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Kiel Bight sediment core liner water-column data from sediment core incubation experiment in 2025

This dataset consists of water chemistry from within three calcite amended and three reference sediment cores from Kiel Bight from February 2025. Dissolved oxygen was monitored non-invasively using optical sensor spots (OXSP5, PyroScience) at 5cm above the sediment. Total alkalinity and calcium ion concentration were measured at regular intervals over four weeks, covering sediment settlement, calcite amendment, deoxygenation and reoxygenated phases. Water exchanges with nitrogen (N2) deoxygenated seawater-maintained calcite dissolution and N2 was determined at the end of the experiment. The dataset enables reconstruction of alkalinity generation, calcium release and oxygen dynamics during enhanced benthic weathering. This is supporting the assessments of carbon dioxide removal (CDR) efficiency and benthic dynamics.

Bottom water chemistry during in-situ incubation experiments on enhanced benthic calcite weathering in July 2025

The data was produced during a 16 day in-situ incubation experiment in the Baltic Sea. In order to assess the potential for enhanced benthic calcite weathering as a ocean alkalinisation and thus negative emissions strategy, a Biogeochemical Observatory (BIGO, Sommer et al., 2009) was deployed at 54° 34.432 N, 10° 10.776 E, at 22 m water depth between 2025-07-12 and 2025-07-29. The BIGO is equipped with two benthic chambers that were lowerd to the sea floor. In chamber two, 29 g of fine calcite powder were added to the bottom water. 7 Samples were taken via an automatted glassyringe sampler from each chamber and the ambient bottom water.

Kiel Bight sedimentary data from sediment core incubation experiment in 2025

This dataset presents porewater and solid-phase geochemistry as well as microbial cell counts and microbial induced sulfate reduction rates from calcite-amended and unamended sediment cores collected in Kiel Bight in February 2025 during cruise L25-02b. Sediment cores were incubated at 8° C under controlled oxygen cycles in the laboratory of the home institute. Porewater was extracted by centrifugation and anoxic filtration. Solid phase analyses included organic carbon (COrg), calcium carbonate (CaCO3), total sulfur (%) and data from sequential iron (Fe) extraction (Cline Assay), calcium ions, Fe total, manganese (Mn total, ICP-OES), sulfate (IC), alkalinity, hydrogen sulfide. Sulfate reduction rates were quantified using 35S-radiotracer incubation and cold chromium distillation (Kallmeyer et al., 2004, Roy et al., 2014). Furthermore, cell counts were determined. The dataset supports evaluation of enhanced benthic weathering effects on sulfur cycling, iron speciation and microbial activity in dynamic and seasonally hypoxic coastal sediments.

Experimental data on enhanced benthic weathering in Baltic Sea sediments from winter 2025

This data collection comprises sedimentary porewater, solid-phase, microprofile measurements, cell counts and microbial sulfate reduction rates, from a calcite amendment laboratory experiment. The sediment cores for the experiment were collected in Kiel Bight in February 2025 (cruise L25-02b). For that, six sediment cores were collected and kept in MUC core liner in the dark in the cool room at 8°C for the timespan of the experiment at GEOMAR, Kiel. Furthermore, water sample data from within the core liner were taken at regular timesteps. Three sediment cores were incubated with 7.86 g of grounded limestone (>99% calcium carbonate) distributed at the sediment surface; additional three unamended treatments were used as reference. All sediment cores were kept under controlled oxygen depletion and subsequent reoxidation cycles. Data includes organic carbon (COrg), calcium carbonate (CaCO3), sulfur (S, %) and data from sequential iron (Fe) extraction from solid-phase, calcium ions, Fe total, manganese (Mn) total (ICP-OES), sulfate (ion chromatography, IC), total alkalinity, hydrogen sulfide and nutrients from porewaters as well as sulfate reduction rates. Bottom water chemistry on top of the sediment core was monitored via optical oxygen sensors, alkalinity was titrated, calcium ion concentrations determined over time and dinitrogen was measured at the end of the experiments. High resolution electrochemical microprofiles resolved vertical gradients of sulfide, oxygen, pH and redox across the sediment-water interface. These datasets enable assessments of calcite dissolution, alkalinity generation and microbial responses to enhanced benthic weathering in seasonally hypoxic Baltic Sea sediments.

