In: Deep Sea Research Part I: Oceanographic Research Papers, 143 . pp. 70-84.
Description: Highlights • next to organic matter degradation, bioirrigation and bottom water percolation through permeable surface sediments enhances benthic TPO43- and Fe2+ release • changes in bottom water oxygenation induce slight changes benthic TPO43- and Fe2+ release rates measured in 2011 and 2014 • deoxygenation experiments imply enhanced TPO43- and Fe2+ release at ongoing deoxygenation in the Mauritanian OMZ Abstract Benthic fluxes of total dissolved phosphate (TPO43-), dissolved iron (Fe2+), and dissolved inorganic carbon (DIC) were determined in situ using benthic chambers at nine stations along a depth transect between 47 and 1108 m water depth at 18 °N off Mauritania (NW Africa) during the upwelling season in 2014 (RV Meteor cruise M107). Bottom water oxygen (O2) concentrations were always ≥ 25 µM, and all fluxes (TPO43-, Fe2+, DIC) were consistently directed from the sediments into the bottom water. The highest benthic TPO43- release of 0.2 ± 0.07 mmol m2 d-1 was found at 47 m water depth (50 µM O2). The highest diffusive Fe2+ flux of 0.03 mmol m2 d-1, determined from porewater Fe2+ concentrations, occurred at 67 m water depth (27 µM O2). This was much lower than the detrital Fe supply as indicated by constant Fe/Al ratios along the depth transect. TPO43- release rates decreased concurrently with DIC flux and water depth. A difference of up to one order of magnitude between benthic chamber and diffusive TPO43- fluxes indicated that the total TPO43- release was strongly enhanced by bioirrigation. The observed fluxes were similar to those measured during an earlier cruise in 2011, generally indicating comparable release rates during both upwelling seasons. Furthermore, ex situ oxygen manipulation experiments showed an increase of the nutrient release (e.g. TPO43-, Fe2+) after seven days of anoxic bottom water conditions. The fluxes were enhanced by a factor of 1.4 for P and 7.3 for Fe compared to the measured release under natural conditions and reached values as high as those measured in the anoxic oxygen minimum zone off Peru. Our observations support the hypothesis that increasing deoxygenation of the oceans will likely enhance sedimentary TPO43- and Fe2+ release and thus contribute to a positive feedback mechanism with increasing nutrient levels and increased ocean productivity.
In: Ocean & Coastal Management, 169 . pp. 129-136.
Description: Highlights: • Designing spawning closures requires consideration of the mechanisms through which the closures can affect the fish stocks. • Small area closures may have unintended negative effects to the stocks due to fishing effort reallocation. • Closures covering most of the stock distribution are more robust to gaps in biological knowledge than small area closures. Abstract: Fisheries management measures often include spatio-temporal closures during the spawning period of the fish with an overarching aim of improving the stock status. The different mechanisms how a spawning closure potentially can influence the stock are often not explicitly considered when designing such closures. In this paper, we review and synthesize the available data and knowledge on potential effects of the implemented spawning closures on cod in the Baltic Sea. The Baltic cod example represents a relatively data rich case, which allows demonstrating how a closure might affect different parameters of stock status via different mechanisms, including potential unintended negative effects. We conclude that designing relatively small area closures appropriately is highly complex and data demanding, and may involve tradeoffs between positive and negative impacts on the stock. Seasonal closures covering most of the stock distribution during the spawning time are more robust to data limitations, and less likely to be counterproductive if suboptimally designed.
Patriat, Martin ; Falloon, Trevor ; Danyushevsky, Leonid ; [et al.] Collot, Julien ; Jean, Marlon M. ; Hoernle, Kaj ; Hauff, Folkmar ; Maas, Roland ; Woodhead, Jon D. ; Feig, Sandrin T.
In: Earth and Planetary Science Letters, 508 . pp. 30-40.
Description: Highlights • The youngest known (2 Ma) volcanically-active subduction system. • Exceptionally diverse range of magma compositions coeval and spatially juxtaposed. • Mixing of an upwelling asthenospheric mantle melt and a slab melt. • Modern example of an immature subduction system building its proto forearc. • Modern analog of the environment where SSZ ophiolites lithosphere forms. Abstract The development of ideas leading to a greater understanding of subduction initiation is limited by the scarcity of present-day examples. Furthermore, the few examples identified so far unfortunately provide few insights into the nature of magmatism at the inception of subduction. Here we report new observations from the Matthew and Hunter (M&H) subduction zone, a very young subduction zone located in the South-West Pacific. Tectonics of the area show it is younger than 2 Ma, making the M&H the youngest known volcanically-active subduction system and hence providing unique insights into the earliest stages of subduction initiation. Volcanism in this area comprises an exceptionally diverse range of contemporaneously erupting magma compositions which are spatially juxtaposed. Pb isotopic compositions and abundance of LILE and REE strongly suggest melting of upwelling asthenospheric mantle (Indian MORB) and subducted oceanic crust (Pacific MORB of the South Fiji Basin) and the mixing of these two components. Volcanism occurs much closer to the trench compared to volcanism in more mature subduction zones. We demonstrate that the M&H subduction zone is a modern example of an immature subduction system at the stage of pre-arc, near-trench magmatism. It is not yet building an arc but what we propose to call a Subduction Initiation Terrane (SITER). Today, the proto-forearc of the M&H subduction zone is a collage of these SITERs, coeval back-arc domains and remnants of pre-existing terranes including old Vitiaz Arc crust. The M&H area represents a modern analog of a Supra Subduction Zone setting where potentially a majority of ophiolites have formed their crustal and lithospheric components. Present-day magmatism in the M&H area therefore provides clues to understanding unforeseen distribution of contrasted magmatic rock types in fossil forearcs, whether they are at the front of mature subduction zones or in ophiolites.
Höfer, Juan ; Giesecke, Ricardo ; Hopwood, Mark J. ; [et al.] Carrera, Vania ; Alarcón, Emilio ; González, Humberto E.
In: Progress in Oceanography .
Description: Highlights • WAP coastal areas are able to sustain massive summer phytoplankton blooms. • WAP coastal areas may act as strong CO2 and NO3 sinks during summer. • Water column stability is the main driver of high phytoplankton growth rates. • Glacier meltwater supplies Fe, allowing phytoplankton to nearly exhaust NO3. • Future higher glacier melting may facilitate complete localized NO3 consumption. Abstract During January and February 2017 massive phytoplankton blooms (chlorophyll 〉 15 mg m−3) were registered in surface waters within two bays in the Western Antarctic Peninsula (WAP). Reflecting these intense blooms, surface waters exhibited high pH (up to 8.4), low pCO2 (〈 175 µatm) and low nitrate concentrations (down to 1.5 µM). These summer phytoplankton blooms consisted mainly of diatoms and were associated with the presence of shallow, surface freshwater plumes originating from glacier-melt outflow which contributed both to stratification and to iron supply, thus facilitating pronounced nitrate and CO2 drawdown. These findings suggest that with future increases in freshwater discharge around the WAP, phytoplankton blooms in the northern WAP may become more dominated by large cells, resembling the blooms occurring further south along the Peninsula. Fresher surface waters enhanced water column stability in both bays, enabling phytoplankton populations to attain high growth rates. Phytoplankton was observed to double their biomass in 2.3 days, consistent with the high net primary production rates recorded in both bays (1.29–8.83 g C m−2 d−1). Phytoplankton growth rates showed a direct mechanistic relationship with changes in water column stability, suggesting that this is a main driver of primary productivity in near-shore Antarctic coastal ecosystems, which agrees with previous findings. After wind induced mixing, the organic matter produced within both bays did not settle inside them, suggesting that it was laterally advected out of the bays. Thus, we hypothesize that highly productive near-shore bay areas in Antarctica may supply organic matter to oceanic waters.
In: Geochimica et Cosmochimica Acta, 245 . pp. 327-351.
Description: Stable isotope compositions of methane (δ13C and δD) and of short-chain alkanes are commonly used to trace the origin and fate of carbon in the continental crust. In continental sedimentary systems, methane is typically produced through thermogenic cracking of organic matter and/or through microbial methanogenesis. However, secondary processes such as mixing, migration or biodegradation can alter the original isotopic and composition of the gas, making the identification and the quantification of primary sources challenging. The recently resolved methane 'clumped' isotopologues Δ13CH3D and Δ12CH2D2 are unique indicators of whether methane is at thermodynamic isotopic equilibrium or not, thereby providing insights into formation temperatures and/or into kinetic processes controlling methane generation processes, including microbial methanogenesis. In this study, we report the first systematic use of methane Δ13CH3D and Δ12CH2D2 in the context of continental sedimentary basins. We investigated sedimentary formations from the Southwest Ontario and Michigan Basins, where the presence of both microbial and thermogenic methane was previously proposed. Methane from the Silurian strata coexist with highly saline brines, and clumped isotopologues exhibit large offsets from thermodynamic equilibrium, with Δ12CH2D2 values as low as -23‰. Together with conventional δ13C and δD values, the variability in Δ13CH3D and Δ12CH2D2 to first order reflects a mixing relationship between near-equilibrated thermogenic methane similar to gases from deeper Cambrian and Middle Ordovician units, and a source characterized by a substantial departure from equilibrium that could be associated with microbial methanogenesis. In contrast, methane from the Devonian-age Antrim Shale, associated with less saline porewaters, reveals Δ13CH3D and Δ12CH2D2 values that are approaching low temperature thermodynamic equilibrium. While microbial methanogenesis remains an important contributor to the methane budget in the Antrim Shale, it is suggested that Anaerobic Oxidation of Methane (AOM) could contribute to reprocessing methane isotopologues, yielding Δ13CH3D and Δ12CH2D2 signatures approaching thermodynamic equilibrium.
