Unlocking the Past to Shape the Future: How Oyster Shells in HRI’s Archives are Helping Researchers Date Ancient Reefs
For more than two years, Kelley Savage ’17, a doctoral candidate in the Coastal Conservation and Restoration lab at the Harte Research Institute for Gulf of Mexico Studies at Texas A&M University-Corpus Christi, has been working on a project to find what role oysters play in the carbon cycle.
By determining the age of oyster reefs and calculating how much organic carbon is stored within them, researchers can estimate the annual carbon capture and storage rates of each reef. This information will reveal the extent to which oyster reefs act as carbon “sinks” and whether they contribute to the long-term burial of carbon, a critical component in understanding their role in the carbon cycle.
The project, though, hit a major hurdle in finding a key piece to the puzzle — pre-1950s oyster shells from the Texas coast.
Savage said they reached out to multiple organizations that might have shells but to no avail. Luckily, though, they found some in the same building they work in every day.
Danielle Downey ’13, ‘18, a research specialist and colleague of, took the search to HRI’s archive room. There Downey found some samples that provided a “eureka” moment for the project.
The oyster shell samples date back to the 1950s in Aransas Bay and were originally identified by former Texas A&M biology professor Dr. H.W. (Harold) Harry and have been in HRI’s archives for nearly two decades.
The time frame for when the samples were taken is important because in the early 1950s nuclear testing ramped up across the globe, spreading ample amounts of radiocarbon across the planet.
Radiocarbon dating relies on understanding natural levels of carbon-14 in the environment, and an oyster shell sample before this testing is prized. During the mid-20th century nuclear testing introduced a “bomb pulse” of carbon-14, complicating the dating of samples from the 1950s and beyond. A shell from before this era is a time capsule or reference point, and researchers can align the data from reef samples to a precise timeline and ultimately it can be determined when the reefs began to form.
“Right now, we don’t know how old the reefs are that we sampled, or how old the (natural) reefs are in Texas,” Savage said. “We’re going to use the shell from Dr. Harry’s collection as a calibration point to date shells from the bottom of our reef cores, helping us determine when these reefs began to form.”
Thanks to these shells, and possibly others coming from elsewhere in Texas, Savage and her team will work to find out the age of the reefs and use that information to determine how much carbon is being stored in reefs and how much oysters act as a carbon “sink”.
The reef cores range in depth from one to three meters, and were taken in St. Charles Bay near Rockport, Texas in 2023. The reef cores were processed and shell samples collected from the base of each natural reef were sent to Woods Hole Oceanographic Institution’s National Ocean Sciences Accelerator Mass Spectrometry Facility in Massachusetts for testing.
The information is important for Savage’s dissertation project titled “Potential Role of Oyster Reefs in Carbon Sequestration: Implications for Reef Conservation and Restoration” because it gives them solid evidence of how much carbon oysters and oyster reefs can store, which could lead to practical solutions coming from the results that could help in guiding sustainable restoration and conservation efforts for oyster reef ecosystems and mitigating climate change.
“At the end of the project we are hoping to provide a tool, it’s going to be a map of where you can restore oyster reefs for the benefit of carbon storage,” Savage said. “This tool has the potential to guide a wide range of conservation and restoration efforts.”