Other language confidence: 0.9720760694191349
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.
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.
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.
Ocean alkalinity enhancement (OAE) is a marine carbon dioxide removal (mCDR) approach that can also mitigate ocean acidification. However, its biological impacts are expected to depend on the magnitude, timing, and dilution of alkalinity additions. To investigate these factors, a mesocosm experiment simulated hydrated lime additions using two six-level alkalinity gradients (up to ΔTA 1250 µmol kg⁻¹): one with immediate full-column mixing and another with mixing delayed by two days. These treatments simulated rapid (e.g. from a moving vessel in open ocean) and slow (e .g. point source or land-based applications in poorly mixed environments)dilution scenarios, representing different hydrodynamic conditions that may occur following real-world alkalinity additions. Gross production (GP), net community production (NCP) and community respiration (CR), determined from in vitro oxygen production and consumption, together with chlorophyll a, were monitored over a 35-day period. Spring bloom initiation was delayed non-linearly at low fCO₂, with reduced absolute and biomass-normalized production occurring in treatments exposed to fCO₂ below ~70 and 30 µatm respectively. These findings indicate that phytoplankton communities may be generally resilient to realistic OAE scenarios while helping to define ecologically relevant fCO₂ thresholds for safe OAE deployment.
This dataset contains species-resolved phytoplankton and microzooplankton abundance and biomass data from the KOSMOS 2023 Helgoland mesocosm experiment conducted in the coastal waters off Helgoland Island in the North Sea, Germany. The experiment investigated the effects of Ocean Alkalinity Enhancement (OAE) on plankton communities during the development of a natural spring bloom. Six mesocosms (~6 m³) were subjected to an immediate dilution OAE scenario, establishing an alkalinity enhancement gradient ranging from ΔTA 0 to 1250 µmol kg⁻¹ in increments of 250 µmol kg⁻¹ through calcium-based alkalinity addition. The dataset includes taxonomically resolved phytoplankton and microzooplankton abundance (cells mL⁻¹), carbon biomass (µg C L⁻¹), functional group classifications, and World Register of Marine Species (WoRMS) taxonomic identifiers. Associated carbonate chemistry measurements, including total alkalinity (TA), dissolved inorganic carbon (DIC), pH, fugacity of carbon dioxide (fCO₂), salinity, temperature, and calculated ΔTA values are provided for each sampling event.
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.
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