In: Progress in Oceanography, 171 . pp. 231-250.
Description: A central aspect of coastal biogeochemistry is to determine how nutrients, lithogenic- and organic matter are distributed and transformed within coastal and estuarine environments. Analyses of the spatio-temporal changes of total suspended matter (TSM) concentration indicate strong and variable linkages between intertidal fringes and pelagic regions. In particular, knowledge about the organic fraction of TSM provides insight to how biogenic and lithogenic particulate matter are distributed in suspension. In our study we take advantage of a set of over 3000 in situ Loss on Ignition (LoI) data from the Southern North Sea that represent fractions of particulate organic matter (POM) relative to TSM (LoI $\equiv$ POM:TSM). We introduce a parameterization (POM-TSM model) that distinguishes between two POM fractions incorporated in TSM. One fraction is described in association with mineral particles. The other represents a seasonally varying fresh pool of POM. The performance of the POM-TSM model is tested against data derived from MERIS/ENVISAT-TSM products of the German Bight. Our analysis of remote sensing data exhibits specific qualitative features of TSM that can be attributed to distinct coastal zones. Most interestingly, a transition zone between the Wadden Sea and seasonally stratified regions of the Southern North Sea is identified where mineral associated POM appears in concentrations comparable to those of freshly produced POM. We will discuss how this transition is indicative for a zone of effective particle interaction and sedimentation.The dimension of this transition zone varies between seasons and with location. Our proposed POM-TSM model is generic and can be calibrated against in situ data of other coastal regions.
Deuerling, Kelly M. ; Martin, Jonathan B. ; Martin, Ellen E. ; [et al.] Abermann, Jakob ; Myreng, Sille Marie ; Petersen, Dorthe ; Rennermalm, Åsa K.
In: Geochimica et Cosmochimica Acta, 245 . pp. 426-440.
Description: Proglacial streams deliver melt water and chemical weathering products, including nutrients and radiogenic isotopes, from continental ice sheets to the ocean. Weathering products are also delivered to the ocean in non-glacial streams that form following ice sheet retreat and are disconnected from ice sheet meltwater by hydrologic divides. If weathering reactions differ in non-glacial and proglacial stream catchments, the streams could deliver different types and magnitudes of solutes to the ocean, depending on relative discharge volumes. Unlike proglacial streams, however, little is known of non-glacial stream solute compositions or discharge. Here we show specific discharges are similar from a proglacial stream draining the Greenland Ice Sheet (GrIS) with several streams disconnected from the ice sheet. We also evaluate weathering reactions across a 170-km transect in western Greenland that contains one proglacial stream draining the GrIS, and two coastal (ice distal) and three inland (ice proximal) areas with non-glacial streams. Non-glacial streams exhibit solute compositions and offsets between dissolved and bedload Sr isotope ratios that indicate weathering increases toward the coast with exposure age and precipitation. Major element mass balance calculations show weathering reactions shift from predominately carbonic acid weathering of carbonate minerals inland near the ice sheet to predominately sulfuric acid weathering of carbonate minerals near the coast. Strontium concentrations and isotopic ratios of the proglacial stream reflect mixing of at least two subglacial sources and minor in-stream weathering that consumes CO2. About 5 times less CO2 is consumed per liter in the proglacial than inland non-glacial streams; however, arid conditions inland suggest limited discharge from the ungauged inland streams leads to less total CO2 weathering than proglacial stream. One coastal area consumes less CO2 per liter than the proglacial stream and another coastal area exhibits net CO2 production. These results indicate estimates for glacial foreland solute fluxes and CO2 weathering consumption and production should include estimates from both non-glacial and proglacial streams. Understanding weathering fluxes from these two types of streams will be important for evaluations of past ice sheet retreat and predictions of future solute and CO2 fluxes associated with continued ice sheet retreat.
Bao, Rui ; Blattmann, Thomas M. ; McIntyre, Cameron ; [et al.] Zhao, Meixun ; Eglinton, Timothy I.
In: Earth and Planetary Science Letters, 505 . pp. 76-85.
Description: Highlights • Continental margin-scale spatial variability in C values among grain size fractions is presented. • Two different hydrodynamic modes influencing in 14C heterogeneity are identified. • A new index (H14 index) is defined to describe overall 14C heterogeneity within marine surface sedimentary OC. Abstract The deposition and long-term burial of sedimentary organic matter (OM) on continental margins comprises a fundamental component of the global carbon cycle. A key unknown in interpretation of carbon isotope records of sedimentary OM is the extent to which OM accumulating in continental shelf and slope sediments is influenced by dispersal and redistribution processes. Here, we present results from an extensive survey of organic carbon (OC) characteristics of grain size fractions (ranging from 〈20 to 250 μm) retrieved from Chinese marginal sea surface sediments in order to assess the extent to which the abundance and isotope composition of OM in shallow shelf seas is influenced by hydrodynamic processes. Our findings show that contrasting relationships exist between 14C contents of OC and grain size in surface sediments associated with two different hydrodynamic modes, suggesting that transport pathways and mechanisms imparted by the different hydrodynamic conditions exert a strong influence on 14C contents of OM in continental shelf sediments. In deeper regions and erosional areas, we infer that bedload transport exerts the strongest influence on (decreases) OC 14C contents of the coarser fraction, while resuspension processes induce OC 14C depletion of intermediate grain size fractions in shallow inner-shelf settings. We use the inter-fraction spread in 14C values, defined here as 14H , to argue that the hydrodynamic processes amplify overall 14C heterogeneity within corresponding bulk sediment samples. The magnitude and footprint of this heterogeneity carries implications for our understanding of carbon cycling in shallow marginal seas.
Schellnhuber, H. J. ; Martin, M.
In: Journal of Geodynamics, 124 . pp. 14-24.
Description: The Earth's ocean floor deforms continuously under the influence of plate tectonic processes. In recent years, the development of deep-sea instruments using acoustic direct-path ranging allows observations of ocean floor deformation with unprecedented spatial and temporal resolution. Due to rapid technological progress, acoustic ranging emerged as a central research field to monitor seafloor deformation. Here we review recent developments and the progress of direct-path ranging applications. We discuss the methodology and examine the effects of the oceanographic environment on the measurement precision. Comparing the resolution of previous deployments, we find that the baseline uncertainty increases linearly with baseline length, at least for distances up to 3 km, but with different linear relations for each deployment. Measurements of displacement at millimeter-level precision across normal, thrust or strike-slip faults are discussed to evaluate the influence of dedicated network designs appropriate for the discrete fault geometries. Furthermore, tectonically quiet areas, such as flanks of coastal or ocean island volcanoes and passive continental margins pose substantial hazards that often lack in-situ monitoring and are therefore a significant target for the application of seafloor geodetic techniques.
In: Tectonophysics, 750 . pp. 434-457.
Description: The Manihiki Plateau, a Large Igneous Province (LIP) in the western Pacific, has been proposed to be emplaced as part of the "Greater Ontong Java Event" during the early Cretaceous. Shortly after its formation, the Manihiki Plateau fragmented into multiple sub-provinces. Plate tectonic reconstructions ignore this fragmentation, treating the Manihiki Plateau as a single crustal block. By analyzing two seismic refraction/wide-angle reflection profiles crossing the two largest sub-provinces of the Manihiki Plateau, we provide new insight into their deep crustal structure and magmatic evolution. Our data indicate that the High Plateau and the Western Plateaus were emplaced as a single unit during an initial phase of massive magmatic activity, but later magmatic stages altered the individual sub-provinces considerably. The High Plateau has a crustal thickness of 20 km and its P-wave velocity distribution is comparable to previously surveyed oceanic LIPs. Strong secondary magmatic phases are visible by eruptive centers and former magmatic pathways in the middle and lower crust. The Western Plateaus, which have a crustal thickness decreasing gradually from 17.3 km (East) to 9.2 km (West), experienced smaller amounts of magmatism mainly along fault zones and on local seamounts. Therefore, we propose a distinct development of the two main sub-provinces of the Manihiki Plateau after their initial joint emplacement. The High Plateau experienced voluminous multi-phase magmatic accretion and extrusion, whereas the thinner Western Plateaus exhibit only relatively minor magmatic growth. Such a large difference in the evolution process has not been reported from any other oceanic LIP so far.
