Florida's urban stormwater ponds are net sources of carbon to the atmosphere despite increased carbon burial over time

Stormwater ponds are engineered ecosystems designed for flood control and sediment retention in urban watersheds. They are the most commonly used stormwater control measure in the USA, but their biogeochemical processes and impacts are often overlooked. Here, we assessed the potential impact of stormwater ponds on regional carbon cycling by coupling carbon burial rates and fluxes of carbon dioxide and methane gases in five sites over an age gradient of 14-34 years. Carbon burial increased logarithmically with site age, ranging from 22 to 217 g carbon m(-2) y(-1), while, median floating chamber diffusive gas fluxes were 1290 g carbon dioxide m(-2) y(-1) and 5 g methane m(-2) y(-1), which, when combined as carbon dioxide equivalents, equates to 2900 g carbon dioxide eq m(-2) y(-1). Comparing carbon burial to gas flux reveals that stormwater ponds can be net carbon sources and need to be considered for regional and global carbon models. Stormwater retention ponds emit the greenhouse gases carbon dioxide and methane but store increasingly large amounts of carbon in their sediments over time, according to an observational study of carbon dynamics in stormwater ponds in southwest Florida.

Automated summary

Observational study reveals that stormwater ponds can be net carbon sources and should be considered in regional and global carbon models.