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  • 1
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    Wiley
    In:  Chichester, Wiley, vol. 231, no. 3, pp. 2-203, (ISBN 0-470-02298-1)
    Publication Date: 1982
    Keywords: Data analysis / ~ processing ; Correlation ; Seismic stratigraphy ; Seismics (controlled source seismology)
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  • 2
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    Wiley
    In:  New York, 2nd Edition, 709 pp., Wiley, vol. 75, no. 2, pp. 2-203, (ISBN: 3-7643-7143-9)
    Publication Date: 1981
    Keywords: Correlation ; Data analysis / ~ processing ; fit ; Textbook of mathematics
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  • 3
    Publication Date: 2016-12-13
    Description: Micro-Raman spectroscopy has been used on adult bivalve shells to investigate organic and inorganic shell components but has not yet been applied to bivalve larvae. It is known that the organic matrix of larval shells contains pigments, but less is known about the presence or source of these molecules in larvae. We investigated Raman spectra of seven species of bivalve larvae to assess the types of pigments present in shells of each species and how the ratio of inorganic : organic material changes in a dorso-ventral direction. In laboratory experiments, we reared larvae of three clam species in waters containing different organic signatures to determine if larvae incorporated compounds from source waters into their shells. We found differences in spectra and pigments between most species but found less intraspecific differences. A neural network classifier for Raman spectra classified five out of seven species with greater than 85% accuracy. There were slight differences between the amount and type of pigment present along the shell, with the prodissoconch I and shell margin areas being the most variable. Raman spectra of 1-day-old larvae were found to be differentiable when larvae were reared in waters with different organic signatures. With micro-Raman spectroscopy, it may be possible to identify some unknown species in the wild and trace their natal origins, which could enhance identification accuracy of bivalve larvae and ultimately aid management and restoration efforts.
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  • 4
    Publication Date: 2020-07-20
    Description: Tephra provides regional chronostratigraphical marker horizons that can link different climate archives with highly needed accuracy and precision. The results presented in this work exemplify, however, that the intermittent storage of tephra in ice sheets and during its subsequent iceberg transport, especially during glacial stages, constitutes a potential source of serious error for the application of tephrochronology to Nordic Seas and North Atlantic sediment archives. The peak shard concentration of the rhyolitic component of the North Atlantic Ash Zone II (NAAZ-II) tephra complex, often used to correlate marine and ice core records in Marine Isotope Stage (MIS) 3, is shown to lag the eruption event by ca. 100–400 years in some North Atlantic and Norwegian Sea cores. While still allowing for a correlation of archives on millennial timescales, this time delay in deposition is a major obstacle when addressing the lead–lag relationship on short timescales (years to centuries). A precise and accurate determination of lead–lag relationships between archives recording different parts of the climate system is crucial in order to test hypotheses about the processes leading to abrupt climate change and to evaluate results from climate models. Copyright # 2011 John Wiley & Sons, Ltd.
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  • 5
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    Wiley
    In:  Journal of Microscopy, 131 (2). pp. 173-186.
    Publication Date: 2017-07-13
    Description: Many of the difficulties of staining plastic embedded tissues for light and electron microscopy derive from physical exclusion of hydrophilic staining reagents by hydrophobic embedding media. Structures which stain most intensely with hydrophilic reagents usually contain less hydrophobic plastic than do non-staining structures. Such incomplete infiltration is apparently caused by exclusion of viscous, hydrophobic monomers by physically dense and/or well hydrated tissue elements. In keeping with this, generalized staining of tissues embedded in hydrophobic media does occur when hydrophobic reagents are used. Staining of plastic-free structures with single hydrophilic reagents or with sequences of such reagents, is, however, largely rate-controlled. The surprising similarity of hydrophilic and hydrophobic plastic embedding media is discussed. Limits of this simple model are explored, with a consideration of the roles of fixative and of monomer-tissue reactions
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  • 6
    Publication Date: 2018-03-15
    Description: INTRODUCTION: Lichens are self-sustaining partnerships comprising fungi as shape-forming partners for their enclosed symbiotic algae. They produce a tremendous diversity of metabolites (1050 metabolites described so far). OBJECTIVES: A comparison of metabolic profiles in nine lichen species belonging to three genera (Lichina, Collema and Roccella) by using an optimised extraction protocol, determination of the fragmentation pathway and the in situ localisation for major compounds in Roccella species. METHODS: Chemical analysis was performed using a complementary study combining a Taguchi experimental design with qualitative analysis by high-performance liquid chromatography coupled with mass spectrometry techniques. RESULTS: Optimal conditions to obtain the best total extraction yield were determined as follows: mortar grinding to a fine powder, two successive extractions, solid:liquid ratio (2:60) and 700 rpm stirring. Qualitative analysis of the metabolite profiling of these nine species extracted with the optimised method was corroborated using MS and MS/MS approaches. Nine main compounds were identified: 1 β-orcinol, 2 orsellinic acid, 3 putative choline sulphate, 4 roccellic acid, 5 montagnetol, 6 lecanoric acid, 7 erythrin, 8 lepraric acid and 9 acetylportentol, and several other compounds were reported. Identification was performed using the m/z ratio, fragmentation pathway and/or after isolation by NMR analysis. The variation of the metabolite profile in differently organised parts of two Roccella species suggests a specific role of major compounds in developmental stages of this symbiotic association. CONCLUSION: Metabolic profiles represent specific chemical species and depend on the extraction conditions, the kind of the photobiont partner and the in situ localisation of major compounds.
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  • 7
    Publication Date: 2020-07-20
    Description: Uncertainty over the identity and age of Toba tephras across peninsular India persists, with radiometric age dates contradicting earlier compositional data, which have been used to identify this important Stratigraphie marker as the Youngest Toba Tuff (YTT). To address this issue, new single glass shard analyses have been performed for samples from Morgaon and Bori (north-western India), which have recently been dated at c. 800 ka. These, and indeed all Toba tephra samples thus far analysed from India, show the presence of four populations of glass shards (defined by their Ba/Y ratio), which uniquely identifies them as products of the c. 75-ka Youngest Toba eruption. Confirmation that the YTT fingerprint is characteristic comes from new analyses of Oldest Toba Tuff (OTT) glass shards from five sites in the Indian Ocean. These are compositionally identical to Layer D from the ODP site 758 Sediment core (c. 800 ka), and belong to a single, low-Ba population, clearly different from YTT. These analyses show that there is essentially no reworked OTT material in the YTT eruption, and indicate unequivocally that all known Toba tephra occurrences in India belong to the c. 75-ka Youngest Toba eruption.
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  • 8
    Publication Date: 2018-02-20
    Description: Fucoidan, a sulfated polysaccharide in brown seaweed, has various biological activities including anti-tumor activity. We investigated the effects of fucoidan on the apoptosis of human promyeloid leukemic cells and fucoidan-mediated signaling pathways. Fucoidan induced apoptosis of HL-60, NB4, and THP-1 cells, but not K562 cells. Fucoidan treatment of HL-60 cells induced activation of caspases-8, -9, and -3, the cleavage of Bid, and changed mitochondrial membrane permeability. Fucoidan-induced apoptosis, cleavage of procaspases, and changes in the mitochondrial membrane permeability were efficiently blocked by depletion of mitogen-activated protein kinase (MAPK) kinase kinase 1 (MEKK1), and inhibitors of MAPK kinase 1 (MEK1) and c Jun NH2-terminal kinase (JNK). The phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) and JNK was increased in fucoidan-treated HL-60, NB4, and THP-1 cells, but not K562 cells. ERK1/2 activation occurred at earlier times than JNK activation and JNK activation was blocked by MEK1 inhibitor. In addition, fucoidan-induced apoptosis was inhibited by addition of glutathione and/or L-NAME, and fucoidan decreased intracellular glutathione concentrations and stimulated nitric oxide (NO) production. Buthionine-[R,S]-sulfoximine rendered HL-60 cells more sensitive to fucoidan. Depletion of MEKK1 and inhibition of MEK1 restored the intracellular glutathione content and abrogated NO production, whereas inhibition of JNK activation by SP600125 restored intracellular glutathione content but failed to inhibit NO production in fucoidan-treated HL-60 cells. These results suggest that activation of MEKK1, MEK1, ERK1/2, and JNK, depletion of glutathione, and production of NO are important mediators in fucoidan-induced apoptosis of human leukemic cells
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  • 9
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    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 14 (6). pp. 1693-1702.
    Publication Date: 2017-01-09
    Description: Axial volcanic ridges (AVRs) are found on most slow-spreading mid-ocean ridges and are thought to be the main locus of volcanism there. In this study we present high-resolution mapping of a typical, well-defined AVR on the Mid-Atlantic Ridge at 45°N. The AVR is characterized by “hummocky terrain,” composed typically of hummocks with pillowed or elongate pillowed flanks with pillowed or lobate lava flow summits, often with small haystacks sitting on their highest points. The AVR is surrounded by several areas of “flat seafloor,” composed of lobate and sheet lava flows. The spatial and morphological differences between these areas indicate different eruption processes operating on and off the AVR. Volcanic fissures are found all around and on the AVR, although those with the greatest horizontal displacement are found on the ridge crest and flat seafloor. Clusters of fissures may represent volcanic vents. Extremely detailed comparisons of sediment coverage and examination of contact relations around the AVR suggest that many of the areas of flat seafloor are of a similar age or younger than the hummocky terrain of the AVR. Additionally, all the lavas surveyed have similar degrees of sediment cover, suggesting that the AVR was either built or resurfaced in the same 50 ka time frame as the flat seafloor.
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  • 10
    Publication Date: 2017-01-24
    Description: Forazoline A, a novel antifungal polyketide with in vivo efficacy against Candida albicans, was discovered using LCMS-based metabolomics to investigate marine-invertebrate-associated bacteria. Forazoline A had a highly unusual and unprecedented skeleton. Acquisition of 13C–13C gCOSY and 13C–15N HMQC NMR data provided the direct carbon–carbon and carbon–nitrogen connectivity, respectively. This approach represents the first example of determining direct 13C–15N connectivity for a natural product. Using yeast chemical genomics, we propose that forazoline A operated through a new mechanism of action with a phenotypic outcome of disrupting membrane integrity.
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  • 11
    Publication Date: 2017-03-22
    Description: Direct estimations of turbulent fluxes and atmospheric stability were performed from a sonic anemometer at 50 m height on a meteorological mast at the Horns Rev wind farm in the North Sea. The stability and flux estimations from the sonic measurements are compared with bulk results from a cup anemometer at 15 m height and potential temperature differences between the water and the air above. Surface flux estimations from the advanced weather research and forecast (WRF) model are also validated against the sonic and bulk data. The correlation between the sonic and bulk estimates of friction velocity is high and the highest among all velocity comparisons. From the sonic–bulk–WRF inter-comparison, it is found that the atmospheric stability measures at the sonic height tend to be closer to the neutral value than the WRF and bulk estimates, which are performed within an air layer closer to the surface, not only from a systematic bulk and WRF under-prediction of the friction velocity when compared with the sonic value but also because of the lower magnitude of the sonic heat flux compared with that from the WRF simulations. Although they are not measured but parameterized or estimated, the bulk–WRF comparisons of friction velocity and 10 m wind speed show good agreement. It is also shown that on a long-term basis, the WRF and bulk estimates of stability are nearly equal and that a correction towards a slightly stable atmospheric condition has to be applied to the long-term wind profile at Horns Rev and at other locations over the North Sea, the correction being larger for points close to the coast.
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  • 12
    Publication Date: 2017-04-03
    Description: Mutations or environmental factors that result in reversal of conspicuous left–right asymmetries provide an opportunity to study developmental mechanisms. They may also provide insight into evolutionary changes in asymmetry states within and between species. King crabs (family Lithodidae) have a larger right claw and females typically exhibit a dextrally offset abdomen. Nevertheless, I observed a high incidence of left handedness in laboratory reared box crabs (Lopholithodes foraminatus) and captured the first known egg-bearing female lithodid to exhibit reversed asymmetry. This provided a unique opportunity to characterize the reversed phenotype and to compare the incidence of reversed asymmetry in the offspring of normal and reversed females. Asymmetry of the chelae became apparent in the first postzoeal stage (glaucothoe) and handedness was maintained through subsequent instars. Females with larger left claws developed reversed abdominal asymmetry by the fourth crab stage. No reversed asymmetry was observed in the mandibles of zoea larvae or juveniles of either handedness. The incidence of reversed asymmetry in glaucothoe reared from one reversed and three normal females was high (between 20% and 30%), and independent of maternity (P=0.67). Removal of the right cheliped of fourth stage zoeae, and the major cheliped of glaucothoe, did not reverse the direction of asymmetry. Elevated larval rearing temperature also did not affect the frequency of reversed individuals. This lack of evidence for either heritability or induction of handedness is enigmatic. Further investigation of reversed asymmetry in lithodid crabs may provide valuable insights into the development and evolution of bilateral asymmetries.
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  • 13
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    Wiley
    In:  In: The last great ice sheets. , ed. by Denton, G. H. and Hughes, T. J. Wiley, New York, pp. 179-206. ISBN 0-471-06006-2
    Publication Date: 2017-04-10
    Type: Book chapter , NonPeerReviewed
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  • 14
    Publication Date: 2017-12-21
    Description: Eutrophication, coupled with loss of herbivory due to habitat degradation and overharvesting, has increased the frequency and severity of macroalgal blooms worldwide. Macroalgal blooms interfere with human activities in coastal areas, and sometimes necessitate costly algal removal programmes. They also have many detrimental effects on marine and estuarine ecosystems, including induction of hypoxia, release of toxic hydrogen sulphide into the sediments and atmosphere, and the loss of ecologically and economically important species. However, macroalgal blooms can also increase habitat complexity, provide organisms with food and shelter, and reduce other problems associated with eutrophication. These contrasting effects make their overall ecological impacts unclear. We conducted a systematic review and meta-analysis to estimate the overall effects of macroalgal blooms on several key measures of ecosystem structure and functioning in marine ecosystems. We also evaluated some of the ecological and methodological factors that might explain the highly variable effects observed in different studies. Averaged across all studies, macroalgal blooms had negative effects on the abundance and species richness of marine organisms, but blooms by different algal taxa had different consequences, ranging from strong negative to strong positive effects. Blooms' effects on species richness also depended on the habitat where they occurred, with the strongest negative effects seen in sandy or muddy subtidal habitats and in the rocky intertidal. Invertebrate communities also appeared to be particularly sensitive to blooms, suffering reductions in their abundance, species richness, and diversity. The total net primary productivity, gross primary productivity, and respiration of benthic ecosystems were higher during macroalgal blooms, but blooms had negative effects on the productivity and respiration of other organisms. These results suggest that, in addition to their direct social and economic costs, macroalgal blooms have ecological effects that may alter their capacity to deliver important ecosystem services.