Jacques, G. ; Hauff, Folkmar ; Hoernle, Kaj ; [et al.] Werner, Reinhard ; Uenzelmann-Neben, G. ; Garbe-Schönberg, Dieter ; Fischer, M.
In: Chemical Geology, 507 . pp. 9-22.
Description: Highlights • The volcanic nature of the Mozambique Ridge is clearly established. • It is a Large Igneous Province. • It is formed by a mantle plume originating from the African LLSVP. Abstract The Mozambique Ridge (MOZR) is one of several bathymetric highs formed in the South African gateway shortly after the breakup of the supercontinent Gondwana. Two major models have been proposed for its formation - volcanic plateau and continental raft. In order to gain new insights into the genesis of the Mozambique Ridge, R/V SONNE cruise SO232 carried out bathymetric mapping, seismic reflection studies and comprehensive rock sampling of the igneous plateau basement. In this study, geochemical data are presented for 51 dredged samples, confirming the volcanic origin of at least the upper (exposed) part of the plateau. The samples have DUPAL-like geochemical compositions with high initial 87Sr/86Sr (0.7024–0.7050), low initial 143Nd/144Nd (0.5123–0.5128) and low initial 176Hf/177Hf (0.2827–0.2831), and elevated initial 207Pb/204Pb and 208Pb/204Pb at a given 206Pb/204Pb (Δ7/4 = 2–16; Δ8/4 = 13–167). The geochemistry, however, is not consistent with exclusive derivation from an Indian MORB-type mantle source and requires a large contribution from at least two components. Ratios of fluid-immobile incompatible elements suggest the addition of an OIB-type mantle to the ambient upper mantle. The MOZR shares similar isotopic compositions similar to mixtures of sub-continental lithospheric mantle end members but also to long-lived, mantle-plume-related volcanic structures such as the Walvis Ridge, Discovery Seamounts and Shona hotspot track in the South Atlantic Ocean, which have been proposed to ascend from the African Large Low Shear Velocity Province (LLSVP), a possible source for DUPAL-type mantle located at the core-mantle boundary. Interestingly, the MOZR also overlaps compositionally with the nearby Karoo-Vestfjella Continental Flood Basalt province after filtering for the effect of interaction with the continental lithosphere. This geochemical similarity suggests that both volcanic provinces may be derived from a common deep source. Since a continuous hotspot track connecting the Karoo with the MOZR has not been found, there is some question about derivation of both provinces from the same plume. In conclusion, two possible models arise: (1) formation by a second mantle upwelling (blob or mantle plume), possibly reflecting a pulsating plume, or (2) melting of subcontinental lithospheric material transferred by channelized flow to the mid-ocean ridge shortly after continental break-up. Based on geological, geophysical and geochemical observations from this study and recent published literature, the mantle-plume model is favored.
Description: The thermal state of polar continental crust plays a crucial role for understanding the stability and thickness of large ice sheets, the visco-elastic response of the solid Earth due to unloading when large ice caps melt and, in turn, the accuracy of future sea-level rise prediction. Various studies demonstrate the need for precise measurements and estimation of geothermal heat flow (GHF) in Antarctica for better constrained boundary conditions to enhance the ice sheet model performance. This study provides ground-truth for regional indirect GHF estimates in the Amundsen Sea Embayment, which is part of the West Antarctic Rift System, by presenting in situ temperature measurements in continental shelf sediments. Our results show regionally elevated and heterogeneous GHF (mean of 65 mWm−2) in the Amundsen Sea Embayment. Considering thermal blanketing effects, induced by inflow of warmer water and sedimentary processes, the estimated GHF ranges between 65 mWm−2and 95 mWm−2.
Gonneea, Meagan Eagle ; Maio, Christopher V. ; Kroeger, Kevin D. ; [et al.] Hawkes, Andrea D. ; Mora, Jordan ; Sullivan, Richard ; Madsen, Stephanie ; Buzard, Richard M. ; Cahill, Niamh ; Donnelly, Jeffrey P.
In: Estuarine, Coastal and Shelf Science, 217 . pp. 56-68.
Description: Salt marshes respond to sea-level rise through a series of complex and dynamic bio-physical feedbacks. In this study, we found that sea-level rise triggered salt marsh habitat restructuring, with the associated vegetation changes enhancing salt marsh elevation resilience. A continuous record of marsh elevation relative to sea level that includes reconstruction of high-resolution, sub-decadal, marsh elevation over the past century, coupled with a lower-resolution 1500-year record, revealed that relative sea-level rose 1.5 ± 0.4 m, following local glacial isostatic adjustment (1.2 mm/yr). As sea-level rise has rapidly accelerated, the high marsh zone dropped 11 cm within the tidal frame since 1932, leading to greater inundation and a shift to flood- and salt-tolerant low marsh species. Once the marsh platform fell to the elevation favored by low-marsh Spartina alterniflora, the elevation stabilized relative to sea level. Currently low marsh accretion keeps pace with sea-level rise, while present day high marsh zones that have not transitioned to low marsh have a vertical accretion deficit. Greater biomass productivity, and an expanding subsurface accommodation space favorable for salt marsh organic matter preservation, provide a positive feed-back between sea-level rise and marsh platform elevation. Carbon storage was 46 ± 28 g C/m2/yr from 550 to 1800 CE, increasing to 129 ± 50 g C/m2/yr in the last decade. Enhanced carbon storage is controlled by vertical accretion rates, rather than soil carbon density, and is a direct response to anthropogenic eustatic sea-level rise, ultimately providing a negative feedback on climate warming.
In: Chemical Geology, 507 . pp. 42-53.
Description: Highlights • Deglacial chemical weathering monitored by adsorbed isotopic and elemental signals • Resilience of authigenic geochemical signals towards variable lake redox conditions • Pronounced early deglacial weathering of labile accessory minerals • Remarkably congruent uranogenic and reduced thorogenic Pb isotope release • Anthropogenic, atmospherically deposited Pb pollution since over 2000 years Abstract Radiogenic Pb and Nd isotopes are well established tools in paleoceanographic science tracing ambient climate and continental runoff to the oceans down to sub-millennial timescales. Particularly in case of Pb isotopes, a clear climate dependency of continental isotopic runoff on glacial-interglacial transitions has been observed. Pb isotopes were reported to be released incongruently during initial chemical weathering. This incongruent release implies that Pb isotopic runoff compositions differ from the bulk catchment Pb isotopic signal. Yet only little is known about the processes leading to the incongruent release and the timescales of weathering on the continents. In this study we targeted the adsorbed trace metal signature in sediments from a Swiss high-Alpine lake that have accumulated since the retreat of the large Alpine ice domes during the last deglaciation to investigate initial Pb and Nd isotope weathering processes in a granitic environment. Additionally, selected adsorbed element concentrations and ratios were analysed to complement the isotopic physico-chemical weathering information. The integrity of the presented isotope records is supported by further investigation into the lake environment (e.g. oxic/anoxic conditions) and its potential influence on the isotopic record. The Pb isotope records during the early lake phase witnessed high-amplitude isotopic fluctuations linked to the initial chemical weathering of fine glacial substrate. This finding is also supported by the lithology of the core and rapidly decreasing adsorbed Th and U concentrations. Following this early lake phase, the majority of the Holocene traced congruent release of 207Pb/204Pb and 206Pb/204Pb and a significant depletion of 208Pb/204Pb in the adsorbed phase. These findings corroborate earlier suggestions of more effective weathering of uranogenic minerals yet also call for the presence of more weathering-resistant thorogenic minerals in the lake catchment. The latest 2.2 ka of the record are significantly overprinted by anthropogenic Pb deposition coinciding with the rise and fall of the Roman Empire. Finally, our data suggest that Nd isotopes are equally affected by incongruent weathering during the initial deglacial weathering processes, albeit at smaller magnitude than seen for Pb isotopes.
In: Journal of Ethnopharmacology, 233 . pp. 94-100.
