Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Curation Notes
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

These data combine measurements reported in Tables 1 and 3 of Mayfield et al. (2024).

Samples were collected as part of the Red Sea Dust, Marine Particulates and Seawater Time Series program. Sinking particulate material was collected using a sediment trap mooring deployed at approximately 120, 220, 340, 450, and 570 meters water depth. Traps were filled with saturated brine poisoned with mercuric chloride to minimize sample degradation. Upon recovery, samples were allowed to settle, the supernatant was partially decanted, and material was sieved through a 1 millimeter mesh to remove large organisms. The remaining material was rinsed with ultrapure water, freeze-dried, and weighed. Subsamples were wet sieved through 500, 125, and 63 micrometer meshes, and the less than 63 micrometer fraction was retained for analysis.

Aerosol samples were collected at the Interuniversity Institute for Marine Sciences in Eilat using total suspended particulate samplers and air filters during dust events.

Sediment samples were obtained using a multi-corer from approximately 720 meters water depth. Samples were subjected to a sequential leaching procedure to remove carbonate, organic matter, iron-manganese oxyhydroxides, and silicate phases, with the remaining fraction containing barite and other refractory minerals. The less than 20 micrometer size fraction was isolated for barium isotope analysis.

Particulate elemental concentrations were determined by external calibration to standards of known concentration.

Barium isotope compositions are reported in delta notation (δ138Ba) relative to NIST SRM 3104a. Instrumental mass bias and isotope ratios were corrected using a double-spike technique. A spiked standard was analyzed every fifth sample, and sample values were normalized to bracketing standards. Analytical precision is reported as the greater of long-term reproducibility (±0.03 permil, 2 standard deviations) or the standard error of replicate analyses. Data processing and calculations were performed using MATLAB R2018a.

- Loaded "Solid Samples.xlsx" with missing values: "", "nd", "N/A", "n.d."
- Converted deployment_start_date from string format %m-%d-%y to date type with output format %Y-%m-%d
- Converted deployment_end_date from string format %m-%d-%y to date type with output format %Y-%m-%d
- Converted sample_collection_date from string format %m-%d-%y to date type with output format %Y-%m-%d
- Renamed table "solid_samples-1" to "1002515_v1_bariumcyclingtimeseries"

NSF Award Abstract:
The biological cycling of carbon in the oceans entrains many other elements, some directly (like nutrients that are essential for life) and some indirectly, as they become chemically involved in the processes that are affecting carbon. One such element is barium (Ba). Particles of the mineral barite (barium sulfate) have been found to form in association with microbial consumption of organic material in the ocean’s “twilight zone.” These particles settle to the ocean floor, and their presence in sediments has been used to infer changes in the conditions in the ocean back in time. Both the amount of barite in sediments and the isotope composition of Ba in barite are potentially sensitive to processes occurring in the twilight zone. However, several long-standing questions remain about Ba cycling in the oceans, which complicates the interpretation of barium-based proxy records. Examples of remaining questions include how much barium enters the oceans at mid-ocean ridge hydrothermal sites, and what controls the precipitation and dissolution of barite in the water column. This project seeks to tackle these questions using new approaches, on three scheduled research expeditions in the Pacific and Southern Oceans. In doing so, this project will support the education, training, and career development of a graduate student, postdoctoral researcher, and junior investigator. Undergraduate students from underrepresented groups will be recruited to conduct complementary shore-based experiments.

This proposal seeks to answer four questions central to the utility of barium-based proxies in oceanography: What are the major inputs of new Ba to the ocean? What are their isotopic compositions? What controls the amount of pelagic barite precipitated during the remineralization of organic matter? What influences its isotopic composition? These questions will be addressed using a field-centric approach combining: in situ and shipboard tracer-incubation experiments, AUV-led adaptive sampling of Ba cycling ‘hotpots’, and section-based surveying of the surrounding oceanographic features. This multi-pronged approach will be used to investigate: the flux and isotopic composition of Ba released from the largest hydrothermal fields in the ocean, the Southern East Pacific Rise, with a focus on low-temperature venting; rates and signatures of pelagic barite precipitation associated with different phytoplankton assemblages in the Southern Ocean; and, the importance of environmental conditions, such as low ambient oxygen concentrations, in setting the efficiency of barite precipitation in the Eastern Tropical Pacific. The significance of each transformation will be assessed, which may lead to ruling out the importance of certain processes, or identifying new dependencies that could form the basis of new proxies.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.