Umweltinformationen zum Vorhaben Kraftwerk Mehrum — CO₂-Jahresemissionen und Folgekosten

auf Grundlage des Umweltinformationsgesetzes (UIG) bzw. des einschlägigen Landesumweltinformationsgesetzes bitte ich zu dem Vorhaben Kraftwerk Mehrum (EPH, ca. 1200 MW elektrisch), das sich nach meinem Kenntnisstand in dem Vorbescheidsverfahren befindet, um folgende Umweltinformationen: 1. Welche CO₂-Jahresemissionen (in Tonnen pro Jahr) sind in den Antragsunterlagen, im UVP-Bericht oder in den bisher ergangenen Bescheiden für die Anlage angegeben bzw. prognostiziert? 2. Liegen Ihnen aus dem Verfahren Unterlagen oder Bewertungen zu den Folgekosten dieser Emissionen vor — insbesondere zu den Kosten einer späteren Entnahme des emittierten CO₂ aus der Atmosphäre (Carbon Dioxide Removal, vgl. § 3b KSG und VO (EU) 2021/1119)? 3. Falls ja: Bitte übersenden Sie mir diese Unterlagen bzw. benennen Sie die Fundstellen. Falls nein: Bitte bestätigen Sie, dass eine Ermittlung oder Bewertung dieser Folgekosten im Verfahren nicht stattgefunden hat. Es handelt sich um Informationen über Umweltbestandteile (§ 2 Abs. 3 Nr. 1 UIG) und über Maßnahmen, die sich auf diese auswirken (§ 2 Abs. 3 Nr. 3 UIG). Ich bitte um Antwort innerhalb der gesetzlichen Frist von einem Monat (§ 3 Abs. 3 UIG). Übermittlung in elektronischer Form genügt.

KOSMOS 2023 Helgoland mesocosm study on ocean alkalinity enhancement: dissolved inorganic nutrients, chlorophyll a and suspended particulate organic matter

We conducted a mesocosm study to investigate ecosystem responses to ocean alkalinity enhancement (OAE) in the temperate waters of the German North Sea on Helgoland in spring 2023. We simulated non-CO2-equilibrated OAE via calcium hydroxide through the addition of calcium chloride and sodium hydroxide. Twelve 6 m³ mesocosms were used to simulate two scenarios: in six mesocosms we established a gradient of added alkalinity from 0 to 1250 µmol/kg in increments of 250 µmol/kg, simulating immediate (imm) dilution of alkalised waters. For the second set of six mesocosms, alkalinity was added only to the top 1 m of each mesocosm, doubling the target added alkalinity. The top layer was mixed with the untreated bottom layer after 48 hours, simulating delayed dilution of alkalised waters (del) and ultimately leading to the same alkalinity gradient as the immediate dilution treatment. This data contains water column biogeochemical variables, including dissolved inorganic nutrient concentrations (µmol/L), chlorophyll a concentrations (µg/L) and suspended particulate matter (biogenic silica, particulate organic carbon, nitrogen and phosphate; µmol/L). Nutrients, particulate organic phosphate and biogenic silica were measured spectrophotometrically (Unicam UV 300, Thermo Spectronic, USA). High-performance liquid chromatography (Thermo Scientific HPLC Ultimate 3000) was performed for chlorophyll a determination and particulate organic carbon and nitrogen were measured using an elemental analyser (Flash EA, Thermo Fisher).