Description: Abstract ETHNOPHARMACOLOGICAL RELEVANCE: The oleoresin of Brazilian Copaifera reticulata is a traditional remedy used for the treatment of skin and urinary tract infections, respiratory diseases, rheumatism, ulcer and tumours; thus, playing an important role in the primary health care of the indigenous population. AIM: As most previous pharmacological tests used the crude oleoresin and only a few studies so far dealt with enriched fractions or pure chemically defined compounds, the aim of this study was to systematically evaluate the antimicrobial and cytotoxic properties of the Copaifera reticulata oleoresin and to assign traditional uses to specific secondary metabolites. MATERIALS AND METHODS: The oleoresin, as well as its neutral and acidic fractions were tested for their activity against six cancer cell lines, two clinically relevant bacterial strains, and two dermatophytes. Both fractions were analysed by GC-MS and UHPLC-ELSD, respectively. The antibacterial acidic phase was further fractionated by preparative chromatography to purify and characterize the compounds responsible for the observed pharmacological effect. RESULTS: Whereas no cytotoxic activity was detected, the crude oleoresin and its acidic fraction showed antibacterial activity against gram-positive bacteria Enterococcus faecium (IC50 values 4.2 and 4.8 µg/mL, respectively) and methicillin-resistant Staphylococcus aureus (MRSA, IC50 values 5.3 and 7.2 µg/mL, respectively). Purification of the acidic fraction of the C. reticulata oleoresin yielded two dicarboxylic diterpene acids and the four main diterpene acids, comprising three different diterpene scaffolds. Interestingly, the activity was not restricted to a particular diterpene-type but rather depended on the compounds' lipophilicity, with the most active constituent showing IC50 values of 1.6 (E. faecium) and 2.5 µg/mL (MRSA), respectively. Furthermore, ent-polyalthic acid, the major diterpenoid, was significantly active against dermatophytes with IC50 values of 6.8 µg/mL (Trichophyton rubrum) and 4.3 µg/mL against (T. mentagrophytes). CONCLUSION: The present study proved the antimicrobial effects of the C. reticulata oleoresin and its diterpenoid constituents, confirming its wide use in folk medicine for the treatment of skin and urinary tract infections. The inhibitory activity of copaiba diterpenoids against dermatophytic fungi as well as the gram-positive bacteria E. faecium and MRSA is being reported for the first time, providing potential lead structures for the treatment of these clinically relevant bacterial strains.
Miest, Joanna J. ; Politis, Sebastian N. ; Adamek, Mikolaj ; [et al.] Tomkiewicz, Jonna ; Butts, Ian A.E.
In: Fish & Shellfish Immunology, 87 . pp. 105-119.
Description: Temperature is a major factor that modulates the development and reactivity of the immune system. Only limited knowledge exists regarding the immune system of the catadromous European eel, Anguilla anguilla, especially during the oceanic early life history stages. Thus, a new molecular toolbox was developed, involving tissue specific characterisation of 3 housekeeping genes, 9 genes from the innate and 3 genes from the adaptive immune system of this species. The spatial pattern of immune genes reflected their function, e.g. complement component c3 was mainly produced in liver and il10 in the head kidney. Subsequently, the ontogeny of the immune system was studied in larvae reared from hatch to first-feeding at four temperatures, spanning their thermal tolerance range (16, 18, 20, and 22 °C). Expression of some genes (c3 and igm) declined post hatch, whilst expression of most other genes (mhc2, tlr2, il1β, irf3, irf7) increased with larval age. At the optimal temperature, 18 °C, this pattern of immune-gene expression revealed an immunocompromised phase between hatch (0 dph) and teeth-development (8 dph). The expression of two of the studied genes (mhc2, lysc) was temperature dependent, leading to increased mRNA levels at 22 °C. Additionally, at the lower end of the thermal spectrum (16 °C) immune competency appeared reduced, whilst close to the upper thermal limit (22 °C) larvae showed signs of thermal stress. Thus, protection against pathogens is probably impaired at temperatures close to the critical thermal maximum (CTmax), impacting survival and productivity in hatcheries and natural recruitment.
In: Current Opinion in Systems Biology, 13 . pp. 108-114.
In: Deep Sea Research Part II: Topical Studies in Oceanography, 159 . pp. 143-151.
Description: The synchrony of pelagic fish population dynamics with climate variability may impose significant alterations in their distribution and biomass, as well as catch composition, with potential effects on ecosystems and fisheries. This work examines the effect of the Atlantic Multidecadal Oscillation (AMO) and North Atlantic Oscillation (NAO) signals across the Mediterranean Sea sub-regions (western, central and eastern), with respect to small (European sardine Sardina pilchardus, European anchovy Engraulis encrasicolus, round sardinella Sardinella aurita and European sprat Sprattus sprattus) and medium (Atlantic mackerel Scomber scombrus, Atlantic chub mackerel Scomber japonicus, Atlantic horse mackerel Trachurus trachurus, Mediterranean horse mackerel Trachurus mediterraneus) pelagic fishes using various catch ratios and the mean temperature of the pelagic catch (MTpC) method for the period 1970–2014. The time until the pelagic fish communities react to the signals of the AMO and NAO, as revealed by the MTpC and catch ratios, varied among the Mediterranean sub-regions. The pelagic fishes of the central and eastern Mediterranean are those that responded most strongly to AMO variability, whereas those of the central and western Mediterranean also responded to the NAO. The effect of the NAO on pelagic fishes of the eastern Mediterranean was not significant.
Alheit, Jürgen ; Gröger, Joachim P. ; Licandro, Priscilla ; [et al.] McQuinn, Ian H. ; Pohlmann, Thomas ; Tsikliras, Athanassios C.
In: Deep Sea Research Part II: Topical Studies in Oceanography, 159 . pp. 130-142.
Description: Northeast Atlantic marine ecosystems such as the Bay of Biscay, Celtic Sea, English Channel, Subpolar Gyre region, Icelandic waters and North Sea as well as the Mediterranean Sea show concomitant 'regime shift'-like changes around the mid-1990s, which involved all biota of the pelagial: phytoplankton, zooplankton, pelagic fish assemblages, demersal fish assemblages and top predators. These shifts were caused by complex ocean-atmosphere interactions initiating large-scale changes in the strength and direction of the current systems, that move water masses around the North Atlantic, and involved the North Atlantic Oscillation (NAO), the Atlantic Meridional Overturning Circulation (AMOC), and the subpolar gyre (SPG). The contractions and expansions of the SPG and fluctuations of the Atlantic Multidecadal Oscillation (AMO) play a key role in these complex processes. Small pelagic fish population trends were the sentinels of these changes in the mid-1990s in the ecosystems under investigation.
In: Marine Geology, 410 . pp. 56-69.
Description: Highlights: • Clay dehydration water expelled from buried sediments drives mud volcanism. • Rise of fluids mediated by crustal-scale strike-slip faults cross-cutting wedge. • On active accretionary wedge, petroleum accumulations were dismantled in Neogene. • 4He enrichment and δ13C-CH4 ~−50‰ in fluids reflect an open hydrocarbon system. • Petroleum pools remain on shallow margin. Microbial gas vented out of active wedge. Abstract: A geochemical study of the composition of hydrocarbon gases and helium isotopes (3He/4He) in fluids from Mud Volcanoes (MVs) located on and out of the active accretionary wedge of the Gulf of Cadiz (GoC) provides information on fluid sources and migrations in deeply buried sediments. The GoC is a tectonically active segment of the Africa-Iberia plate boundary occluded beneath the thick sediments of an accretionary wedge dissected by crustal-scale strike-slip faults. Initially built during the Miocene Gibraltar Arc subduction, the wedge has since developed toward the W-NW in an oblique convergent setting. Interstitial water expelled from clays undergoing diagenesis in buried sediments drives mud volcanism on the wedge, with MVs located along strike-slip faults mediating fluid ascent. The large excess of radiogenic helium (4He) in all GoC fluids agrees with a clay mineral dehydration source of water. Hydrocarbon gases from all deepwater MVs bear methane having similar stable carbon isotope compositions of ~−50‰VPDB whether fluids are highly enriched in methane relative to heavier homologues (C2+) or not (Methane / (Ethane + Propane) ~10 to 10,000). We suggest that methane with −50‰VPDB was largely diffused out of early generating source rocks, and became dissolved in the water expelled by the buried sediments. Consistently, low 3He/4He ratios suggest an open hydrocarbon system: Petroleum accumulations and 3He dissolved in the original sedimentary pore water have mostly escaped into the water column during the major Late Neogene compressional events. At present, some MVs vent CH4-rich fluids from dewatering sediments, while other structures located on active thrusts additionally vent C2+-rich gases generated by active Cretaceous source intervals. By contrast, evaporitic seals preserved petroleum accumulations on the shallow Moroccan Margin, while the westernmost MVs located out of the accretionary wedge vent microbial gas.
Vieira, Lucia Helena ; Achterberg, Eric P. ; Scholten, Jan ; [et al.] Beck, Aaron J. ; Liebetrau, Volker ; Mills, Matthew M. ; Arrigo, Kevin R.
In: Marine Chemistry, 208 . pp. 43-55.
