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Reactive iron (Fe) oxides in marine sediments may represent a source of bioavailable Fe to the ocean via reductive dissolution and sedimentary Fe release or can promote organic carbon preservation and long‐term burial. Furthermore, enrichments of reactive Fe (sum of Fe oxides, carbonates and sulfides normalized to total Fe) in ancient sediments are utilized as a paleo‐proxy for anoxic conditions. Considering the general importance of reactive Fe oxides in marine biogeochemistry, it is important to quantify their terrestrial sources and fate at the land‐ocean interface. We applied sequential Fe extractions to sediments from the Amazon shelf to investigate the transformation of river‐derived Fe oxides during early diagenesis. We found that ∼22% of the Amazon River‐derived Fe oxides are converted to Fe‐containing clay minerals in Amazon shelf sediments. The incorporation of reactive Fe into authigenic clay minerals (commonly referred to as reverse weathering) is substantiated by the relationship between Fe oxide loss and potassium (K) uptake from sedimentary pore waters, which is in agreement with the previously reported Fe/K stoichiometry of authigenic clay minerals. Mass balance calculations suggest that widely applied sequential extractions do not separate Fe‐rich authigenic clay minerals from reactive Fe oxides and carbonates. We conclude that the balance between terrestrial supply of reactive Fe and reverse weathering in continental margin sediments has to be taken into account in the interpretation of sedimentary Fe speciation data. Key Points Reactive Fe is transferred from river‐derived Fe oxides into Fe‐containing silicate minerals during early diagenesis Standard sequential extraction schemes do not separate Fe oxides and carbonates from authigenic silicate minerals in Amazon shelf sediments Terrigenous supply of reactive Fe and reverse weathering need to be considered in the interpretation of sedimentary Fe speciation

Natural seafloor depressions, known as pockmarks, are common subaqueous geomorphological features found from the deep ocean trenches to shallow lakes. Pockmarks can form rapidly or over millions of years and have a large variety of shapes created and maintained by a large variety of mechanisms. In the sandy sediments of the southeastern North Sea, abundant shallow pockmarks are ubiquitous and occur at shallow water depths (<50 m). Their formation has previously been linked to methane seepage from the seafloor. Here, we characterize over 50,000 pockmarks based on their morphology, geochemical signature, and the subsurface pre‐conditions using a new integrated geoscientific data set, combining geophysical and sedimentological data with geochemical porewater and oceanographic analysis. We test whether the methane seepage is indeed responsible for pockmark formation. However, our data suggest that neither the seepage of light hydrocarbons nor groundwater is driving pockmark formation. Because of this lack of evidence for fluid seepage, we favor the previously suggested biotic formation but also discuss positive feedback mechanisms in ocean bottom currents as a formation process. Based on a comparison of pockmarks to the central and southeastern North Sea, we find that local lithology significantly affects pockmark morphology. Muddy lithologies favor the formation of larger, long‐lived structures, while sandy lithologies lead to short‐lived, small‐scale structures that are large in area but with shallow incision depth. We conclude that pockmarks in sandy environments might have been overlooked globally due to their shallow incision depth and recommend reevaluating the role of hydrocarbon ebullition in pockmark formation. Plain Language Summary Pockmarks are natural depressions on the seafloor, found everywhere from deep oceans to shallow lakes. These underwater features can form quickly or over millions of years, sometimes reaching impressive sizes—tens of meters deep and kilometers wide. Pockmarks are created by different processes depending on where they are found, but they are often linked to the release of gases such as methane from the seafloor. In the southeastern North Sea, thousands of shallow pockmarks have been discovered in sandy areas less than 50 m deep. Initially thought to be caused by methane gas leaks, our research shows this is unlikely. We studied over 50,000 pockmarks using geological, chemical, and oceanographic data and found little evidence that methane or groundwater seepage is responsible. Instead, these pockmarks are more likely created by either marine animals such as harbor porpoises or turbulent ocean currents. We also found that the grainsize of the sediment greatly affects pockmark morphology and lifespan. In muddy areas, pockmarks are larger and longer‐lasting, whereas in sandy areas, they are shallower and shorter‐lived. Our findings suggest that many pockmarks in sandy environments may have been overlooked due to their shallow depth. We recommend reconsidering the role of methane in pockmark formation. Key Points Pockmarks in the German Bight form in sandy environments and are likely not related to fluid venting Pockmarks in sandy sediments are shallow in depth, large in area and short‐lived structures compared to muddy host sediments Despite the widespread occurrence of pockmarks in the southeastern North Sea, the processes leading to their formation remain unclear

