distributions were mainly determined by physical processes. Dissolved budget results for Cr and Ni for the Valdivia and Discovery (data in parentheses) cruises of -572 (55) and -439 (369) t yr-1 were calculated, indicating that the dissolved budgets for these elements were well balanced. The budget deficits and surpluses for dissolved Cr and Ni were small compared to the mass fluxes involved in the calculation of the mass balances.
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  • 40
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    Effects of epibiosis on consumer-prey interactions (1997)
    Springer
    In:  Hydrobiologia, 355 (1/3). pp. 49-59.
    Details
    Publication Date: 2014-03-12
    Description: In many benthic communities predators play a crucial role in the population dynamics of their prey. Surface characteristics of the prey are important for recognition and handling by the predator. Because the establishment of an epibiotic assemblage on the surface of a basibiont species creates a new interface between the epibiotized organism and its environment, we hypothesised that epibiosis should have an impact on consumer-prey interactions. In separate investigations, we assessed how epibionts on macroalgae affected the susceptibility of the latter to herbivory by the urchin Arbacia punctulata and how epibionts on the blue mussel Mytilus edulis affected its susceptibility to predation by the shore crab Carcinus maenas. Some epibionts strongly affected consumer feeding behavior. When epibionts were more attractive than their host, consumer pressure increased. When epibionts were less attractive than their host or when they were repellent, consumer pressure decreased. In systems that are controlled from the top-down, epibiosis can strongly influence community dynamics. For the Carcinus/Mytilus system that we studied, the insitu distribution of epibionts on mussels reflected the epibiosis-determined preferences of the predator. Both direct and indirect effects are involved in determining these epibiont-prey-consumer interactions.
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  • 41
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    Bacterial induction and inhibition of a fast necrotic response in Gracilaria conferta (Rhodophyta) (1997)
    Springer
    In:  Journal of Applied Phycology, 9 (3). pp. 277-285.
    Details
    Publication Date: 2018-06-01
    Description: Of 45 bacterial isolates from healthy tips of Gracilaria conferta (Schousboe ex Montagne) J. et G. Feldmann, 29% were identified as 'conditional inducers' of an apical necrosis. That is, the isolates induced necrotic tips in G. conferta within 16 h after elimination of most of the resident microflora from the alga. Several disinfectants and antibiotics were screened for their ability to induce algal susceptibility to the bacteria and to suppress uncontrolled appearance of tip necrosis. Treatment with 100 mg L-1 Cefotaxim + 100 mg L-1 Vancomycin over three days was the least damaging and most efficient. Tip necrosis was related to isolates of the Corynebacterium-Arthrobacter-group and to the Flavobacterium-Cytophaga-group. The damaging effect occurred due to the bacterial excretion of active agents and was not correlated with a capability to degrade agar. The damaging influence of four Cytophaga-like strains was inhibited by 20 of 40 isolates. This protective effect was caused by very different organisms. In five of six cases examined further, the effect was not cellbound, but due to the excretion of agents. These were not antimicrobially active, but inactivated necrosis-inducing excretions. These results indicate that epiphytic bacterial degradation or inactivation of damaging agents is a protecting factor in Gracilaria, which prevents the alga from being harmed by epiphytes.
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  • 42
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    The acoustic turbid layer in muddy sediments of Eckernfoerde Bay, Western Baltic: methane concentration, saturation and bubble characteristics (1997)
    Elsevier
    In:  Marine Geology, 137 (1-2). pp. 137-147.
    Details
    Publication Date: 2013-07-16
    Description: In Eckernfoerde Bay in the western Baltic, an enclosed basin with organic-rich mud, acoustic turbidity has been observed since 1952. To investigate the relationships between acoustic properties and free gas we developed a method for rapid sub-sampling of gravity cores to determine the total methane content. From temperature measurements, determinations of the salinity of the pore water and data from the literature, saturation limits were calculated for each core. It is demonstrated that there is a certain amount of free gas in the mud of Eckernfoerde Bay but subbottom depths of the oversaturation and of the acoustic turbidity do not correspond. The existence of free gas implies the existence of bubbles in the sediment which are regarded to be responsible for the acoustic turbidity. Bubble sizes observed by X-ray computed tomography while still under in situ pressure and temperature vary between 1 and 10 mm equivalent diameter. The distribution of bubbles is discontinuous, occurring in depth zones from 2 to 20 cm thickness.
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  • 43
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    Du volcan au sédiment: la dynamique du talus volcanoclastique sous-marin de Gran Canaria, canaries (Atlantique oriental, Leg ODP 157) (1997)
    Elsevier
    In:  Comptes Rendus de l'Académie des Sciences - Series IIA - Earth and Planetary Science, 324 (11). pp. 891-898.
    Details
    Publication Date: 2019-02-27
    Description: Résumé Quatre sites ont été forés dans le talus volcanoclastique sous-marin de l'île volcanique de Gran Canaria au cours du Leg ODP 157. La sédimentation du talus enregistre l'évolution volcanique de l'île. Les grandes phases éruptives s'expriment clairement par d'importants apports clastiques contemporains au niveau du talus. En revanche, les périodes d'inactivité volcanique se traduisent par des taux de sédimentation très faibles. II est possible ainsi d'établir un découpage volcanostratigraphique à partir des sédiments marins. Abstract Four sites have been drilled in the submarine volcaniclastic apron of the volcanic island of Gran Canaria during the ODP Leg 157. The volcaniclastic submarine apron reflects the volcanological evolution of the island. The main volcanic phases are recorded in the sedimentation by an important contemporaneous clastic influx on the apron. However, periods of volcanic quiescence are characterized by very weak sedimentation rates. Consequently, it is possible to establish a volcanostratigraphy from the sedimentary record of the apron.
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  • 44
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    Effects of end restraint and strain rate in triaxial tests (1997)
    Elsevier
    In:  Computers and Geotechnics, 21 (3). pp. 163-182.
    Details
    Publication Date: 2019-09-20
    Description: Inhomogeneities caused by end restraint and insufficient drainage during conventional compression triaxial tests are analysed by a numerical method. A finite element model is presented to simulate the testing procedure. The soil-platen interaction is represented by contact elements which allow frictional sliding between contacting nodes. The soil mass is represented by the modified Cam clay model. Coupled hydro-mechanical analyses are carried out in order to simulate both drained and undrained tests. The distributions of stresses and strains in the specimen for different end conditions are compared with the ideal case where no end restraint exists, in order to find representative measuring positions in the sample. Different rates of axial strain are tested in order to study the inhomogeneities caused by insufficient drainage during drained tests. Simulated results show that both end restraint and insufficient drainage can cause the barrel-shape deformation of the specimen. Stress-strain and strength properties based on global measurements are not a good representation of the true material behaviour of one single soil element at constitutive level.