Description: Highlights • Frequent sediment resuspension may have buffered D-Fe released from shelf sediments. • 228Ra was used to estimate trace element fluxes from the Chukchi shelf sediments. • The estimated sediment 228Ra flux ranks among the highest reported globally. • About 10–25% of the Chukchi shelf sediment Fe flux is exported to the Arctic Ocean. The Chukchi Sea is a primary site for shelf-ocean exchange in the Arctic region and modifies Pacific-sourced water masses as they transit via the Bering Strait into the Arctic Ocean. The aim of this study was to use radium and trace metal distributions to improve our understanding of biogeochemical cycles in the Bering and Chukchi Seas, and evaluate their potential response to future changes in the Arctic. We investigated the distributions of dissolved and total dissolvable trace metals (Cd, Fe, Ni, Cu, Zn, Mn, Co, and Pb) in the Bering and Chukchi Seas during spring. In addition, the long-lived radium isotopes (226Ra and 228Ra) were measured as tracers of benthic trace metal inputs. Trace metal concentrations, especially Fe and Mn, were highly elevated in Chukchi shelf waters compared with the open Arctic Ocean and Bering Strait. Trace metal, nutrient, and Ra patterns suggested that Fe, Mn, and Co concentrations were predominantly controlled by reductive benthic inputs, whereas the other trace metals were influenced by biological uptake and release processes. We propose that Fe, Mn, and Co in the Chukchi Sea are supplied from shelf sediments during winter overturning, and we combine the 228Ra fluxes with the distributions of Fe, Mn, and Co to provide a first estimate of their benthic fluxes in the region. The average benthic flux of 228Ra was 1.49 × 108 atoms m−2 d−1, which is among the highest rates reported globally. Estimated dissolved Fe (D-Fe) flux from the sediments was 2.5 μmol m−2 d−1, whereas D-Mn and D-Co fluxes were 8.0 μmol m−2 d−1 and 0.2 μmol m−2 d−1, respectively. The off-shelf transport of D-Fe to the Arctic Ocean is estimated to be about 10–25% of the benthic Fe flux, with the remainder retained on the shelf due to scavenging and/or phytoplankton uptake. Our results highlight the importance of the Chukchi Sea as a major source of the micro-nutrients to the Arctic Ocean, thereby supporting primary production. Long-term changes in factors that affect cross-shelf mixing, such as the observed reduction in ice cover, may therefore enhance shelf nutrient inputs and primary productivity in the Arctic.
In: Lithos, 326-327 . pp. 540-555.
Description: Highlights: • Researcher Ridge, a chain of volcanic seamounts in the central Atlantic is identified as a classical hotspot track; • The underlying small mantle plume is believed to get captured by the westward migrating Mid-Atlantic Ridge; • The bathymetric/geochemical anomaly of the Mid-Atlantic-Ridge at 14° N can therefore be explained by plume-ridge interaction. Abstract: Researcher Ridge is a 400 km long, WNW-ESE oriented chain of volcanic structures, located on ~20 to 40 Ma old oceanic crust on the western flank of the Mid-Atlantic Ridge (MAR) at ~15° N. Researcher Ridge has been little studied, and its age and origin are currently unclear. At roughly the same latitude (14–15° N), the MAR axis is bathymetrically elevated and geochemically enriched (hereafter referred to as the 14° N MAR anomaly). This study presents 40Ar/39Ar age data, major and trace elements, and Sr-Nd-Pb-Hf isotopic compositions of volcanic rocks dredged from several seamounts of the Researcher Ridge. In addition, new geochemical data of MORBs from two 13–14° N dredge sites on the MAR are also presented. The results reveal that Researcher Ridge lavas have geochemically enriched ocean island basalt compositions (chondrite-normalized [La/Sm]N = 1.7–5.0, and [Ce/Yb]N = 1.58–11.3) with isotopic signatures (143Nd/144Nd = 0.51294–0.51316, 87Sr/86Sr = 0.70266–0.70405, 206Pb/204Pb = 19.14–19.93, 207Pb/204Pb = 15.57–15.63, 208Pb/204Pb = 38.82–39.17, and 176Hf/177Hf = 0.28307–0.28312) trending towards the FOZO or HIMU mantle end member composition. Based on the new age and geochemical data, Researcher Ridge is interpreted as a classic hotspot track, albeit formed by a relatively weak melting anomaly. The lavas from the 14° N MAR anomaly have an enriched E-MORB type composition ([La/Sm]N = 1.81–2.29, [Ce/Yb]N = 1.6–3.9). Their isotopic compositions (143Nd/144Nd = 0.51298–0.51313, 87Sr/86Sr = 0.70250–0.70282, 206Pb/204Pb = 18.90–19.31, 207Pb/204Pb = 15.52–15.58, 208Pb/204Pb = 38.45–38.95, 176Hf/177Hf = 0.28315–0.28320) plot at the enriched end of the local MORB array and partly overlap the Researcher Ridge lava compositions, suggesting a genetic relationship. We propose that the 14° N MAR anomaly is caused by deflection of upwelling Researcher Ridge plume material towards the westward migrating MAR, causing the production of E-MORBs with similar isotopic compositions to the Researcher Ridge lavas. Once the plume was captured by the spreading ridge, off-axis hotspot track volcanism ceased, resulting in a seamount gap between the eastern end of the Researcher Ridge and the 14° N MAR anomaly.
Description: Rapid declines in Arctic sea ice have captured attention and pose significant challenges to a variety of stakeholders. There is a rising demand for Arctic sea ice prediction at daily to seasonal time scales, which is partly a sea ice initial condition problem. Thus, a multivariate data assimilation that integrates sea ice observations to generate realistic and skillful model initialization is needed to improve predictive skill of Arctic sea ice. Sea ice data assimilation is a relatively new research area. In this review paper, we focus on two challenges for implementing multivariate data assimilation systems for sea ice forecast. First, to address the challenge of limited spatiotemporal coverage and large uncertainties of observations, we discuss sea ice parameters derived from satellite remote sensing that (1) have been utilized for improved model initialization, including concentration, thickness and drift, and (2) are currently under development with the potential for enhancing the predictability of Arctic sea ice, including melt ponds and sea ice leads. Second, to strive to generate the "best" estimate of sea ice initial conditions by combining model simulations/forecasts and observations, we review capabilities and limitations of different data assimilation techniques that have been developed and used to assimilate observed sea ice parameters in dynamical models.
Hermann, Bernd T. ; Würtz, Sven ; Vanselow, Klaus H. ; [et al.] Schulz, Carsten ; Stiller, Kevin T.
In: Aquatic Toxicology, 206 . pp. 72-80.
Description: Elevated concentrations of carbon dioxide are a common stressor for fish and other aquatic animals. In particular, intensive aquaculture can impose prolonged periods of severe environmental hypercapnia, manifold exceeding CO2 concentrations of natural habitats. In order to cope with this stressor, gills are essential and constitute the primary organ in the acclimatization process. Yet, despite a general understanding of changes in ion regulation, not much is known with regard to other cellular mechanisms. In this study, we apply RT-qPCR to investigate changes in the expression of several genes associated with metabolism, stress and immunity within gills of juvenile turbot (Psetta maxima) after an eight-week exposure to different concentrations of CO2 (low = ~3000 μatm, medium = ~15000 μatm and high = ~25000 μatm CO2). Histological examination of the gill tissue only found a significant increase of hypertrophied secondary lamella in the highest tested treatment level. gene expression results, on the other hand, implied both, mutual and dose-dependent transcriptional adjustments. Comparable up-regulation of IL-1ß, LMP7 and Grim19 at medium and high hypercapnia indicated an increase of reactive oxygen species (ROS) within gill cells. Simultaneous increase in Akirin and PRDX transcripts at medium CO2 indicated enhanced anti-oxidant activity and regulation of transcription, while reduced mRNA concentrations of COX, EF1α and STAT2 at high CO2 denoted suppressed protein synthesis and reduced metabolic capacity. In addition to upregulated DFAD and ApoE expression, implying compensating repair measures, gills exposed to the highest tested treatment level seemed to operate close to or even beyond their maximum capacity. Thus, fitting the model of capacity limitation, our results provide evidence for accretive intracellular hypoxia and oxidative stress in the gills of turbot, dependent on the level of environmental hypercapnia. Further, genes, such as COX, may be valuable biomarkers when attempting to discriminate between a successful and an overpowered stress response.
In: Chemical Geology, 509 . pp. 45-63.