Sediment resuspension of blue carbon ecosystems (e.g., seagrass beds) and muddy sediments exposes buried particulate organic carbon to oxygenated waters and remineralization, potentially enhancing carbon dioxide fluxes. However, the kinetics of carbon degradation under oxic and anoxic conditions are poorly constrained. We report the results of incubation experiments with sediments from Kiel Bight to simulate sediment resuspension events induced by natural and anthropogenic resuspension in this area. A numerical model determined that oxic carbon remineralization rates were up to two-fold higher than those under anoxic conditions. A coupled sediment-water column model demonstrated that pyrite oxidation, rather than carbon oxidation, has the potential to induce large carbon dioxide emissions to the atmosphere following anthropogenic sediment disturbance by trawling. Upscaling to muddy areas of Kiel Bight suggests an annual emission of up to ~14 k tonnes of carbon dioxide per year. Pyrite oxidation may contribute to a weakening of the carbon shelf pump and a reduction of anthropogenic carbon dioxide uptake. Sediment resuspension doubles oxic particulate organic carbon remineralisation compared with anoxic conditions, while concurrent pyrite oxidation reduces uptake of atmospheric carbon dioxide, according to experimental data from Kiel Bight, Germany.

The Skagerrak basin represents the main sink area for fine-grained sediment in the North Sea region and constitutes a natural deposition center for sediments that are supplied from the Atlantic, the Baltic Sea and the surrounding continental margins and coasts. However, the exact sources and their proportional contributions to the North Sea sediments and to the Skagerrak deposits are not well understood. To trace the predominant sources of the sediment and to gain a better understanding of the sedimentary processes in the North Sea and the Skagerrak basin, radiogenic Sr, Nd, and Hf isotope signatures and clay mineral compositions of the detrital clay fraction of surface sediment samples from the North Sea, the Scandinavian margins and the Baltic Sea were measured. The results indicate that the major source for Skagerrak clay-size sediments is the northern North Sea but Scandinavia as well as the southern North Sea including the southern England coast also contribute material. Seabed and coastal erosion in the northern North Sea are enhanced by the inflowing Atlantic Currents, which provide the Skagerrak with high amounts of clay size sediments. In contrast, the southern North Sea, the Baltic Sea and mid-European rivers such as Weser, Elbe and Ems are only minor contributors. As Skagerrak deposits are dominated by clay sized material (up to 60%), the reconstructed sediment processes in this study deviate from findings in previous sediment budget studies, which were based on both clay and silt fraction and indicated predominant influences from the southern North Sea. These results highlight that coastal and seabed erosion in the North Sea is a previously underestimated source of fine-grained sediments for depocenters in the entire North Sea. With regard to climate change, the global sea-level rise will likely enhance erosional processes and can therefore significantly influence the sediment budget of the entire North Sea.