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  • 45
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    Physical properties of a porcellanite layer (Southwest Indian Ridge) constrained by geophysical logging (1997)
    Elsevier
    In:  Marine Geology, 140 (3-4). pp. 415-426.
    Details
    Publication Date: 2019-07-01
    Description: A distinct porcellanite layer from the Southwest Indian Ridge intercalated in Pleistocene diatom ooze was studied using nondestructive physical property measurements and sedimentological data. This bed was sampled by two piston cores at a water depth of 2615 m. The 3–5 cm thick porcellanite layer appears in the cores at a depth of 6.03 m (Core PS2089-2) and 7.73 m (Core PS2089-1) below the seafloor. Due to its characteristic physical properties the porcellanite bed can be detected with core measurements, and its distribution and lateral extent mapped with echosounding. The physical index properties, wet bulk density and electrical resistivity, increase significantly across this bed. Magnetic susceptibility is used to compare the lithological units of both cores and to distinguish whether resistivity anomalies are caused by a higher amount of terrigenous components or by the presence of porcellanite. The porcellanite has the special characteristic to affect a positive anomaly in resistivity but not in susceptibility. Most marine sediments, in contrast, show a positive correlation of magnetic susceptibility versus electrical resistivity; therefore a combination of electrical resistivity and magnetic susceptibility logs yields a definite detection of the porcellanite bed. Images from the X-ray CT survey indicate that the porcellanite is lithified and brittle and fragmented when the piston corer penetrated the bed.
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  • 46
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    The Baltic Sea: current and future status and impact of agriculture (1997)
    Springer
    In:  AMBIO: A Journal of the Human Environment, 26 (7). pp. 424-431.
    Details
    Publication Date: 2019-04-04
    Description: A large, densely populated catchment area dominating water quality of land runoff, stratification of the brackish water, a residence time of 25 years, intermittent renewal of oxygenated bottom water from the North Sea, few plant and animal species already stressed by low salinity, make the Baltic Sea vulnerable to changes in external forcings such as increased inputs of nutrients and toxic substances. A severalfold increase of nutrient inputs and primary production since the beginning of the century has increased the area of anoxic bottoms, decreased the transparency of the water by 2.5-3 m, favored filamentous annual algae at the expense of coarse, perennial ones-like the important bladderwrack (Fucus vesiculosus)-changed the fish community from cod, salmon, pike and perch toward herring, sprat, bream, and roach. Because they are a major source of external nitrogen, a shift in current agricultural practices has to be made including: tree curtains to increase patchiness, biodiversity and natural pest control; catch crops along rivers; matching animal density and crop types to achieve optimal recycling of nutrients. So far, integrated land use, based on operative ecological-socioeconomic models, is the most powerful policy instrument for a sustainable agriculture.
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  • 47
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    Age, growth and maturation of the deepwater squid Moroteuthis ingens (Cephalopoda: Onychoteuthidae) in New Zealand waters (1997)
    Springer
    In:  Polar Biology, 17 . pp. 268-274.
    Details
    Publication Date: 2021-01-19
    Description: Individuals of the deepwater squid Moroteuthis ingens were obtained from New Zealand waters at depths between 500 and 1452m. Depth distribution suggested that there was an ontogenetic migration to deeper water by females in association with maturity. Males did not show any clear pattern in their depth distribution. Statoliths increment analysis was also undertaken to obtain putative age and life span information. Based on statolith age estimates, M. ingens appears to be predominantly an annual species with the oldest individuals aged at 358 and 393 days for males and females respectively. The form of growth over the size range sampled was linear with females having a growth rate almost twice that of males. Back-calculated hatching dates revealed a peak in hatching in the austral winter between June and August. maturation in males was more closely related to size rather than age whereas in females the pattern in ovary growth in relation to both mantle length and age was similar.
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  • 48
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    Sea-ice processes in the Laptev Sea and their importance for sediment export (1997)
    Elsevier
    In:  Continental Shelf Research, 17 (2). pp. 205-233.
    Details
    Publication Date: 2019-09-23
    Description: Based on remote-sensing data and an expedition during August-September 1993, the importance of the Laptev Sea as a source area for sediment-laden sea ice was studied. Ice-core analysis demonstrated the importance of dynamic ice-growth mechanisms as compared to the multi-year cover of the Arctic Basin. Ice-rafted sediment (IRS) was mostly associated with congealed frazil ice, although evidence for other entrainment mechanisms (anchor ice, entrainment into freshwater ice) was also found. Concentrations of suspended particulate matter (SPM) in patches of dirty ice averaged at 156 g m(-3) (standard deviation sigma = 140 g m(-3)), with a background concentration of 5 g m(-3). The potential for sediment entrainment over the broad, shallow Laptev Sea shelf during fall freeze-up was studied through analysis of remote-sensing data and weather-station records for the period 1979-1994. Freeze-up commences on 26 September (sigma = 7 d) and is completed after 19 days (sigma = 6 d). Meteorological conditions as well as ice extent prior to and during freeze-up vary considerably, the open-water area ranging between 107 x 10(3) and 447 x 10(3) km(2). Ice motion and transport of IRS were derived from satellite imagery and drifting buoys for the period during and after the expedition (mean ice velocities of 0.04 and 0.05 m s(-1), respectively). With a best-estimate sediment load of 16 t km(-2) (ranging between 9 and 46 t km(-2)), sediment export from the eastern Laptev Sea amounts to 4 x 10(6) t yr(-1), with extremes of 2 x 10(6) and 11 x 10(6) t yr(-1). Implications for the sediment budget of the Laptev shelf, in particular with respect to riverine input of SPM, which may be of the same order of magnitude, are discussed.
