Table of Contents

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

This dataset is one of three datasets presenting marine biogeochemistry data from four sites in Clayoquot Sound, Vancouver Island, British Columbia from water, sediment, and porewater samples that were collected aboard the R/V Rachel Carson in October 2023. These sites were selected because they represent hotspots of organic carbon burial spanning a range of geochemical conditions. They represent a range of oxic to historically anoxic water columns, and receive organic matter inputs varying from predominantly terrestrial to predominantly marine sources. Together, these datasets provide a framework to evaluate the controls and drivers of organic matter preservation in fjord sediments. See the "Related Datasets" section for the other datasets.

Water samples were collected using a CTD with 12-liter (L) Niskin bottles from four sites in Clayoquot Sound, Vancouver Island, British Columbia in October 2023. To sample methane, 60 milliliters (mL) of unfiltered water was added to a 72 mL serum vial containing 2 NaOH pellets, sealed, and refrigerated until analysis. For DIC and pH samples, 0.2 micron (um) filtered water was added to exetainers; samples were refrigerated until analysis. To sample alkalinity, 0.2 micron filtered water was added to a 20 mL serum vial and sealed; samples were refrigerated until analysis. For nutrient samples, 0.2 micron filtered water was added to a falcon tube; samples were frozen at -20 degrees Celsius (°C) until analysis. To sample sulfate, 1 mL of 0.2 micron filtered water was added to a tube containing 100 microliters (uL) of 1 N HCl; sulfate samples were frozen at -20°C until analysis.

Methane was analyzed via GC-FID (Shimadzu GC14A). DIC and δ13C of DIC were analyzed at the UC Davis Stable Isotope Facility. Alkalinity was determined by titration of the sample with 0.03 M HCl (Metrohm 888 Titrando). Nutrients were analyzed by the MSI Analytical Lab at UC Santa Barbara. pH was determined using the dye meta-cresol purple via a UV-Vis spectrophotometer (Genesys 150) (Clayton and Byrne 1993). Sulfate was measured via ion chromatography (Metrohm 930 Compact IC Flex).

Samples analyzed in this study were collected within Ahousaht Territory, on the west coast of Vancouver Island, British Columbia. We respectfully acknowledge the Ahousaht Nation and the Maaqutusiis Hahoulthee Stewardship Society for their stewardship of these lands and for the opportunity to conduct research within their territory.

Sulfate concentrations were calibrated using a sulfate standard curve (0.1 – 100 parts per million (ppm)). Methane concentrations were calibrated using a standard curve (1.446 ppm – 50 ppm). Alkalinity was calibrated using CO2 in Seawater Reference Material (CRM) from Scripps Institution of Oceanography.

- Imported original file "20251007_FJ_watercolumn.csv" into the BCO-DMO system.
- Removed "nd" from the dataset (missing data are empty/blank in the final csv file).
- Converted the date field to YYYY-MM-DD format.
- Saved the final file as "992821_v1_rc0107_water_column.csv".

NSF Award Abstract:

CAREER: Particle-Hosted Sulfur Cycling and Organic Matter Burial in Oxygen Deficient Zones

Areas of the ocean without dissolved oxygen are called anoxic zones. These environments are increasing due to human activities and climate change. Large amounts of organic carbon are buried in sediments below anoxic zones. However, we do not fully understand why organic carbon is preserved in these zones. This project seeks to understand a newly discovered process that may contribute to carbon preservation in anoxic zones. The process is called organic matter sulfurization. Through this process, organic matter is transformed and effectively ?pickled? by reacting with sulfide. Rapid sulfurization reactions were identified for the first time in sinking marine particles and may have larger effect on carbon burial in sediments than previously thought. This project will be the first to provide measurements of the scale and significance of rapid organic matter sulfurization in modern anoxic zones. This project includes field and laboratory studies. The research will involve a team of students, including a graduate student and six undergraduates, who will be supported through a peer mentorship program. Undergraduate researchers will be recruited from the inaugural class of a newly developed Practical Research Skills course (Earth 101A) at the University of California Santa Barbara. It seeks to help undergraduates develop critical thinking and observational skills that have broad applicability. This project will launch a self-sustaining and vigorous research program in marine biogeochemistry, heavily invested in undergraduate research education, with impacts that will outlast its five-year duration.

The overarching research goal of this project is to assess the contribution of sulfurization reactions to organic carbon preservation in anoxic environments. After constructing and testing a set of customized particle traps, an expedition will be conducted to the marine anoxic zone off the coast of Mexico. Sinking particles, suspended materials, and surface sediments will be collected at three sites on the Mexican shelf and slope, that have generally high local productivity and gradients in bottom-water oxygen concentration. In the field, the rates and isotopic fractionation of microbial sulfate reduction and organic sulfur formation will be measured with stable and radioactive isotope tracers. Subsequently, organic sulfur sources from both natural samples and laboratory experiments will be characterized using mass spectrometry, X-ray absorption spectroscopy, and other geochemical techniques. Together, the results of this work will identify the timing and location of organic matter sulfurization in this environment, which have substantial implications for both modeling marine carbon fluxes and interpreting the geologic record. This study will provide the first quantitative estimates of the scale of organic matter sulfurization in anoxic marine zones, its contribution to sedimentary carbon burial, and its sensitivities to environmental change. Simultaneously, this project will improve the Earth Science undergraduate curriculum at the University of California Santa Barbara through the development of a clear, supportive, and accessible mechanism for including students in research.

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.