Study Reveals Surprising Insights on Pond Emissions in New York

Researchers at Cornell University have uncovered significant insights into greenhouse gas emissions from ponds, revealing complex mechanisms that influence carbon dioxide and methane release. Their study, published on November 26, 2023, in the journal Limnology & Oceanography, focuses on two ponds in central New York: Mud Pond and Texas Hollow Pond. Despite their similar sizes, the two bodies of water demonstrate markedly different greenhouse gas emission patterns.

In 2020, when Meredith Holgerson joined Cornell, she embarked on a quest to find suitable study sites. Through meticulous mapping and field explorations, Holgerson and her team identified these two ponds to understand the often-overlooked role of smaller water bodies in carbon budgeting. Their findings show that Texas Hollow emits more than twice the amount of carbon dioxide than Mud Pond, despite being only slightly deeper.

The research explores how pond stratification, which refers to the layering of water at different temperatures, impacts methane emissions. Surprisingly, Mud Pond, which has a weaker stratification, released nearly double the amount of methane from its sediments compared to Texas Hollow. This unexpected outcome challenges previous assumptions about the relationship between stratification and gas emissions.

“It’s important to figure out these mechanisms,” Holgerson stated, serving as associate professor of ecology and evolutionary biology within the College of Agriculture and Life Sciences. “Identifying mechanisms will allow us to model carbon fluxes more accurately.”

Both ponds are categorized as “biogeochemical hotspots,” storing significant amounts of carbon in their sediments. The bubbling of methane from Mud Pond has been recorded at some of the highest levels ever observed in similar ecosystems.

The research team initially posited that stronger stratification would correlate with increased methane production and emissions. However, the results contradicted this expectation. Carbon dioxide emissions were higher in Texas Hollow, attributed to greater oxygen levels. In contrast, Mud Pond’s lower carbon dioxide emissions may be linked to its ability to support plant growth, which absorbs carbon dioxide.

The researchers theorize that when plants die, they decompose in the sediment, leading to increased methane emissions. In Texas Hollow, the stratified layers may trap methane produced at the bottom, preventing its release into the atmosphere. Holgerson described this relationship as a “Goldilocks situation,” suggesting that moderate stratification, coupled with light penetration and plant growth, could create conditions conducive to higher methane emissions.

Moving forward, Holgerson’s team aims to deepen their investigation. In 2024, they plan to simulate a summer storm in Texas Hollow to assess its impact on emissions. The ponds will also be included in a broader survey of 16 ponds across New York State to determine if the observed patterns hold true on a larger scale.

“We’re especially interested in how stratification influences methane emissions in the context of climate change,” Holgerson added, highlighting concerns over rising temperatures and their potential to affect pond dynamics.

The study was supported by the New York State Water Resources Institute and the National Science Foundation. Co-authors of the research include former postdoctoral researcher Nicholas Ray, former lab technician Kathryn Gannon, and Adam Heathcote from the St. Croix Watershed Research Station.

These findings contribute critical knowledge to the understanding of carbon emissions and sequestration in freshwater ecosystems, emphasizing the need for accurate calculations in local management practices.