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  • 49
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    Gonatid Squids in the Subarctic North Pacific Ecology, Biogeography, Niche Diversity and Role in the Ecosystem (1997)
    Elsevier
    In:  In: The biogeography of the oceans. , ed. by Gebruk, A. V. Advances in marine biology, 32 . Elsevier, San Diego, Calif., pp. 243-324, 82 pp. ISBN 0-12-026132-4
    Details
    Publication Date: 2021-05-11
    Description: This review is based on the author's own data and all available published data (mostly Russian and Japanese) on the ecology, biogeography and role in the ecosystem of gonatid squids in the northern North Pacific. For the best studied species, Berryteuthis magister, information is given on size, horizontal and vertical distribution, diel and ontogenetic vertical migrations, maturation, mating, spawning, fecundity, population structure, age, growth, life cycle, horizontal migrations, underwater behaviour, food and feeding, and predators. The assessed biomass and its interannual dynamics and the fisheries importance are also covered. For other, less studied, species of the genera Berryteuthis (B. anonychus), Gonatopsis (three species) and Gonatus (seven species) all available ecological and biogeographical data are included. All species are compared according to their size, horizontal and vertical distribution, spawning habitats, diel vertical migrations and gelatinous degeneration associated with maturation. The “ecological individuality” of each species is evaluated. It is shown that each occupies its own ecological niche but these niches overlap to different degrees. The history of niche divergence in North Pacific gonatids during the Neogene-Pleistocene period is briefly reviewed. Common features are described of the horizontal and vertical distribution, relative abundance and biomass of North Pacific gonatids in general. Their roles in the ecosystem, as predators, prey, competitors and hosts of parasites is evaluated. The total biomass of gonatid squids in the whole subarctic North Pacific and the Russian Far Eastern seas is estimated as approximately 15–20 million t. They contribute some 10–15% of the total production of mesopelagic cephalopods in the World Ocean. Their yearly food consumption is assessed at 100–200 million t. The life cycle of gonatids is shorter and their P/B-coefficient much higher than that of subarctic mesopelagic fishes. As a result, though the squid biomass (calculations for the Okhotsk Sea) is less than 10% of the total mesopelagic fish and squid population, they form 58–67% of annual total fish and squid production. Thus gonatid squids have an important place in the ecosystem of the northern North Pacific and the Far Eastern seas of Russia.
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  • 50
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    Summer distribution of seabirds in the North-East Water polynya, Greenland (1997)
    Elsevier
    In:  Journal of Marine Systems, 13 (1-4). pp. 51-59.
    Details
    Publication Date: 2021-04-16
    Description: The distribution at sea of seabirds was studied in the North-East Water (NEW) polynya, Greenland, during transect counts in the summers of 1991, 1992 and 1993 on board the ice-breaking RVs Polarstern and Polar Sea. Data collected within the polynya ‘box’ (78–82°N; 5–18°W) concern observations of 8000 birds counted during 1350 half-hour counts. Distribution is presented as density (N/km2) and calculated daily food intake. Five bird species were selected for discussion, representing more than 95% of the total numbers encountered: Fulmar (Fulmarus glacialis), Ivory Gull (Pagophila eburnea), Kittiwake (Rissa tridactyla), Glaucous Gull (Larus hyperboreus) and Ross's Gull (Rhodostethia rosea). For these species, densities are comparable in the NE Greenland polynya and in other European Arctic seas. The main difference is the absence in NEW of the species playing the main role in Arctic seas: Brünnich's Guillemot (Uria lomvia) and Little Auk (Alle alle). In the absence of fish-eating birds and of birds consuming zooplankton in the water column, the NEW polynya ecosystem is thus dominated by surface feeders and, closer to the coast, by benthic feeders like eiders, Somateria mollissima and S. spectabilis, and walrus, Odobenus rosmarus. The density and daily food intake for all seabirds are one order of magnitude lower in the polynya than in the Arctic seas. The distribution and abundance of seabirds in the NEW polynya seems to reflect a very low density of pelagic fish and Zooplankton in the water column, while Zooplankton must be present at ‘normal’ concentrations in the upper layer.
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  • 51
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    Effects of food availability on fledging condition and post-fledging survival in king penguin chicks (1997)
    Springer
    In:  Polar Biology, 18 (3). pp. 161-165.
    Details
    Publication Date: 2021-04-19
    Description: Effects of summer food shortage on king penguin Aptenodytes patagonicus chicks were studied at South Georgia. Two cohorts were compared, fledging in the austral summers of 1992 (n = 32) and 1994 (n = 33) when availability of food was judged good and poor, respectively. The former cohort had a higher pre-fledging mean mass (12.78 kg vs ≤ 10.03 kg), fledged earlier (median 5 January vs 21 January), and a higher proportion was re-sighted within 2 years of fledging (28% vs 0%). Within 4 years, 47% of the former cohort had been re-sighted (i.e. post-fledge survival); in addition, one was observed at the Falkland Islands, and 22% had bred (i.e. recruitment) in their colony of origin. The re-sighted chicks of the 1992 cohort fledged earlier than those not re-sighted (median 24 December vs 10 January), but it remain unclear if they were heavier at fledging. All chicks in this study (n = 65) were marked with both transponders (subcutaneously implanted) and flipper bands (on one flipper), and no losses of any markings were found (controlled up to 4 years afterwards). Therefore, data on chick post-fledging survival and recruitment were not adjusted for losses of markings, as has been done in other studies.
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  • 52
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    Food and feeding of the short-finned squid Illex argentinus (Cephalopoda: Ommastrephidae) off southern Brazil (1997)
    Elsevier
    In:  Fisheries Research, 33 (1-3). pp. 139-147.
    Details
    Publication Date: 2021-04-21
    Description: Diet and feeding habits of the short-finned squid Illex argentinus were studied from the analysis of 729 stomachs of juveniles, subadults and adults caught with trawls on the continental shelf and slope off southern Brazil (26 °35′S–34 °31′S) from 1981 to 1992. Food, in different degrees of digestion, was found in 363 stomachs (49.8%). Feeding activity occurred at day and night and seemed to be most intense at dusk and early night. The proportion of stomachs with food increased with size and sexual maturity. Fish occurred in 43.8%, cephalopods in 27.5% and crustaceans in 18.7% of the stomachs with food. Identified prey included the fish Diaphus dumerilii, Maurolicus muelleri and Merluccius hubbsi, the cephalopods I. argentinus, Loligo sanpaulensis, Spirula spirula, Semirossia tenera and Eledone gaucha and the crustaceans Oncaea media and Euphausia sp. The occurrence of fish increased with squid size, but both cephalopods and crustaceans were equally important for all sizes. Cannibalism was observed at all sizes. The overall low proportion of stomachs with food, the high rate of cannibalism and the low frequency of occurrence of crustaceans for the juveniles and subadults in all seasons, but particularly in the summer and autumn, may reflect a limited availability of food in the region. If this is true, the main nursery grounds for the spawners off southern Brazil are likely to be off the Rio de La Plata Front or in the offshore confluence between the Brazil and Malvinas Currents, where primary and secondary production is higher than off southern Brazil.
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  • 53
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    A comparative study of the diet of Loligo vulgaris (Lamarck, 1799) (Mollusca:Cephalopoda) from the south coast of Portugal and the Saharan Bank (Central-East Atlantic) (1997)
    Elsevier
    In:  Fisheries Research, 29 (3). pp. 245-255.