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  • 15
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    Wiley
    In:  Journal of Experimental Zoology Part A: Ecological Genetics and Physiology, 313A (9). pp. 618-621.
    Publication Date: 2020-07-24
    Description: Transfer of the small gaseous molecules CO2 and NH3 across biological membranes, long thought to occur solely by simple diffusion, is now known to be facilitated by members of two multigene families: aquaporins (AQP) and rhesus (Rh) proteins. Although it is accepted that AQP1 and Rh proteins are involved in CO2 and NH3 transfer, respectively, the idea that a single channel can exhibit selectivity for both gases is controversial. Indeed, studies using the same in vitro model (human red blood cells) have provided evidence both for and against a role for Rh proteins as CO2 channels. Thus, this study was initiated to provide in vivo evidence for a dual function of Rh proteins as ammonia and CO2 channels. Here, we show that in zebrafish (Danio rerio), direct ammonia–CO2 competition experiments in adults or translational knockdowns of Rh proteins in larvae affects both ammonia and CO2 excretion. These results suggest that Rh proteins in zebrafish may be common pathways for transport of ammonia and CO2.
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  • 16
    Publication Date: 2018-01-31
    Description: Metagenomic techniques are used to analyse bacterial communities allowing both culturable and unculturable species to be represented. However, the screening of oral metagenomic samples can be hindered by high animal host DNA content. This study evaluated methods for the reduction of human DNA concentrations within oral metagenomic samples. Plaque samples were collected from 27 patients presenting with periodontal disease and treated to remove human DNA using either selective lysis of eukaryotic cells at several buffer concentrations or differential centrifugation after treatment with trypsin and/or detergents. Human and bacterial DNA levels were determined by quantitative polymerase chain reaction (qPCR). The human DNA content of plaque extracts was significantly reduced by all treatments compared with an untreated control (P 〈 0.05). However, differential centrifugation simultaneously reduced the bacterial DNA content unless samples were pretreated with a detergent. Observations of Gram stained samples that were processed using differential centrifugation without detergent suggest that many bacteria remain adhered to human cells. An approach that uses differential centrifugation in parallel with selective lysis is recommended to fully represent the oral microbiota in metagenomic samples, including those tightly adhered to human cells and more delicate bacteria such as Mycoplasma.
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  • 17
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    Wiley
    In:  International Journal for Numerical and Analytical Methods in Geomechanics, 35 (2). pp. 264-292.
    Publication Date: 2018-04-11
    Description: The evolution of internal structure plays a pivotal role in the macroscopic response of granular materials to applied loads. A case in point is the so‐called ‘stress–dilatancy relation’, a cornerstone of Soil Mechanics. Numerous attempts have been made to unravel the connection between stress–dilatancy and the evolution of fabric and contact forces in a deforming granular medium. We re‐examine this connection in light of the recent findings on force chain evolution, in particular, that of collective force chain failure by buckling. This study is focussed on two‐dimensional deformation of dense granular assemblies. Analysis of individual and collective force chain bucklings is undertaken using data from a discrete element simulation. It is shown that the kinematics of force chain buckling lead to significant levels of local dilatation being developed in the buckling force chain particles and their confining first‐ring neighbors. Findings from the simulation are used to guide the development of a lattice model of collective, localized force chain buckling. Consideration of the statics and kinematics of this process yields a new stress–dilatancy relation. The physics of buckling, even at its simplest form, introduces a richness into the stress–dilatancy formulation in a way that preserves the essential aspects of fabric evolution, specifically the buckling mode.
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  • 18
    Publication Date: 2016-12-01
    Description: Marine myxobacteria (Enhygromyxa, Plesiocystis, Pseudoenhygromyxa, Haliangium) are phylogenetically distant from their terrestrial counterparts. Salimabromide is the first natural product from the Plesiocystis/Enhygromyxa clade of obligatory marine myxobacteria. Salimabromide has a new tetracyclic carbon skeleton, comprising a brominated benzene ring, a furano lactone residue, and a cyclohexane ring, bridged by a seven-membered cyclic moiety. The absolute configuration was deduced from experimental and calculated CD data. Salimabromide revealed antibiotic activity towards Arthrobacter cristallopoietes.
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  • 19
    Publication Date: 2017-07-03
    Description: Cormorants, Phalacocorax spp., have great potential to affect recreational fisheries and have increased substantially in abundance over the last decades in UK inland waters. Fabricated refuges provide a potential means of reducing fish losses, yet the benefits of such structures may be marginal if natural shelters are abundant and favoured, or if strong density-dependence limits refuge use. This study examined the efficacy of artificial shelters in mesocosm enclosures that allowed standardised and replicated observations of roach, Rutilus rutilus (L.), distribution. When given a choice between occupying open water, simulated reedbeds and artificial brushwood shelters, roach used brushwood shelters extensively across a range of fish densities. When fish had a choice of occupying open water or reedbeds offering no overhead cover, they actively avoided reedbeds and used open water almost exclusively. Occupation of reedbeds was positively related to the amount of overhead cover they provided. When artificial brushwood shelters and reedbeds offered complete overhead cover, brushwood shelters were occupied twice as much as reedbeds. Artificial shelters may therefore have wide application in stillwaters with abundant reedbeds unless the reedbeds are coupled with extensive overhead cover.
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  • 20
    Publication Date: 2017-09-01
    Description: Methane is a potent greenhouse gas and large-scale rapid release of methane from hydrate may have contributed to past abrupt climate change inferred from the geological record. The discovery in 2008 of over 250 plumes of methane gas escaping from the seabed of the West Svalbard continental margin at ~400 m water depth (mwd) suggests that hydrate is dissociating in the present-day Arctic. Here we model the dynamic response of hydrate-bearing sediments over a period of 2300 years and investigate ocean warming as a possible cause for present-day and likely future dissociation of hydrate, within 350–800 mwd, west of Svalbard. Future temperatures are given by two climate models, HadGEM2 and CCSM4, and scenarios, Representative Concentration Pathways (RCPs) 8.5 and 2.6. Our results suggest that over the next three centuries 5.3–29 Gg yr−1 of methane may be released to the Arctic Ocean on the West Svalbard margin.
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  • 21
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    Wiley
    In:  Journal of Raman Spectroscopy, 45 (1). pp. 133-138.
    Publication Date: 2017-09-14
    Description: This article compares the quality of Raman images obtained using metallurgical and oil immersion objectives to map complex structures in two and three dimensions. While the performance of these objectives for depth profiling planar structures has been discussed at length in the literature, the same comparison has not yet been made for 3D mapping of complex objects, where additional complications are introduced by non-planar geometries. Studying samples with increasing complexity shows that the oil immersion objective is strongly preferred because it yields brighter images with better contrast, and eliminates some new and confusing artefacts that do not arise with simple planar objects.
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  • 22
    Publication Date: 2017-12-14
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  • 23
    Publication Date: 2018-07-18
    Description: Although it has been more than 30 years since the discovery of deep-sea hydrothermal vents, comprehending the interconnections between hydrothermal venting and microbial life remains a challenge. Here we investigate abiotic-biotic linkages in low-temperature hydrothermal biotopes at Desperate and Lilliput on the southern Mid-Atlantic Ridge. Both sites are basalt-hosted and fluids exhibit the expected chemical signatures. However, contrasting crustal permeabilities have been proposed, supporting pervasive mixing at Desperate but restricting circulation at Lilliput. In Desperate fluids, sulfide and O2 were readily available but H2 hardly detectable. Under incubation conditions (oxic unamended, sulfide-spiked, oxic and anoxic H2 -spiked at 18°C), only sulfide oxidation by Thiomicrospira fuelled biomass synthesis. Microbial phylogenies from Desperate incubation experiments resembled those of the natural samples suggesting that the incubation conditions mimicked the environment. In Lilliput fluids, O2 was limited, whereas sulfide and H2 were enriched. Autotrophy appeared to be stimulated by residual sulfide and by amended H2 . Yet, based on bacterial phylogenies only conditions in anoxic H2 -spiked Lilliput incubations appeared similar to parts of the Lilliput habitat. In anoxic H2 -spiked Lilliput enrichments Campylobacteraceae likely supported biomass production through H2 oxidation. We argue that the diverging circulation patterns arising from different subseafloor permeabilities act as major driving forces shaping these biotope structures.
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  • 24
    Publication Date: 2018-01-29
    Description: 1. The hypothesis that cyanobacteria have higher optimum growth temperatures and higher growth rates at the optimum as compared to chlorophytes was tested by running a controlled experiment with eight cyanobacteria species and eight chlorophyte species at six different temperatures (20–35 °C) and by performing a literature survey. 2. In the experiment, all organisms except the chlorophyte Monoraphidium minutum grew well up to 35 °C. The chlorophyte Chlamydomonas reinhardtii was the fastest-growing organism over the entire temperature range (20–35 °C). 3. Mean optimum growth temperatures were similar for cyanobacteria (29.2 °C) and chlorophytes (29.2 °C). These results are concordant with published data, yielding slightly higher mean optimum growth temperatures for cyanobacteria (27.2 °C) than for chlorophytes (26.3 °C). 4. Mean growth rates of cyanobacteria at 20 °C (0.42 day−1) were significantly lower than those of chlorophytes at 20 °C (0.62 day−1). However, at all other temperatures, there were no differences between mean growth rates of cyanobacteria and chlorophytes. 5. Mean growth rates at the optimum temperature were similar for cyanobacteria (0.92 day−1) and chlorophytes (0.96 day−1). However, analysis of published data revealed that growth rates of cyanobacteria (0.65 day−1) were significantly lower than those of chlorophytes (0.93 day−1) at their optimum temperatures. 6. Although climate warming will probably lead to an intensification of cyanobacterial blooms, our results indicate that this might not be as a result of higher growth rates of cyanobacteria compared with their chlorophyte competitors. The competitive advantage of cyanobacteria can more likely be attributed to their ability to migrate vertically and prevent sedimentation in warmer and more strongly stratified waters and to their resistance to grazing, especially when warming reduces zooplankton body size.
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  • 25
    Publication Date: 2018-02-22
    Description: The Swedish UNESCO World Cultural Heritage site of the Birka and Hovgården Iron Age settlements is well suited for the testing of high-resolution archaeological prospection methods. In May 2006 ground-penetrating radar (GPR) and magnetometer test measurements were conducted at Birka, resulting in data of outstanding quality and new archaeological discoveries, but also demonstrating the need for increased spatial sampling regarding GPR prospection at complex Scandinavian sites. Therefore Birka was selected as a testing ground for a pilot study investigating the suitability of the novel multichannel GPR array system MIRA (MALÅ Imaging Radar Array) for efficient, large-scale GPR surveys with very dense spatial sampling. The study was conducted in May 2008 by MALÅ Geoscience AB in collaboration with the archaeological prospection unit of the Swedish National Heritage Board. The very high-resolution three-dimensional GPR pilot survey demonstrated that it is possible to survey 1 ha and more per day with 8 cm cross-line spacing, mapping archaeological structures in unprecedented resolution, such as postholes of only 25 cm diameter. This paper describes the tested technology and methodology as well as the fieldwork and the results of the study.
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  • 26
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    Wiley
    In:  International Journal for Numerical and Analytical Methods in Geomechanics, 34 . pp. 1634-1650.
    Publication Date: 2018-04-11
    Description: In many geotechnical systems, it is not uncommon to observe failure in zones of high localized strain called shear bands. The existing models predict the existence and the extent of these localizations, but provide little insight into the micromechanics within the shear bands. This research captures and compares the variation in microstructure both inside and outside of shear bands that formed in physical laboratory plane strain and companion numerical two-dimensional discrete element method (DEM) biaxial compression experiments. Unsheared and sheared laboratory specimens of Ottawa 20–30 sand of varying dilatancy were solidified using a two-stage resin impregnation procedure. The solidified specimens were sectioned and the resulting surfaces were prepared for microstructure observation using optical bright-field microscopy and stereological analysis. Statistical properties of microstructural parameters for sub-regions in a grid pattern and along predefined inclined zones were determined. Similar measurements were performed on 2D DEM simulation specimens at varying strain levels to characterize the evolution of microstructure with increasing strain. The results showed how differences evolved in the mean, standard deviation, and entropy of void distributions with increasing global strain levels. The results indicate how disorder increases and that the material within the shear band does not adhere to the classical concept of critical state, but reaches a terminal void ratio that is largely a function of initial void ratio. Furthermore, there appears to be a transition zone between the far field and the fully formed shear block, as opposed to an abrupt delineation as is traditionally inferred.
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  • 27
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    Wiley
    In:  Acta Zoologica, 10 (3). pp. 401-484.
    Publication Date: 2017-02-08
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  • 28
    Publication Date: 2020-07-20
    Description: Based on quantitative X-ray diffraction mineralogical analysis of cores HU2008029-0006/0008 (857-m water depth) located south of the Davis Strait sill, we seek answers to two questions: (i) the temporal correlation of NW Labrador Shelf Sea Heinrich (H-) and Baffin Bay detrital carbonate (BBDC) events, and (ii) the provenance of the sediments? A sediment-unmixing model (SedUnMix) is used to determine provenance variations. Although 12 radiocarbon dates were obtained there were many age reversals and we favour a depth/age model for HU2008029-0008PC based on correlations to well-dated neighbouring cores north and south of Davis Strait. We find no correlation between H- and BBDC events except for H-0, which appears to be a broadly synchronous event along the NE Canadian margin and is correlative with an episode of major moraine building along this flank of the Laurentide Ice Sheet. Unmixing of the sediment composition based on six potential glacial source regions indicates that the bulk of the sediment in 0008PC is derived from glacial erosion of West Greenland, but is punctuated by intervals when dolomite-rich sediments, derived from outcrops north of Baffin Bay, dominate the composition. Estimated dates on these BBDC events are -13, 25 and 30–38 cal ka BP.
