Community carbon cycle project leads to student thesis work

Last fall, Professor of Biology and Environmental Studies Brad Oberle’s Forest Ecology class participated in a worldwide research project to study the global carbon cycle using tea bags. The students, along with staff from the Sarasota Bay National Estuary Program, Tampa Bay National Estuary Program, and Manatee County Parks and Recreation, planted tea bags at various sites around Manatee County to measure carbon absorption in different environments.

One of Oberle’s students, Angela McTigue, is replicating the study on Tidy Island, a spit of land attached to the mainland, across Sarasota bay from Longboat Key.
Coastal ecosystems like Tidy Island are important to Florida’s environment because they store carbon and are a feeding ground for fish. McTigue’s thesis consists of two experiments: the first examines leaf litter decay, and the second measures leaf litter fall.
“We’re now planting tea bags to do a direct comparison with Tidy Island and the decay there, the decay at Ungarelli Preserve, and also in the restored areas around Sarasota,” said McTigue. Each site also has a bucket that collects leaf litter for the second experiment. McTigue is measuring the variation in litter fall at each site.
Forest ecologists recently began using tea bags to measure carbon decay because their leaves, which are organic matter, resemble leaf litter.
“The leaves that are dried up in this tea are basically our surrogate for the leaves that would come from the trees and grasses and other plants in the area,” explained Oberle, who is overseeing McTigue’s thesis work.
McTigue buried tea bags at eight sites of varying traits around Tidy Island’s mangrove fields. Some bags are buried in small mounds created with mud dredged up to build mosquito barrier canals. The mounds hold less water than other locations on lower ground.
McTigue and Oberle will return to the site to dig up the tea bags, weigh each one, and compare the results to those of the other sites.
“If the soil organisms aren’t very active, and if they don’t have much of an appetite for tea, what we’ll see after a long period of time is that the tea remains basically the way that it was when we put it in the ground: same color, same texture, and importantly, same quantity,” said Oberle.
The opposite is also true. If the organisms are active, Oberle and McTigue will find the bags weigh less and their contents will be vastly different.
“That’s relevant to thinking about how carbon stays in the soil because, if the microorganisms are really active, that means those habitats are places where we don’t expect carbon to stay in the soil for as long a period of time,” said Oberle.
Understanding which restored ecosystems are better at storing carbon could help scientists develop more efficient restoration techniques.
— Liz Lebron is associate director of communications and marketing at New College of Florida.