    Details
    Publication Date: 2021-04-30
    Description: This paper presents data on the diet of the squid, Loligo vulgaris (Lamarck, 1799) from the south coast of Portugal (Algarve) and from the Saharan Bank (Central-East Atlantic). A total of 964 squid was collected from the Algarve coast, between March 1993 and October 1994, from bottom trawling. An additional sample of 70 stomachs was obtained in the Algarve coast from the hand jigging fishery during 1991 and 1992. In the Saharan Bank, 848 squid were obtained, between June 1993 and January 1994, with bottom trawling. Stomachs with contents for trawled squid from the Algarve coast, and the Saharan Bank represented 28.1% and 40.8%, respectively. Fish was always the main component of the diet in both regions, representing 88.6% of the total weight of the prey found in the stomachs, for the Algarve coast, and 70.9% for the Saharan Bank. The occurrence percentage and the percentage in number indicated that Trachurus trachurus and fish belonging to the family Gobiidae were the most frequent fish found in the Algarve samples, while flatfish were the most common fish in the Saharan Bank samples. Loligo vulgaris was the dominant cephalopod found in the stomachs for both regions. No differences in the diet were found between males and females. The comparison between immature and mature squid showed that the importance of fish was higher in mature squid, for both regions. The squid captured from the Algarve coast by bottom trawling (at greater depths and offshore) fed primarily on fish, while those captured with hand jigging (inshore, at lower depths) contained an important percentage of crustaceans.
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  • 54
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    Seabird abundance, biomass and prey consumption within Prydz Bay, Antarctica, 1980/1981–1992/1993: (1997)
    Springer
    In:  Polar Biology, 17 (4). pp. 371-383.
    Details
    Publication Date: 2021-06-14
    Description: Annual observations of seabirds within Prydz Bay, East Antarctica, between the 1980/1981 and 1992/1993 seasons revealed siginificant changes in abundance of the 9 resident and 15 non-resident species. An estimated 4.85 million individual residents and 2.35 million individual non-residents were present each season. For resident and non-resident species, mean abundance was 3.75 and 1.81 birds/km2, and mean biomass was 6.67 and 1.70 kg/km2, respectively. Based on estimated abundances, the total consumption of marine resources by the seabird community within Prydz Bay ranged from 471,000 to 1.1 million tonnes (mean 752,000±176,000 tonnes) per 6-month summer, or between 2.02 and 4.53 kg/km2 per day (mean 3.23±0.76 kg/km2 per day). The mean energy flux to the seabird community within Prydz Bay each summer was 3.13*1012 kJ, (range: 2.0*1012 kJ–4.4*1012 kJ), of which 66% went to the resident species. Regional abundance and biomass estimates for resident and non-resident species were both negatively correlated; when the estimated abundance and biomass of resident species were high, those of non-resident species were low.
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  • 55
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    Organochlorine residues in deep-sea organisms from Suruga Bay, Japan (1997)
    Elsevier
    In:  Marine Pollution Bulletin, 34 (4). pp. 250-258.
    Details
    Publication Date: 2021-02-22
    Description: Residue levels of persistent organochlorines in deep-sea organisms collected from Suruga Bay, Japan, were determined. PCBs (polychlorinated biphenyls) were the predominant group of organochlorines ranging in concentrations from 380 to 2800 ng g−1 on a lipid weight basis. DDTs (DDT and its metabolises) were the next most abundant organochlorine compounds followed by CHLs (chlordane compounds), HCHs (hexachlorocyclo-hexanes) and HCB (hexachlorobenzene). In comparison with coastal shallow water organisms, higher concentrations of HCHs were found in deep-sea organisms, while no significant difference was noted for other organochlorines. Organochlorine residue levels in Suruga Bay were comparatively lower than those in other deep-sea organisms reported elsewhere. The deep-sea organisms showed no consistent trend between organochlorine concentrations and food chain relationships. Lipid-dependent accumulation of organochlorines by equilibrium partitioning may be attributable to this residue pattern. Among DDT compounds, p,p′-DDE was the highest in most deep-sea organisms. Trans-nonachlor and β-HCH were the major constituents of CHLs and HCHs, respectively, in these organisms.
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  • 56
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    Fish prey of Antarctic fur seals Arctocephalus gazella at Ile de Croy, Kerguelen (1997)
    Springer
    In:  Polar Biology, 17 (1). pp. 87-90.
    Details
    Publication Date: 2021-04-20
    Description: The composition of Antarctic fur seal prey was assessed through analysis of scats collected in March 1994 on Ile de Croy, Iles Nuageuses. Fish remains predominated in samples, occurring in 95% of droppings. A total of 968 otoliths allowed the identification of 16 fish species. Myctophid fish (12 species) dominated the diet both by number (94% of the otoliths) and by fish reconstituted mass (76%). Three fish species constituted together 87% of the reconstituted mass: the myctophids Gymnoscopelus nicholsi (52%) and G. piabilis (12%), and the channichthyid Champsocephalus gunnari (23%). Prey distribution suggests that during late summer seals forage in upper slope waters in the northeast of the Kerguelen Archipelago.
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  • 57
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    Age and growth of the neon flying squid, Ommastrephes bartrami, in the North Pacific Ocean (1997)
    Elsevier
    In:  Fisheries Research, 29 (3). pp. 257-270.
    Details
    Publication Date: 2021-04-30
    Description: Longitudinal sections of statoliths were observed by light microscopy on 237 individuals (158–510 mm mantle length, ML) of Ommastrephes bartrami, obtained from the North Pacific (26 °–46 °N, 143 °E–149 °W) during 1991–1994. The width of each increment sharply decreased from 5–7 μm to about 1–2 μm between the 80th and 100th increment, with a transition zone where increments were inconspicuous. ML-age relationships were linear, and slope and intercept values differed by geographic area, hatch season and sex. Overall growth rates (mm day−1) were generally higher in females (1.1–2.5) than in males (1.1–2.1). Since these values were similar to the growth rates of four individuals which were tagged and recaptured (0.8–2.4), the increments were assumed to be formed daily. The growth rate was highest for individuals hatched in summer, followed by those hatched in spring. Growth rate obtained by length-based methods may be underestimated. The hatch dates of neon flying squid are almost year-round, and the life span is likely 1 year since mature individuals were 7–10 months old.
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  • 58
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    Restricted gene flow and evolutionary divergence between geographically separated populations of the Antarctic octopus Pareledone turqueti (1997)
    Springer
    In:  Marine Biology, 129 (1). pp. 97-102.
    Details
    Publication Date: 2021-04-22
    Description: Samples of the Antarctic octopus Pareledone turqueti were taken from three locations on the Scotia Ridge in the Southern Ocean. The genetic homogeneity of these populations was investigated using isozyme electrophoresis. Whilst panmixia appeared to be maintained around South Georgia (F ST = 0) gene flow between this island and Shag Rocks, an island only 150 km away but separated by great depths, was extremely limited (F ST = 0.74). These results are examined with respect to the discontinuous distribution of P. turqueti throughout Antarctica. An estimate of effective population size was also calculated (N e = 3600).