Seamounts are abundant features on the seafloor that serve as hotspots and barriers for the dispersal of benthic organisms. The primary focus of seamount ecology has typically been on the composition and distribution of faunal communities, with far less attention given to microbial communities. Here, we investigated the microbial communities in the water column (0-3400 m depth) and sediments (619-3883 m depth, 0-16 cm below seafloor) along the ice-covered Arctic ridge system called the Langseth Ridge. We contextualized the microbial community composition with data on the benthic trophic state (i.e., organic matter, chlorophyll- a content, and porewater geochemistry) and substrate type (i.e., sponge mats, sediments, basaltic pebbles). Our results showed slow current velocities throughout the water column, a shift in the pelagic microbial community from a dominance of Bacteroidia in the 0-10 m depth towards Proteobacteria and Nitrososphaeria below the epipelagic zone. In general, the pelagic microbial communities showed a high degree of similarity between the Langseth Ridge seamounts to a northern reference site. The only notable differences were decreases in richness between ~600 m and the bottom waters (~10 m above the seafloor) that suggest a pelagic-benthic coupling mediated by filter feeding of sponges living on the seamount summits. On the seafloor, the sponge spicule mats, and polychaete worms were the principal source of variation in sedimentary biogeochemistry and the benthic microbial community structure. The porewater signature suggested that low organic matter degradation rates are accompanied by a microbial community typical of deep-sea oligotrophic environments, such as Proteobacteria, Acidimicrobiia, Dehalococcoidia, Nitrospira, and archaeal Nitrososphaeria. The combined analysis of biogeochemical parameters and the microbial community suggests that the sponges play a significant role for pelagic-benthic coupling and acted as ecosystem engineers on the seafloor of ice-covered seamounts in the oligotrophic central Arctic Ocean.

Recent studies have proposed calcite and dunite as possible alkaline materials for enhanced benthic weathering in shallow depocenters of the Baltic Sea as a marine carbon dioxide removal strategy. In this study, insights on calcite and dunite weathering from laboratory incubations and long-term benthocosm experiments are combined with a numerical box-model to assess the carbon dioxide uptake potential of mineral addition to organic-rich sediments in the southwest Baltic Sea. The results reveal that calcite has an up to 10-fold higher carbon dioxide uptake efficiency and is therefore the preferable material for enhanced benthic weathering as a marine carbon dioxide removal method, with costs per tonne of sequestered carbon dioxide ranging between 82 and 462 euro for calcite while reaching 558–1920 euro for dunite. These findings could be applicable to other areas in the Baltic Sea and also globally to sediments in the wider coastal shelf with similar geochemical properties. Calcite has a higher carbon dioxide uptake efficiency and lower cost than dunite, and it is a preferable material for enhanced benthic weathering as a carbon dioxide removal method, according to an analysis that combines laboratory incubation, benthocosm experiment, and numerical box model.

Sediment fluxes to the seafloor govern the fate of elements and compounds in the ocean and serve as a prerequisite for research on elemental cycling, benthic processes and sediment management strategies. To quantify these fluxes over seafloor areas, it is necessary to scale up sediment mass accumulation rates (MAR) obtained from multiple sample stations. Conventional methods for spatial upscaling involve averaging of data or spatial interpolation. However, these approaches may not be sufficiently precise to account for spatial variations of MAR, leading to poorly constrained regional sediment budgets. Here, we utilize a machine learning approach to scale up porosity and 210 Pb data from 145 and 65 stations, respectively, in the Skagerrak. The models predict the spatial distributions by considering several predictor variables that are assumed to control porosity and 210 Pb rain rates. The spatial distribution of MAR is based on the predicted porosity and existing sedimentation rate data. Our findings reveal highest MAR and 210 Pb rain rates to occur in two parallel belt structures that align with the general circulation pattern in the Skagerrak. While high 210 Pb rain rates occur in intermediate water depths, the belt of high MAR is situated closer to the coastlines due to lower porosities at shallow water depths. Based on the spatial distributions, we calculate a total MAR of 34.7 Mt yr -1 and a 210 Pb rain rate of 4.7 · 10 14 dpm yr -1 . By comparing atmospheric to total 210 Pb rain rates, we further estimate that 24% of the 210 Pb originates from the local atmospheric input, with the remaining 76% being transported laterally into the Skagerrak. The updated MAR in the Skagerrak is combined with literature data on other major sediment sources and sinks to present a tentative sediment budget for the North Sea, which reveals an imbalance with sediment outputs exceeding the inputs. Substantial uncertainties in the revised Skagerrak MAR and the literature data might close this imbalance. However, we further hypothesize that previous estimates of suspended sediment inputs into the North Sea might have been underestimated, considering recently revised and elevated estimates on coastal erosion rates in the surrounding region of the North Sea.

