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Reading the Tea Leaves

Jan 3, 2023

Nicole Marks, former Coastal Management Fellow for the Delaware Coastal Management Program, gives a happy thumbs up upon successfully finding a tea site after 90 days in Delaware’s St. Jones Reserve.

Tea leaves aren’t just good for predicting our future, they also can help us predict the future condition of marshes. Exhibit A: researchers at 16 Reserves across the System are using tea bags as part of an international experiment to determine the role of environmental factors and microbial activity in salt marsh decomposition. 

“We have demonstrated that Reserve scientists can deploy this easy method to capture decomposition rate,” says Dr. Kari St. Laurent, physical scientist at NOAA and former research coordinator at the Delaware Reserve. “Students and staff interested in field work also got hands-on experience.”

The goal is to better understand the effect of decomposition on a marsh’s capacity to store and retain carbon dioxide so that we can more accurately predict levels of greenhouse gasses stored in estuaries as organic matter.

The process is straightforward: place tea bags in screen pouches—to protect them and make them easier to deploy and retrieve—and bury them in marshes. The two types of tea used have different proportions and types of carbon, causing them to decay at different rates, which allows researchers to determine the overall organic matter decay rate of the soil, a key factor of wetland health. Tea bags are a perfect open source research supply because they are readily available and standardized across the world.

Kelley Savage, research scientist associate with the Mission-Aransas Reserve, lays out a transect line for multiple tea bag samples in the salt marsh on Mustang Island.

Once they pull the bags, they are dried and the tea is removed and weighed to calculate the decomposition rate. Tea leaves are a proxy for organic matter in the marsh and point towards overall microbial activity.

In a parallel study, Reserve scientists are also studying how factors such as salinity, temperature, and nutrients affect marsh decomposition. Some of the tea bags are buried with fertilizer. They are unearthed after 90 days and measured to see how nutrients affect the decomposition process by measuring how much carbon is left and which microbes are present.

This experiment is being conducted at 49 sites across the globe, which will allow researchers to understand how temperature and latitude impact decomposition and microbial communities. The effort is led by the Smithsonian MarineGEO (Global Earth Observatory), a global network focused on understanding how coastal marine ecosystems work. In the United States, the Mission-Aransas, Delaware, and Chesapeake Bay Maryland Reserves are among 18 sites participating in this project.

Participating Reserves co-located their tea kits with nearby SET plots when possible and used the closest SWMP station to find correlations with “local conditions” such as salinity and temperature.

“This project really demonstrates the power of the Reserve System,” says St. Laurent. “This is all voluntary, and look at the participation!” 

Both the international and national experiments will wrap up this year and the researchers will get to ‘read the tea leaves’ next summer. “The upcoming data analysis and manuscript will uncover a lot, so stay tuned,” says St. Laurent.

Christina Marconi, Research Scientist Assistant with the Mission-Aransas Reserve, buries a tea bag in the salt marsh.

Christina Marconi, research scientist assistant with the Mission-Aransas Reserve, places three tea bag samples in PVC tubes in the estuary.

Kyle Derby, research coordinator at the Chesapeake Bay Reserve in Maryland, deploys a set of tea bags at the Reserve’s Monie Bay component.

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ReservesChesapeake Bay, MarylandReading the Tea Leaves