Schweppe Seminar

Nature-based infrastructure, such as oyster reefs and saltmarshes, is increasingly being promoted as effective breakwaters to protect communities from storm waves and as carbon burial hotspots to mitigate greenhouse gas emissions. The function of oyster reefs as breakwaters and carbon sinks is often supported by information extracted from extant reefs <10 years old; however, both services depend on accretion, which operate over decadal to millennial time scales. Here we show the rate of sea-level rise (SLR) drives oyster reef vertical accretion and carbon burial. As relative SLR increased after 1800 CE to the modern rate of ~2.4 mm y-1, intertidal reefs grew three times faster than during the previous 18 centuries when SLR was ~0.9 mm y-1. Reef-accretion rates were driven by the flux of shell and organic-rich sediments to the subsurface; however, none of the 25 reefs sampled functioned as net carbon sinks because the organic carbon buried was offset by the CO2 emitted during shell formation. Assuming estuarine conditions are conducive to healthy oysters, our results suggest that as SLR accelerates, the vertical growth of reefs will rapidly respond and there will be ecosystem-service tradeoffs, with reefs becoming larger sources of CO2 but maintaining their effectiveness at damping waves.

Biography

Tony received his BA from Hamilton College (1994) and PhD from Rice University (1999) before being appointed as an Assistant Professor at the University of Alabama, Department of Geological Sciences in 2000. In 2005 he began working at the UNC Institute of Marine Sciences in Morehead City and moved to Chapel Hill in 2024. He is a sedimentologist and stratigrapher conducting field-based research on coastal depositional systems. Tony’s research emphasis is on estuaries, and he collaborates with many colleagues at UNC examining the multifaceted impacts of human activities and climate change on salt marshes, oyster-reefs, seagrass beds, deltaic systems, and beach environments. Some ongoing research projects focus on 1) carbon burial in salt marsh, sea grass, and oyster reef habitats, 2) impacts of upstream changes in watershed land cover on downstream coastal depositional environments, and 3) barrier island response to sea-level rise and storms. His retrospective approach relies on interpreting the sedimentary record from seismic and lithologic data, using radiometric techniques to develop geochronologies, and characterizing morphologic change from remote sensing datasets such as aerial photos, structure from motion, and LiDAR. Tony was the IMS Morehead City Field Site Director 2020–2024, the EMES Associate Chair 2021–2025, and will be the Chair of EMES starting July 2025.