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  • 29
    Publication Date: 2020-07-20
    Description: Core HU97048-007PC was recovered from the continental Labrador Sea slope at a water depth of 945 m, 250km seaward from the mouth of Cumberland Sound, and 400km north of Hudson Strait. Cumberland Sound is a structural trough partly floored by Cretaceous mudstones and Paleozoic carbonates. The record extends from 10 to 58 ka. On-board logging revealed a complex series of lithofacies, including buff-colored detrital carbonate-rich sediments [Heinrich (H)-events] frequently bracketed by black facies. We investigate the provenance of these facies using quantitative X-ray diffraction on drill-core samples from Paleozoic and Cretaceous bedrock from the SE Baffin Island Shelf, and on the〈2-mm sediment fraction in a transect of five cores from Cumberland Sound to the NW Labrador Sea. A sediment unmixing program was used to discriminate between sediment sources, which included dolomite-rich sediments from Baffin Bay, calcite-rich sediments from Hudson Strait and discrete sources from Cumberland Sound. Results indicated that the bulk of the sediment was derived from Cumberland Sound, but Baffin Bay contributed to sediments coeval with H-0 (Younger Dryas), whereas Hudson Strait was the source during H-events 1–4. Contributions from the Cretaceous outcrops within Cumberland Sound bracket H-events, thus both leading and lagging Hudson Strait-sourced H-events.
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  • 30
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    In:  Geografiska Annaler: Series A, Physical Geography, 97 (1). pp. 123-135.
    Publication Date: 2017-07-25
    Description: In virtually every assessment of responses to large-scale crises and disasters, coordination is identified as a critical failure factor. After the crisis, official committees and political opponents often characterize the early phases of the response as a ‘failure to coordinate.’ Not surprisingly, improved coordination quickly emerges as the prescribed solution. Coordination, then, is apparently both the problem and the solution. But the proposed solutions rarely solve the problem: coordination continues to mar most crises and disasters. In the absence of a shared body of knowledge on coordination, it is hard to formulate a normative framework that allows for systematic assessment of coordination in times of crisis. As coordination is widely perceived as an important function of crisis and disaster management, this absence undermines a fair and balanced assessment of crisis management performance. This paper seeks to address that void. We aim to develop a framework that explains both the failure and success of crisis coordination. We do this by exploring the relevant literature, reformulating what coordination is and distilling from research the factors that cause failure and success.
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  • 31
    Publication Date: 2017-09-20
    Description: The purine alkaloid caffeine is a major component of many beverages such as coffee and tea. Caffeine and its metabolites theobromine and xanthine have been shown to have antioxidant properties. Caffeine can also act as adenosine-receptor antagonist. Although it has been shown that adenosine and antioxidants promote wound healing, the effect of caffeine on wound healing is currently unknown. To investigate the effects of caffeine on processes involved in epithelialisation, we used primary human keratinocytes, HaCaT cell line and ex vivo model of human skin. First, we tested the effects of caffeine on cell proliferation, differentiation, adhesion and migration, processes essential for normal wound epithelialisation and closure. We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) proliferation assay to test the effects of seven different caffeine doses ranging from 0·1 to 5 mM. We found that caffeine restricted cell proliferation of keratinocytes in a dose-dependent manner. Furthermore, scratch wound assays performed on keratinocyte monolayers indicated dose-dependent delays in cell migration. Interestingly, adhesion and differentiation remained unaffected in monolayer cultures treated with various doses of caffeine. Using a human ex vivo wound healing model, we tested topical application of caffeine and found that it impedes epithelialisation, confirming in vitro data. We conclude that caffeine, which is known to have antioxidant properties, impedes keratinocyte proliferation and migration, suggesting that it may have an inhibitory effect on wound healing and epithelialisation. Therefore, our findings are more in support of a role for caffeine as adenosine-receptor antagonist that would negate the effect of adenosine in promoting wound healing.
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  • 32
    Publication Date: 2018-03-08
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  • 33
    Publication Date: 2018-02-21
    Description: Geoengineering, especially its potentially fast and high-leverage versions, is often justified as a necessary response to possible future climate emergencies. In this article, we take the notion of ‘necessity’ in international law as a starting point in assessing how rapid, high-leverage geoengineering might be justified legally. The need to specify reliably ‘grave and imminent peril’ makes such a justification difficult because our scientific ability to predict abrupt climate change, for example, as tipping elements, is limited. The time it takes to establish scientific consensus as well as policy acceptance restricts the scope for effective forewarning and so pre-emptive justifications for geoengineering become more tempting. While recognizing that dangerous, large-scale impacts of climate change is becoming increasingly difficult to avoid, the pre-emptive, emergency frame is problematic. We suggest that arguments from emergency operate on a high level of uncertainty and tend toward hubristic attempts to shape the future, as well as tending to close down rather than open up space for deliberation. We conclude that the emergency frame is not likely to go away, that ignoring or repressing it is a dangerous response, and that more effort is required to defuse and disarm emergency rhetoric.
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  • 34
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    American Medical Associa | Wiley
    In:  Archaeological Prospection, 21 (3). pp. 185-199.
    Publication Date: 2020-06-12
    Description: In May 2006 high-resolution measurements using ground-penetrating radar (GPR) and magnetic gradiometer systems conducted over selected areas at the site of the Viking Age settlement and trading place Birka in central Sweden demonstrated the suitability of these methods for archaeological prospection of Scandinavian proto-urban settlements. The non-invasive geophysical surveys revealed numerous structural details of the settlement: houses, property boundaries, track-ways, buried remains of the town ramparts dating from different building periods, including a gate, were mapped with a manually operated single-channel GPR system and a four-channel magnetometer array. The combination of these two prospection methods, state-of-the-art data processing and visualization and archaeological interpretation within a geographical information system resulted in valuable new information about the UNESCOWorld Cultural Heritage Site Birka-Hovgården.We present methodology and results of this first archaeological prospection case study conducted in 2006.
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  • 35
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    AGU (American Geophysical Union) | Wiley
    In:  In: The Mediterranean Sea. , ed. by Borzelli, G. L. E., Gačić, M., Lionello, P. and Malanotte‐Rizzoli, P. Geophysical Monograph Series, 202 . AGU (American Geophysical Union), Wiley, Washington, pp. 75-83.
    Publication Date: 2020-08-03
    Description: The eastern Mediterranean transient (EMT) was caused by a combination of high‐salinity waters intruding into the Aegean Sea and the two particularly strong winters of 1991–1992 and 1992–1993. The approach in this chapter is to search for specific signatures in the historic hydrographic observations, which date back to 1910. To deal with the problem that up into the 1950s the data not only are of limited precision but also have gaps of about 20 years, it is advantageous to consider the fact that the evolution of the actual EMT is rather well documented over a similar time span. The chapter begins by outlining the characteristics of the current EMT. Thereafter, a selection of suitable hydrographic observations among the available historic data is provided to compare these with signatures expected from the evolution of the actual EMT.
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  • 36
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    In:  International Journal for Numerical and Analytical Methods in Geomechanics, 37 (8). pp. 832-854.
    Publication Date: 2018-04-11
    Description: This article presents a fundamental study on the role of particle breakage on the shear behavior of granular soils using the three-dimensional (3-D) discrete element method. The effects of particle breakage on the stress ratio, volumetric strain, plastic deformation, and shear failure behavior of dense crushable specimens undergoing plane strain shearing conditions are thoroughly investigated through a variety of micromechanical analyses and mechanism demonstrations. The simulation of a granular specimen is based on the effective modeling of realistic fracture behavior of single soil particles, which is demonstrated by the qualitative agreement between the results from platen compression simulations and those from physical laboratory tests. The simulation results show that the major effects of particle breakage include the reduction of volumetric dilation and peak stress ratio and more importantly the plastic deformation mechanisms and the shear failure modes vary as a function of soil crushability. Consistent macro- and micromechanical evidence demonstrates that shear banding and massive volumetric contraction depict the two end failure modes of a dense specimen, which is dominated by particle rearrangement–induced dilation and particle crushing–induced compression, respectively, with a more general case being the combination and competition of the two failure modes in the medium range of soil crushability and confining stress. However, it is further shown that a highly crushable specimen will eventually develop a shear band at a large strain because of the continuous decay of particle breakage.
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  • 37
    Publication Date: 2021-05-18
    Description: Zonal wind anomalies in the western equatorial Atlantic during late boreal winter to early summer precondition boreal summer cold/warm events in the eastern equatorial Atlantic (EEA) that manifest in a strong interannual Atlantic cold tongue (ACT) variability. Local intraseasonal wind fluctuations, linked to the St. Helena anticyclone, contribute to the variability of cold tongue onset and strength, particularly during years with preconditioned shallow thermoclines. The impact of cold tongue sea surface temperature (SST) anomalies on the wind field in the Gulf of Guinea is assessed. It contributes to the northward migration of humidity and convection and possibly the West African monsoon (WAM) jump. Copyright @ 2010 Royal Meteorological Society
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  • 38
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    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 14 (5). pp. 1523-1537.
    Publication Date: 2018-02-27
    Description: Understanding the pre-anthropogenic Pb cycle of central North Pacific deep water has attracted a lot of attention in recent years, partly because of its unique geographical location in that it is a remote gyre system characterized by high dust fluxes and sluggish overturning circulation. However, the factors controlling Pb isotope evolution in this area over the Cenozoic are still controversial and various mechanisms have been proposed in previous studies. Here we report new Pb and Nd isotope time series of four ferromanganese crusts (two from the western Pacific near the Mariana arc and the other two from the central Pacific). Together with previously published records, we discuss for the first time the significance of a persistent and systematic Pb isotopic provinciality recorded by central North Pacific crusts over the Cenozoic. We propose that globally well mixed stratosphere volcanic aerosols could contribute Pb but have not been the major factors controlling the Pb isotope distribution in the central North Pacific over time. Island arc input (and probably enhanced hydrothermal input between about 45 and 20 Ma) likely controlled the Pb isotope provinciality and evolution prior to ~20 Ma, when coeval Pb isotope records in different crusts showed large differences and atmospheric silicate dust flux was extremely low. After the Eocene, in particular after 20 Ma, Asian dust input has become an isotopically resolvable source, while island arc-derived Pb has remained important to balance the dust input and to produce the observed Pb isotope distribution in the central North Pacific during this period.
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  • 39
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    AGU (American Geophysical Union) | Wiley
    In:  Journal of Geophysical Research: Oceans, 118 . pp. 2761-2773.
    Publication Date: 2018-02-27
    Description: A realistic primitive-equation model of the Southern Ocean at eddying spatial resolution is used to examine the effect of ocean-surface-velocity dependence of the wind stress on the strength of near-inertial oscillations. Accounting for the ocean-surface-velocity dependence of the wind stress leads to a large reduction of wind-induced near-inertial energy of approximately 40 percent and of wind power input into the near-inertial frequency band of approximately 20 percent. A large part of this reduction can be explained by the leading-order modification to the wind stress if the ocean-surface velocity is included. The strength of the reduction is shown to be modulated by the inverse of the ocean-surface-mixed-layer depth. We conclude that the effect of surface-velocity dependence of the wind stress should be taken into account when estimating the wind-power input into the near-inertial frequency band and when estimating near-inertial energy levels in the ocean due to wind forcing.
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  • 40
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    In:  Wiley Interdisciplinary Reviews: Climate Change, 2 (1). pp. 128-139.
    Publication Date: 2016-02-23
    Description: The history of climate modeling begins with conceptual models, followed in the 19th century by mathematical models of energy balance and radiative transfer, as well as simple analog models. Since the 1950s, the principal tools of climate science have been computer simulation models of the global general circulation. From the 1990s to the present, a trend toward increasingly comprehensive coupled models of the entire climate system has dominated the field. Climate model evaluation and intercomparison is changing modeling into a more standardized, modular process, presenting the potential for unifying research and operational aspects of climate science
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  • 41
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    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 28 (7). pp. 631-647.
    Publication Date: 2016-02-25
    Description: This study presents a new estimate of the oceanic anthropogenic CO2(Cant) sink over the industrial era (1780 to present), from assimilation of potential temperature, salinity, radiocarbon, and CFC-11 observations in a global steady state ocean circulation inverse model (OCIM). This study differs from previous data-based estimates of the oceanic Cant sink in that dynamical constraints on ocean circulation are accounted for, and the ocean circulation is explicitly modeled, allowing the calculation of oceanic Cant storage, air-sea fluxes, and transports in a consistent manner. The resulting uncertainty of the OCIM-estimated Cant uptake, transport, and storage is significantly smaller than the comparable uncertainty from purely data-based or model-based estimates. The OCIM-estimated oceanic Cant storage is 160–166 PgC in 2012, and the oceanic Cant uptake rate averaged over the period 2000–2010 is 2.6 PgC yr−1 or about 30% of current anthropogenic CO2 emissions. This result implies a residual (primarily terrestrial) Cant sink of about 1.6 PgC yr−1 for the same period. The Southern Ocean is the primary conduit for Cant entering the ocean, taking up about 1.1 PgC yr−1 in 2012, which represents about 40% of the contemporary oceanic Cant uptake. It is suggested that the most significant source of remaining uncertainty in the oceanic Cant sink is due to potential variability in the ocean circulation over the industrial era.
