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  • OceanRep  (161)
  • American Institute of Physics (AIP)
  • Blackwell Science Ltd
  • Wiley-Blackwell
  • 1
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    Fishing impact and environmental status in European seas: a diagnosis from stock assessments and ecosystem indicators (2014)
    Wiley-Blackwell
    In:  Fish and Fisheries, 17 (1). pp. 31-55.
    Details
    Publication Date: 2018-03-21
    Description: Stock‐based and ecosystem‐based indicators are used to provide a new diagnosis of the fishing impact and environmental status of European seas. In the seven European marine ecosystems covering the Baltic and the North‐east Atlantic, (i) trends in landings since 1950 were examined; (ii) syntheses of the status and trends in fish stocks were consolidated at the ecosystem level; and (iii) trends in ecosystem indicators based on landings and surveys were analysed. We show that yields began to decrease everywhere (except in the Baltic) from the mid‐1970s, as a result of the over‐exploitation of some major stocks. Fishermen adapted by increasing fishing effort and exploiting a wider part of the ecosystems. This was insufficient to compensate for the decrease in abundance of many stocks, and total landings have halved over the last 30 years. The highest fishing impact took place in the late 1990s, with a clear decrease in stock‐based and ecosystem indicators. In particular, trophic‐based indicators exhibited a continuous decreasing trend in almost all ecosystems. Over the past decade, a decrease in fishing pressure has been observed, the mean fishing mortality rate of assessed stocks being almost halved in all the considered ecosystems, but no clear recovery in the biomass and ecosystem indicators is yet apparent. In addition, the mean recruitment index was shown to decrease by around 50% in all ecosystems (except the Baltic). We conclude that building this kind of diagnosis is a key step on the path to implementing an ecosystem approach to fisheries management.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/faf.12090
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    The non-hierarchical, non-uniformly branching topology of a leuconoid sponge aquiferous system revealed by 3D reconstruction and morphometrics using corrosion casting and X-ray microtomography (2011)
    Wiley-Blackwell
    In:  Acta Zoologica, 93 (2). pp. 160-170.
    Details
    Publication Date: 2018-06-14
    Description: As sessile filter feeders, sponges rely on a highly efficient fluid transport system. Their physiology depends on efficient water exchange, which is performed by the aquiferous system. This prominent poriferan anatomical character represents a dense network of incurrent and excurrent canals on which we lack detailed 3D models. To overcome this, we investigated the complex leucon‐type architecture in the demosponge Tethya wilhelma using corrosion casting, microtomography, and 3D reconstructions. Our integrative qualitative and quantitative approach allowed us to create, for the first time, high‐resolution 3D representations of entire canal systems which were used for detailed geometric and morphometric measurements. Canal diameters lack distinct size classes, and bifurcations are non‐uniformly ramified. A relatively high number of bifurcations show previously unknown and atypical cross‐sectional area ratios. Scaling properties and topological patterns of the canals indicate a more complex overall architecture than previously assumed. As a consequence, it might be more convenient to group canals into functional units rather than hierarchical clusters. Our data qualify the leucon canal system architecture of T. wilhelma as a highly efficient fluid transport system adapted toward minimal flow resistance. Our results and approach are relevant for a better understanding of sponge biology and cultivation techniques.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1463-6395.2010.00492.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    A Late Younger Dryas-Early Holocene tephrostratigraphy for Fosen, Central Norway (2013)
    Wiley-Blackwell
    In:  Journal of Quaternary Science, 28 (8). pp. 803-811.
    Details
    Publication Date: 2018-09-05
    Description: A number of rapid climate oscillations occur during the Lateglacial–Early Holocene, 15–8 ka BP period and a well-developed tephrostratigraphy in association with these oscillations increases the possibilities to correlate climate archives around the North Atlantic. This paper presents a tephrostratigraphy for Fosen peninsula, Central Norway. Both the Vedde Ash ca.12.1 ka BP and the Saksunarvatn Ash ~10.3 ka BP are important isochrones for correlations of Late Quaternary palaeoenvironmental records in the North Atlantic region and have been assigned ages in GICC05. Beside these tephras we have also identified a new tephra, the Fosen Tephra, with a Borrobol-type geochemistry that occurs above both the Vedde Ash and the Saksunarvatn Ash with an age ~10.2 ka BP. Several tephras with Borrobol-type geochemistry have been identified around the North Atlantic. One group is the Borrobol/Penifiler tephras dated to Greenland Interstadial-1 and another group is dated to the Early Holocene. We suggest that some of the Early Holocene Borrobol-type tephras and the Fosen Tephra may actually be the same layer. If so, the Fosen Tephra is spread over a large area of the North Atlantic and has the potential to become an important marker for short-term climate variability in Scandinavia and in the northern hemisphere.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    DOI: 10.1002/jqs.2676
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Causes and consequences of Arctic freshwater routing into the Nordic Seas during late Marine Isotope Stage 5 (2018)
    Wiley-Blackwell
    In:  Journal of Quaternary Science, 33 (7). pp. 794-803.
