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 COrg, CaCO3, total sulfur (%) and data from sequential Fe extraction (Cline Assay), calcium ions, Fe total, 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.
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 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 CDR efficiency and benthic dynamics.
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.
This data collection comprises sedimentary porewater, solid-phase, microprofile measurements, cell counts and microbial sulfate reduction rates, from sediment cores collected in Kiel Bight in February 2025 (cruise L25-02b) and incubated under specific conditions over time. Furthermore, water sample data from within the core liner were taken. Cores were incubated at in-situ temperature under controlled oxygen depletion and subsequent reoxidation with calcite amended and unamended treatments. Data includes organic carbon (C org), 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), 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.