Description: A long-standing question has been whether the Lower Nicaraguan Rise in the western Caribbean Sea represents thinned continental crust or is part of the Caribbean Large Igneous Province (CLIP). During the R/V Meteor cruise M81/2, the northeastern part of the Lower Nicaraguan Rise including the Hess Escarpment was extensively sampled. Only volcanic and carbonate rocks were recovered and no metamorphic rocks or rocks with continental crustal affinities, indicating that at least the uppermost basement is volcanic and belongs to a volcanic province, probably the CLIP. We provide a comprehensive geochemical dataset, including major and trace elements and Sr-Nd-Hf-Pb double spike isotope ratios, for the volcanic rocks. The basalts are geochemically subdivided into two groups: 1) depleted and 2) enriched. The majority belong to the depleted group with 6–9 wt% MgO and highly depleted incompatible element (e.g. (La/Yb)N = 0.15–0.76, (La/Sm)N = 0.21–0.65) compositions and depleted radiogenic isotope (e.g. εNdi = 8.9–11.0, εHfi = 13.6–16.5, 206Pb/204Pbi = 18.28–18.98) ratios. The subordinate enriched group basalts have 5–8 wt% MgO and were solely recovered from the lower part of the central Hess Escarpment. These rocks possess enriched incompatible element ((La/Sm)N = 1.15–1.60, (La/Yb)N = 1.40–2.57) and isotopic (εNdi = 7.52–8.34, εHfi = 12.6–12.9, 206Pb/204Pbi = 18.87–19.07) ratios resembling E-MORB. The depleted group is distinct from Pacific and Atlantic MORB based on combined 206Pb/204Pb, 143Nd/144Nd and 176Hf/177Hf data. It is similar, but not identical to the highly depleted Gorgona komatiites, thought to be generated during the CLIP event, and depleted Galápagos hotspot track lavas accreted to the Pacific margin of Central America. Ages of ~81 Ma from rocks drilled on the Hess Escarpment postdate the main CLIP phase (95-83 Ma), and indicate that at least the northeastern part of the Nicaraguan Rise formed during a later volcanic event. Lithospheric thinning after the main CLIP phase is suggested to have triggered upwelling of still anomalously hot, partially-melted or unmelted CLIP mantle material to form the younger depleted group of lavas. Our investigations imply that second-stage melting to generate depleted compositions during formation of oceanic large igneous provinces, as has been recently proposed for the Manihiki Plateau, is a more common process than originally thought.
Dosseto, Anthony ; Menozzi, Davide ; Kinsley, Leslie P.J.
In: Geochimica et Cosmochimica Acta, 246 . pp. 213-233.
Description: The development of weathering profiles shapes Earth's surface and regulates its climate via chemical weathering. Hence, it is essential to be able to determine the age of weathering profiles and quantify how fast they form. Uranium-series isotopes allow for such quantification. However, isotope compositions are generally measured in bulk regolith, which represents a complex mixture of mineral and organic phases of different origins that can impact the reliability of the information derived from U-series isotopes. Thus, in this study, we assess whether sequential extraction and mineral separation could provide more reliable estimates of weathering ages and rates. We focus on a granitic profile developed under temperate climate in southeastern Australia, a tectonically quiescent environment. Regolith production rates have been independently estimated in the region using cosmogenic isotopes. As expected, the mineralogy and geochemistry of the bulk regolith show that biotite and feldspar are the main phases lost during weathering, progressively replaced by clay minerals. There is no evidence for significant input of element from external sources, such as via aerosol deposition. While sequential extraction does not seem to affect major mineral phases and element concentrations, it is suspected of producing artificial radioactive disequilibrium. Biotite separates show very large accumulation of U and Th, which increases with decreasing depth. Regolith production rates and mineral dissolution rates calculated with weathering rates estimated using the bulk saprolite and quartz separate compositions yield values comparable to independent estimates. Conversely, weathering ages derived from the compositions of saprolite leached experimentally or biotite separates underestimate regolith production rates and mineral dissolution rates. Thus, sequential extraction or biotite separation are not recommended methods to derive reliable rates of regolith production and mineral dissolution. Despite the potential complexity of the composition of bulk regolith, the use of regolith without any pre-treatment seems to yield satisfying estimates of regolith production and mineral dissolution rates. The composition of quartz separates yields rates similar to those derived from bulk compositions. This provides an alternative method, potentially allowing reliable results to be obtained from a single mineral phase rather than a complex mixture of weathering products.
In: Lithos, 328-329 . pp. 69-87.
Description: Highlights • At least parts of the Beata Ridge formed during the main CLIP stage at 95–83 Ma. • Sampling of numerous volcanic rocks indicates a broad extrusive magmatic event. • Depleted and enriched geochemical signatures point to a heterogeneous mantle source. • Geochemical heterogeneities can occur on a small scale of tens of kilometers. Abstract The Caribbean Large Igneous Province (CLIP), a Cretaceous oceanic flood basalt province, presumably formed at the initiation of the Galápagos hotspot. During the M81 cruise of the German R/V METEOR, we sampled the Beata Ridge, a prominent submarine structure in the Caribbean Sea belonging to the CLIP. The ridge offers the opportunity to directly sample basement sequences of the central, submarine part of the CLIP, complementing numerous studies of accreted CLIP sequences exposed on land around the margins of this LIP. The majority of the recovered Beata Ridge samples are volcanic, implying that at least parts of the Beata Ridge were formed during a large extrusive event in contrast to previous assumptions that the structure is primarily composed of intrusive rocks. Several stratigraphically controlled profiles were sampled along the western slope of the Beata Ridge using the remotely operated vehicle (ROV) Kiel 6000 and revealed variously alternating sequences of magmatic rocks (lavas, pillow breccias, tuffs and gabbros) and sediment plains. We report new 40Ar/39Ar age and geochemical (major and trace element, Sr-Nd-Hf-Pb isotope) data for the recovered magmatic samples. Although the 40Ar/39Ar analyses display disturbed age spectra, they suggest an age range of 92.4–76.9 Ma. Thus our age data show for the first time that the Beata Ridge also formed during the main magmatic stage of the CLIP (~95–83 Ma). Previous studies suggested that the Beata Ridge was formed during a second, lower-volume magmatic phase of the CLIP (~81–71 Ma), possibly related to decompression melting during an extensional phase in the Caribbean. Most samples display relatively flat chondrite-normalized rare earth element (REE) patterns commonly observed throughout the CLIP, but light REE enriched and depleted compositions are also present. The occurrence of enriched and depleted incompatible element and radiogenic isotope signatures implies a heterogeneous mantle source region, as is observed for other LIPs worldwide. Since a high degree of geochemical variability is observed over short stratigraphic intervals within the ROV profiles, melt homogenization did not operate as effectively as commonly assumed for LIPs. Instead the plume head probably preserved some domains of enriched and depleted components, whereas most of the melts during the main stage have intermediate compositions (with flat REE patterns), representing mixtures of the enriched and depleted components.
Liu, Xiao-Ming ; Hardisty, Dalton S. ; Lyons, Timothy W. ; [et al.] Swart, Peter K.
In: Geochimica et Cosmochimica Acta, 248 . pp. 25-42.
Description: Inferring redox conditions for ancient marine environments is critical to our understanding of biogeochemical cycles over Earth history. Because of the redox sensitivity of cerium (Ce) relative to other rare earth elements (REEs) and its uptake in marine carbonates, the Ce anomaly (Ce/Ce*) is widely applied to ancient carbonates as a proxy for local redox conditions in the water column. However, carbonate sediments and rocks are particularly vulnerable to multiple stages and styles of post-depositional diagenetic alteration where the diagenetic redox conditions and fluid compositions can vary widely from overlying seawater. Evaluations of the effects of this post-depositional alteration for the Ce anomaly have mostly been limited to ancient carbonate rocks rather than recent, well-characterized analog facies. Here, we report on analyses of REE plus yttrium concentrations (REY) and Ce anomalies in bulk carbonate samples from drill cores collected in the Bahamas (Clino and Unda) that allow us to track loss or retention of primary signals of initial oxic deposition through a range of subsequent alteration scenarios mostly under anoxic conditions. Specifically, these materials have experienced well-constrained overprints linked to meteoric processes and marine burial diagenesis, including dolomitization. Our results show that, regardless of mineralogy, diagenetic fluid composition, and redox state, the REY patterns in these carbonates, including the Ce anomaly, are similar to those of modern oxic seawater, indicating that they likely record the seawater signatures of primary deposition. As such, the Ce anomaly in shallow marine carbonates has the potential to preserve records of primary deposition even when subject to multiple stages and styles of diagenetic alteration, confirming its utility in studies of ancient marine redox.
In: Geochimica et Cosmochimica Acta, 248 . pp. 370-386.
Description: CO2-induced ocean acidification and associated decrease of seawater carbonate saturation state contributed to multiple environmental crises in Earth's history, and currently poses a major threat for marine calcifying organisms. Owing to their high abundance and good preservation in the Phanerozoic geological record, brachiopods present an advantageous taxon of marine calcifiers for palaeo-proxy applications as well as studies on biological mechanism to cope with environmental change. To investigate the geochemical and physiological responses of brachiopods to prolonged low-pH conditions we cultured Magellania venosa, Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years. Our experiments demonstrate that brachiopods form their calcite shells under strong biological control, which enables them to survive and grow under low-pH conditions and even in seawater strongly undersaturated with respect to calcite (pH = 7.35, Ωcal = 0.6). Using boron isotope (δ11B) systematics including MC-ICP-MS as well as SIMS analyses, validated against in vivo microelectrode measurements, we show that this resilience is achieved by strict regulation of the calcifying fluid pH between the epithelial mantle and the shell. We provide a culture-based δ11B−pH calibration, which as a result of the internal pH regulatory mechanisms deviates from the inorganic borate ion to pH relationship, but confirms a clear yet subtle pH dependency for brachiopods. At a micro-scale level, the incorporation of 11B appears to be principally driven by a physiological gradient across the shell, where the δ11B values of the innermost calcite record the internal calcifying fluid pH while the composition of the outermost layers is also influenced by seawater pH. These findings are of consequence to studies on biomineralisation processes, physiological adaptations as well as past climate reconstructions.
