Collaborative Research: An examination of dissolved organic sulfur biogeochemistry

Sulfur is a major element in the ocean and is found primarily as dissolved inorganic sulfate. However, trace amounts of sulfur exist as dissolved organic sulfur (DOS). Research on DOS in the ocean began in the 2000’s.

This is because it is difficult to measure DOS concentration in a solution having almost one million times more inorganic sulfate. While relatively small in quantity compared to inorganic sulfur, DOS plays critical roles in oceanic and atmospheric processes. For example, sunlight degrades DOS into carbonyl sulfide gas, which moves into the upper atmosphere, forming sulfate particles that block sunlight reaching the Earth.

Many DOS compounds are essential for microbial growth in the ocean. Additionally, some DOS compounds react with essential (e.g., zinc) and toxic (e.g., mercury) trace metals to affect their solubility and biological availability. To uncover the mysteries of DOS, this study will utilize archived samples collected from over 100 locations in the Pacific Ocean from Alaska to Antarctica and collect fresh samples in the North Atlantic Ocean near Bermuda.

The scientists will measure the total concentrations of DOS in these samples and determine the compounds that make up DOS. Graduate and undergraduate education is a central part of this project. The project will support one graduate student at Old Dominion University and graduate and undergraduate students at Texas A&M University-Corpus Christi.

The scientists will share their research with the public through already scheduled lectures and forums. They will also develop and use a virtual reality (VR) experience to simulate what it is like to go to sea and collect samples for DOS.

This research project will uncover the processes governing the marine DOS cycle in the Pacific Ocean, with three primary objectives: 1) Accurately quantify the DOS inventory across the entire Pacific Ocean to clarify its role in the global sulfur cycle. 2) Identify the abiotic and biotic processes responsible for DOS production and removal along two meridional Pacific transects, encompassing different biogeochemical regimes, hydrothermal plumes, and oxygen minimum zones. 3) Conduct a year-long, monthly collection of depth profiles at the Bermuda-Atlantic Time Series (BATS) to investigate the reactivity of DOS and its components. The research will leverage archived samples from three Pacific meridional transects, spanning from Alaska to Antarctica and Antarctica to Mexico, along with newly collected samples from the monthly BATS cruises.

The project will improve understanding of the inventory and cycling of DOS in the ocean and provide research training opportunities for graduate and undergraduate students. Results from this study will be communicated to the public through lectures and a virtual reality experience.

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.