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  • 42
    Publication Date: 2016-03-18
    Description: Contemporary genetic diversity is the product of both historical and contemporary forces, such as climatic and geological processes affecting range distribution and continuously moulded by evolutionary forces selection, gene flow and genetic drift. Predatory freshwater fishes, such as Northern Pike Esox lucius, commonly exhibit small population sizes, and several local populations are considered endangered. Pike inhabit diverse habitat types, including lakes, rivers and brackish marine waters, thus spanning from small isolated patches to large open marine systems. However, pike population structure from local to regional scales is relatively poorly described, in spite of its significance to developing conservation measures. We analysed microsatellite variation in a total of 1185 North European pike from 46 samples collected across both local and regional scales, as well as over time, to address two overarching questions: Is pike population structure associated with local and/or regional connectivity patterns, and which factors likely have the main influence on the contemporary distribution of genetic diversity? To answer this, we combined estimators of population diversity and structure to assess evidence of whether populations within (i) habitats, (ii) drainage systems and (iii) geographical regions are closer related than among these ranges, and whether patterns are temporally stable. Contrasting previous predictions that genetic drift obscures signals of postglacial colonisation history, we identified clear regional differences in population genetic signatures, suggesting a major effect of drainage divides on colonisation history and connectivity. However, several populations deviated from the general pattern, showing that local processes may be complex and need to be examined case-by-case.
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  • 43
    Publication Date: 2016-04-18
    Description: Gas hydrate-related bottom-simulating reflectors mark the phase boundary between hydrate and free gas in the subsurface, and therefore may be used to estimate geothermal gradients and hence heat flow. The depth and temperature of the phase boundary depend on the composition of the hydrateforming gas and of the pore fluid. In the absence of direct sampling, these compositions remain unknown. We develop an alternative approach that is less sensitive to compositional uncertainties and can be applied when the bottom-simulating reflector is densely sampled in a region with significant seabed relief. We apply this approach to a three-dimensional seismic dataset from the eastern Black Sea.
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  • 44
    Publication Date: 2016-05-02
    Description: Stratospheric ozone depletion and emission of greenhouse gases lead to a trend of the southern annular mode (SAM) toward its high-index polarity. The positive phase of the SAM is characterized by stronger than usual westerly winds that induce changes in the physical carbon transport. Changes in the natural carbon budget of the upper 100 m of the Southern Ocean in response to a positive SAM phase are explored with a coupled ecosystem-general circulation model and regression analysis. Previously overlooked processes that are important for the upper ocean carbon budget during a positive SAM period are identified, namely, export production and downward transport of carbon north of the polar front (PF) as large as the upwelling in the south. The limiting micronutrient iron is brought into the surface layer by upwelling and stimulates phytoplankton growth and export production but only in summer. This leads to a drawdown of carbon and less summertime outgassing (or more uptake) of natural CO2. In winter, biological mechanisms are inactive, and the surface ocean equilibrates with the atmosphere by releasing CO2. In the annual mean, the upper ocean region south of the PF loses more carbon by additional export production than by the release of CO2 into the atmosphere, highlighting the role of the biological carbon pump in response to a positive SAM event.
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  • 45
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    AGU (American Geophysical Union) | Wiley
    In:  Global Biogeochemical Cycles, 27 (1). pp. 11-20.
    Publication Date: 2016-05-02
    Description: We combined data sets of measured sedimentary calcium carbonate (CaCO3) and satellite-derived pelagic primary production to parameterize the relation between CaCO3 content on the Antarctic shelves and primary production in the overlying water column. CaCO3 content predicted in this way was in good agreement with the measured data. The parameterization was then used to chart CaCO3 content on the Antarctic shelves all around the Antarctic, using the satellite-derived primary production. The total inventory of CaCO3 in the bioturbated layer of Antarctic shelf sediments was estimated to be 0.5 Pg C. This quantity is comparable to the total CO2 uptake by the Southern Ocean in only one to a few years (dependent on the uptake estimate and area considered), indicating that the dissolution of these carbonates will neither delay ocean acidification in this area nor augment the Southern Ocean CO2 uptake capacity.
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  • 46
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    In:  Journal of Petroleum Geology, 4 (3). pp. 235-266.
    Publication Date: 2020-07-20
    Description: Before making a critical evaluation of the crude oil and natural gas prospects for the years to the end of the century, it is necessary to review the geology and structure of the three German hydrocarbon-producing provinces. Furthermore, past exploration, production and reserves should be discussed. The three hydrocarbon-producing provinces are: the NW German Basin, the Upper Rhine Graben and the Molasse Basin, which together make up about 41% of West German territory (Fig. 1). The NW German Basin contains a sedimentary sequence over 8,000 m thick ranging in age from Permian to Quaternary. Gas and oil, the two natural hydrocarbons, are generally confined to separate lower and higher stratigraphic levels respectively (Fig. 2). The NW German Basin is the most important prospective area in West Germany. It extends into the North Sea. The tectonic rift feature of the Upper Rhine Graben originated in the Eocene. The Tertiary fill is over 4,000 m thick. Oil is found mainly in Mesozoic, Eocene and Oligocene rocks; the Miocene and Pliocene reservoir rocks contain natural gas almost exclusively (Fig. 3). The Molasse Basin is part of the foredeep north of the Alpine and Carpathian mountain ranges. The basin is filled with Upper Eocene to Pliocene and Quaternary sediments which, near the Alpine nappes, reach a thickness of over 5,000m (Fig. 4). During this century there were peaks in annual oil-production in 1910, 1940 and 1968 (see Fig. 5). The 1910 peak was the result of drilling activity in the Wietze oilfield. During the period 1934–1945, government financial aid was made available for drilling exploration wells. The success of this collaboration is demonstrated by the oil output in 1940 of 1 × 106 t. After World War II, many different types of oil-bearing structure were found, particularly by reflection seismic techniques in conjunction with detailed stratigraphical and palaeogeographical investigations. The success achieved can be seen by the peak of 8 × 106 t oil production for 1968 (Fig. 5) and in the growth of oil reserves (Fig. 7). Intensive exploration also enabled many new gasfields to be developed, especially in the deeper horizons of the NW German Basin. In 1971, estimated gas reserves reached 360 × 109 m3 (Fig. 11), and annual gas production in 1979 was 20.7 × 109 m3 (731 Bcf) (Fig. 9). There is, no doubt, still scope for the discovery and exploitation of oil and gas in Germany, especially in the NW German Basin where the best prospects for the future lie. This is borne out by two recent offshore oil discoveries and also by the successful application of enhanced recovery methods in the oilfields. The chances of finding more gas at the lower stratigraphic levels are promising now that gas has been discovered in the deeper parts of the Permian basin. The results of massive-hydraulic-fracturing tests in low-permeability pay-horizons are also encouraging. The deeper parts of oil- and gas-producing basins contain interesting prospects and have yet to be tested by ultra-deep wells. Provided that the economic climate remains favourable, there should be no difficulty in finding and supplying German oil and gas in the future. Geologically and technically possible reserves should be converted into proven and/or probable reserves. German crude oil will be available for several years beyond the year 2000, and German natural gas for a far longer time. A production rate of 19 to 20 × 109 m3 of gas per annum is feasible over the next twenty years, and oil production will probably not sink below 3 × 106 t/a in this period.
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  • 47
    Publication Date: 2019-07-08
    Description: Correlations between particulate organic carbon (POC) and mineral fluxes in the deep ocean have inspired the inclusion of “ballast effect” parameterizations in carbon cycle models. A recent study demonstrated regional variability in the effect of ballast minerals on the flux of POC in the deep ocean. We have undertaken a similar analysis of shallow export data from the Arctic, Atlantic, and Southern Oceans. Mineral ballasting is of greatest importance in the high-latitude North Atlantic, where 60% of the POC flux is associated with ballast minerals. This fraction drops to around 40% in the Southern Ocean. The remainder of the export flux is not associated with minerals, and this unballasted fraction thus often dominates the export flux. The proportion of mineral-associated POC flux often scales with regional variation in export efficiency (the proportion of primary production that is exported). However, local discrepancies suggest that regional differences in ecology also impact the magnitude of surface export. We propose that POC export will not respond equally across all high-latitude regions to possible future changes in ballast availability.
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  • 48
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    In:  Molecular Ecology, 23 (21). pp. 5291-5303.
    Publication Date: 2019-09-23
    Description: Because the vast majority of species are well diverged, relatively little is known about the genomic architecture of speciation during the early stages of divergence. Species within recent evolutionary radiations are often minimally diverged from a genomic perspective, and therefore provide rare opportunities to address this question. Here, we leverage the hamlet radiation (Hypoplectrus spp., brightly coloured reef fishes from the tropical western Atlantic) to characterize genomic divergence during the early stages of speciation. Transect surveys and spawning observations in Belize, Honduras and Panama confirm that sympatric barred (H. puella), black (H. nigricans) and butter (H. unicolor) hamlets are phenotypically distinct and reproductively isolated, although hybrid spawnings and individuals with intermediate phenotypes are seen on rare occasions. A survey of approximately 100 000 restriction site-associated SNPs in 126 samples from the three species across the three replicate populations reveals extremely slight genomewide divergence among species (FST = 0.0038), indicating that ecomorphological differences and functional reproductive isolation are maintained in sympatry in a backdrop of extraordinary genomic similarity. Nonetheless, a very small proportion of SNPs (0.05% on average) are identified as FST outliers among sympatric species. Remarkably, a single SNP is identified as an outlier in repeated populations for the same species pair. A minicontig assembled de novo around this SNP falls into the genomic region containing the HoxCa10 and HoxCa11 genes in 10 teleost species, suggesting an important role for Hox gene evolution in this radiation. This finding, if confirmed, would provide a better understanding of the links between micro- and macroevolutionary processes.
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  • 49
    Publication Date: 2021-04-23
    Description: In the vast Low Nutrient Low-Chlorophyll (LNLC) Ocean, the vertical nutrient supply from the subsurface to the sunlit surface waters is low, and atmospheric contribution of nutrients may be one order of magnitude greater over short timescales. The short turnover time of atmospheric Fe and N supply (〈1 month for nitrate) further supports deposition being an important source of nutrients in LNLC regions. Yet, the extent to which atmospheric inputs are impacting biological activity and modifying the carbon balance in oligotrophic environments has not been constrained. Here, we quantify and compare the biogeochemical impacts of atmospheric deposition in LNLC regions using both a compilation of experimental data and model outputs. A metadata-analysis of recently conducted field and laboratory bioassay experiments reveals complex responses, and the overall impact is not a simple “fertilization effect of increasing phytoplankton biomass” as observed in HNLC regions. Although phytoplankton growth may be enhanced, increases in bacterial activity and respiration result in weakening of biological carbon sequestration. The application of models using climatological or time-averaged non-synoptic deposition rates produced responses that were generally much lower than observed in the bioassay experiments. We demonstrate that experimental data and model outputs show better agreement on short timescale (days to weeks) when strong synoptic pulse of aerosols deposition, similar in magnitude to those observed in the field and introduced in bioassay experiments, is superimposed over the mean atmospheric deposition fields. These results suggest that atmospheric impacts in LNLC regions have been underestimated by models, at least at daily to weekly timescales, as they typically overlook large synoptic variations in atmospheric deposition and associated nutrient and particle inputs. Inclusion of the large synoptic variability of atmospheric input, and improved representation and parameterization of key processes that respond to atmospheric deposition, is required to better constrain impacts in ocean biogeochemical models. This is critical for understanding and prediction of current and future functioning of LNLC regions and their contribution to the global carbon cycle.
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  • 50
    Publication Date: 2017-06-09
    Description: Summary 1. Parasitized females in mammals, fish and birds can enhance the immune defence of their offspring by transferring specific antibodies for the embryo. Likewise, social insect mothers transfer immunity despite the fact that invertebrates lack antibodies. 2.  Female trans-generational immune priming is consistent with parental investment theory, because mothers invest more into rearing their offspring than fathers. However, when immune priming is not directly linked to parental care, as is often the case in insects that abandon their eggs after oviposition, both sexes might benefit from protecting their offspring. 3. Using the red flour beetle, Tribolium castaneum, we show that after parental exposure to heat-killed bacteria, trans-generational immune priming occurs through fathers as well as mothers. 4. This novel finding challenges the traditional view that males provide only genes to their offspring in species without paternal care, and raises the possibility of a division of tasks with respect to immune protection between parents.
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  • 51
    Publication Date: 2019-09-23
    Description: Marine macroalgae are constantly exposed to epibacterial colonizers. The epiphytic bacterial patterns and their temporal and spatial variability on host algae are poorly understood. To investigate the interaction between marine macroalgae and epiphytic bacteria, this study tested if the composition of epibacterial communities on different macroalgae was specific and persisted under varying biotic and abiotic environmental conditions over a 2-year observation time frame. Epibacterial communities on the co-occurring macroalgae Fucus vesiculosus, Gracilaria vermiculophylla and Ulva intestinalis were repeatedly sampled in summer and winter of 2007 and 2008. The epibacterial community composition was analysed by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene libraries. Epibacterial community profiles did not only differ significantly at each sampling interval among algal species, but also showed consistent seasonal differences on each algal species at a bacterial phylum level. These compositional patterns re-occurred at the same season of two consecutive years. Within replicates of the same algal species, the composition of bacterial phyla was subject to shifts at the bacterial species level, both within the same season but at different years and between different seasons. However, 7–16% of sequences were identified as species specific to the host alga. These findings demonstrate that marine macroalgae harbour species-specific and temporally adapted epiphytic bacterial biofilms on their surfaces. Since several algal host-specific bacteria were highly similar to other bacteria known to either avoid subsequent colonization by eukaryotic larvae or to exhibit potent antibacterial activities, algal host-specific bacterial associations are expected to play an important role for marine macroalgae.
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  • 52
    Publication Date: 2017-01-09
    Description: A wind-driven meso-scale pattern of temperature, salinity and oxygen was found along a transect in the northern Bornholm Basin (southern Baltic Sea). Strong winds caused currents along this transect, which shifted cold intermediate water (minimum: 3.6C) towards the south. The transect was surveyed with a towed CTD-system and hydroacoustics in parallel to investigate the distribution of sprat, Sprattus sprattus balticus (Schn.) in relation to the observed meso-scale pattern. In those parts of the transect where the cold intermediate water was observed, sprat were restricted to water layers below the halocline. In other parts of the transect, sprat moved into higher water layers and occupied a wider depth range. The important factor was temperature, which set an upper limit to the vertical sprat distribution. The development of hydrography, as measured in the field, was evaluated with a hydrodynamic model.