Dissolved silicate (H 4 SiO 4 ) is essential for the formation of the opaline skeletal structures of diatoms and other siliceous plankton. A fraction of particulate biogenic silica (bSi) formed in surface waters sinks to the seabed, where it either dissolves and returns to the water column or is permanently buried. Global silica budgets are still poorly constrained since data on benthic bSi cycling are lacking, especially on continental margins. This study describes benthic bSi cycling in the Skagerrak, a sedimentary depocenter for particles from the North Sea. Biogenic silica burial fluxes, benthic H 4 SiO 4 fluxes to the water column and bSi burial efficiencies are reported for nine stations by evaluating data from in-situ benthic landers and sediment cores with a diagenetic reaction-transport model. The model simulates bSi contents and H 4 SiO 4 concentrations at all sites using a novel power law to describe bSi dissolution kinetics with a small number of adjustable parameters. Our results show that, on average, 1100 mmol m -2 yr -1 of bSi rains down to the Skagerrak basin seafloor, of which 50% is released back to overlying waters, with the remainder being buried. Biogenic silica cycling in the Skagerrak is generally consistent with previously reported global trends, showing higher Si fluxes and burial efficiencies than deep-sea sites and similar values compared to other continental margins. A significant finding of this work is a molar bSi-to-organic carbon burial ratio of 0.22 in Skagerrak sediments, which is distinctively lower compared to other continental margins. We suggest that the continuous dissolution of bSi in suspended sediments transported over long distances from the North Sea leads to the apparent decoupling between bSi and organic carbon in Skagerrak sediments.

Bottom trawling represents the most widespread anthropogenic physical disturbance to seafloor sediments on continental shelves. While trawling-induced changes to benthic ecology have been widely recognized, the impacts on long-term organic carbon storage in marine sediments remains uncertain. Here we combined datasets of sediment and bottom trawling for a heavily trawled region, the North Sea, to explore their potential mutual dependency. A pattern emerges when comparing the surface sediment organic carbon-to-mud ratio with the trawling intensity represented by the multi-year averaged swept area ratio. The organic carbon-to-mud ratio exhibits a systematic response to trawling where the swept area ratio is larger than 1 yr −1 . Three-dimensional physical–biogeochemical simulation results suggest that the observed pattern is attributed to the correlated dynamics of mud and organic carbon during transport and redeposition in response to trawling. Both gain and loss of sedimentary organic carbon may occur in weakly trawled areas, whereas a net reduction of sedimentary organic carbon is found in intensely trawled grounds. Cessation of trawling allows restoration of sedimentary carbon stock and benthic biomass, but their recovery occurs at different timescales. Our results point out a need for management of intensely trawled grounds to enhance the CO 2 sequestration capacity in shelf seas. Intensive bottom trawling causes a long-term reduction of organic carbon stored in seafloor sediments, suggesting a need for more effective management, according to observations and biogeochemical modelling.

