Ponds Are Net Greenhouse Gas Emitters Due to Methane Release, Study Reveals

Though ponds are capable of sequestering and releasing greenhouse gases, they could be net emitters when things are added up.

Role of Ponds on Global Greenhouse Emissions

This was discovered in two studies that looked into quantifying the effects of natural and human-made bonds on the global greenhouse gas budget. This is a measurement that still lacks understanding.

According to Meredith Holgerson, the senior author of the two studies and an assistant ecology and evolutionary biology professor from the College of Agriculture and Life Sciences, global climate predictions and models depend on the right accounting of carbon storage and greenhouse gas emissions.

Professor Holgersons and the team estimated before that ponds, which span 5 hectares or less, could account for 5% of the world's methane emissions into the atmosphere. There could be as many as 1 billion ponds all over the planet.

Carbon Sequestration

However, if there are no measurements that boast of remarkable accuracy, true figures could actually be equivalent to half or double these estimates. There are also few estimates regarding carbon burial rates within ponds.

One of the studies looked into the amount of sequestered carbon within 22 Cronell Experimental Ponds, which are identical ponds that were made in 1964. These ponds offered environments that were remarkably controlled and offered insights based on earlier studies. This data enabled the researchers to examine how managing the ponds affected carbon storage.

The researchers looked into earlier management activities while simultaneously measuring sediment thickness and getting sediment cores. They gauged the amount of carbon present within the sediment, used the measurements for the whole pond, and divided the figure by the pond's age to know the quantity of carbon sequestered each year in every square meter. The researchers also discovered how aquatic plants, fish, and high nitrogen level additions all affected carbon burial rates.

As they extrapolated their data, the researchers were able to estimate the total carbon burial rate in both artificial and natural ponds on a global scale. Their findings showed that both kinds of ponds sequester around 65% to 87% of the total amounts that lakes store.

Greenhouse Gas Emissions by Season

The second study looked into greenhouse gas emissions by seasons, focusing on four Cornell Experimental Ponds. They monitored the ponds' gas emissions around every two weeks in 2021, when the area was free of ice.

The authors discovered that methane, which is 25 times stronger compared to carbon dioxide, was responsible for the biggest chunk of annual greenhouse emissions and that both methane and carbon dioxide emissions had season-dependent variations.

They found out that during early summer months, ponds absorbed carbon dioxide. The ponds then emitted the gas later when the plants were decomposed. Methane, on the other hand, got emitted during warm months, with weekly emissions shifts being high.

Aside from this, the researchers also discovered that in cases where water was stratified, methane ended up getting built up and led to generally higher emissions.

Net Greenhouse Gas Emitters

Both studies support the notions that ponds are net greenhouse gas emitters. This is mainly due to methane releases that overwhelm carbon amounts stored within sediments.

The findings also posit the possibilities of minimizing methane releases through underwater circulators or bubblers. Holgerson explains that if the methane issue could be addressed, these ponds could turn into net sinks.

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