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  • 59
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    Age and growth of the mesopelagic squid Ancistrocheirus lesueurii (Oegopsida: Ancistrocheiridae) from the central-east Atlantic based on statolith microstructure (1997)
    Springer
    In:  Marine Biology, 129 (1). pp. 103-111.
    Details
    Publication Date: 2021-04-22
    Description: Statolith microstructure was studied in 56 Ancistrocheirus lesueurii (25 to 423 mm of mantle length, ML) caught in the central-east Atlantic. Statolith growth increments were grouped into three main growth zones, distinguished mainly by increment width. The second transition in the statolith microstructure (from Zone 2 to Zone 3) coincides with the life history shift from epipelagic and upper mesopelagic to a bathyal habitat. Second-order bands (mean 27.65 growth increments) and sub-bands (mean 13.6 growth increments) within statolith microstructure appeared to be related to the lunar cycle. Striking sexual dimorphism is reflected in the age and growth rates: males live ca. 1 yr, while females only start maturing at this age and obviously live 〉1.5 yr. A. lesueurii is a slow growing squid, attaining 25 to 30 mm ML at the age of 100 d. After ontogenetic migrations into bathypelagic waters at ML 〉 30 to 35 mm, growth rates gradually decrease to the minimum known values for squids. Based on back-calculated hatching dates, A. lesueurii hatches throughout the year with a peak between November and March.
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  • 60
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    Locomotion modes of deep-sea cirrate octopods (Cephalopoda) based on observations from video recordings on the Mid-Atlantic Ridge (1997)
    Springer
    In:  Marine Biology, 129 (1). pp. 113-122.
    Details
    Publication Date: 2021-02-22
    Description: The behaviour of cirrate octopods of the genera Cirroteuthis and Grimpoteuthis in their natural habitat was studied using video recordings. Sequences were filmed during the French cruise “Faranaut”, from the manned submersible “Nautile” at depths between 2702 and 4527 m, in two zones in the Fifteen-Twenty Fracture Zone on the Mid-Atlantic Ridge. Four different modes of active locomotion, namely crawling, take-off, fin-swimming, and pumping, and one apparently passive mode of locomotion, umbrella-style drifting, were observed. Jet-propulsion, a characteristic mode of locomotion typically employed by cephalopods, was not observed in the cirrate octopods filmed, although breathing movements of the mantle to aerate the gills were assumed to generate some slight propulsion through the funnel. Fin-swimming was the mode of active locomotion most frequently observed. Neutral buoyancy was confirmed in one individual after capture. This buoyancy enables passive drifting in the umbrella-style attitude observed in Cirroteuthis spp., possibly using near-bottom ocean currents. Pumping, a mode of slow locomotion generated by peristaltic waves in the primary and intermediate webs, also observed in Cirroteuthis sp., is described here for the first time. The take-off mode of locomotion, a sudden, single contraction of the brachial crown and web, is also described; it was always followed by fin-swimming. No medusoid swimming of the type previously described for opisthoteuthid cirrates was observed. A flight response to the approach of or contact with a strange object, i.e. the submersible, using the crawling, take-off, or fin-swimming modes was observed. A ballooning response was observed in a high-stress situation when a C.magna individual was captured.
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  • 61
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    Quantitative micro-PIXE mapping of squid statoliths (1997)
    Elsevier
    In:  Nuclear Instruments & Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 130 (1-4). pp. 374-380.
    Details
    Publication Date: 2021-07-07
    Description: Distribution of elements in statoliths of squid Loligo vulgaris reynaudii d'Orbigny, 1845 was studied, using the true elemental imaging system (Dynamic Analysis) of the NAC nuclear microprobe. The analysis revealed various patterns of Ca and Sr distributions. The biological interpretation of the most frequent pattern is linked with the role of Sr in the statolith deposition process. Other patterns are linked with the technique used and the specific characteristics of the sample. Traces of other elements (Cr, Mn, Fe, Cu, Zn, Br, Pb) were also found. Likewise, their presence may have the biological interpretation (Zn, Cu and Br), or is an artefact linked to the methods and conditions of sample preparation and/or analysis. Methodical aspects of using proton backscattering for PIXE X-ray yield corrections are also discussed.
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  • 62
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    The diet of the Weddell seal Leptonychotes weddelli at Harmony Point, South Shetland Islands (1997)
    Springer
    In:  Polar Biology, 18 (6). pp. 371-375.
    Details
    Publication Date: 2021-02-15
    Description: A total of 41 faeces and 5 vomits of the Weddell seal Leptonychotes weddelli was collected at Harmony Point, Nelson Island, South Shetland Islands, from 14 January to 1 February 1996. The diet indicated by the remains in the samples was diverse and comprised both pelagic and benthic-demersal species. Fish were the most frequent (95.7%) and numerous prey (46.2%), but molluscs were the most important by mass (65.8%). Octopods, mainly Pareledone charcoti, constituted the bulk of the diet (63.1% by mass), but the importance of the remaining molluscs was negligible. Otoliths represented 510 fish of which 491 were identified as belonging to 5 species: Gymnoscopelus nicholsi, Electrona antarctica, Lepidonotothen nudifrons, Gobionotothen gibberifrons and Nototheniops nybelini. The myctophid Gymnoscopelus nicholsi was the most important fish prey, and the contribution of benthic-demersal species was low. However, the importance of that fish was over-estimated since 96% of the specimens were obtained from the five vomits analysed. The biases associated with the faecal analysis technique are discussed.
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  • 63
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    Feeding ecology and interannual variations in diet of southern bluefin tuna, Thunnus maccoyii, in relation to coastal and oceanic waters off eastern Tasmania, Australia (1997)
    Springer
    In:  Environmental Biology of Fishes, 50 (3). Art.Nr. 275.
    Details
    Publication Date: 2021-06-17
    Description: The diets of 1219 southern bluefin tuna, Thunnus maccoyii, from inshore (shelf) and offshore (oceanic) waters off eastern Tasmania were examined between 1992 and 1994. Immature fish (〈 155 cm fork length) made up 88% of those examined. In all, 92 prey taxa were identified. Inshore, the main prey were fish (Trachurus declivis and Emmelichthys nitidus) and juvenile squid (Nototodarus gouldi). Offshore, the diversity was greater, reflecting the diversity of micronekton in these waters. Interestingly, macrozooplankton prey (e.g. Phronima sedentaria) were prevalent in tuna 〉 150 cm. The offshore tuna, when in subantarctic waters, ate relatively more squid than when in the East Australia Current. In the latter, fish and crustacea were more important, although there were variations between years. No relationship was found between either prey type or size with size of tuna. Feeding was significantly higher in the morning than at other times of the day. The mean weight of prey was significantly higher in inshore-caught tuna than in those caught offshore. We estimated that the mean daily ration of southern bluefin tuna off eastern Tasmania was 0.97% of wet body weight day−1. However, the daily ration of inshore-caught tuna was ∼ 3 times higher (2.7%) than for tuna caught offshore (0.8%) indicating that feeding conditions on the shelf were better than those offshore. Our results indicate that the inshore waters of eastern Tasmania are an important feeding area for, at least, immature southern bluefin tuna.
