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Iron (Fe) speciation in marine sediments and suspended particulate matter (SPM) are widely used to investigate the role of Fe minerals in marine biogeochemical cycling and to reconstruct paleo-redox conditions. A traditional method for the determination of Fe speciation are sequential extractions, in which operationally defined Fe pools are dissolved by specific extraction solutions. More recently, many studies make use of synchrotron radiation-based X-ray absorption near edge spectroscopy (XANES), especially if little sample material is available or a high spatial resolution is required. However, few studies have systematically compared Fe speciation obtained by the two methods. Here, we report Fe speciation for marine sediments (both wet and freeze-dried) and SPM from contrasting marine environments (western Baltic Sea and Amazon shelf) obtained by sequential extraction and XANES. The two methods yield comparable results regarding the approximate proportion of reactive Fe ((oxyhydr)oxides, carbonate and sulfide minerals) in the total Fe pool and the extent to which reactive Fe minerals have been converted to pyrite. However, methodological issues associated with both approaches complicate a direct comparison of specific mineral groups. Pyrite concentrations obtained by XANES are lower than those obtained by extraction, which is attributed to an underestimation by XANES due to self-absorption effects and an overestimation by the chromium reduction method due to dissolution of reduced sulfur phases that are not associated with Fe. As substantial amounts of pyrite are oxidized during freeze-drying and sample storage, we recommend to analyze wet sediments in modern marine environments. The XANES spectra of Fe (oxyhydr)oxide and Fe(III)-containing (ferric) clay minerals are similar, which is why these components cannot be differentiated by XANES. Similarly, sequential extraction schemes are known to dissolve a variable proportion of ferric clay minerals along with Fe carbonates and Fe (oxyhydr)oxides. Further investigating the role of ferric clay minerals in the low-temperature marine Fe cycle may therefore require the use of additional methods. Our findings may help to assess the transferability of XANES-based Fe speciation for small sediment and SPM samples to those reported in more traditional studies on Fe biogeochemical cycling and paleo-redox conditions.

We present pore-fluid geochemistry and heat-flow data along the SWIM1 fault in the Horseshoe Abyssal Plain (northeastern Atlantic Ocean). The SWIM1 fault is part of the transcurrent plate boundary between Africa and Eurasia and cuts through as much as 5-km-thick sediments overlying >140 Ma oceanic lithosphere. In a number of places, restraining segments (as long as 15 km) of the SWIM1 fault generate anticlines (positive flower structures) that protrude as ∼100-m-high hills above the abyssal plain. Heat flow and gradients of dissolved constituents in pore water are enhanced at these seafloor highs. Transport-reaction modeling confirms that slow advection of deep-seated fluids, depleted in Mg and enriched in Sr and CH4, can explain the observations. The geochemical signature is similar to the one observed at deep-sea mud volcanoes located eastward on the SWIM1 fault. The upward-migrating fluids have interacted with carbonate rocks at maximum 5 km depth, which represent the oldest sedimentary unit on top of the basement. We argue that deep-rooted fluids can generally be mobilized and transported upward along flower structures that formed in restraining-bend segments of long strike-slip faults. Such tectonic settings represent largely unrecognized corridors for mass exchange between lithosphere and ocean.

Ratios of (un)reactive iron species, authigenic molybdenum contents (Moauth), and molybdenum isotope compositions (δ98Moauth) in sedimentary rocks are geochemical proxies that are widely used to reconstruct past marine redox states, which have been calibrated in modern marine settings covering oxic to euxinic conditions. However, syn- and postdepositional processes can result in alterations and ambiguities of proxy-derived redox signals that can challenge the validity of paleoreconstructions. We present new data from modern organic-rich sediments of two oxygen minimum zone settings in the Gulf of California and the Peruvian margin. The results show that Mo is fully immobilized shortly after deposition by reaction with hydrogen sulfide (H2S) produced during organoclastic sulfate reduction. Thus, any H2S produced deeper in the sediment (e.g., by sulfate reduction coupled to anaerobic methane oxidation) leaves the initially deposited Mo concentrations and δ98Mo signatures unaltered, which supports the robustness of Mo-based redox proxies. In contrast, the Fe speciation data reveal continued pyritization due to constant exposure of Fe minerals to H2S. Importantly, both Fe bound to oxides and carbonates (highly reactive Fe) and also poorly reactive Fe (e.g., sheet silicates) undergo pyritization during early diagenesis. This process generates Fe-based proxy signatures that falsely imply ferruginous or euxinic conditions.