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  • 53
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    In:  Wiley Interdisciplinary Reviews: Climate Change, 1 (5). pp. 627-635.
    Publication Date: 2019-01-21
    Description: During the last decade, global surface temperatures did not increase as rapidly as in the preceding decades. Although relatively small compared to the observed centennial scale global warming, it has renewed interest in understanding and even predicting climate on time scales of decades, and sparked a community initiative on near‐term prediction that will feature in the fifth intergovernmental panel on climate change assessment report. Decadal prediction, however, is in its infancy, with only a few publications existing. This article has three aims. The first is to make the case for decadal prediction. Decadal fluctuations in global climate similar to that of recent decades were observed during the past century. Associated with large regional changes in precipitation and climate extremes, they are of socioeconomic importance. Climate models, which capture some aspects of observed decadal variability, indicate that such variations might be partly predictable. The second aim is to describe the major challenges to skilful decadal climate prediction. One is poor understanding of mechanisms of decadal climate variability, with climate models showing little agreement. Sparse observations in the past, particularly in the ocean, are also a limiting factor to developing and testing of initialization and prediction systems. The third aim is to stress that despite promising initial results, decadal prediction is in a highly experimental stage, and care is needed in interpreting results and utilizing data from such experiments. In the long‐term, decadal prediction has the potential to improve models, reduce uncertainties in climate change projections, and be of socioeconomic benefit. Copyright © 2010 John Wiley & Sons, Ltd.
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  • 54
    Publication Date: 2017-02-23
    Description: Environmental perturbation, climate change and international commerce are important drivers for biological invasions. Climate anomalies can further increase levels of habitat disturbance and act synergistically to elevate invasion risk. Herein, we use a historical data set from the upper San Francisco Estuary to provide the first empirical evidence for facilitation of invasions by climate extremes. Invasive zooplankton species did not become established in this estuary until the 1970s when increasing propagule pressure from Asia coincided with extended drought periods. Hydrological management exacerbated the effects of post-1960 droughts and reduced freshwater inflow even further, increasing drought severity and allowing unusually extreme salinity intrusions. Native zooplankton experienced unprecedented conditions of high salinity and intensified benthic grazing, and life history attributes of invasive zooplankton were advantageous enough during droughts to outcompete native species and colonise the system. Extreme climatic events can therefore act synergistically with environmental perturbation to facilitate the establishment of invasive species.
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  • 55
    Publication Date: 2019-09-23
    Description: Recent seismic evidence suggested that most oceanic plate hydration is associated with trench-outer rise faulting prior to subduction. Hydration at trenches may have a significant impact on the subduction zone water cycle. Previous seismic experiments conducted to the northwest of Nicoya Peninsula, Northern Costa Rica, have shown that the subducting Cocos lithosphere is pervasively altered, which was interpreted to be due to both hydration (serpentinization) and fracturing of the crustal and upper-mantle rocks. New seismic wide-angle reflection and refraction data were collected along two profiles, running parallel to the Middle American trench axis offshore of central Nicaragua, revealing lateral changes of the seismic properties of the subducting lithosphere. Seismic structure along both profiles is characterized by low velocities both in the crust and upper mantle. Velocities in the uppermost mantle are found to be in the range 7.3–7.5 km s−1; thus are 8–10 per cent lower than velocities typical for unaltered peridotites and hence confirm the assumption that serpentinization is a common process at the trench-outer rise area offshore of Nicaragua. In addition, a prominent velocity anomaly occurred within the crust beneath two seamounts. Here, velocity reduction may indicate increased porosity and perhaps permeability, supporting the idea that seamounts serve as sites for water percolation and circulation.
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  • 56
    Publication Date: 2018-07-10
    Description: Wide-angle seismic data have been used to determine the velocity and density structure of the crust and uppermost mantle beneath the Cape Verdes mid-plate swell. Seismic modelling reveals a ‘standard’ oceanic crust, ∼8 km in thickness, with no direct evidence for low-density bodies at the base of the crust. Gravity anomaly modelling within the constraints and resolution provided by the seismic model, does not preclude, however, a layer of crustal underplate up to 3 km thick beneath the swell crest. The modelling shows that while the seismically constrained crustal structure accounts for the short-wavelength free-air gravity anomaly, it fails to fully explain the long-wavelength anomaly. The main discrepancy is over the swell crest where the gravity anomaly, after correcting for crustal structure, is higher by about 30 mGal than it is over its flanks. The higher gravity can be explained if the top 100 km of the mantle beneath the swell crest is less dense than its surroundings by 30 kg m−3. The lack of evidence for low densities and velocities in the uppermost mantle, and high densities and velocities in the lower crust, suggests that neither a depleted swell root or crustal underplate are the origin of the observed shallower-than-predicted bathymetry and that, instead, the swell is most likely supported by dynamic uplift associated with an anomalously low density asthenospheric mantle.
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  • 57
    Publication Date: 2018-05-17
    Description: Indoor mesocosms were used to study the combined effect of warming and of different densities of overwintering mesozooplankton (mainly copepods) on the spring development of phytoplankton in shallow, coastal waters. Similar to previous studies, warming accelerated the spring phytoplankton peak by ca. 1 day 1C1 whereas zooplankton did not significantly influence timing. Phytoplankton biomass during the experimental period decreased with warming and with higher densities of overwintering zooplankton. Similarly, average cell size and average effective particle size (here: colony size) decreased both with zooplankton density and warming. A decrease in phytoplankton particle size is generally considered at typical footprint of copepod grazing. We conclude that warming induced changes in the magnitude and structure of the phytoplankton spring bloom cannot be understood without considering grazing by overwintering zooplankton.
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  • 58
    Publication Date: 2018-10-10
    Description: Aim: We investigate the relationship between local and regional richness in marine fouling assemblages using an expanded and globally replicated approach by incorporating two dimensions of diversity (taxonomic and functional) and different successional stages. Location: Global. Methods: In eight different biogeographic regions (Australia, Brazil, Chile, England, Italy, Japan, Portugal and Sweden) 68 polyvinylchloride (PVC) panels (15 × 15 × 0.3 cm) were deployed for colonization. Communities colonizing panels were analysed by measuring percentage cover at each of four different successional ages: 2, 4, 6 and 8 months. Local richness was assessed as the average number of species and functional groups (FGs) per panel and regional richness was evaluated as the estimated (Jack2) asymptote of the sample-accumulation curves for species and FG on experimental panels. Results: We found that the shape of the relationship between local and regional richness depended on successional stage and the type of richness considered, i.e. taxonomic or functional richness. Hardly any relationship was detectable between local taxonomic richness and regional taxonomic richness at any successional stage. In contrast, the relation between local functional and regional functional richness shows a unimodal pattern of change during succession, passing through the stages ‘independent’, ‘unsaturated rising’, ‘saturated rising’ and once again ‘independent’. Main conclusions: The relationship between local and regional richness, whether taxonomic or functional, frequently displays independence of the two scales, particularly in early and late phases of the successional process.
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  • 59
    Publication Date: 2016-06-20
    Description: Novel high-pressure biotechnical systems that were developed and applied for the study of anaerobic oxidation of methane (AOM) are described. The systems, referred to as high-pressure continuous incubation system (HP-CI system) and high-pressure manifold-incubation system (HP-MI system), allow for batch, fed-batch, and continuous gas-phase free incubation at high concentrations of dissolved methane and were designed to meet specific demands for studying environmental regulation and kinetics as well as for enriching microbial biomass in long-term incubation. Anoxic medium is saturated with methane in the first technical stage, and the saturated medium is supplied for biomass incubation in the second stage. Methane can be provided in continuous operation up to 20 MPa and the incubation systems can be operated during constant supply of gas-enriched medium at a hydrostatic pressure up to 45 MPa. To validate the suitability of the high-pressure systems, we present data from continuous and fed-batch incubation of highly active samples prepared from microbial mats from the Black Sea collected at a water depth of 213 m. In continuous operation in the HP-CI system initial methane-dependent sulfide production was enhanced 10- to 15-fold after increasing the methane partial pressure from near ambient pressure of 0.2 to 10.0 MPa at a hydrostatic pressure of 16.0 MPa in the incubation stage. With a hydraulic retention time of 14 h a stable effluent sulfide concentration was reached within less than 3 days and a continuing increase of the volumetric AOM rate from 1.2 to 1.7 mmol L−1 day−1 was observed over 14 days. In fed-batch incubation the AOM rate increased from 1.5 to 2.7 and 3.6 mmol L−1 day−1 when the concentration of aqueous methane was stepwise increased from 5 to 15 mmol L−1 and 45 mmol L−1. A methane partial pressure of 6 MPa and a hydrostatic pressure of 12 MPa in manifold fed-batch incubation in the HP-MI system yielded a sixfold increase in the volumetric AOM rate. Over subsequent incubation periods AOM rates increased from 0.6 to 1.2 mmol L−1 day−1 within 26 days of incubation. No inhibition of biomass activity was observed in all continuous and fed-batch incubation experiments. The organisms were able to tolerate high sulfide concentrations and extended starvation periods.
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  • 60
    Publication Date: 2016-10-26
    Description: Epsilonproteobacteria have been found globally distributed in marine anoxic/sulfidic areas mediating relevant transformations within the sulfur and nitrogen cycles. In the Baltic Sea redox zones, chemoautotrophic epsilonproteobacteria mainly belong to the Sulfurimonas gotlandica GD17 cluster for which recently a representative strain, S. gotlandica GD1T, could be established as a model organism. In this study, the potential effects of changes in dissolved inorganic carbon (DIC) and pH on S. gotlandica GD1T were examined. Bacterial cell abundance within a broad range of DIC concentrations and pH values were monitored and substrate utilization was determined. The results showed that the DIC saturation concentration for achieving maximal cell numbers was already reached at 800 μmol L−1, which is well below in situ DIC levels. The pH optimum was between 6.6 and 8.0. Within a pH range of 6.6–7.1 there was no significant difference in substrate utilization; however, at lower pH values maximum cell abundance decreased sharply and cell-specific substrate consumption increased.
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  • 61
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    In:  In: The Ocean Floor : Bruce Heezen Commemorative Volume. , ed. by Scrutton, R. A. and Talwani, M. Wiley, Chicago, Ill., USA, pp. 148-163. ISBN 0-471-10091-9
    Publication Date: 2015-12-10
    Type: Book chapter , NonPeerReviewed
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  • 62
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    In:  FEMS Microbiology Ecology, 88 (1). pp. 1-25.
    Publication Date: 2015-05-27
    Description: Harmful, bloom-forming cyanobacteria (CyanoHABs) are occurring with increasing regularity in freshwater and marine ecosystems. The most commonly occurring cyanobacterial toxins are the hepatotoxic microcystin and nodularin. These cyclic hepta- and pentapeptides are synthesised nonribosomally by the gene products of the toxin gene clusters mcy and nda, respectively. Understanding of the regulation of hepatotoxin production is incomplete, although there is strong evidence supporting the roles of iron, light, higher nitrate availability and inorganic carbon in modulating microcystin levels. The majority of these studies have focused on the unicellular freshwater, microcystin-producing strain of Microcystis aeruginosa, with little attention being paid to terrestrial or marine toxin producers. This review intends to investigate the regulation of microcystin and nodularin production in unicellular and filamentous diazotrophic cyanobacteria against the background of changing climate conditions. Special focus is given to diazotrophic filamentous cyanobacteria, for example Nodularia spumigena, capable of regulating their nitrogen levels by actively fixing dinitrogen. By combining data from significant studies, an overall scheme of the regulation of toxin production is presented, focussing specifically on nodularin production in diazotrophs against the background of increasing carbon dioxide concentrations and temperatures envisaged under current climate change models. Furthermore, the risk of sustaining and spreading CyanoHABs in the future ocean is evaluated.
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  • 63
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    Wiley
    In:  Journal of Applied Ichthyology, 29 (4). pp. 743-750.
    Publication Date: 2015-09-25
    Description: The two stocks of cod (Gadus morhua L.) in the Baltic Sea are separated by two main spawning areas and main spawning periods. Migrations of juveniles and adults result in the mixing of both stocks. At present, the two stocks have been discriminated using inter alia meristics and morphometry, genetics and tagging experiments. However, using these techniques it is not possible to assign single, non-spawning individuals to a certain stock. Since otolith shape analysis has become a common method for stock discrimination and has been applied successfully to several Atlantic cod stocks, it was applied here for the Baltic cod stocks. To obtain baseline samples, spawning cod were sampled between 2005 and 2009 in the main spawning areas during the spawning periods. The otolith contours were digitized and elliptical Fourier descriptors were analyzed. Both stocks differed significantly in their otolith shapes, and individuals could be allocated with 〉90% accuracy to one of the stocks. Both Baltic cod stocks and cod from West Greenland were discriminated with 93% correct classification. These results highlight otolith shape analysis as a useful tool to discriminate adults of Baltic cod stocks.
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  • 64
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    In:  Wiley Interdisciplinary Reviews: Climate Change, 3 (2). pp. 115-129.