Description: This paper is based on the results of a comprehensive investigations of sediments from seven cores sampled during the International Russian-Chinese Cruise 53 of the R/V "Akademik Lavrentyev" (2010) in the frames of the Russian-Chinese collaboration between the Pacific Oceanological Institute of the Far-Eastern Branch of the Russian Academy of Sciences (POI FEB RAS, Vladivostok, Russia), and the First Institute of Oceanography (FIO, Qingdao, China). Baitoushan (Chanbaishan) Volcano had several powerful explosive eruptions during the Middle Pleistocene-Holocene, which produced widespread tephra layers. The paper reports chemical composition of volcanic glasses and minerals from six tephra layers labeled as B-Og, B-Sado, B-J, B-Un1, B-V, and B-Tm, which belong to Baitoushan Volcano and were identified in sediments of the northwestern part of the Sea of Japan. The tephras were dated using geochronological data for the host sediments. The estimated ages for the Middle Pleistocene tephra is 488 ka; the Late Pleistocene tephras are 71.1–71.9 cal. kа (B-Sado), 50.8 cal. ka (B-J), 38.3 cal. ka (B-Un1), and 29.0–29.4 cal. ka (B-V). The ash layers consist of alkali-rich glass of trachydacitic to alkaline rhyolitic composition and specific assemblage of minerals including Fe-rich augite-hedenbergite, aegirine-augite, aegirine, arfvedsonite, and fayalite. The mineral assemblage is typical for alkalic volcanic rocks from continental rift setting. Aenigmatite, a rare mineral from the group of inosilicates, was firstly identified in distal tephra of Baitoushan Volcano, supplied into marine sediments. The composition of glasses and minerals from all layers are similar. It testifies about steady-state conditions of the magma accumulation under Baitoushan Volcano and about the bimodal character of magmatic chambers during the Late Pleistocene and Holocene (since 100 ka).
Description: Time series derived from paleoclimate archives are often irregularly sampled in time and thus not analysable using standard statistical methods such as correlation analyses. Although measures for the similarity between time series have been proposed for irregular time series, they do not account for the time scale dependency of the relationship. Stochastically distributed temporal sampling irregularities act qualitatively as a low-pass filter reducing the influence of fast variations from frequencies higher than about 0.5 (Δtmax) − 1, where Δtmax is the maximum time interval between observations. This may lead to overestimated correlations if the true correlation increases with time scale. Typically, correlations are underestimated due to a non-simultaneous sampling of time series. Here, we investigated different techniques to estimate time scale dependent correlations of weakly irregularly sampled time series, with a particular focus on different resampling methods and filters of varying complexity. The methods were tested on ensembles of synthetic time series that mimic the characteristics of Holocene marine sediment temperature proxy records. We found that a linear interpolation of the irregular time series onto a regular grid, followed by a simple Gaussian filter was the best approach to deal with the irregularity and account for the time scale dependence. This approach had both, minimal filter artefacts, particularly on short time scales, and a minimal loss of information due to filter length.
In: Geochimica et Cosmochimica Acta, 248 . pp. 43-60.
Description: Assessing the physicochemical variability of the deeper ocean is currently hampered by limited instrumental time series and proxy records. Bamboo corals (Isididae) form a cosmopolitan family of calcitic deep sea corals that could fill this information gap via geochemical information recorded in their skeletons. Here we evaluate the suitability of high-resolution chemical imaging of bamboo coral skeletons for temperature and nutrient reconstruction. The applied elemental mapping techniques allow to verify the suitability of the chosen transect on the sample section for paleo-reconstructions and enhance the statistical precision of the reconstruction. We measured Mg/Ca via electron microprobe at 1 µm resolution and Ba/Ca via laser ablation ICP-MS at 35 µm resolution in a historic specimen of Keratoisis grayi from the Blake Plateau off Eastern Florida. Long-term growth temperatures of 7.1 ± 3.4 °C (± 2 SD) that are in agreement with recent ambient temperature range can be reconstructed from Mg/Ca ratios provided that anomalously Mg-enriched structural features around the central axis and isolated features related to tissue attachment are avoided for reconstruction. Skeletal Ba/Ca measurements reflect mean seawater barium [Ba]SW concentrations ([Ba]SW = 51 ± 24 nmol kg-1 (± 2 SD)), in agreement with instrumental data (47 nmol kg-1). We show for the first time that Ba/Ca forms concentric structures in a bamboo coral skeleton section. Our investigations suggest that, while bamboo coral skeletons do record environmental parameters in their mean chemical composition, the magnitude of environmental variability reconstructed from high-resolution chemical maps exceeds that expected from instrumental time series. This necessitates additional investigation of the factors driving bamboo coral skeletal composition.
In: Journal of Natural Gas Science and Engineering, 62 . pp. 330-339.
Description: Highlights • CO2-methane exchange in a pressure vessel was simulated. • The model uses a detailed description of the kinetics for the CO2-methane exchange and simplifies the transport phenomena. • Irreversible dissociation rate of CH4- and CO2-hydrate in the pressure vessel was estimated as 0.02 and 0.03 mol m−3.s−1. • Formation of CO2-hydrate not only improved the quality of CO2 retention but also enhanced the methane recovery. Carbon dioxide exchange with methane in the clathrate structure has been shown beneficial in laboratory experiments and has been suggested as a field-scale technique for production of natural gas from gas-hydrate bearing sediments. Furthermore, the method is environmentally attractive due to the formation of CO2-hydrate in the sediments, leading to the geosequestration of carbon dioxide. However, the knowledge is still limited on the impact of small-scale heterogeneities on hydrate dissociation kinetics. In the present study, we developed a model for simulating laboratory experiments of carbon dioxide injection into a pressure vessel containing a mixture of gas hydrate and quartz sand. Four experiments at different temperature and pressure conditions were modeled. The model assumes that the contents are ideally mixed and aims to estimate the effective dissociation rate of gas hydrate by matching the model results with the experimental observations. Simulation results indicate that with a marginal offset the model was able to simulate different hydrate dissociation experiments, in particular, those that are performed at high pressures and low temperatures. At low pressures and high temperatures large discrepancies were noticed between the model results and the experimental observations. The mismatches were attributed to the development of extremely heterogeneous flow patterns at pore-scale, where field-scale models usually assume the characteristics to be uniform. Through this modeling study we estimated the irreversible dissociation rate of methane- and CO2-hydrate as 0.02 and 0.03 mol m(-3) s(-1), respectively.
Han, B. ; Zhao, W. ; Zheng, Y. ; [et al.] Meng, J. ; Wang, T. ; Han, Y. ; Wang, W. ; Su, Y. ; Duan, T. ; Xie, X.
In: Optics Communications, 434 . pp. 184-190.
Description: In this paper, we propose a transmitter with 150°divergence angle and more than 90% uniformity of rndiation intensity for quasi-omni-directional underwater wireless optical communication (UWOC) by applying freeform lens into LED array. We demonstrate its performance under different transmitting directions with 19Mbps data rate and 8m communication distance in an experimental tank whose volume is 20mx20mx14m and attenuation coefficient is about 0.40m-1. The result shows that the variation of bit error rate (BER) is about three orders of magnitude with the help of freefonn lens when direction deviation angle is between -75°and +75°, which is reduced five orders compared with the situation without the lens. The presented result is useful to make it easier lo establish communication link and improve the performance ofUWOC syste"1) when transmitter direction shake exists. Also, it implies that we could apply different freefonn lenses into LED array to reshape transmitting illumination according to different demands for UWOC application.
Bautista-Chamizo, E. ; Sendra, M. ; De Orte, M.R. ; [et al.] Riba, I.
In: Science of The Total Environment, 649 . pp. 224-232.
Description: In order to gain knowledge about the potential effects of acidification in aquatic ecosystems, global change research based on microalgae as sentinel species has been often developed. However, these studies are limited to single species tests and there is still a research gap about the behaviour of microalgal communities under this environmental stressor. Thus, the aim of this study was to assess the negative effects of CO2 under an ecologically realistic scenario. To achieve this objective, two types of toxicity tests were developed; i) single toxicity tests and ii) multispecies toxicity tests, in order to evaluate the effects on each species as well as the interspecific competition. For this purpose, three microalgae species (Tetraselmis chuii, Phaeodactylum tricornutum and Nannochloropsis gaditana) were exposed to two selected pH levels (7.4, 6.0) and a control (pH 8.0). The pH values were choosen for testing different scenarios of CO2 enrichment including the exchange atmosphere-ocean (pH 7.4) and natural or anthropogenic sources of CO2 (pH 6.0). The effects on growth, cell viability, oxidative stress, plus inherent cell properties (size, complexity and autofluorescence) were studied using flow cytometry (FCM). Results showed that T. chuii was the most resistant species to CO2 enrichment with less abrupt changes in terms of cell density, inherent cell properties, oxidative stress and cell viability. Although P. tricornutum was the dominant species in both single and multispecies tests, this species showed the highest decrease in cell density under pH 6.0. Effects of competence were recorded in the multispecies control (pH 8) but this competence was eclipsed by the effects of low pH. The knowledge of biological interactions made by different microalgae species is a useful tool to extrapolate research data from laboratory to the field.