A new box model is employed to simulate the oxygen-dependent cycling of nutrients in the Peruvian oxygen minimum zone (OMZ). Model results and data for the present state of the OMZ indicate that dissolved iron is the limiting nutrient for primary production and is provided by the release of dissolved ferrous iron from shelf and slope sediments. Most of the removal of reactive nitrogen occurs by anaerobic oxidation of ammonium where ammonium is delivered by aerobic organic nitrogen degradation. Model experiments simulating the effects of ocean deoxygenation and warming show that the productivity of the Peruvian OMZ will increase due to the enhanced release of dissolved iron from shelf and slope sediments. A positive feedback loop rooted in the oxygen-dependent benthic iron release amplifies, both, the productivity rise and oxygen decline in ambient bottom waters. Hence, a 1% decline in oxygen supply reduces oxygen concentrations in sub-surface waters of the continental margin by 22%. The trend towards enhanced productivity and amplified deoxygenation will continue until further phytoplankton growth is limited by the loss of reactive nitrogen. Under nitrogen-limitation, the redox state of the OMZ is stabilized by negative feedbacks. A further increase in productivity and transition to sulfidic conditions is only possible if the rate of nitrogen fixation increases drastically under anoxic conditions. Such a transition would lead to a wide-spread accumulation of toxic sulfide with detrimental consequences for fishery yields in the Peruvian OMZ that currently provides a significant fraction of the global fish catch.

Metastasis Associated in Colon Cancer 1 (MACC1) is a novel prognostic, predictive and causal biomarker for tumor progression and metastasis in many cancer types, including colorectal cancer. Besides its clinical value, little is known about its molecular function. Its similarity to SH3BP4, involved in regulating uptake and recycling of transmembrane receptors, suggests a role of MACC1 in endocytosis. By exploring the MACC1 interactome, we identified the clathrin-mediated endocytosis (CME)-associated proteins CLTC, DNM2 and AP-2 as MACC1 binding partners. We unveiled a MACC1-dependent routing of internalized transferrin receptor towards recycling. Elevated MACC1 expression caused also the activation and internalization of EGFR, a higher rate of receptor recycling, as well as earlier and stronger receptor activation and downstream signaling. These effects are limited by deletion of CME-related protein interaction sites in MACC1. Thus, MACC1 regulates CME and receptor recycling, causing increased growth factor-mediated downstream signaling and cell proliferation. This novel mechanism unveils potential therapeutic intervention points restricting MACC1-driven metastasis. Supplementary Information The online version contains supplementary material available at 10.1007/s00018-020-03734-1.

Dendritic cell (DC) maturation is a prerequisite for the induction of adaptive immune responses against pathogens and cancer. Transcription factor (TF) networks control differential aspects of early DC progenitor versus late-stage DC cell fate decisions. Here, we identified the TF C/EBPβ as a key regulator for DC maturation and immunogenic functionality under homeostatic and lymphoma-transformed conditions. Upon cell-specific deletion of C/EBPβ in CD11c(+)MHCII(hi) DCs, gene expression profiles of splenic C/EBPβ(−/−) DCs showed a down-regulation of E2F cell cycle target genes and associated proliferation signaling pathways, whereas maturation signatures were enriched. Total splenic DC cell numbers were modestly increased but differentiation into cDC1 and cDC2 subsets were unaltered. The splenic CD11c(+)MHCII(hi)CD64(+) DC compartment was also increased, suggesting that C/EBPβ deficiency favors the expansion of monocytic-derived DCs. Expression of C/EBPβ could be mimicked in LAP/LAP* isoform knockin DCs, whereas the short isoform LIP supported a differentiation program similar to deletion of the full-length TF. In accordance with E2F1 being a negative regulator of DC maturation, C/EBPβ(−/−) bone marrow-derived DCs matured much faster enabling them to activate and polarize T cells stronger. In contrast to a homeostatic condition, lymphoma-exposed DCs exhibited an up-regulation of the E2F transcriptional pathways and an impaired maturation. Pharmacological blockade of C/EBPβ/mTOR signaling in human DCs abrogated their protumorigenic function in primary B cell lymphoma cocultures. Thus, C/EBPβ plays a unique role in DC maturation and immunostimulatory functionality and emerges as a key factor of the tumor microenvironment that promotes lymphomagenesis.