    Publication Date: 2015-10-06
    Description: Climate and weather extremes are sporadically recurring events that may have major local or regional impacts on the society and the environment. These events are typically related to unusually high or low temperature, prolonged dry or wet conditions, heavy precipitation, or extreme winds. Extreme events are part of the overall climate and weather alongside average conditions and variability, and thus are not unexpected as such. Climate change is expected to affect not only means but also variability and extremes. Some inferences can be based on past and present observations, but analyses of especially rare events are hampered by the availability of long time series. Over time, depending on how far the on-going global warming takes us from the present and the past climate conditions, the weather and climate statistics may well come to shift in ways that are well outside observational data. This may lead to shifts in frequency, intensity and geographical distribution of different extremes. Indeed, projected changes in some extremes over the 21st century are quite robust, such as generally increasing warm and decreasing cold extremes. Possible changes in some other aspects, for example storms, remain much more uncertain. Science-based information both on robust findings and on relevant uncertainties on changing extremes can provide useful information for sectorial planning, disaster risk prevention and overall reduction of societal vulnerability related to climate and weather
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  • 65
    Publication Date: 2015-12-14
    Description: In this overview, we consider the rationale and practice of invertebrate introductions into Lithuanian waters, the current distribution of introduced species, test the theoretical expectations of introduction of peracaridan species into lakes, and summarize the large-scale consequences of these translocations. After some early attempts to transfer locally available species within the country, peracaridan species from the Ponto-Caspian region were introduced into Lithuanian waters during the 1960s (Pontogammarus robustoides, Obesogammarus crassus, Chaetogammarus warpachowskyi, Paramysis lacustris, Limnomysis benedeni and Hemimysis anomala). After their establishment at the site of first introduction in a newly constructed water reservoir on the Nemunas River, further deliberate introductions into Lithuanian lakes and water reservoirs, as well as into more distant areas, were undertaken. These introduced species soon contributed to fish diet and a subsequent increase in the production of commercially important fish was envisaged. However, our collation of available data does not support the enhancement of fish production in Lithuanian lakes. Although perch (selected as a model fish species) assimilated the introduced species into diet and sometimes in large quantities, there was no subsequent influence on somatic growth rates when compared with perch from lakes devoid of alien peracaridans. Comparisons of littoral fish communities of different lakes, and commercial catches in the lake with the most numerous populations of introduced species also indicate no significant effect on fish production. Negative consequences of introduction are more than obvious in contrast. To date, most of the introduced Ponto-Caspian amphipod and mysid species occur in different sites of the Baltic Sea basin outside Lithuania, and their further dispersal may be expected. These species, especially amphipods, have proved to be highly ecologically aggressive, inducing change in resident macroinvertebrate communities and causing increase of biological contamination (i.e. detract from naturalness). Thus, the introduction of alien fodder species was ill advised from an economic, and even adverse from an environmental perspective.
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  • 66
    Publication Date: 2020-07-01
    Description: 1. Macroecology has prospered in recent years due in part to the wide array of climatic data, such as those provided by theWorldClim and CliMond data sets, which has become available for research. However, important environmental variables have still been missing, including spatial data sets on UV-B radiation, an increasingly recognized driver of ecological processes. 2. We developed a set of globalUV-B surfaces (glUV) suitable to match common spatial scales in macroecology. Our data set is based on remotely sensed records fromNASA’sOzone Monitoring Instrument (Aura-OMI). Following a similar approach as for theWorldClim and CliMond data sets, we processed daily UV-B measurements acquired over a period of eight years into monthly mean UV-B data and six ecologically meaningful UV-B variables with a 15-arc minute resolution. These bioclimatic variables represent Annual Mean UV-B, UV-B Seasonality, Mean UV-B of Highest Month, Mean UV-B of Lowest Month, Sum of Monthly Mean UV-B during Highest Quarter and Sum of Monthly Mean UV-B during Lowest Quarter. We correlated our data sets with selected variables of existing bioclimatic surfaces for land and with Terra–MODIS Sea Surface Temperature for ocean regions to test for relations to known gradients and patterns. 3. UV-B surfaces showed a distinct seasonal variance at a global scale, while the intensity of UV-B radiation decreased towards higher latitudes and was modified by topographic and climatic heterogeneity. UV-B surfaces were correlated with global mean temperature and annual mean radiation data, but exhibited variable spatial associations across the globe.UV-B surfaces were otherwise widely independent of existing bioclimatic surfaces. 4. Our data set provides new climatological information relevant for macroecological analyses. As UV-B is a known driver of numerous biological patterns and processes, our data set offers the potential to generate a better understanding of these dynamics inmacroecology, biogeography, global change research and beyond. The glUV data set containing monthly mean UV-B data and six derived UV-B surfaces is freely available for download at: http://www.ufz.de/gluv.
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  • 67
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    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 40 (18). pp. 4933-4937.
    Publication Date: 2017-10-24
    Description: The tropospheric response to sudden stratospheric warmings (SSWs) is analyzed in an idealized model setup regarding the respective roles of planetary-scale and synoptic-scale waves. The control model run includes a full interactive wave spectrum, while a second run includes interactive planetary-scale waves but only the time-mean synoptic-scale wave forcing from the control run. In both runs, the tropospheric response is characterized by the negative phase of the respective tropospheric annular mode. But given their different latitudinal structure, the control run shows the expected response, i.e., an equatorward shift of the tropospheric jet, whereas the response in the absence of interactive synoptic eddies is characterized by a poleward jet shift. This opposite jet shift is associated with a different planetary wave variability that couples with the zonal flow between the stratosphere and the surface. These results indicate that the synoptic eddy feedback is necessary for the observed tropospheric response to SSWs.
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  • 68
    Publication Date: 2015-06-18
    Description: Natural antifouling products have been the subject of considerable attention. We screened marine algae for antifouling activity and discovered omaezallenes, the new bromoallene-containing natural products isolated from the red alga Laurencia sp. Described is the isolation, structure elucidation, and total syntheses of omaezallenes. The relative and absolute configurations of natural omaezallenes were unambiguously established through total synthesis. The antifouling activities and ecotoxicity of omaezallenes were also evaluated.
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  • 69
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    AGU (American Geophysical Union) | Wiley
    In:  Eos, Transactions American Geophysical Union, 94 (22). pp. 197-198.
    Publication Date: 2016-01-13
    Description: At 8:04 P.M. Pacific daylight time (PDT) on 27 October 2012 (03:04 universal time (UT), 28 October), Canada's second largest instrumentally recorded earthquake rocked Haida Gwaii (formerly Queen Charlotte Islands) and the mainland coast of British Columbia. The M 7.7 event off the west coast of Moresby Island caused a tsunami with local runup of more than 7 meters and amplitudes up to 0.8 meter on tide gauges 4000 kilometers away in Hawaii. Shaking was felt as far away as the Yukon, Alberta, Washington, and Montana, up to 1500 kilometers away. Little damage was caused, as the immediate region is an uninhabited National Park Reserve. The closest point of the rupture zone, as defined by aftershocks (Figures 1a and 1c), was 50 kilometers from the nearest community, Queen Charlotte, where damage was confined to a few chimneys and slumped roads.
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  • 70
    Publication Date: 2021-09-07
    Description: Dosidicus gigas (jumbo or Humboldt squid) is a semelparous, major predator of the eastern Pacific that is ecologically and commercially important. In the Gulf of California, these animals mature at large size (〉55 cm mantle length) in 1-1.5 years and have supported a major commercial fishery in the Guaymas Basin during the last 20 years. An El Niño event in 2009-2010, was accompanied by a collapse of this fishery, and squid in the region showed major changes in the distribution and life-history strategy. Large squid abandoned seasonal coastal-shelf habitats in 2010 and instead were found in the Salsipuedes Basin to the north, an area buffered from the effects of El Niño by tidal upwelling and a well-mixed water column. The commercial fishery also relocated to this region. Although large squid were not found in the Guaymas Basin from 2010 to 2012, small squid were abundant and matured at an unusually small mantle-length (〈30 cm) and young age (approximately 6 months). Juvenile squid thus appeared to respond to El Niño with an alternative life-history trajectory in which gigantism and high fecundity in normally productive coastal-shelf habitats were traded for accelerated reproduction at small size in an offshore environment. Both small and large mature squid, were present in the Salsipuedes Basin during 2011, indicating that both life- history strategies can coexist. Hydro-acoustic data, reveal that squid biomass in this study area nearly doubled between 2010 and 2011, primarily due to a large increase in small squid that were not susceptible to the fishery. Such a climate-driven switch in size-at-maturity may allow D. gigas to rapidly adapt to and cope with El Niño. This ability is likely to be an important factor in conjunction with longerterm climate-change and the potential ecological impacts of this invasive predator on marine ecosystems.
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  • 71
    Publication Date: 2017-09-26
    Description: Hyperthermophilic iron reducers are common in hydrothermal chimneys found along the Endeavour Segment in the northeastern Pacific Ocean based on culture-dependent estimates. However, information on the availability of Fe(III) (oxyhydr) oxides within these chimneys, the types of Fe(III) (oxyhydr) oxides utilized by the organisms, rates and environmental constraints of hyperthermophilic iron reduction, and mineral end products is needed to determine their biogeochemical significance and are addressed in this study. Thin-section petrography on the interior of a hydrothermal chimney from the Dante edifice at Endeavour showed a thin coat of Fe(III) (oxyhydr) oxide associated with amorphous silica on the exposed outer surfaces of pyrrhotite, sphalerite, and chalcopyrite in pore spaces, along with anhydrite precipitation in the pores that is indicative of seawater ingress. The iron sulfide minerals were likely oxidized to Fe(III) (oxyhydr) oxide with increasing pH and Eh due to cooling and seawater exposure, providing reactants for bioreduction. Culture-dependent estimates of hyperthermophilic iron reducer abundances in this sample were 1740 and 10 cells per gram (dry weight) of material from the outer surface and the marcasite-sphalerite-rich interior, respectively. Two hyperthermophilic iron reducers, Hyperthermus sp. Ro04 and Pyrodictium sp. Su06, were isolated from other active hydrothermal chimneys on the Endeavour Segment. Strain Ro04 is a neutrophilic (pHopt 7–8) heterotroph, while strain Su06 is a mildly acidophilic (pHopt 5), hydrogenotrophic autotroph, both with optimal growth temperatures of 90–92 °C. Mössbauer spectroscopy of the iron oxides before and after growth demonstrated that both organisms form nanophase (〈12 nm) magnetite [Fe3O4] from laboratory-synthesized ferrihydrite [Fe10O14(OH)2] with no detectable mineral intermediates. They produced up to 40 mm Fe2+ in a growth-dependent manner, while all abiotic and biotic controls produced 〈3 mm Fe2+. Hyperthermophilic iron reducers may have a growth advantage over other hyperthermophiles in hydrothermal systems that are mildly acidic where mineral weathering at increased temperatures occurs.
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  • 72
    Publication Date: 2019-01-10
    Description: Marine sponges are generally classified as high microbial abundance (HMA) and low microbial abundance (LMA) species. Here, 16S rRNA amplicon sequencing was applied to investigate the diversity, specificity and transcriptional activity of microbes associated with an LMA sponge (Stylissa carteri), an HMA sponge (Xestospongia testudinaria) and sea water collected from the central Saudi Arabia coast of the Red Sea. Altogether, 887 068 denoised sequences were obtained, of which 806 661 sequences remained after quality control. This resulted in 1477 operational taxonomic units (OTUs) that were assigned to 27 microbial phyla. The microbial composition of S. carteri was more similar to that of sea water than to that of X. testudinaria, which is consistent with the observation that the sequence data set of S. carteri contained many more possibly sea water sequences (~24%) than the X. testudinaria data set (~6%). The most abundant OTUs were shared between all three sources (S. carteri, X. testudinaria, sea water), while rare OTUs were unique to any given source. Despite this high degree of overlap, each sponge species contained its own specific microbiota. The X. testudinaria-specific bacterial taxa were similar to those already described for this species. A set of S. carteri-specific bacterial taxa related to Proteobacteria and Nitrospira was identified, which are likely permanently associated with S. carteri. The transcriptional activity of sponge-associated microorganisms correlated well with their abundance. Quantitative PCR revealed the presence of Poribacteria, representing typical sponge symbionts, in both sponge species and in sea water; however, low transcriptional activity in sea water suggested that Poribacteria are not active outside the host context.
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  • 73
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    In:  Environmental Microbiology Reports, 2 (4). pp. 507-513.
    Publication Date: 2017-03-30
    Description: Whole genome amplification (WGA) approaches provide genomic information on single microbial cells and hold great promise for the field of environmental microbiology. Here, the microbial consortia of the marine sponge Aplysina aerophoba were sorted by fluorescence-activated cell sorting (FACS) and then subjected to WGA. A cosmid library was constructed from the WGA product of a sample containing two bacterial cells, one a member of the candidate phylum Poribacteria and one of a sponge-specific clade of Chloroflexi. Library screening led to the genomic characterization of three cosmid clones, encoding a polyketide synthase (PKS), a non-ribosomal peptide synthetase (NRPS) and the Chloroflexi 16S rRNA gene. PCR screening of WGA products from additional, FACS-sorted single bacterial symbiont cells supports the assignment of the Sup-PKS gene to the Poribacteria and the novel NRPS gene to the Chloroflexi. This promising single-cell genomics approach has permitted cloning of entire gene clusters from single microbial cells of known phylogenetic origin and thus provides a sought-after link between phylogeny and function.
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  • 74
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    Wiley
    In:  Pharmazie in unserer Zeit, 39 (1). pp. 62-66.
    Publication Date: 2020-06-12
    Description: Das Phylum Schwämme und die mit ihnen assoziierten mikrobiellen Konsortien sind eine reichhaltige Quelle an neuartigen Wirkstoffen. Insbesondere die Naturstoffdiversität der Schwamm-assoziierten mikrobiellen Konsortien ist noch wenig untersucht. Methoden wie die klassische Kultivierung und die Metagenomik sind vielversprechende Ansätze zur umweltschonenden und nachhaltigen Gewinnung von neuen, bioaktiven Wirkstoffen aus Mikroorganismen. Insbesondere angesichts des vermehrten Auftretens von Antibiotika-resistenten Keimen sowie der ständigen Konfrontation mit neuen Infektionskrankheiten ist die Suche nach neuen Antibiotika/Antiinfektiva weiterhin dringend geboten.
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  • 75
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    AGU (American Geophysical Union) | Wiley
    In:  In: The Mediterranean Sea: Temporal variability and spatial patterns. Geophysical Monograph Series, 202 . AGU (American Geophysical Union), Wiley, Washington, USA, pp. 75-83.
    Publication Date: 2015-09-28
    Type: Book chapter , PeerReviewed
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  • 76
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    Wiley
    In:  Geophysical Journal International, 199 (1). pp. 441-458.