Kiel Bight microprofiling data from sediment core incubation experiment in 2025

This dataset consists of high-resolution electrochemical microprofiles of sulfide, oxygen, pH and redox potential from sediment core incubation experiment with one calcite amended and one untreated reference core. Measurements used 50 µm tip microsensors (SULF-50, OX-50, pH-50, RD-50; Unisense A/S) with a motorized micromanipulator (250 µm steps, 5.5 cm profiles). Duplicate profiles were measured and this dataset resolves vertical gradient across the sediment-water interface. These datasets provide insights into how carbonate addition alters redox stratification and pH-dynamics in benthic systems following perturbation of temporal equilibrium, supporting interpretation of associated microbial community and activity data.

KOSMOS 2023 Helgoland mesocosm study on ocean alkalinity enhancement: sediment trap particle flux data and water column biogeochemistry

The data presented herein originates from a mesocosm study conducted as part of the BMBF CDRmare, Retake project (grant agreement no. 03F0895A), aimed at investigating the ecological ramifications of ocean alkalinity enhancement (OAE). Twelve mesocosms were deployed in Helgoland South Harbor, Germany, and systematically sampled using integrated water samplers over the period spanning from March 12th to April 20th, 2023. Six alkalinity levels under two dilution scenarios were established to differentiate between localized and uniform OAE additions. Alkalinity was increased stepwise to ΔTAmax = 1250 μmol kg-1 (250 μmol TA kg-1 increments) using sodium hydroxide (NaOH) with calcium chloride (CaCl2) to simulate cation release during calcium-based mineral dissolution, causing strong carbonate chemistry perturbations (e.g., pHT > 9.25). The dataset encompasses a spectrum of sediment trap particle flux data, water column biogeochemistry including pigment variables, inorganic nutrients, carbonate chemistry parameters. The study and data set offer insights into impacts of alkalinity enhancement on marine ecosystems and their associated biogeochemistry.

Total carbohydrates quantified in sediment cores from coastal vegetated ecosystems

50-cm deep sediment cores were taken in saltmarsh, seagrass, mangroves and unvegetated areas around the German Bight, Malaysia and Columbia in 2022 and 2023. Up to 3 points per ecosystem were sampled along a transect, in total 93 cores were analysed. Carbohydrates were sequentially extracted using MilliQ-water and 0.3 M EDTA for later analyses. The total carbohydrate content was assessed using the phenol-sulfuric acid assay (Dubois et al., 1956). Briefly, 100 µL of resuspended samples or extracts were mixed with 100 µL of 5% phenol solution, followed by the addition of 500 µL of concentrated sulfuric acid. The reaction mixture was incubated at room temperature for 10 minutes, then further incubated at 30°C for 20 minutes. Absorbance at 490 nm was measured using a Spectramax Id3 plate reader (Molecular Devices) and quantified against a glucose standard curve.

Polysaccharides quantified in sediment cores from coastal vegetated ecosystems

50-cm deep sediment cores were taken in saltmarsh, seagrass, mangroves and unvegetated areas around the German Bight, Malaysia and Columbia in 2022 and 2023. Up to 3 points per ecosystem were sampled along a transect, in total 93 cores were analysed. Carbohydrates were sequentially extracted using MilliQ-water and 0.3 M EDTA for later analyses. Polysaccharides were screened using microarray analysis following the method described by Vidal-Melgosa et al. (2022). Briefly, sediment extracts from MilliQ-water and EDTA were combined in equal volumes, and 30 µL of the mixture was transferred into wells of 384-microwell plates. Two consecutive two-fold dilutions were performed using a printing buffer (55.2% glycerol, 44% water, 0.8% Triton X-100). The plates were then centrifuged at 3,500 × g for 10 minutes at 15 °C. Each microarray was individually probed with a monoclonal antibody (mAb), and binding was detected using a secondary antibody conjugated to alkaline phosphatase. In the presence of its substrate, this reaction produced a colorimetric signal. Developed arrays were scanned at 2400 dots per inch, and binding signal intensity was quantified using Array-Pro Analyzer 6.3 software (Media Cybernetics).

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