Um von dem Wachstum des Logistikdienstleistungsmarktes zu profitieren, sich vom harten Preiswettkampf zu lösen und Kunden nachhaltig an sich zu binden, müssen insbesondere die Anbieter komplexer, kundenindividueller Kontraktlogistikleistungen ihre Fähigkeit steigern, neue Servicekonzepte effizient zu entwickeln. Dabei stellen innovative Technologien nicht nur strategisch wichtige Hebel zur Differenzierung und Realisierung neuer Marktpotenziale, sondern auch zentrale Wandlungstreiber dar. Aus den heute festzustellenden technologischen Trends ergeben sich vollkommen neue, technologiebasierte Wertschöpfungsszenarien und ein erheblicher Veränderungsdruck für die Branche. Kontraktlogistikunternehmen, die in der Lage sind, aufkommende technologische Potenziale zu erkennen und für die eigenen Herausforderungen im Rahmen innovativer Services zu nutzen, verschaffen sich entscheidende Vorteile im Wettbewerb. Viele Anbieter, deren Erfahrungen und Kompetenzen eher auf betriebsorientierten, operativen Projekten basieren, sehen sich jedoch der Herausforderung innovationshemmender Strukturen sowie mangelnder strategischer, prozessualer und methodischer Fähigkeiten gegenüber. Der Aufbau eines proaktiven Technologie- und Innovationsmanagements setzt für sie einen grundlegenden, bis auf die Ebene der Unternehmenskultur reichenden Wandlungsprozess voraus. Die Dissertation befasst sich daher mit der Konzeption eines auf die Anforderungen von Kontraktlogistikunternehmen angepassten Gestaltungsmodells für ein technologieorientiertes Service Engineering. Dem Paradigma der anwendungsbezogenen, zweckorientierten Forschung folgend, wird den verantwortlichen Entscheidungsträgern eine Unterstützung geboten, die Strukturen und Abläufe der Dienstleistungsentwicklung so zu gestalten, dass neue Services unter Berücksichtigung innovativer oder in neuem Zusammenhang eingesetzter Technologien systematisch und erfolgreich entwickelt werden können. Im Sinne des gefolgten Logistik- und Forschungsverständnisses wird ein interdisziplinärer, ganzheitlicher Ansatz aufgebaut, der den Kunden als bestimmendes Element des Handlungskontextes einbezieht und berücksichtigt. Das methodische Vorgehen gliedert sich entsprechend der Teilziele des definierten formallogischen Forschungskonzeptes in fünf Phasen. Zur Spezifikation des praxisrelevanten Problems, zur Erfassung und Interpretation der problemrelevanten Theorien und zum Aufbau des konzeptionellen Bezugsrahmens werden systematische Literaturanalysen eingesetzt. Die anschließende Erfassung und Untersuchung des Anwendungszusammenhangs unter direkter Einbindung der Praxis erfolgt dann mit Hilfe einer Kombination quantitativer und qualitativer empirischer Methoden. So wird die kausalanalytische Fragestellung nach den in der Kontraktlogistik erfolgskritischen Gestaltungsfeldern eines technologieorientierten Service Engineerings auf Basis der Ergebnisse einer explorativen Faktorenanalyse und daran anknüpfender Regressionsanalysen beantwortet. Die Erkenntnisse der inferenzstatistischen Untersuchung werden durch eine ergänzende deskriptive Analyse unterlegt. Der qualitative Teil der Untersuchung konzentriert sich auf die Frage nach den wichtigsten Herausforderungen und Maßnahmen aus Sicht der Praxis. Methodisch wird der Forschungsschritt durch den Einsatz einer Gruppendiskussion vollzogen. Die empirisch gewonnenen Erkenntnisse werden anschließend im Rahmen eines abduktiv-konzeptionellen Schrittes bei der Ableitung des Gestaltungsmodells verwertet. Das als ganzheitlicher Managementansatz ausgelegte Gestaltungsmodell bringt mit der kulturellen und strategischen Basis sowie dem markt- und technologieorientierten Entwicklungsprozess die als wesentlich erkannten Gestaltungsfelder eines technologieorientierten Service Engineerings in der Kontraktlogistik in einen Zusammenhang. Die leitende Rolle der Dienstleistungsentwicklung und die Unterstützungsfunktion des Technologiemanagements werden durch integrierte Ablaufsystematiken verdeutlicht. Mit ihnen wird die Relevanz einer prozessorientierten Logik in den Ansatz übertragen. Der Entwurf des Gestaltungsmodells wird durch praxisgerechte Hinweise zur inhaltlichen Bearbeitung der Gestaltungsfelder ergänzt. Die im Modell verankerten Maßnahmen und Werkzeuge werden auf Grundlage definierter Erfolgskriterien abgeleitet und konzentrieren sich auf insgesamt sieben Kernbereiche. Der erarbeitete Ansatz wird abschließend kritisch unter Einbeziehung von Praxisexperten bewertet und die Voraussetzungen für seine erfolgreiche Implementierung diskutiert. Insgesamt richtet sich die Dissertation, auf die weitere Forschungsarbeiten aufbauen können, an Entscheidungsträger der Kontraktlogistik. Sie erhalten eine Hilfestellung, ihre Fähigkeit zu steigern, Marktumbrüche und neue technologische Potenziale im Rahmen einer effizienten Weiterentwicklung ihres Leistungsportfolios zu erfassen, zu bewerten und zu nutzen, um von dem technologischen Fortschritt nachhaltig profitieren zu können.