It has been hypothesized that vanadium (V) isotopes have the potential to track sedimentary redox conditions due to multiple valence states occurring in nature, which might induce variable V isotope fractionation as a function of sedimentary redox state. These characteristica could make V isotopes a useful paleo-redox proxy. However, in order to understand the mechanisms driving V isotope fractionation, it is crucial to build a framework for the depositional and post-depositional controls on sedimentary V isotope records from a diverse set of sedimentary environments. This study, for the first time, investigates the V isotope variations of modern marine sediments deposited under a range of redox environments. Our results document that changes in local redox conditions impart a significant isotopic fractionation from seawater as recorded in the local sedimentary V isotopic signature. Importantly, there is a significant difference between the V isotope composition of sediments deposited in the open ocean setting with oxygen-deficient bottom waters compared to less reducing environments, whereby oxic sediments (benthic oxygen contents > 10 μΜ) exhibit Δoxic = −1.1 ± 0.3‰ and anoxic sediments exhibit Δanoxic = −0.7 ± 0.2‰. Combined with previous studies on seawater particulate and sediment pore fluid analysis, our results indicate that V is mainly delivered and enriched in anoxic sediments through settling particulates. Authigenic V isotope compositions in marine sediments are likely controlled by isotope fractionation between V species bound to particulates and dissolved in seawater, which likely varies with the speciation and adsorption properties of V that are strongly controlled by local redox conditions. In addition, the euxinic Cariaco Basin sediments exhibit distinctive Δeuxinic = −0.4 ± 0.2‰, which is likely influenced by the relationship between the seawater V removal rate and the seawater renewal rate. Our results highlight the direct link between authigenic marine sedimentary V isotope compositions and the overlying local redox conditions. This investigation of V isotopes in modern marine environments provides an initial framework for the utilization of V isotopes to reconstruct ancient redox fluctuations, which has the potential to track subtle redox variations of local oxygen-deficient to low oxygen environments.

Sediments in oxygen-depleted marine environments can be an important sink or source of bio-essential trace metals in the ocean. However, the key mechanisms controlling the release from or burial of trace metals in sediments are not exactly understood. Here, we investigate the benthic biogeochemical cycling of iron (Fe) and cadmium (Cd) in the oxygen minimum zone off Peru. We combine bottom water and pore water concentrations, as well as benthic fluxes determined from pore water profiles and from in situ benthic chamber incubations, along a depth transect at 12∘ S. In agreement with previous studies, both concentration–depth profiles and in situ benthic fluxes indicate a release of Fe from sediments to the bottom water. Diffusive Fe fluxes and Fe fluxes from benthic chamber incubations (−0.3 to −17.5 mmol m−2 yr−1) are broadly consistent at stations within the oxygen minimum zone, where the flux magnitude is highest, indicating that diffusion is the main transport mechanism of dissolved Fe across the sediment–water interface. The occurrence of mats of sulfur-oxidizing bacteria on the seafloor represents an important control on the spatial distribution of Fe fluxes by regulating hydrogen sulfide (H2S) concentrations and, potentially, Fe sulfide precipitation within the surface sediment. Rapid removal of dissolved Fe after its release to anoxic bottom waters hints at oxidative removal by nitrite and interactions with particles in the near-bottom water column. Benthic flux estimates of Cd suggest a flux into the sediment within the oxygen minimum zone. Fluxes from benthic chamber incubations (up to 22.6 µmol m−2 yr−1) exceed diffusive fluxes ( µmol m−2 yr−1) by a factor of more than 25, indicating that downward diffusion of Cd across the sediment–water interface is of subordinate importance for Cd removal from benthic chambers. As Cd removal in benthic chambers covaries with H2S concentrations in the pore water of surface sediments, we argue that Cd removal is mediated by precipitation of cadmium sulfide (CdS) within the chamber water or directly at the sediment–water interface. A mass balance approach, taking the contributions of diffusive and chamber fluxes as well as Cd delivery with organic material into account, suggests that CdS precipitation in the near-bottom water could make an important contribution to the overall Cd mass accumulation in the sediment solid phase. According to our results, the solubility of trace metal sulfide minerals (Cd ≪ Fe) is a key factor controlling trace metal removal and, consequently, the magnitude and the temporal and spatial heterogeneity of sedimentary fluxes. We argue that, depending on their sulfide solubility, sedimentary source or sink fluxes of trace metals will change differentially as a result of declining oxygen concentrations and the associated expansion of sulfidic surface sediments. Such a trend could cause a change in the trace metal stoichiometry of upwelling water masses with potential consequences for marine ecosystems in the surface ocean.