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  • 64
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    Dissolved organic matter and its utilisation by bacteria during spring in the Southern Ocean (1997)
    Elsevier
    In:  Deep-Sea Research Part II-Topical Studies in Oceanography, 44 (1-2). pp. 341-354.
    Details
    Publication Date: 2016-10-10
    Description: Concentrations of dissolved organic carbon (DOC) and nitrogen (DON) were measured during early austral Spring 1992 at a number of stations along the 6°W meridian between 47° and 60°S. This included the Polar Front in the north, the zone of melting sea-ice in the south, and waters of the Antarctic Circumpolar Current in between. Concentrations of DOC were low in deep water (34–38 μM) with generally similar or slightly higher values in the surface mixed layer (38–55 μM). DOC:DON ratios are wider in surface water than in deep water, i.e. surface accumulations contain relatively C-rich dissolved organic matter. The highly variable distribution of the surface DOC was not related to hydrographic or biotic features (fronts, plankton development) indicating the lability and transient occurrence of this material. Growth rates of bacteria were determined in subsamples from 51 0.8-μm-filtered batches of seawater incubated in the dark at in-situ temperature. Thymidine and leucine uptake and bacterial biomass change as well as changes in dissolved organic carbon in the batches, and oxygen consumption in parallel incubations correlated linearly over 2 weeks of incubation which allowed extrapolation to in-situ conditions. Bacterial growth in these experiments depended strongly on the amount of initial DOC. Growth in water from greater depth (1000 m) containing 38 μM DOC was minimal, as were DOC-decrease and oxygen consumption. Higher rates were observed in surface water slightly enriched with DOC, and highest rates in surface water amended with DOC-rich melted sea ice. Bacterial growth efficiencies (biomass C-increase vs DOC consumed) were about 30%. The experiments showed that at least 40–60% of the DOC in excess of deep water concentrations was available to bacteria.
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  • 65
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    13C isotope depletion in ikaite crystals: evidence for methane release from the Siberian shelves? (1997)
    Springer
    In:  Geo-Marine Letters, 17 . pp. 169-174.
    Details
    Publication Date: 2017-05-22
    Description: Ikaite crystals (CaCO3×6H2O) have been found at 232- to 238-cm sediment depth in R/V Polarstern core PS2460-4 from the Laptev Sea continental margin in a water depth of 204 m. δ13C values of this phase average −36.3±0.4‰ PDB (N=2), which is significantly outside the range of normal marine carbonates. The CO2 involved in the precipitation of the ikaite is most probably derived from methane, which has extremely depleted 13C isotope values. Two possible sources of methane in these sediments are: (1) methanogenesis (decomposition of organic matter under anaerobic conditions); and (2) gas hydrates, which are known to occur in the Siberian shelf regions.
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  • 66
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    Photosynthetic pigment fingerprints as indicators of phytoplankton biomass and development in different water masses of the Southern Ocean during austral spring (1997)
    Elsevier
    In:  Deep Sea Research Part II: Topical Studies in Oceanography, 44 (1/2). pp. 261-282.
    Details
    Publication Date: 2020-08-05
    Description: The development of phytoplankton biomass and composition was investigated on three occasions along a longitudinal transect (6°W) between 60°S and 47°S from October 13 to November 21, 1992 by measurement of photosynthetic pigments with high performance liquid chromatography (HPLC). Measured accessory pigment concentrations were multiplied by conversion factors to derive the proportions of phytoplankton groups contributing to the biomass indicator chlorophyll a. Phytoplankton blooms developed in the Polar Frontal region (PFr) and were dominated (80%) by diatoms. Other groups contributing to the phytoplankton included prymnesiophytes, green algae, autotrophic dinoflagellates, cryptophytes, pelagophytes and micromonadophytes, and their distributions varied with time. In contrast, phytoplankton biomass remained low in the southern Antarctic Circumpolar Current (ACC) and was dominated by flagellates, particularly green algae and prymnesiophytes. Green algae contributed more to total biomass than in previous investigations, partly attributed to “Chlorella-like” type organisms rather than prasinophytes. Cryptophytes decreased during the investigation, possibly due to salp grazing. No bloom was observed at the retreating ice-edge, presumably due to strong wind mixing. Only a slight increase in phytoplankton biomass, composed primarily of diatoms, was found at the ACC-Weddell Gyre front. Cluster analysis revealed that different phytoplankton communities characterised the different water masses of the PFr and southern ACC; the history of different water masses in the PFr could be reconstructed on this basis.
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  • 67
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    New production in the Northeast Water Polynya: 1993 (1997)
    Elsevier
    In:  Journal of Marine Systems, 10 . pp. 199-209.
    Details
    Publication Date: 2017-06-26
    Description: The Northeast Water Polynya has been suggested as acting as a sink for carbon, especially during the spring and summer when phytoplankton growth is active. During 1993 the polynya was sampled for the entire growing period (late May through mid-August) in order to more accurately assess the magnitude, controls and patterns of new and total (ammonium, nitrate and urea) nitrogen production. This represents the first assessment of new production throughout an entire season in the Arctic. We found that, in 1993, new production, based on 15N-tracer techniques and integrated over the euphotic zone, was 0.141 mmol N m−2 h−1 (0.361 g C m−2 d−1 when converted using observed C/N ratios). Measured f ratios averaged 0.65 and demonstrate that the system, to a great extent, was using nitrate as a nitrogen source. In general f ratios were greatest early in the season and minimal in mid-summer. Urea uptake was highly variable and contributed slightly less than ammonium to phytoplankton nitrogen demand. Nitrate uptake at stations with low (〈 0.5μM) nitrate concentrations was significantly reduced, implying that nitrate concentrations limited phytoplankton growth late in the growing season. Long-term new production rates calculated from nutrient depletion patterns from the polynya as a whole as well as a time-series constructed from a single location were ca. 0.144-0.281 g C m−2 d−1. The relationship between new production as measured by incubations and nutrient depletion budgets suggests that phytoplankton growth is the dominant factor influencing the nitrogen budget of the polynya. The amount of material available for removal from the euphotic zone is limited and constrains the degree to which the polynya can act as a regional carbon sink.
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  • 68
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    A 200 kyr record of cosmogenic radionuclide production rate and geomagnetic field intensity from 10Be in globally stacked deep-sea sediments (1997)
    Elsevier
    In:  Earth and Planetary Science Letters, 149 . pp. 121-129.