    Details
    Publication Date: 2021-02-08
    Description: Sediment core PS1904 reveals continuous records of planktic and benthic foraminiferal stable isotopes (δ18O/δ13C) from the north-eastern Greenland continental margin. The data show good comparability with other records from the Nordic Seas, allowing the stratigraphic range of PS1904 to be dated to Marine Isotope Stage (MIS) 6. Focusing on MIS 5 reveals light δ18O values during MIS 5a compared to the last interglacial peak (MIS 5e) which indicates that surface and bottom water layers were strongly affected by freshwater during the former event. We present two possible scenarios explaining the origin and routing of the freshwater: (i) drainage of a Eurasian proglacial lake coupled with the collapse of the Kara Sea Ice Sheet at the MIS 5b/a boundary, and (ii) destabilization and melting of the nearby Greenland Ice Sheet. Although both scenarios could have acted simultaneously, sediment records from the Eurasian sector of the Arctic Ocean hint at the proglacial lake system in north-western Siberia as the largest freshwater source. Regardless of the actual source, the freshwater lowered the surface ocean salinity causing water column stratification and sea ice expansion. Increased sea-ice abundance led to a higher albedo and probably contributed to the cooling and global ice sheet growth that occurred subsequently during MIS 4.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/jqs.3060
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Episodic Quaternary volcanism in France and Germany (2006)
    Wiley-Blackwell
    In:  Journal of Quaternary Science, 21 (6). pp. 645-675.
    Details
    Publication Date: 2018-10-22
    Description: Intra‐plate volcanism in western Europe shows statistically significant episodicity during the Quaternary period. By comparing the known ages for eruptions in France and Germany, which are compiled here, with a composite oxygen isotope record, we have investigated the link between this episodic volcanism and the climate record over the last two million years. We show that increased volcanism between 415–400 ka and 17–5 ka correlates with warming phases at the end of the last Weichselian (Devensian) and earlier Elsterian (Anglian) glacial stages. The three significant caldera explosions in the eastern Eifel, Germany, are all associated with warming phases at the onset of interglacials. The growth and decay of nearby ice sheets suggest that surface changes in continental mass distribution during glacial Milankovich cycles could provide a mechanism for this correlation by means of the distal effects of flexural loading on the lithosphere.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/jqs.1005
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Growth, reproduction and life span ofSepia officinalis(Cephalopoda: Mollusca) cultured through seven consecutive generations (2012)
    Wiley-Blackwell
    In:  Journal of Zoology, 233 (2). pp. 175-192.
    Details
    Publication Date: 2020-07-17
    Description: Hundreds of Sepia officinalis were hatched and cultured through the life cycle in each of 13 populations. Two genetic lines were maintained: one for an unprecedented seven generations and another presently in its fourth. All generations—save one—produced animals in excess of 1·0 kg body weight. Seven of eight generations with adequate data records had mean weights of 1–2 kg, and the largest cuttlefish reared were a male 2·6 kg and a female 2·9 kg. Fecundity levels were high, but there was a trend towards decreased fertility in later generations, with fertilization rates dropping below 10%. In the 7th generation, most mature animals failed to engage in agonistic courtship and mating behaviour. Almost no normal eggs were laid and none was fertile, thus ending the lineage. Most culture took place at 20–24°C and temperature generally explained variations in life span duration: being of shorter length at higher temperatures. Life spans were consistently longer at 20°C and sizes were greater than predicted from previously published literature. In both lines there was a trend towards larger individuals and longer life spans in subsequent generations. Survival of hatchlings typically exceeded 90% for two months post-hatching, and survival averaged 50% or higher to sexual maturity when corrected for animals removed from the populations for experimental use.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1469-7998.1994.tb08582.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Tephrochronology of the Toba tuffs: four primary glass populations define the 75-ka Youngest Toba Tuff, northern Sumatra, Indonesia (2013)
    Wiley-Blackwell
    In:  Journal of Quaternary Science, 28 (8). pp. 772-776.