Oceanic anoxic events (OAEs) document major perturbations of the global carbon cycle with repercussions for the Earth's climate and ocean circulation that are relevant to understanding future climate trends. Here, we compare the onset and development of Cretaceous OAE1a and OAE2 in two drill cores with unusually high sedimentation rates from the Vocontian Basin (southern France) and Tarfaya Basin (southern Morocco). OAE1a and OAE2 exhibit remarkable similarities in the evolution of their carbon isotope (δ13C) records, with long-lasting negative excursions preceding the onset of the main positive excursions, supporting the view that both OAEs were triggered by massive emissions of volcanic CO2 into the atmosphere. However, there are substantial differences, notably in the durations of individual phases within the δ13C positive excursions of both OAEs. Based on analysis of cyclic sediment variations, we estimate the duration of individual phases within OAE1a and OAE2. We identify (1) a precursor phase (negative excursion) lasting ∼430 kyr for OAE1a and ∼130 kyr for OAE2, (2) an onset phase of ∼390 and ∼70 kyr, (3) a peak phase of ∼600 and ∼90 kyr, (4) a plateau phase of ∼1340 and ∼200 kyr, and (5) a recovery phase of ∼380 and ∼440 kyr. The total duration of the positive δ13C excursion is estimated at 2700 kyr for OAE1a and 790 kyr for OAE2, and that of the main carbon accumulation phase is estimated at 980 and 180 kyr. The long-lasting peak, plateau and recovery phases imply fundamental changes in global nutrient cycles either (1) by submarine basalt–seawater interactions, (2) through excess nutrient inputs to the oceans by increasing continental weathering and river discharge, or (3) through nutrient recycling from the marine sediment reservoir. We investigated the role of phosphorus in the development of carbon accumulation by analysing phosphorus speciation across OAE2 and the mid-Cenomanian Event (MCE) in the Tarfaya Basin. The ratios of organic carbon and total nitrogen to reactive phosphorus (Corg∕Preact and Ntotal∕Preact) prior to OAE2 and the MCE hover close to or below the Redfield ratio characteristic of marine organic matter. Decreases in reactive phosphorus resulting in Corg∕Preact and Ntotal∕Preact above the Redfield ratio during the later phase of OAE2 and the MCE indicate leakage from the sedimentary column into the water column under the influence of intensified and expanded oxygen minimum zones. These results suggest that a positive feedback loop, rooted in the benthic phosphorus cycle, contributed to increased marine productivity and carbon burial over an extended period of time during OAEs.

Aim: There is a growing body of data on real-world use of talimogene laherparepvec (T-VEC). We aimed to characterize real-world T-VEC use using a nationally representative German prescription database covering 60% of prescriptions reimbursed. Patients & methods: A retrospective analysis was conducted using the German IMS® LRx prescription database, analyzing patients aged ≥18 years with an initial T-VEC prescription at 106 plaque-forming units (PFU)/ml and ≥1 subsequent prescription at 108 PFU/ml. Median time on T-VEC treatment, patient characteristics and patterns of T-VEC use were described. Results: Of 127 patients prescribed T-VEC, 72 patients (57%) met study criteria. About two-thirds of these patients initiated T-VEC in 2017. Median age at T-VEC initiation was 74 years (range: 44 to 91). Most prescriptions (88%) were dispensed from hospitals. At study end, 26 (36%) patients remained on T-VEC; 46 (64%) had ended treatment. Median duration of T-VEC treatment for all patients was 18.7 weeks (95% CI: 15.3–26.9) and was longer among those who initiated treatment in 2017 versus 2016 (26.7 vs 15.6 weeks, respectively). Median volume administered for the first 106 PFU/ml and second 108 PFU/ml was 4 ml; the volume decreased for subsequent administrations (2 ml by the eighth administration and 1 ml by the 16th administration). Conclusion: This real-world prescription database study showed that patients who initiated treatment in 2017 had a treatment duration in clinical practice that corresponded with the European Summary of Product Characteristics guideline of continuing T-VEC for ≥6 months. Additional long-term data linking drug use with clinical outcomes are needed.

The benthic boundary layer plays a crucial role in the exchange of trace metals between surface sediments and the water column. So far it has been difficult to study dissolved–particulate interactions of trace metals in this highly reactive interface layer due to the lack of suitable sampling methods. We developed a new device, called Benthic Trace Profiler (BTP), which enables simultaneous sampling of near-bottom water and suspended particles in high depth resolution within the first 3 m above the seafloor. The device was tested successfully in the Baltic Sea. The concentrations of several trace metals (Co, Ni, Cu, Zn, and Cd) in the collected bottom waters overlapped with concentrations in water column samples above collected with conventional methods. This observation indicates that the sampling device and method is trace metal clean. The trace metals Fe and Mn showed concentration gradients within the benthic boundary layer indicating an upward diffusive flux. This observation is consistent with a diffusive benthic flux of these trace metals across the sediment–water interface, which was independently verified using pore-water profiles. Suspended particles can be used to study precipitation processes and to determine the carrier phases of trace metals. The BTP fulfilled all the intended requirements as it allowed a simultaneous, uncontaminating and oxygen-free sampling of seawater and suspended particles to gather high-resolution profiles of dissolved and particulate trace metal concentrations above the seafloor. The device closes the gap between water column and sediment sampling and helps researchers to better understand trace metal exchange processes across the ocean's lower boundary.

Climate change is expected to result in smaller fish size, but the influence of fishing has made it difficult to substantiate the theorized link between size and ocean warming and deoxygenation. We reconstructed the fish community and oceanographic conditions of the most recent global warm period (last interglacial; 130 to 116 thousand years before present) by using sediments from the northern Humboldt Current system off the coast of Peru, a hotspot of small pelagic fish productivity. In contrast to the present-day anchovy-dominated state, the last interglacial was characterized by considerably smaller (mesopelagic and goby-like) fishes and very low anchovy abundance. These small fish species are more difficult to harvest and are less palatable than anchovies, indicating that our rapidly warming world poses a threat to the global fish supply. Species shifts Our anthropogenically warmed climate will lead to a suite of organismal changes. To predict how some of these may occur, we can look to past warm (interglacial) periods. Salvatteci et al. used this approach and looked at a marine sediment record of the Humboldt Current system off the coast of Peru (see the Perspective by Yasuhara and Deutsch). They found that previous warm periods were dominated by small, goby-like fishes, whereas this ecosystem currently is dominated by anchovy-like fishes. Such a shift is not only relevant to ecosystem shifts but also to fisheries because anchovies are heavily fished as a food source and gobies are much less palatable than anchovies.

