Award: OCE-1924585

This collaborative project investigated the driving factors of marine secondary clay formation (MSCF) in the laboratory (co-principal investigator at Georgia Institute of Technology, GTech, OCE 1923802) and field. MSCF reactions are poorly understood, yet appear to be a major loss process in the environmental cycle of many elements (silicon, lithium studied here, but also iron, aluminum, magnesium, potassium, etc.) and can create carbon dioxide (which can affect global climate) as a reaction byproduct. Among many results, key findings fall into four broad categories: 1) MSCF occurs rapidly: from days to weeks in controlled laboratory conditions (i.e. GTech group) to weeks-months in complicated natural field conditions for both silicon and lithium. 2) Sedimentary silicon phases (including isotopes) react quickly in the presence of oxygen, but this appears to accelerate in conditions with little/no oxygen (“suboxic”); such a suboxic condition alters how silicon develops in sediments, and thereby affects our interpretation of sedimentary cores which are used to infer past processes. 3) Extreme weather events like hurricanes can affect silicon sedimentary processes at least one year post event, opposed to relatively rapid carbon processing post event, and the response in the sediments is strongly affected by site characteristics (e.g. bathymetry of the water column, size distribution of sediment particles). 4) Accounting for MSCF in sediment cores alters the temporal trends inferred from down-core changes in silica properties (i.e. newer material shallow, older material deep) compared to prior work which did not account for this process; this suggests that prior interpretations of regional processes in the mid-late 20^th century may require revision.

This work supported training of multiple PhD level scientists. The main project-supported student leveraged their extensive mass spectrometer analytical expertise, developed through this project, to go into industry. Two other PhD students (one partially supported) leveraged this project’s field opportunity for their dissertations; one student graduated and is currently a postdoctoral scholar, the other earned a Knauss Marine Policy Fellowship (National Oceanic and Atmospheric Administration) following their graduation and is working at the interface of science and policy. Institutional undergraduate students were trained using samples from this work through DISL's NSF-supported Research Experience for Undergraduates program.

This project facilitated educational development at multiple levels. The project’s research cruise provided a platform to develop field experience for regional gap-year students, two teachers from the Alabama School of Math and Science, a National Academies of Science Gulf Research Program Science Policy Fellowship scholar, and an educator from the Alabama Aquarium. This project also supported a teacher workshop at DISL, institutional vessel time to bring ASMS students to sea (to integrate classroom and field concepts), and students from McDonald County High School (MCHS; located in Missouri) to develop school-year research projects. MCHS students conducted experiments, analyzed data, and created posters to present at an undergraduate research symposium at a nearby university. Finally, three high school students from Tennessee, New Hampshire, and Georgia competitively earned the Russell Quackenbush Research Scholarship from 2020 through 2022; this scholarship supports them to attend the 5-week DISL Marine Science summer course, which blends instruction and a short research project. Among this Quackenbush Scholar cohort, two pursued STEM degrees in universities after graduating high school.

Last Modified: 05/05/2025
Modified by: Jeffrey W Krause