    Publication Date: 2015-10-13
    Description: Several slope failures are observed near the deformation front on the frontal ridges of the northern Cascadia accretionary margin off Vancouver Island. The cause for these events is not clear, although several lines of evidence indicate a possible connection between the occurrence of gas hydrate and submarine landslide features. The presence of gas hydrate is indicated by a prominent bottom-simulating reflector (BSR), at a depth of ∼265–275 m beneath the seafloor (mbsf), as interpreted from vertical-incidence and wide-angle seismic data beneath the ridge crests of the frontal ridges. For one slide, informally called Slipstream Slide, the velocity structure inferred from tomography analyses shows anomalous high velocities values of about 2.0 km s−1 at shallow depths of 100 mbsf. The estimated depth of the glide plane (100 ± 10 m) closely matches the depth of these shallow high velocities. In contrast, at a frontal ridge slide just to the northwest (informally called Orca Slide), the glide plane occurs at the same depth as the current BSR. Our new results indicate that the glide plane of the Slipstream slope failure is associated with the contrast between sediments strengthened by gas hydrate and overlying sediments where little or no hydrate is present. In contrast, the glide plane of Orca Slide is between sediment strengthened by hydrate underlain by sediments beneath the gas hydrate stability zone, possibly containing free gas. Additionally, a set of margin perpendicular normal faults are imaged from seafloor down to BSR depth at both frontal ridges. As inferred from the multibeam bathymetry, the estimated volume of the material lost during the slope failure at Slipstream Slide is about 0.33 km3, and ∼0.24 km3 of this volume is present as debris material on the ocean basin floor. The 20 per cent difference is likely due to more widely distributed fine sediments not easily detectable as bathymetric anomalies. These volume estimates on the Cascadia margin are approaching the mass failure volume for other slides that have generated large tsunamis—for example 1–3 km3 for a 1998 Papua New Guinea slide.
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  • 77
    Publication Date: 2015-11-04
    Description: [1] To assess the temporal variability in the methane fluxes from marine sediments that overly gas hydrate bearing sediments and the factors that might control its rate, in situ methane concentrations were measured near Bullseye Vent on the Northern Cascadia continental margin. A long-term sampling device collected overlying water and pore-fluid samples from 25 cm above seafloor, at the sediment-water interface (SWI), and 7 cmbsf (centimeters below seafloor) over a 9 month period (August 2009–May 2010). These samples provide a record at ∼4 day resolution of in situ methane, ethane, propane, sulfate, and chloride concentrations, as well as stable carbon isotope ratios of methane (δ13C-CH4) and dissolved inorganic carbon (δ13C-DIC). We show that pore fluids near the SWI are saturated or supersaturated with respect to methane (∼80 mM) and the methane flux from the seabed is variable over time. We hypothesized that regional seismic activity controlled this variable CH4 flux in the Northern Cascadia continental margin setting. However, we found no direct correlation between earthquakes and CH4 flux. We also posited alternative controls on CH4 flux variability, such as storms, regional oceanography and microbial activity. Again, no direct correlation was seen. This study takes first steps toward exploring which physical factors play a role in methane flux from hydrate-bearing sediments.
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  • 78
    Publication Date: 2015-10-20
    Description: We hypothesize that heritable epigenetic changes can affect rates of fitness increase as well as patterns of genotypic and phenotypic change during adaptation. In particular, we suggest that when natural selection acts on pure epigenetic variation in addition to genetic variation, populations adapt faster, and adaptive phenotypes can arise before any genetic changes. This may make it difficult to reconcile the timing of adaptive events detected using conventional population genetics tools based on DNA sequence data with environmental drivers of adaptation, such as changes in climate. Epigenetic modifications are frequently associated with somatic cell differentiation, but recently epigenetic changes have been found that can be transmitted over many generations. Here, we show how the interplay of these heritable epigenetic changes with genetic changes can affect adaptive evolution, and how epigenetic changes affect the signature of selection in the genetic record.
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  • 79
    Publication Date: 2020-07-29
    Description: A brief description of the Deterministic Modelling Hydrological System (DMHS) ‘Runoff–Erosion–Pollution’ proposed by the first author is presented. This system is being developed with the aim of giving it a universal character so that it can be applied in mountainous and flat terrain, and in basins of different natural climatic zones regardless of their size. The main feature of the model is its independence of the scaling problem. The basis of our approach consists of a simple theory of runoff elements. This is different from the generally accepted use of partial differential equations such as the Saint Venant equation for surface and channel flow and the Boussinesq equation for underground waters describing the water movement from runoff formation origins to the basin outlet. The results of runoff simulation for six mountainous watersheds of different sizes across Eastern Siberia within the Lena River basin and their statistical evaluation are presented. The selected river basins ranged in size from about 40 km2 (small scale) to the entire Lena River basin (2·4 million km2), classified as a large-scale basin.
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  • 80
    Publication Date: 2017-03-30
    Description: Sponges are important components of marine benthic environments and are associated with microbial symbionts that carry out ecologically relevant functions. Stylissa carteri is an abundant, low-microbial abundance species in the Red Sea. We aimed to achieve the functional and taxonomic characterization of the most actively expressed prokaryotic genes in S. carteri. Prokaryotic mRNA was enriched from sponge total RNA, sequenced using Illumina HiSeq technology and annotated using the metagenomics Rapid Annotation using Subsystem Technology (MG-RAST) pipeline. We detected high expression of archaeal ammonia oxidation and photosynthetic carbon fixation by members of the genus Synechococcus. Functions related to stress response and membrane transporters were among the most highly expressed by S. carteri symbionts. Unexpectedly, gene functions related to methylotrophy were highly expressed by gammaproteobacterial symbionts. The presence of seawater-derived microbes is indicated by the phylogenetic proximity of organic carbon transporters to orthologues of members from the SAR11 clade. In summary, we revealed the most expressed functions of the S. carteri-associated microbial community and linked them to the dominant taxonomic members of the microbiome. This work demonstrates the applicability of metatranscriptomics to explore poorly characterized symbiotic consortia and expands our knowledge of the ecologically relevant functions carried out by coral reef sponge symbionts.
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  • 81
    Publication Date: 2017-03-30
    Description: It has long been recognized that sponges differ in the abundance of associated microorganisms, and they are therefore termed either 'low microbial abundance' (LMA) or 'high microbial abundance' (HMA) sponges. Many previous studies concentrated on the dense microbial communities in HMA sponges, whereas little is known about microorganisms in LMA sponges. Here, two LMA sponges from the Red Sea, two from the Caribbean and one from the South Pacific were investigated. With up to only five bacterial phyla per sponge, all LMA sponges showed lower phylum-level diversity than typical HMA sponges. Interestingly, each LMA sponge was dominated by a large clade within either Cyanobacteria or different classes of Proteobacteria. The overall similarity of bacterial communities among LMA sponges determined by operational taxonomic unit and UniFrac analysis was low. Also the number of sponge-specific clusters, which indicate bacteria specifically associated with sponges and which are numerous in HMA sponges, was low. A biogeographical or host-dependent distribution pattern was not observed. In conclusion, bacterial community profiles of LMA sponges are clearly different from profiles of HMA sponges and, remarkably, each LMA sponge seems to harbour its own unique bacterial community
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  • 82
    Publication Date: 2020-07-27
    Description: Many marine sponges contain massive numbers of largely uncultivated, phylogenetically diverse bacteria that seem to be important contributors to the chemistry of these animals. Insights into the diversity, origin, distribution, and function of their metabolic gene communities are crucial to dissect the chemical ecology and biotechnological potential of sponge symbionts. This study reveals a sharp dichotomy between high and low microbial abundance sponges with respect to polyketide synthase (PKS) gene content, the presence of methyl-branched fatty acids, and the presence of members of the symbiotic candidate phylum "Poribacteria". For the symbiont-rich sponge Cacospongia mycofijiensis, a source of the tubulin-inhibiting fijianolides (=laulimalides), near-exhaustive large-scale sequencing of PKS gene-derived PCR amplicons was conducted. Although these amplicons exhibit high diversity at the sequence level, almost all of them belong to a single, architecturally unique group of PKSs present in "Poribacteria" and are proposed to synthesize methyl-branched fatty acids. Three components of this PKS were studied in vitro, providing initial insight into its biochemistry.
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  • 83
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    Wiley
    In:  In: Lagrangian Modeling of the Atmosphere. Wiley, pp. 225-233. ISBN 978-0-87590-490-0
    Publication Date: 2015-09-09
    Type: Book chapter , NonPeerReviewed
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  • 84
    Publication Date: 2020-06-26
    Description: Recent studies suggest that cigarette smoking may trigger the development of psoriasis through oxidative, inflammatory and genetic mechanisms. Smoking initiates formation of free radicals that stimulate cell signalling pathways active in psoriasis including mitogen-activated protein kinase (MAPK), nuclear factor-κB (NF-κB) and Janus kinase/signal transducers and activators of transcription (JAK-STAT). Smoking damages the skin by increasing formation of reactive oxygen species and decreasing the gene expression of antioxidants. Nicotine also stimulates innate immune cells integral to the pathogenesis of psoriasis including dendritic cells, macrophages and keratinocytes. These cells release cytokines that activate T lymphocytes and perpetuate a cycle of chronic inflammation. Smoking also enhances expression of genes known to confer an increased risk of psoriasis, including HLA-Cw6, HLA-DQA1*0201 and CYP1A1. Improved understanding of the possible link between smoking and psoriasis pathogenesis may provide further insight into mechanisms underlying smoking, psoriasis and risk of subsequent cardiovascular disease.
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  • 85
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    Wiley
    In:  Molecular Ecology, 21 (23). pp. 5675-5688.
    Publication Date: 2015-09-14
    Description: Marine biologists have gone through a paradigm shift, from the assumption that marine populations are largely ‘open’ owing to extensive larval dispersal to the realization that marine dispersal is ‘more restricted than previously thought’. Yet, population genetic studies often reveal low levels of genetic structure across large geographic areas. On the other side, more direct approaches such as mark-recapture provide evidence of localized dispersal. To what extent can direct and indirect studies of marine dispersal be reconciled? One approach consists in applying genetic methods that have been validated with direct estimates of dispersal. Here, we use such an approach—genetic isolation by distance between individuals in continuous populations—to estimate the spatial scale of dispersal in five species of coral reef fish presenting low levels of genetic structure across the Caribbean. Individuals were sampled continuously along a 220-km transect following the Mesoamerican Barrier Reef, population densities were estimated from surveys covering 17 200 m2 of reef, and samples were genotyped at a total of 58 microsatellite loci. A small but positive isolation-by-distance slope was observed in the five species, providing mean parent-offspring dispersal estimates ranging between 7 and 42 km (CI 1–113 km) and suggesting that there might be a correlation between minimum/maximum pelagic larval duration and dispersal in coral reef fishes. Coalescent-based simulations indicate that these results are robust to a variety of dispersal distributions and sampling designs. We conclude that low levels of genetic structure across large geographic areas are not necessarily indicative of extensive dispersal at ecological timescales.
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  • 86
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    Wiley
    In:  Environmetrics, 22 (4). pp. 501-515.
    Publication Date: 2020-07-31
    Description: Parameter estimation for stochastic dynamic systems is a core problem for the environmental and ecological sciences. This study considers parameter estimation for a simple nonlinear numerical model of marine biogeochemistry. We present a nonlinear stochastic differential equation based model for estimating parameters from non-Gaussian ocean measurements collected at a coastal ocean observatory. A sequential Monte Carlo procedure, or particle filter, provides for estimation of the time evolving state and also the basis for parameter estimation. Two approaches for estimating static parameters of the system are contrasted. The first is based on likelihood calculations, and the second on augmenting the system state with the static parameters. Sensitivity analysis identified two ecological parameters (in the differential equations model) and one statistical parameter (governing the level of dynamical noise) as candidates for estimation. Computed likelihood surfaces were found to be rough due to the sample based calculations; they also indicated the ubiquitous problem of ecological parameter dependence and identifiability. A modified state augmentation procedure, incorporating a smoothed bootstrap step, was used here for parameter estimation. Realizations for the parameter values provided by this method allowed for calculation of moments and density estimates that matched well the properties of the likelihood. Incorporation of prior information on the parameters was also considered within this context. It is concluded that such a modified state augmentation procedures provides a promising avenue in parameter estimation in numerical models
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  • 87
    Publication Date: 2020-07-01
    Description: Single crystal (U-Th)/He dating was applied to 24 apatite and 23 zircon grains from the Wetumpka impact structure, Alabama, USA. This small approximately 5–7.6 km impact crater was formed in a shallow marine environment, with no known preserved impact melt, thus offering a challenge to common geochronological techniques. A mean (U-Th)/He apatite and zircon age of 84.4 ± 1.4 Ma (2σ) was obtained, which is within error of the previously estimated Late Cretaceous impact age of approximately 83.5 Ma. In addition, helium diffusion modeling of apatite and zircon grains during fireball/contact, shock metamorphism, and hydrothermal events was undertaken, to show the influence of these individual thermal processes on resetting (U-Th)/He ages in the Wetumpka samples. This study has shown that the (U-Th)/He geochronological technique has real potential for dating impact structures, especially smaller and eroded impact structures that lack impact melt lithologies.
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  • 88
    Publication Date: 2016-10-05
    Type: Article , NonPeerReviewed
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  • 89
    Publication Date: 2016-06-17
    Description: The present study investigated the fine-scale population genetic structure of sympatric asterinid sea stars with contrasting modes of larval development (benthic versus pelagic). Parvulastra exigua lacks a dispersive life phase yet is one of the worlds most widely distributed and abundant sea stars, whereas Meridiastra calcar, a sea star with a dispersive larva, has a more limited regional scale distribution. Populations of P. exigua sampled from tide pools on three adjacent headlands showed significant genetic substructure (mitochodrial DNA control region) at fine spatial scales (tide pools 〈 300 m apart: FST = 0.249, P 〈 0.01; headlands 5–15 km apart: FST = 0.125, P = 0.04). As expected, M. calcar populations sampled from the same headlands did not exhibit significant genetic structuring (FST = 0.029, P = 0.14). The life-history traits of P. exigua, a mixed mating system (selfing + outcrossing), pseudocopulation among closely-related conspecifics, and an entirely benthic life cycle with a philopatric larva, undoubtedly influence its strong genetic structure across fine spatial scales. Localized genetic structure, especially at the very fine-scale of tide pools, would not be detected in the more typical regional scale approaches adopted by most studies of marine invertebrate populations.
