RAPID: Assessing the role of hurricanes and microbes in enhancing coastal sediment accumulation

University Of Colorado At Boulder, Boulder CO

Investigators

Abstract

Over 60 million Americans live along the coasts of the Gulf of Mexico and Atlantic. These regions of the United States are the most vulnerable to hurricanes and sea level rise. However, stabilizing coastlines and increasing sediment accumulation can reduce these hazards. This study explores how microbes affect these processes on Little Ambergris Cay, a small uninhabited island in the Turks and Caicos Islands. In September 2022, Hurricane Fiona passed near the island. This study examines how microbes stabilize sediment in both lagoonal and coastal settings after the hurricane. Results from this study will be shared with local communities through partnership with the Turks and Caicos Islands Department of Environment and Coastal Resources (DECR). This study also provides proof of concept for interventions that could help communities stabilize their coastlines. This would enhance resilience against sea level rise and increasing hurricane intensity. The project educational Broader Impacts include participation of a graduate student from University of Colorado and a postdoc from University of California, Berkeley in the sampling trips. This study tracks responses of microbial mat sediment stabilization and cementation of hurricane breccias that occur during the recovery from Hurricane Fiona, which passed close to Little Ambergris Cay as a Category 3 hurricane in September 2022. Observations from a prior field season in June 2022 provide a pre-hurricane baseline. Proposed work includes: (i) microelectrode profiles of dissolved O2, H2S, and pH to track re-establishment of geochemical gradients in mats and 16S rRNA gene sequencing to compare community recovery to our pre/post-Irma and pre-Fiona observations; (ii) installation of small-scale surface elevation table devices to quantitatively track net thickness of mat growth in a suite of locations; (iii) repeated in situ microscopy observations and short-term trapping-and-binding experiments to determine whether mat response to added sediment is the same over time (i.e., the delivery of new sediment is the primary requirement for vertical accretion) or if the mat response changes as the ecosystem recovers (i.e., the hurricane perturbation to the microbial ecosystem is as important as the delivery of sediment); and (iv) in situ hurricane breccia lithification experiments to measure the timescale of lithification and the microbial activity present. This work will be carried out over three field seasons during 2023, allowing both short-term (daily) and medium-term (months-long) observations of the island response during the first year following hurricane perturbation. 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.