    Details
    Publication Date: 2016-11-14
    Description: The reconstruction of geomagnetic field intensity variations during the last 200 kyr from paleomagnetic data is at present the subject of numerous studies and major debate. There is currently no generally accepted record. Here we present a global stacked record of (230Thex-normalized)10Be deposition in marine sediments representing relative variations in 10Be production rate which are translated into field intensity variations. The record shows major periods during which the field intensity was between 10% and 40% of the present day value; namely 30–42, 60–75, 85–110 and 180–192 kyr B.P. Our results are compared to independently derived paleomagnetic studies and Th/U calibrations of 14C dates on corals. During most of the observed period the geomagnetic field intensity was weaker than today, resulting in an overall 30% reduced value for the last 200 kyr.
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  • 69
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    Diffusion and reactions in the vicinity of plankton: A refined model for inorganic carbon transport (1997)
    Elsevier
    In:  Marine Chemistry, 59 . pp. 17-34.
    Details
    Publication Date: 2017-08-18
    Description: Inorganic carbon uptake by phytoplankton depletes the immediate cell environment and disturbs the carbonate system equilibrium. Uptake is balanced by both diffusional transport across and chemical reactions within the depleted boundary layer. In this study, we have derived a model that simulates inorganic carbon diffusion and reactions in the vicinity of phytoplankton cells. To allow a general application of the model, the reaction kinetics of the carbonate system are reviewed and temperature- and salinity-dependence of the various rate constants are discussed. A consistency condition for some of the kinetic rates is derived. The effective thickness of the diffusive boundary layer in spherical and planar geometry is discussed. In addition, the effect of cell shape on diffusive transport to phytoplankton is examined and a simple means to account for this effect in model calculations is presented. In a second step, the complete description of the diffusion-reaction system is simplified to consider two special cases in which (1) algal production relies on CO2(aq) as the single source of inorganic carbon, and (2) CO2, HCO3−, or CO32− are utilized independently for organic matter production combined with calcite precipitation. In the size range typical for phytoplankton cells model predictions of these simplified versions are nearly identical to those of the complete model, indicating that the simplified models represent good approximations of the complete diffusion-reaction system.
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  • 70
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    Gravimetric preparation of gas phase working standards containing volatile halogenated compounds for oceanographic applications (1997)
    Elsevier
    In:  Deep Sea Research Part I: Oceanographic Research Papers, 44 . pp. 1725-1738.
    Details
    Publication Date: 2016-10-20
    Description: Gas phase standards, containing CCl3F (CFC-11), CCl2F2 (CFC-12), CCl2FCClF2 (CFC-113), CH3CCl3 and CCl4 in the pmol mol−1 range, were prepared gravimetrically in dry N2. The standards were prepared with the relative ratios of the various compounds close to those found in seawater, to facilitate calibration of oceanic halocarbon measurements. The standards made in this study were intercalibrated against an atmospheric-ratio-based standard that was analyzed at both Scripps Institution of Oceanography (SIO) and NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL). A total of 21 standards was made, with the concentrations of the above halocarbons reported on both the CMDL and SIO 1993 scales. These standards are currently being used by ten different research groups making oceanic halocarbon measurements. The average systematic deviation of all compounds in our standards was generally ± 5% or less from the SIO 1993 and CMDL scales. Deviations for CH3CCl3 between our standards and the CMDL scale were slightly larger, with our standards, on average, approximately 10% lower.
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  • 71
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    Iron reduction through the tangreen transition in deep-sea sediments (1997)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 61 (8). pp. 1679-1683.
    Details
    Publication Date: 2017-09-26
    Description: Mössbauer spectroscopic investigations of deep-sea sediments from the Peru Basin revealed a prominent downcore increase of the bulk sediment Fe(II)/Fe(III) ratio across the well-known tan-green color transition. This increase occurs along a continuous gradient extending over a 3 cm zone at the two deep-sea sites that we report. Remarkably constant values of the Fe(II)/Fe(III) ratios above (11 ± 2%/89 ± 2%) and below (37 ± 2%/63 ± 2%) the iron redox transition-zone delimit the gradient clearly. A minor peak of diagenetic iron enrichment is manifest at the redox front. This Fe enrichment has accumulated in a redox cycle and amounts to 16 ± 4% of the total Fe at the peak maximum. The data imply that 26 ± 4% of the detrital iron has experienced in situ redox transition from Fe(III) to Fe(II) within the iron redox transition-zone.
    Type: Article , PeerReviewed
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    Excess helium and argon of radiogenic origin in Mediterranean brine basins (1997)
    Elsevier
    In:  Earth and Planetary Science Letters, 151 . pp. 225-231.
    Details
    Publication Date: 2016-11-14
    Description: Extraordinary helium and argon signatures were observed in a recently discovered brine lake district in the eastern Mediterranean Sea at water depths of ∼ 3500 m. In the Urania Basin 4He concentrations are enriched by a factor of up to 32000 compared to normal seawater. Low 3He/4He ratios of 1 × 10−7 and high 40Ar/36Ar ratios of up to 470 indicate a radiogenic source. These data represent by far the highest radiogenic supersaturations ever observed in an oceanic environment. We propose a new conceptional model assuming that the Urania Basin is fed by advective transport from a deep fluid reservoir below the Messinian evaporite sequence. The evaporite seal provides the unique condition for accumulating the extraordinary high amounts of radiogenic helium from deep sedimentary strata. Injection of radiogenic helium from brine pools like the Urania Basin may contribute significantly to the inventory of terrigenic helium in the deep waters of the eastern Mediterranean.
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    Do rooted macrophytes increase sediment phosphorus release? (1997)
    Springer
    In:  Hydrobiologia, 342/343 . pp. 27-34.
    Details
    Publication Date: 2016-04-21
    Description: Sediment cores were collected from two of the Norfolk Broadsandtwo of the West Midland Meres, to test the hypothesis thatrootedmacrophytes increase the sediment release rate of phosphorusduringthe growing season.These were taken from inside and outside plant beds (mixedMyriophyllum spicatum and Chara sp. in Hickling BroadandNuphar lutea in Burntfen Broad, Mere Mere and LittleMere).The overlying water was replaced with a standard waterdesigned tomimic lowland freshwater. After an overnight ‘batch’incubation thewater was analysed for TP and SRP. From this their releaserateswere calculated. Interstitial measurements of SRP were alsomadefor some of the Broads cores at the end of the incubationperiod.The data were analysed using General Linear Models. TP and SRPwerethe responses for both data sets. Factors for the Broads wereinside/outside plant beds, date, and site, whilst for theMeres thefactors of date and site could not be delineated.Release rates in this study were affected by a number offactors(plants, site and date). The picture emerging so far is thatwhenrooted macrophytes have a significant effect on phosphorusreleasethey increase it. However the large variability betweenreplicateshighlights the logistical difficulties in running suchexperiments.