Extreme periods of global warming in Earth's history have been strongly associated with declining oxygen concentrations in the oceans, a scenario not unlike the evolution observed in the oceans in recent times. One of the most intense Phanerozoic deoxygenation events (so called Ocean Anoxic Events (OAE)) is the late Cretaceous OAE2 approximately 94 Ma ago. Although several studies have investigated the evolution of redox sensitive geochemical proxies during the OAE2 event, geochemical records that span the time period leading up to OAE2, in particular for molybdenum (Mo) and its isotopes are rare. Here, we investigate Mo cycling in the Tarfaya upwelling system in the Cretaceous proto-North Atlantic Ocean before and during OAE 2 throughout a 5 Ma record. The observed changes in sedimentary Mo isotope compositions can be explained by a mode of Mo cycling similar to that in modern oxygen minimum zones. Based on this interpretation we estimate the pre-OAE2 Mo isotope composition of seawater to be 1.6‰ indicating that late Cretaceous pre-OAE2 seawater had a lighter Mo isotope composition than the modern ocean. We suggest that Mo burial in oxic sediments was likely diminished under conditions of globally reduced oxygen concentrations. This allows us to model the Mo isotope composition of late Cretaceous pre-OAE2 seawater without lowering of the seawater Mo inventory (e.g., −55% oxic sink, + 40% anoxic sink). Previous estimations of the Mo seawater isotope composition during OAE2 are close to the signal observed pre-OAE here. The Mo isotope variation associated with the onset of OAE2 is therefore small, which is unexpected because strong expansion of anoxic sedimentation in OAE2 is indicated by e.g. sulfur isotopes. A further decrease of Mn burial rates in the open ocean during OAE2 could “buffer” the Mo seawater isotope signal during OAE2, to account for the small offset. Our findings emphasize that changes to the relative size of not only the anoxic sink but also the oxic sink are important considerations when interpreting paleo-Mo isotope data.

During the last glacial interval, marine sediments recorded reduced current ventilation within the ocean interior below water depths of approximately >1,500 m [B. A. Hoogakker et al., Nat. Geosci. 8, 40–43 (2015)]. The degree of the associated oxygen depletion in the different ocean basins, however, is still poorly constrained. Here, we present sedimentary records of redox-sensitive metals from the southwest African margin. These records show evidence of continuous bottom water anoxia in the eastern South Atlantic during the last glaciation that led to enhanced carbon burial over a prolonged period of time. Our geochemical data indicate that upwelling-related productivity and the associated oxygen minimum zone in the eastern South Atlantic shifted far seaward during the last glacial period and only slowly retreated during deglaciation times. While increased productivity during the last ice age may have contributed to oxygen depletion in bottom waters, especially on the upper slope, slow-down of the Late Quaternary deep water circulation pattern [Rutberg et al., Nature 405, 935–938 (2000)] appears to be the ultimate driver of anoxic conditions in deep waters.

Enrichments of highly reactive iron (Fe) (sum of Fe (oxyhydr)oxide, carbonate and sulfide minerals) in marine sediments and sedimentary rocks are commonly interpreted as an indication of anoxic conditions in the bottom water at the time of deposition. The model system for this proxy rationale is the semi-restricted Black Sea, where sediments underneath the anoxic and sulfidic (i.e., euxinic) deep-water are enriched in reactive Fe, which was mobilized from the surrounding shelf areas. To test whether such a shelf-to-basin Fe shuttle can operate in semi-restricted basins without euxinic deep water, we investigated sedimentary Fe speciation and Fe isotope compositions in sediments of the Guaymas Basin, Gulf of California. Sediments on the slope underneath the eastern equatorial Pacific oxygen minimum zone and sediments within the oxic deep basin are both enriched in reactive Fe, with reactive Fe making up 45 ± 11 % of the total Fe pool. The following mechanisms may contribute to these Fe enrichments: (1) Release of dissolved Fe from anoxic shelf and slope sediments followed by lateral transport of dissolved and/or particulate Fe in the water column; (2) preferential transport of fine-grained, terrigenous particles with a high reactive Fe content into the basin; (3) microbially mediated conversion of non-reactive silicate minerals to reactive Fe minerals during transport; (4) hydrothermal venting and lateral Fe transport within the deep water. The first process can explain reactive Fe enrichments in slope sediments, whereas all processes may contribute to sedimentary Fe enrichments in the deeper basin. The δ 56 Fe value of sediments increases from shelf to slope and decreases from the slope into the basin. This lateral pattern of δ 56 Fe, as well as the pattern of Fe enrichment, is similar to that observed in other marine systems with a Fe shuttle. However, the size of the Fe enrichment, and the range in δ 56 Fe (-0.06 to +0.16‰) is smaller. This difference is due to higher terrigenous sedimentation rates in the Guaymas Basin and, therefore, more intense dilution of shuttle-derived reactive Fe. We argue that, depending on the extent of bathymetric restriction and terrigenous background sedimentation, reactive Fe enrichments can form under a broad range of redox conditions and in diverse sedimentary environments. The concepts applied in this study can be used to identify those circumstances in the paleo-record.

