Florida ponds emit more carbon than they store, study finds

When you look at ponds, you may see birds and fish, but you probably don’t think of carbon. In fact, Florida’s 76,000 ponds store a lot of carbon, and much of it escapes into the atmosphere.

In fact, ponds lose more carbon via gas than they store in mud, according to a new study from the University of Florida.

“This finding means that some ponds are doing us a ‘disservice’ to the ecosystem,” said Mary Lusk, UF/IFAS assistant professor of soil and water sciences. “Globally, we anticipate that as urbanization continues, there will be more and more of these small man-made ponds in urban landscapes.”

This research will inform scientists’ attempts to estimate the amount of carbon entering the atmosphere from these ponds on a regional basis, said UF/IFAS Gulf Coast Center for Research and Education faculty member Lusk. .

“Then once people start to understand this better, hopefully they will consider stormwater ponds for policies related to carbon control,” she said. “Stormwater ponds are all over Florida. But they are understudied in terms of their impact on local ecosystems. Because they are man-made parts of the landscape, they are kind of overlooked and people might assume that they are not ecologically very important.

“When I learned that I had the chance to work in storm basins, like in what I had grown up in my neighborhood, I immediately asked myself, well, what about of these small urban basins? How do they compare to other aquatic ecosystems? asked Audrey Goeckner, now a Ph.D. soil and water science student at UF/IFAS main campus in Gainesville. COURTESY PHOTO

The sheer number of ponds compelled Ms Lusk to investigate whether they could have greater environmental effects than people realize. Initially, she wanted to focus on nitrogen and phosphorus in ponds, but one of her graduate students, Audrey Goeckner, wanted to study carbon.

“When I learned that I had the chance to work in storm basins, like in what I had grown up in my neighborhood, I immediately asked myself, well, what about of these small urban basins? How do they compare to other aquatic ecosystems? asked Ms. Goeckner, now a Ph.D. soil and water science student at UF/IFAS main campus in Gainesville. “It turns out that despite their small size, they can quickly store and process carbon, which adds up when you consider how many of them exist in developed landscapes and how many continue to be built on.”

For the study, carried out as part of her master’s thesis at GCREC, Ms Goeckner devised a way to measure the amount of carbon leaving ponds. Although Ms. Goeckner has studied ponds in Manatee County, her findings have implications for carbon emissions from ponds globally.

She took two canoes (tied together) to the ponds. She and a lab technician each sat in a canoe to balance the weight. Next, she collected mud from the bottom of the ponds and measured the depth of the mud above a layer of sandy sediment, indicating when the pond was built and how much organic carbon is stored there.

This is how Mrs. Goeckner found the amount of carbon buried in the ponds.

Second, she modified a chamber that is normally used to measure greenhouse gases – carbon dioxide and methane – from the soil. Instead, Ms. Goeckner used the chamber to measure these gases at the surface of ponds.

She found the amount of these gases that escape from the ponds each year, then compared the carbon stored in the pond mud to the carbon lost through gaseous loss. As a result, scientists now know that ponds emit more carbon than they store, and the amount lost changes over the lifetime of a pond.

As Florida continues to grow, it will become more urbanized. New developments often come with new stormwater ponds, which are not as efficient at storing carbon as older ones, Lusk said.

As ponds age, their sediments and biogeochemical properties can favor the amount of carbon stored, rather than emitted as a gas, Goeckner said. This results in better storage efficiency for organic carbon that enters the water.

“Our results suggest that when new, they emit large proportions of landscape carbon and potentially increase storage over time,” Lusk said. “This means that older ponds provide us with fewer ecosystem services than younger ponds. But if you think about the rate of new housing development in Florida and the rate at which new stormwater ponds are being built in all of this new development, that means we’re always going to have a new batch of young ponds that are just pump carbon into the atmosphere.”

– The mission of the Institute of Food and Agricultural Sciences at the University of Florida is to develop relevant knowledge of agricultural, human, and natural resources and to make that knowledge available to maintain and improve the quality of human life. With more than a dozen research facilities, 67 county extension offices, and award-winning UF College of Agricultural and Life Sciences students and faculty, UF/IFAS brings science-based solutions to the agricultural and natural resource industries. of the State and to all residents of Florida. . ¦