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    A Mid Cretaceous origin for the Galápagos hotspot: volcanological, petrological and geochemical evidence from Costa Rican oceanic crustal segments (1997)
    Springer
    Details
    Publication Date: 2022-03-10
    Description: The Quepos, Nicoya and Herradura oceanic igneous terranes in Costa Rica are conspicuous features of a Mid to Late Cretaceous regional magmatic event that encompasses similar terranes in Central America, Colombia, Ecuador and the Caribbean. The Quepos terrane (66 Ma), which consists of ol-cpx phyric, tholeiitic pillow lavas overlain by highly vesicular hyaloclastites, breccias and conglomerates, is interpreted as an uplifted seamount/ocean island complex. The Nicoya (∼90 Ma) and Herradura terranes consist of fault-bounded sequences of sediments, tholeiitic volcanics (pillow lavas and massive sheet flows) and plutonic rocks. The volcanic rocks were emplaced at relatively high eruption rates in moderate to deep water, possibly forming part of an oceanic plateau. Major and trace element data from Nicoya/Herradura tholeiites indicate higher melting temperatures than inferred for normal mid-ocean-ridge basalts (MORB) and/or a different source composition. Sr–Nd–Pb isotopic ratios from all three terranes are distinct from MORB but resemble those from the Galápagos hotspot. The volcanological, petrological and geochemical data from Costa Rican volcanic terranes, combined with published age data, paleomagnetic results and plate tectonic reconstructions of this region, provide strong evidence for a Mid Cretaceous (∼90Ma) age for the Galápagos hotspot, making it one of the oldest known, active hotspots on Earth. Our results also support an origin of the Caribbean Plate through melting of the head of the Galápagos starting plume.
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    Gap Models, Forest Dynamics and the Response of Vegetation to Climate Change Huntley, B.; Cramer, W.; Morgan, A.V.; Prentice, H.C.; Allen J.R.M. Past and Future Rapid Environmental Changes: The Spatial and Evolutionary Responses of Terrestrial Biota (1997)
    Springer
    In:  Gap Models, Forest Dynamics and the Response of Vegetation to Climate Change Huntley, B.; Cramer, W.; Morgan, A.V.; Prentice, H.C.; Allen J.R.M. Past and Future Rapid Environmental Changes: The Spatial and Evolutionary Responses of Terrestrial Biota
    Details
    Publication Date: 2022-03-21
    Type: info:eu-repo/semantics/bookPart
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  • 76
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    HAPEX Sahel. Special Issue of Journal of Hydrology (1997)
    Elsevier
    In:  HAPEX Sahel. Special Issue of Journal of Hydrology
    Details
    Publication Date: 2022-03-21
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  • 77
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    Welt im Wandel: Wege zu einem nachhaltigen Umgang mit Süßwasser (1997)
    Springer
    In:  Welt im Wandel: Wege zu einem nachhaltigen Umgang mit Süßwasser
    Details
    Publication Date: 2022-03-21
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  • 78
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    Gap models, forest dynamics and the response of vegetation to climate change (1997)
    Springer
    In:  Gap models, forest dynamics and the response of vegetation to climate change | Past and future rapid environmental changes: the spatial and evolutionary responses of terrestrial b, 47
    Details
    Publication Date: 2022-03-21
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  • 79
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    Glacimarine Drainage Systems in Deep-sea: The NAMOC System of the Labrador Sea and its Sibling (1997)
    Springer
    Details
    Publication Date: 2022-05-30
    Description: The continental Pleistocene Laurentide Ice Sheet (LIS) had far-reaching marine influence in shaping the ocean-floor adjacent to ice margin. The basinwide submarine-canyon and deep-sea channel system of the Northwest Atlantic Mid-Ocean Channel (NAMOC) of the Labrador Sea is the submarine continuation of the drainge system of the LIS on land, forming an interconnected land/sea drainage system 6,000 km long, one of the word’s longest drainage systems of Pleistocene age. The submarine portion forms a dual system, consisting of the mud-dominated NAMOC with its tributaries and a submarine sandy braid-plain.
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    On the redistribution of Pb in the oceanic crust during hydrothermal alteration (1997)
    Elsevier
    Details
    Publication Date: 2023-09-19
    Description: Major- and trace-element as well as Pb-isotope data are presented for greenschist- to amphibolite-facies greenstones from two locations: (1) metabasalt-breccias from the Galfipagos Rift at 100°W; and (2) metabasalt-breccias and unbrecciated greenstones from the Chile Ridge at 38°S. Greenstone-breccias from both locations display stockwork-like sulfide mineralizations related to the upflow portion of a hydrothermal convection system. Whereas Galfipagos Rift stockwork sulfides belong to the "normal" type containing Cu-Fe-sulfides, Chile Ridge stockwork sulfides are galena-rich Pb-Zn _ Cu-sulfides and represent a previously unknown type of sulfide mineralisation in a MORB environment. Geochemically, the greenstones can be divided into two types: (1) The unbrecciated galena-free greenstones from both Chile Ridge and Galfipagos Rift show at least a 10-20-fold Pb enrichment compared to fresh MORB. With respect to similar Pb enrichment measured in greenstones from two other locations, i.e. DSDP Hole 504B and Galfipagos Rift near 86°W, we suggest that this may be a general feature of all stockwork-mineralised oceanic greenstones. (2) The galena- and quartz-rich metabasalt-breccias from the Chile Ridge are up to 3000-fold enriched in Pb (up to 1000 Ixg/g Pb in the whole-rock analyses) compared to MORB and indicate Pb mineralisation two orders of magnitude higher than that of the "normal" greenstone-type. A mass-balance calculation carried out using crustal column thickness of 3000 m with a 200-m-thick greenstone layer and 0.15 m of galena-beating breccias shows that at the Chile Ridge ~ 42% of the entire Pb is concentrated in the greenstones. This suggests that the rest of the crustal column is depleted in 58% of its primary Pb content. This degree of depletion matches well with previous calculations that a 56% depletion of Pb in oceanic crust subjected to mantle-recycling via subduction would be necessary to yield a HIMU mantle source within 2 Ga. Despite the need for future investigations into the extent and volume of the Pb enrichment in Chile Ridge greenstones, we believe that this process of major Pb redistribution is capable of creating huge volumes of oceanic crust that on average are extremely Pb-depleted and which when recycled would produce the HIMU source. Keywords: Chile Ridge; Galfipagos Ridge; Hydrothermal alteration; Greenstones; Geochemistry; Mineralogy
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