Chromium (Cr) isotope fractionation is sensitive to redox changes and the Cr isotopic composition (δ 53 Cr) of sedimentary rocks has been used to reconstruct marine redox conditions and atmospheric oxygenation in the past. However, little is known about the behaviour of chromium isotopes across modern marine redox boundaries. We investigated Cr concentrations and δ 53 Cr variations in seawater and sediment across the Peruvian oxygen minimum zone (OMZ) to provide a better understanding of Cr cycling in the ocean. We found that seawater δ 53 Cr values ranged from 0.02 ± 0.16‰ to 0.59 ± 0.11‰ (2SD) and sediment values from 0.31 ± 0.07 to 0.92 ± 0.12‰. Neither Cr concentrations nor δ 53 Cr values in the water column revealed significant shifts across the oxic-anoxic boundaries. Instead, processes that operate at a local scale, such as Cr scavenging by Fe-rich particles and Cr release from reducing sediments, are identified as the main controls on Cr concentrations and isotope compositions in the water column. The δ 53 Cr values of sediments deposited in permanently anoxic waters (0.77 ± 0.19‰, n = 5) are significantly different from the δ 53 Cr values of sediments deposited in oxic bottom waters (0.46 ± 0.19‰, n = 4). This suggests that sediment Cr concentrations and δ 53 Cr values are to some extent influenced by water column redox (e.g. reductive dissolution and transport of Fe oxides) and/or early diagenetic (e.g. redistribution of Cr during phosphogenesis) processes as well as biologic activity. Our data demonstrate that local scale water column redox gradients and sediment exchange can lead to a large range of δ 53 Cr values in sediments, comparable to the range found in the entire geologic record to date. Given the increasing prominence of Cr isotope measurements in constraining atmospheric oxygenation in deep time, we argue that the processes influencing Cr cycling under different conditions and from the water column to the sediment need to be better resolved to verify the utility of such measurements as paleoenvironmental proxies.

Marine sediments are an important source and sink of bio-essential trace metals to the ocean. However, the different mechanisms leading to trace metal release or burial are not fully understood and the associated fluxes are not well quantified. Here, we present sediment, pore water , sequential extraction and benthic flux data of Mn, Co, Ni, Cu, Zn and Cd along a latitudinal depth transect across the Peruvian oxygen minimum zone at 12°S. Sediments are depleted in Mn and Co compared to the lithogenic background. Diffusive Mn fluxes from the sediments into the bottom water (−26 to −550 μmol m −2 y−1) are largely consistent with the rate of Mn loss from the solid phase (−100 to −1160 μmol m−2 yr−1 ) suggesting that 50% or more of the sedimentary Mn depletion is attributed to benthic efflux . In contrast, benthic Co fluxes (~ −3 μmol m −2 yr−1) are lower than the rate of Co loss from the solid phase (up to −120 μmol m−2 yr−1 ), implying Co dissolution in the water column. The trace metals Ni, Cu, Zn and Cd are enriched within the sediments with respect to the lithogenic background. Uptake of Ni by phytoplankton in the photic zone and delivery with organic matter to the sediment surface can account for up to 100% of the excess Ni accumulation (87 to 180 μmol m −2 y−1 ) in shelf sediments near the coast, whereas at greater water depth additional scavenging by Mn- and Fe-oxides may contribute to Ni accumulation. Up to 20% of excess Cu (33 to 590 μmol m −2 y−1) and generally less than 20% of excess Zn (58 to 2170 μmol m−2 y−1) and Cd (6 to 260 μmol m−2 y−1 ) can be explained by delivery with fresh organic matter. Sequential extraction data suggest that the discrepancies between the known sources of Cd (and Cu) and their excess accumulation may be driven by the delivery of allochthonous sulphide minerals precipitated from the water column. Additionally, Cu may be scavenged by downward sinking organic material. In contrast, precipitation of Zn sulphide chiefly takes place in the sediment. Diffusive Zn fluxes into the sediment (21 to 1990 μmol m −2 y−1 ) match the excess Zn accumulation suggesting that Zn delivery is mediated by molecular diffusion from bottom waters. Considering the diverse behavioural pattern of trace metals observed in this study, we argue that declining oxygen and increasing hydrogen sulphide concentrations in a future ocean will modify trace metal fluxes at the seafloor and the trace metal stoichiometry of seawater .