    Details
    Publication Date: 2017-11-16
    Description: Four primary glass populations, well defined by their Sr, Ba and Y concentrations, occur in the Youngest Toba Tuff (YTT), which was deposited during a Supereruption of the Toba caldera complex in northern Sumatra 75 ka. Average concentrations of major and trace elements indicate a coherent, systematic Variation of glass composition across populations. No clear pattern in the areal distribution of these four glass groups can be discerned. The multiple glass populations of the YTT easily distinguish it from the single homogeneous glass population of the Middle Toba Tuff (~500 ka), as represented by its basal vitrophyre, and that of the Oldest Toba Tuff (~800 ka), as represented by ash Layer D at the Ocean Drilling Program site 758 in the Indian Ocean.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/jqs.2672
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Determination of In and Sn Mass Fractions in Sixteen Geological Reference Materials by Isotope Dilution MC-ICP-MS (2018)
    Wiley-Blackwell
    In:  Geostandards and Geoanalytical Research, 42 (3). pp. 361-377.
    Details
    Publication Date: 2021-02-08
    Description: Mass fractions of Sn and In were determined in sixteen geological reference materials including basaltic/mafic (BCR‐2, BE‐N, BHVO‐1, BHVO‐2, BIR‐1, OKUM, W‐2, WS‐E), ultramafic (DTS‐2b, MUH‐1, PCC‐1, UB‐N) and felsic/sedimentary reference materials (AGV‐2, JA‐1, SdAR‐M2, SdAR‐H1). Extensive digestion and ion exchange separation tests were carried out in order to provide high yields (〉 90% for Sn, 〉 85% for In), low total procedural blanks (~ 1 ng for Sn, 〈 3 pg for In) and low analytical uncertainties for the elements of interest in a variety of silicate sample matrices. Replicate analyses (n = 2–13) of Sn‐In mass fractions give a combined measurement uncertainty of 2u that are generally 〈 3% and in agreement with literature data, where available. We present the first high precision In data for reference materials OKUM (32.1 ± 1.5 ng g−1), DTS‐2b (2.03 ± 0.25 ng g−1), MUH‐1 (6.44 ± 0.30 ng g−1), and PCC‐1 (3.55 ± 0.35 ng g−1) as well as the first Sn data for MUH‐1 (0.057 ± 0.010 μg g−1) and DTS‐2b (0.623 ± 0.018 μg g−1).
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/ggr.12211
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Reproductive ecology and scientific inference of steepness: a fundamental metric of population dynamics and strategic fisheries management (2010)
    Wiley-Blackwell
    In:  Fish and Fisheries, 11 (1). pp. 89-104.
    Details
    Publication Date: 2018-03-28
    Description: The relationship between the biomass of reproductively mature individuals (spawning stock) and the resulting offspring added to the population (recruitment), the stock–recruitment relationship, is a fundamental and challenging problem in all of population biology. The steepness of this relationship is commonly defined as the fraction of recruitment from an unfished population obtained when the spawning stock biomass is 20% of its unfished level. Since its introduction about 20 years ago, steepness has become widely used in fishery management, where it is usually treated as a statistical quantity. Here, we investigate the reproductive ecology of steepness, using both unstructured and age‐structured models. We show that if one has sufficient information to construct a density‐independent population model (maximum per capita productivity and natural mortality for the unstructured case or maximum per capita productivity, natural mortality and schedules of size and maturity at age for the structured model) then one can construct a point estimate for steepness. Thus, steepness cannot be chosen arbitrarily. If one assumes that the survival of recruited individuals fluctuates within populations, it is possible, by considering the early life history, to construct a prior distribution for steepness from this same demographic information. We develop the ideas for both compensatory (Beverton–Holt) and over‐compensatory (Ricker) stock–recruitment relationships. We illustrate our ideas with an example concerning bluefin tuna (Thunnus thynnus/orientalis, Scombridae). We show that assuming that steepness is unity when recruitment is considered to be environmentally driven is not biologically consistent, is inconsistent with a precautionary approach, and leads to the wrong scientific inference (which also applies for assigning steepness any other single value).
    Type: Article , PeerReviewed
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    Format: text
    DOI: 10.1111/j.1467-2979.2009.00345.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    A thousand-year record of temperature variations for Germany and Central Europe based on documentary data (2009)
    Wiley-Blackwell
    In:  Journal of Quaternary Science, 24 (5). pp. 437-449.
    Details
    Publication Date: 2018-05-15
    Description: This paper presents a temperature reconstruction of the past 1000 years for Central Europe, based on chronological records. The advantages and limitations of this hermeneutic, text-based approach are discussed and the statistic methodology is introduced. Historical documents represent direct observation of weather and atmospheric conditions with highest temporal resolution available and precise dating. A major advantage of these extensive data is that they allow the reconstruction of large numbers of variables such as winter temperature, precipitation, pressure patterns or climate extremes as well as floods or storms. Within this hermeneutic climatological research approach, even human impacts and social dimensions of climate development can be examined. In order to quantify the historical information, statistical methods are applied, based on an index approach.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1002/jqs.1302
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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