Collaborative Research: Three decades of foraminiferal assemblages in the Santa Barbara Basin provide a link between present and past

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Modern day releases of the greenhouse gas, carbon dioxide, into the atmosphere are the highest observed over the last 30 million years. This has resulted in major changes in the ocean. This work focuses on using a group of shell-forming organisms, planktic foraminifera. The carbonate shells of foraminifera are found in seafloor sediments. They provide a history of the environment in which they grew. The goal of this project is to use the shells of foraminifera to better understand how quickly and why the abundances of different foraminifera species change in response to climate. A thirty-year record of planktic foraminifera abundances will be created from stored samples collected from the Santa Barbara Basin, California. The results will be connected to modern day oceanographic measurements and the foraminifera found in older seafloor sediments. This will allow a better understanding of how climate change has impacted the ocean environment over very long time periods and allow future predictions. This project will provide hands on research training for students. Classroom activities will be developed that promote quantitative and data visualization skills with a real-world dataset. Foraminifera have species-specific environmental preferences that influence their assemblages in the water column and in marine sediments. Moreover, the geochemistry of foraminiferal shells has become the foundation for widely used paleoceanographic proxies. However, interpretation of the fossil foraminiferal record must be fundamentally grounded in foraminiferal ecology. For example, use of geochemical proxies relies on the assumption of negligible change in seasonality or habitat through time, with violations potentially responsible for key errors in the paleoceanographic record. In addition to assessing rates and drivers of foraminiferal faunal change, this research would fulfill goals including: 1) testing how changing seasonality influences interpretations of foraminiferal-based proxy records, 2) evaluating whether sediment trap faunas are representative of underlying sediment, and 3) integrating 21st century foraminiferal faunal change with the geological record. Assemblages from biweekly sediment traps and near-annually resolved samples from a sediment core will be generated to accomplish these goals. Santa Barbara Basin was chosen because it has an archive of sediment trap material, extensive overlapping observational measurements, a well-preserved fossil record, and experiences climatic oscillations at timescales from seasonal to anthropogenic and longer. Quantitative assemblages will be supported by stable isotope and trace elemental analyses of a subset of shells to test interpretations of geochemical proxy records.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.