The availability of major nutrients, nitrogen (N) and phosphorus (P), largely controls primary productivity in eastern boundary upwelling systems. The oxygen minimum zone (OMZ) on the Namibian shelf is characterized by high productivity and extraordinarily high particulate organic carbon (POC) contents (up to 19 % dry weight) in the surface sediments. The anaerobic degradation of POC by bacterial sulfate reduction leads to the production of hydrogen sulfide (H2S) that supports extensive communities of large sulfur bacteria Thiomargarita namibiensis in surface shelf sediments. These bacteria oxidize sulfide by reducing nitrate (NO3-) to either ammonium (NH4+) or dinitrogen (N2). Thiomargarita also affect phosphorus cycling by intracellular incorporation of polyphosphates and extracellular formation of hydroxyapatites. In order to understand and quantify the complexity of the coupled benthic cycles of C, N, P, S, Fe in the Benguela Upwelling System, a reaction-transport model (RTM) was used to simulate sediment biogeochemical data collected from the RV Meteor cruise (M157, August 4th-September 16th 2019) off Namibia. This allowed deeper insights into the role of sulfur-oxidizing bacteria on P and N fluxes across the sediment surface. Results are presented that point toward potentially strong feedbacks by Thiomargarita on primary production in response to ongoing global warming and ocean deoxygenation.

Iron is a key micronutrient controlling phytoplankton growth in vast regions of the global ocean. Despite its importance, uncertainties remain high regarding external iron source fluxes and interna...

An extensive data set of biogenic silica (BSi) fluxes is presented for the Peruvian oxygen minimum zone (OMZ) at 11°S and 12°S. Each transect extends from the shelf to the upper slope (∼1,000 m) and dissects the permanently anoxic waters between ∼200 and 500 m water depth. BSi burial (2,100 mmol m−2 yr−1) and recycling fluxes (3,300 mmol m−2 yr−1) were highest on the shelf with mean preservation efficiencies (34% ± 15%) that exceed the global mean of 10%–20%. BSi preservation was highest on the inner shelf (up to 56%), decreasing to 7% and 12% under anoxic waters and below the OMZ, respectively. The data suggest that the main control on BSi preservation is the rate at which reactive BSi is transported away from undersaturated surface sediments by burial and bioturbation to the underlying saturated sediment layers where BSi dissolution is thermodynamically and/or kinetically inhibited. BSi burial across the entire Peruvian margin between 3°S to 15°S and down to 1,000 m water depth is estimated to be 0.1–0.2 Tmol yr−1; equivalent to 2%–7% of total burial on continental margins. Existing global data permit a simple relationship between BSi rain rate to the seafloor and the accumulation of unaltered BSi, giving the possibility to reconstruct rain rates and primary production from the sediment archive in addition to benthic Si turnover in global models., Key Points: Biogenic silica (BSi) preservation is high on the shelf and low under predominantly anoxic bottom waters BSi burial across the Peruvian margin down to 1,000 m water depth accounts for up to 7% of the global burial on continental margins Existing global data permit a simple relationship between BSi accumulation and rain rate, Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659

Highlights • Geochemical analyses highlight multiple diagenesis processes occurring in the sediment. • Intense methane seepages and organic matter degradation contribute to the sulfate reduction. • Chemical of dissolved and mineral iron species indicate that iron is associated with clay minerals. • In response to seawater intrusion, ion exchange, dissolution and reverse weathering reactions change the composition of clay constituting the sediment. Abstract Pore water and sediment geochemistry in the western Black Sea were investigated on long Calypso piston core samples. Using this type of coring device facilitates the recovery of the thick sediment record necessary to analyze transport-reaction processes in response to the postglacial sea-level rise and intrusion of Mediterranean salt water 9 ka ago, and thus, to better characterize key biogeochemical processes and process changes in response to the shift from lacustrine to marine bottom water composition. Complementary data indicate that organic matter degradation occurs in the upper 15 m of the sediment column. However, sulfate reduction coupled with Anaerobic Methane Oxidation (AOM) is the dominant electron-accepting process and characterized by a shallow Sulfate Methane Transition Zone (SMTZ). Net silica dissolution, total alkalinity (TA) maxima and carbonate peaks are found at shallow depths. Pore water profiles clearly show the uptake of K+, Mg2+ and Na + by, and release of Ca2+ and Sr2+ from the heterogeneous lacustrine sediments, which is likely controlled by chemical reactions of silicate minerals and changes in clay mineral composition. Iron (Fe2+) and manganese (Mn2+) maxima largely coincide with Ca2+ peaks and suggest a close link between Fe2+, Mn2+ and Ca2+ release. We hypothesize that the Fe2+ maxima below the SMTZ result from deep Fe3+ reduction linked to organic matter degradation, either driven by DOC escaping from the shallow sulfate reduction zone or slow degradation of recalcitrant POC. The chemical analysis of dissolved and solid iron species indicates that iron is essentially associated with clay minerals, which suggests that microbial iron reduction is influenced by clay mineral composition and bioavailability of clay mineral-bound Fe(III). Overall, our study suggests that postglacial seawater intrusion plays a major role in shaping redox zonation and geochemical profiles in the lacustrine sediments of the Late Quaternary.