In: Quaternary Science Reviews, 208 . pp. 105-117.
Description: Highlights • Colder and fresher subsurface waters during glacials in the Central South Pacific. • Depth of source waters forming the AAIW in the CSP shifts between LGM and PGM. • LGM-PGM conditions resemble the oceanographic changes caused by SAM. Abstract Southern Ocean Intermediate Waters (SOIWs), such as Antarctic Intermediate Water and Subantarctic Mode Water, play a key role in modulating the global climate on glacial-interglacial time scales. They link the Southern Ocean and the tropics via mechanisms such as "oceanic tunneling" that transport climatic signals across latitudes. Despite their importance, the past evolution of the SOIWs in the Central South Pacific is largely unknown. Here we compare paired Mg/Ca-temperature, stable carbon (δ13C) and oxygen (δ18O) isotope records from surface-dwelling and deep-dwelling planktic foraminifera to infer changes in the water column structure for the last 260 ka in the Central South Pacific (54° S). Our study focuses on the subsurface oceanographic variability controlled by SOIWs, which are subducted at the Subantarctic Front. Our data show that the subsurface ocean in the Central South Pacific was colder and fresher during glacial stages than during the Holocene (0–10 ka BP), suggesting a general glacial enhanced presence of Antarctic Intermediate Water, in agreement with previous studies from the Eastern Equatorial Pacific and the Southeast Pacific. However, the subsurface ocean salinity differs for both glacial stages, with fresher condition during the Last Glacial Maximum (LGM; ∼26.5–19 ka BP) and more saline condition during the Penultimate Glacial Maximum (PGM; ∼155–140 ka BP). The δ13C data also show contrasting conditions for both glacial time windows in the upper water column, with a large depletion of 0.37‰ in δ13C from the LGM values, suggests a larger contribution of "old" low δ13C deep waters at intermediate depths at the study site during the PGM, plausibly due to stronger upwelling in high southern latitudes. The dissimilar scenarios between the LGM and the PGM may have been caused by processes that are analogous to the phase-switch in modern day Southern Annular Mode.
In: Chemical Geology, 507 . pp. 64-84.
Description: The role of accessory minerals in the incongruent release of Hf and Pb during continental weathering and its implications for the generation of distinct seawater isotope compositions is subject of debate. While it has been suggested that radiogenic Hf and Pb isotope signatures released during the dissolution of rocks are controlled by the relative abundances of minerals with distinct isotope compositions and differences in their resistance to dissolution there has not been a comprehensive experimental investigation of these processes to date. We carried out systematic sequential leaching experiments on fresh and partly weathered granitic rock samples as well as separated zircons from the Central Aar Granite in Switzerland. Combined with major and rare earth element concentrations our new quantitative experimental data reveal systematic preferential release of radiogenic Nd, Hf and Pb isotopes primarily controlled by dissolution characteristics of the host rock's easily dissolvable accessory and major minerals, in particular apatite and sphene, during weak chemical weathering. Moreover, Pb isotope signatures of incipient weathering conditions, contrary to expectations, indicate initial congruent release of Pb from freshly exposed mineral surfaces that becomes subsequently incongruent. During more advanced chemical weathering stages, as well as enhanced physical weathering conditions, the dissolution of major minerals (i.e. feldspars) becomes dominant for Nd and Pb isotope signatures, whereas Hf isotopes are still dominated by contributions from highly radiogenic accessories. Additional leaching experiments of zircon separates were performed to test the specific role of zircons for Hf isotope compositions of riverine runoff. It is demonstrated that zircon is more efficiently dissolved when physical weathering is enhanced. This increased Hf release originating from partial dissolution of zircons, however, is quantitatively not sufficient to explain less radiogenic Hf isotope signatures in seawater during episodes of enhanced mechanical erosion alone. Moreover, the observed addition of Hf from the more congruent dissolution of the zircon-free fractions of the parent rock due to enhanced physical weathering indicate that these minerals also play an important role in controlling Hf isotope signatures released under deglacial conditions.
Reeve, Jennifer L. ; Hamme, Roberta C. ; Williams, William J.
In: Deep Sea Research Part I: Oceanographic Research Papers, 143 . pp. 127-138.
Description: The global marine fixed nitrogen budget acts as a strong control on oceanic primary productivity, and the Arctic plays a disproportionately large role in the sink terms for this budget. This paper aims to quantify the impact of nitrogen cycling on the Canada Basin, utilizing two tracers of denitrification: N2/Ar, a dissolved gas tracer, and N*, a nutrient ratio tracer. In the Pacific Winter Water (PWW), which forms in the Chukchi Sea, we observe a disconnect between N2/Ar and N*, where the excess N2 expected from N* observations is far larger than the N2 excess we measure. We show that loss of N2 to the atmosphere through ventilation on the Chukchi Shelf likely accounts for this disparity, highlighting the importance of using N2/Ar as a denitrification tracer only in isolated water masses. We additionally observe increasing N2/Ar and decreasing N* in the old deep waters of the Canada Basin, suggesting benthic denitrification has been operating in the deep sediments over the 500-year age of this water mass. We use a one-dimensional vertical reaction-diffusion model to estimate denitrification rates of 0.0053–0.0130 mmol-N m−2 d−1, or 0.04–0.1 Tg N y−1 integrated over the whole basin, which is about half the rates estimated for other deep basins, in-line with lower remineralization rates in the deep Canada Basin. Further measurements of these tracers in the Arctic, particularly directly in the Chukchi Sea, will help constrain the relative importance of physical vs. biological processes on N2 in this region.


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La fuerza de Planck es la unidad de fuerza derivada de la definición de las unidades de Planck básicas para el tiempo, la longitud y la masa. Es igual a la unidad natural de momento dividida entre la unidad natural de tiempo:

Otras definiciones
La fuerza de Planck también está asociada a la equivalencia de la energía potencial gravitatoria y la energía electromagnética, y en este contexto se puede entender como la fuerza que confina una masa autogravitante a la mitad de su radio de Schwarzschild:
 ,

donde G es la constante de gravitación universal, c es la velocidad de la luz en el vacío, m es una masa cualquiera y rG es la mitad del radio de Schwarzschild, rs, de dicha masa.

Como la dimensión de la fuerza es una razón de energía por longitud, la fuerza de Planck se puede calcular como la energía dividida entre la mitad del radio de Schwarzschild.

Como se ha mencionado anteriormente, la fuerza de Planck está íntimamente asociada con la masa de Planck. Esta asociación única también se manifiesta cuando la fuerza se calcula como cualquier energía dividida entre la longitud de onda de Compton reducida por 2π de esa misma energía:

Aquí la fuerza es diferente para cada masa (por ejemplo, para el electrón, al fuerza es responsable del efecto Schwinger. Es igual a la fuerza de Planck únicamente para la masa de Planck (aproximadamente 2.18 × 10-8 kg). Esto se deduce del hecho de que la longitud de Planck es una longitud de onda de Compton reducida igual a la mitad del radio de Schwarzschild de la masa de Planck:

que a su vez se deduce de otra relación fundamental:

Relatividad general
La fuerza de Planck tiene utilidad en trabajos científicos como la razón entre la energía electromagnética y la longitud gravitacional. Por ejemplo, se presenta en las ecuaciones de campo de Einstein que describen las propiedades de un campo gravitatorio que envuelve una masa dada:

donde  es el tensor de Einstein y  es el tensor energía-momento.

Referencias

Unidades de fuerza
Unidades naturales
Unidades epónimas

redpajama_set_name: RedPajamaWikipedia


An adverse supply side shock is an event that causes an unexpected increase in costs or disruption to production. This will cause the short-run aggregate supply curve to shift to the left, leading to higher inflation and lower output.
SRAS shifting to the left causes a higher price level and lower real GDP.
Rising oil prices e.g. cartel activity by OPEC restricting supply and pushing up prices.
Bad weather – Hurricane Katrina disrupted supply in the US.
Wage-push inflation. The 1970s were generally a period of rising wages, leading to cost-push inflationary pressures.
Devaluation/depreciation in the exchange rate. A depreciation in the exchange rate causes import prices to rise and this can lead to inflation. A rapid devaluation can cause a significant increase in inflation.
A consequence of a supply side shock is cost-push inflation. This causes higher inflation due to AS shifting to left.
The difficulty of a supply side shock is that conventional monetary policy cannot deal with both higher inflation and lower real GDP at the same time.
For example, in 2009 and 2012, with cost-push inflation, the Bank of England kept interest rates very low at 0.5% – because they were more worried about fall in GDP than the rise in inflation.


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