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  • 90
    Publication Date: 2017-05-31
    Description: The effects of different phases of semidiurnal and spring-neap tidal cycles on phytoplankton and environmental drivers were evaluated in a tidal, freshwater location of a mesotidal estuary (Guadiana estuary, SW Iberia). An Eulerian approach was used and sampling covered different seasons during 2008. Samples were collected during spring and neap tides, at high tide, mid-ebb, low tide and mid-flood. Several physical-chemical variables were measured, as well as phytoplankton abundance and biomass. Salinity was higher at high-tide and suspended particulate matter was higher during spring tides and flood, due to higher vertical mixing and resuspension of bottom sediments. Chlorophyll a concentration during winter and summer neap tides was higher than during spring tides, whilst the abundance of pennate diatoms was higher during winter and Spring spring tides than during neap tides, probably reflecting differences in river discharge. Overall, tidally-induced differences detected in the freshwater tidal reaches of the Guadiana estuary were not as considerable as those observed in the lower estuary. However, the occurrence of tidally-induced variability in some seasons reflects that thorough sampling programs to study estuarine tidal dynamics should be conducted throughout the year. Occasional sampling will not reflect the typical variability of these highly dynamic systems. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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  • 91
    Publication Date: 2017-07-03
    Description: The Baltic Sea is characterised by a heterogeneous oceanographic environment. The deep water layers forming the habitat of Baltic cod (Gadus morhua callarias L.) are subjected to frequently occurring pronounced anoxic conditions. Adverse oxygen conditions result in physiological stress for organisms living under these conditions. For cod e.g. a direct relationship between oxygen availability and food intake with a decreasing ingestion rate at hypoxia could be revealed. In the present study, the effects of oxygen deficiency on consumption rates were investigated and how these translate to stock size estimates in multi-species models. Based on results from laboratory experiments, a model was fitted to evacuation rates at different oxygen levels and integrated into the existing consumption model for Baltic cod. Individual mean oxygen corrected consumption rates were 0.1–10.9% lower than the uncorrected ones. At the currently low predator stock size, however, the effect of oxygen-reduced consumption on the total amount of eaten prey biomass and thus predation mortalities was only marginal. But should successful management lead to higher cod stock sizes in the future, then total predation mortalities will greatly increase and thus improved precision of these estimates would be valuable for the assessment of prey stocks.
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  • 92
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    Wiley | Blackwell
    In:  Journal of Fish Biology, 77 (9). pp. 2023-2047.
    Publication Date: 2019-08-08
    Description: Parasitism is a common form of life and represents a strong selective pressure for host organisms. In response to this evolutionary pressure, vertebrates have developed genetically coded defences such as the major histocompatibility complex (MHC). Mechanisms of parasite-mediated selection not only maintain outstanding polymorphism in these genes but have also been proposed to further promote host population divergence and ultimately speciation because it can drive evolution of local adaptation in which MHC genes play a crucial role. This review first highlights the dynamics and complexity of parasite-mediated selection in natural systems, which not only depends on dominating parasite strategies and on the taxonomic diversity of the parasite community but also includes the differences in parasite communities between habitats and niches, creating divergent selection on locally adapted populations. Then the different ways in which MHC genes potentially allow vertebrates to respond to these dynamics and to adapt locally are outlined. Finally, it is proposed that varying selection strength in time and space may lead to variation in the strength of precopulatory reproductive isolation which has evolved to maintain local adaptation.
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  • 93
    Publication Date: 2018-07-10
    Description: We present a 3-D joint inversion framework for seismic, magnetotelluric (MT) and scalar and tensorial gravity data. Using large-scale optimization methods, parallel forward solvers and a flexible implementation in terms of model parametrization allows us to investigate different coupling approaches for the various physical parameters involved in the joint inversion. Here we compare two different coupling approaches, direct parameter coupling where we calculate conductivities and densities from seismic slownesses and cross-gradient coupling, where each model cell has an independent value for each physical property and a structural similarity is enforced through a term in the objective function. For both types of approaches we see an improvement of the inversion results over single inversions when the inverted data sets are generated from compatible models. As expected the direct coupling approach results in a stronger interaction between the data sets and in this case better results compared to the cross-gradient coupling. In contrast, when the inverted MT data is generated from a model that violates the parameter relationship in some regions but conforms with the cross-gradient assumptions, we obtain good results with the cross-gradient approach, while the direct coupling approach results in spurious features. This makes the cross-gradient approach the first choice for regions were a direct relationship between the physical parameters is unclear.
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  • 94
    Publication Date: 2019-09-23
    Description: Summer heat waves have already resulted in mortality of coastal communities, including ecologically important seagrass meadows. Gene expression studies from controlled experiments can provide important insight as to how species/genotypes react to extreme events that will increase under global warming. In a common stress garden, we exposed three populations of eelgrass, Zostera marina, to extreme sea surface temperatures, simulating the 2003-European heat wave. Populations came from locations widely differing in their thermal regime, two northern European locations [Ebeltoft (Kattegat), Doverodde (Limfjord, Baltic Sea)], and one southern population from Gabicce Mare (Adriatic Sea), allowing to test for population specificity in the response to a realistic heat stress event. Eelgrass survival and growth as well as the expression of 12 stress associated candidate genes were assessed during and after the heat wave. Contrary to expectations, all populations suffered equally from 3 weeks of heat stress in terms of shoot loss. In contrast, populations markedly differed in multivariate measures of gene expression. While the gene expression profiles converged to pre-stress values directly after the heat wave, stress correlated genes were upregulated again 4 weeks later, in line with the observed delay in shoot loss. Target genes had to be selected based on functional knowledge in terrestrial plants, nevertheless, 10/12 genes were induced relative to the control treatment at least once during the heat wave in the fully marine plant Z. marina. This study underlines the importance of realistic stress and recovery scenarios in studying the impact of predicted climate change.
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  • 95
    Publication Date: 2016-11-04
    Description: We examined the influence of forecasted changes in global temperatures and pCO2 on N2 fixation and assimilation in the ecologically important cyanobacterium Trichodesmium spp. Changes of mRNA transcripts (nifH, glnA, hetR, psbA, psaB), protein (nitrogenase, glutamine synthetase) pools and enzymatic activity (nitrogenase) were measured under varying pCO2 and temperatures. High pCO2 shifted transcript patterns of all genes, resulting in a more synchronized diel expression. Under the same conditions, we did not observe any significant changes in the protein pools or in total cellular allocations of carbon and nitrogen (i.e. C : N ratio remained stable). Independently of temperature, high pCO2 (900 µatm) elevated N2 fixation rates. Levels of the key enzymes, nitrogenase and glutamine synthetase that mediate nitrogen assimilation did not increase, implying that the high pCO2 allowed higher reaction turnover rates through these key enzymes. Moreover, increased temperatures and high pCO2 resulted in higher C : P ratios. The plasticity in phosphorous stoichiometry combined with higher enzymatic efficiencies lead to higher growth rates. In cyanobacteria photosynthesis, carbon uptake, respiration, N2 fixation and nitrogen assimilation share cellular components. We propose that shifted cellular resource and energy allocation among those components will enable Trichodesmium grown at elevated temperatures and pCO2 to extend its niche in the future ocean, through both tolerance of a broader temperature range and higher P plasticity.
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  • 96
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    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 40 (5). pp. 927-932.
    Publication Date: 2021-04-21
    Description: Transient tracer measurements can constrain the rates and pathways of ocean ventilation and act as proxies for biogeochemically relevant gases such as CO2 and oxygen. Various techniques have deduced changes in ocean ventilation over decadal timescales using transient tracer measurements made on repeat sections, but these require a priori assumptions about mixing in the ocean interior. Here, we introduce a simple, direct observational method that takes advantage of the similar atmospheric increase rates of chlorofluorocarbon-12 and sulfur hexafluoride, but with a time lag (offset) of 1415 years. Such repeat measurements can be directly compared without prior assumptions about mixing. A difference larger than similar to 2 years between modern sulfur hexafluoride and historical chlorofluorocarbon-12 tracer ages implies a change in ventilation, although lack of difference does not necessarily imply no change. Several tracer data sets are presented, which suggest changes in ventilation in the South Pacific and North Atlantic Oceans.
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  • 97
    Publication Date: 2019-01-22
    Description: The Cape Verde mid-plate swell is the largest amplitude oceanic mid-plate swell on Earth at similar to 1800 km in diameter, with a crest similar to 2.2 km high, and long-wavelength positive geoid, gravity and heat flow anomalies of 8 m, 30 mGal and 10 15 mW m(-2), respectively. These characteristics and its location on the slow moving-to-stationary African Plate, which concentrates the volcanism and associated geophysical anomalies within a relatively small areal extent, makes it an ideal location to test various proposed mechanisms for swell support. Wide-angle seismic refraction data have been acquired along a similar to 474 km profile extending north-south from the swell crest. In this paper, the 2-D velocity-depth crustal model derived from forward modelling of phase traveltime picks is tested using two independent inversion approaches. The final crustal velocity-depth model derived from the combined modelling, shows no evidence for widespread thickened crust or for lower crustal velocities exceeding 7.3 km s(-1) that are indicative of undercrustal magmatic material. Using the final velocity-depth model to constrain the crust for 3-D 'whole plate' lithospheric flexure modelling of island loading alone, we show that the lithosphere of the Cape Verde region appears stronger than expected for its age. Regional-scale modelling suggests that the majority of the swell height is supported by dynamic upwelling within the asthenosphere coupled with, but to a lesser degree, the effect of a region of low density in the deeper lithosphere, originating most likely from conductive reheating of the overlying plate due to its slow-to-stationary motion. When this regional upward-acting buoyancy force is considered in the context of the shorter wavelength flexure associated with island loading, modelling suggests that the apparent high plate strength is a consequence of, in effect, a regional unbending of a lithosphere that has a long-term strength typical for its age
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  • 98
    Publication Date: 2018-02-27
    Description: Results from an interannually forced, 0.08 degrees eddy-resolving simulation based on the Hybrid Coordinate Ocean Model, in conjunction with a small but well-determined transport database, are used to investigate the currents and transports associated with the Atlantic meridional overturning circulation (AMOC) in the subpolar North Atlantic (SPNA). The model results yield a consistent warming in the western SPNA since the early 1990s, along with mean transports similar to those observed for the trans-basin AMOC across the World Ocean Circulation Experiment hydrographic section AR19 (16.4 Sv) and boundary currents at the exit of the Labrador Sea near 53 degrees N (39.0 Sv) and east of the Grand Banks near 43 degrees N (15.9 Sv). Over a 34 year integration, the model-determined AMOC across the AR19 section and the western boundary current near 53 degrees N both exhibit no systematic trend but some long-term (interannual and longer) variabilities, including a decadal transport variation of 3-4 Sv from relatively high in the 1990s to low in the 2000s. The decadal variability of the model boundary current transport near 53 degrees N lags the observed winter time North Atlantic Oscillation index by about 2 years and leads the model AMOC across the AR19 section by about 1 year. The model results also show that the long-term variabilities are low compared to those on shorter time scales. Thus, rapid sampling of the current over long time intervals is required to filter out high-frequency variabilities in order to determine the lower frequency variabilities of interest
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 99
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    AGU (American Geophysical Union) | Wiley
    In:  Geophysical Research Letters, 40 (5). pp. 916-920.
    Publication Date: 2019-09-23
    Description: To investigate the mechanisms of the offset of seawater radiogenic Nd-Hf isotope compositions from those of the upper continental crust rocks, combined Nd-Hf isotope compositions of desert and loess samples from northern China (which integrate a wide range of lithologies and ages of continental rocks) are presented in this study. The results show significant and systematic fractionation of Hf isotopes between finegrained detritals/leachates (〈5 mm) and coarser fractions (〈75 mm) of the same samples. A small but systematic difference of Nd isotope compositions between leachates and detrital silicates is also revealed. Overall, the leaching data either plot along or slightly above the Nd-Hf seawater array, providing strong direct support that the seawater Nd-Hf isotope relationship is predominantly generated by weathering of upper continental crust. Our study supports the application of dissolved Hf isotopes as a proxy for different modes of weathering regimes rather than for continental source provenances.
    Type: Article , PeerReviewed
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  • 100
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    AGU (American Geophysical Union) | Wiley
    In:  Geochemistry, Geophysics, Geosystems, 14 (7). pp. 2460-2473.
    Publication Date: 2018-02-28
    Description: Large internal wave breaking is observed exceeding a vertical array of 61 high-resolution temperature sensors at 1 m intervals between 7 and 67 m above the bottom. The array was moored for 5 days at 969 m of Opouawe Bank, New Zealand, a known methane seep area. As breaking internal waves dominate sediment resuspension above sloping topography in other ocean areas, they are expected to also influence methane transport. Despite being visible in single beam echosounder data, indications for turbulence due to rising gas bubbles are not found in the present 1 Hz sampled temperature records. Likely, the mooring was too far away from the very localized bubble release spot. Instead, the temperature sensors show detailed internal wave-turbulence transitions. Every tidal cycle, a solibore (a frontal turbulent bore with a train of trailing solitary waves) changes shape and intensity. These solibores are highly turbulent and they restratify the bottom boundary layer, thereby maintaining efficient mixing. Details of different turbulent bore developments are discussed. Averaged over a few tidal cycles and over the sensors range, mean vertical eddy diffusivity amounts to 3 ± 1 × 10−3 m2 s−1 and mean turbulent kinetic energy dissipation to 1.6 ± 0.7 × 10−7 W kg−1, with variations over 4 orders of magnitude. Such turbulence will affect the distribution of dissolved methane and other geochemical species in the lower 100–150 m above the bottom and their release from the bottom. The above mean values are remarkably similar to those found at various other sites in the NE Atlantic Ocean.
    Type: Article , PeerReviewed
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