Since the enactment of the Austrian Code of Civil Procedure of 1898, the role and function of the Austrian Supreme Court (Oberster Gerichtshof) has changed. Instead of safeguarding individual rights by securing the correct decision in individual cases, currently the main purpose of the court is described as providing guidelines for the development and uniform application of the law. The changed role of the court is clearly reflected in today’s rules on access to the court. The reason for the change in its role was partly triggered by the need for effective restrictions on access in the 1980s. Then, the court faced an overburdening caseload that could not sufficiently be met by means of the traditional access filters which were in force at that time. The history of reforms in the last four decades can be described as an on-going attempt to keep the caseload of the court at a reasonable level without causing too drastic restrictions in terms of access to Supreme Court review. Today there are about 2800 appeals to the Austrian Supreme Court per year; about 1000 require a decision on the merits.

R/V Alkor Cruise AL543 was planned as a six-day cruise with a program of water column and sediment sampling in Kiel Bight and the western Baltic Sea. Due to restrictions related to the Covid-19 pandemic, the original plan had to be changed and the cruise was realized as six oneday cruises with sampling in Kiel Bight exclusively. The first day was dedicated to water column and sediment sampling for radionuclide analyses at Boknis Eck and Mittelgrund in Eckernförde Bay. On the remaining five days, water column, bottom water, sediment and pore water samples were collected at eleven stations covering different types of seafloor environment (grain size, redox conditions) in western Kiel Bight. The data and samples obtained on cruise AL543 will be used to investigate (i) the sedimentary cycling of bio-essential metals (e.g., nickel, zinc, and their isotopes) as a function of variable redox conditions, (ii) the impact of submarine groundwater discharge and diffusive benthic fluxes on the distribution of radium and radon as well as greenhouse gases (methane and nitrous oxide) in the water column, and (iii) to characterize and quantify the impact of coastal erosion on sedimentary iron, phosphorus and rare earth element cycling in Kiel Bight.

The development and application of geochemical techniques to identify redox conditions in modern and ancient aquatic environments has intensified over recent years. Iron (Fe) speciation has emerged as one of the most widely used procedures to distinguish different redox regimes in both the water column and sediments, and is the main technique used to identify oxic, ferruginous (anoxic, Fe(II) containing) and euxinic (anoxic, sulfidic) water column conditions. However, an international sediment reference material has never been developed. This has led to concern over the consistency of results published by the many laboratories that now utilise the technique. Here, we report an interlaboratory comparison of four Fe speciation reference materials for palaeoredox analysis, which span a range of compositions and reflect deposition under different redox conditions. We provide an update of extraction techniques used in Fe speciation and assess the effects of both test portion mass, and the use of different analytical procedures, on the quantification of different Fe fractions in sedimentary rocks. While atomic absorption spectroscopy and inductively coupled plasma-optical emission spectrometry produced comparable Fe measurements for all extraction stages, the use of ferrozine consistently underestimated Fe in the extraction step targeting mixed ferrous–ferric minerals such as magnetite. We therefore suggest that the use of ferrozine is discontinued for this Fe pool. Finally, we report the combined data of four independent Fe speciation laboratories to characterise the Fe speciation composition of the reference materials. These reference materials are available to the community to provide an essential validation of in-house Fe speciation measurements. (Less)

In a multi-source, lagged design field study of 197 leader-follower dyads, we test a model that predicts positive interactive effects of visionary and empowering leadership on follower performance. Based on the paradox perspective, we argue that visionary and empowering leadership are synergistic in that their combination enables leaders to address a key paradox inherent to leader behavior identified by Waldman and Bowen (2016): Maintaining control while simultaneously letting go of control. We argue that visionary leadership addresses the former and empowering leadership addresses the latter pole of this pair of opposites. Hence, in line with paradox thinking, we posit that leaders will engender more positive effects on follower performance when they enact visionary and empowering leadership behaviors simultaneously and adopt a “both-and” approach, rather than focus on one of these behaviors without the other. Our results support our hypothesized interactive effect of visionary and empowering leadership on goal clarity, as well as a conditional indirect effect such that goal clarity mediates the interactive effect of visionary and empowering leadership on individual follower performance.