Carbon dioxide, methane, and nitrous oxide fluxes from managed distributaries across the Rio Grande Delta

Aquatic ecosystems are globally important emitters of greenhouse gases (GHG), with small and human-made systems exhibiting a disproportionally high contribution to emissions compared to their global coverage. The Rio Grande Delta region along the US-Mexico border harbors a unique system of abandoned channels, distributaries, and their associated ox-bows—locally known as ‘resacas’—that serve as sources of biodiversity refuge, human recreation, flood control, and irrigation. Formed by the Rio Grande’s natural flooding cycles over the past 10,000 years, resacas are now artificially sustained due to human alterations in the river’s flood cycles by dams, levees, and diversion systems. Patterns of GHG emissions from these uniquely managed natural aquatic ecosystems remain largely unexplored. To understand spatial and temporal variations in GHG emissions, we focus on biweekly sampling across three distinct resacas, each managed under different hydrologic regimes. We use portable GHG analyzers to quantify diffusive fluxes of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O), as well as ebullitive fluxes of greenhouse gases, particularly CH₄. In addition, we quantify basic limnological parameters such as dissolved oxygen, chlorophyll-a, temperature, pH, turbidity, and conductivity using a portable water quality probe. Our initial findings suggest that warmer conditions are associated with increased emissions of CO₂, CH₄, and N₂O. Further, there are differences in GHG emission rates across the three resacas, which may be linked to different water management regimes. This research offers novel insight into the GHG dynamics of the Rio Grande Delta and their potential responses to future hydrological and temperature changes.

Primary Presenter: Siena Stassi, University of Texas- Rio Grande Valley (siena.stassi01@utrgv.edu)

Authors:

Siena Stassi, University of Texas- Rio Grande Valley  (siena.stassi01@utrgv.edu)

Rafael Almeida, University of Texas- Rio Grande Valley  (rafael.almeida@utrgv.edu)

Jude Benavides, University of Texas- Rio Grande Valley  (jude.benavides@utrgv.edu)

Marcelo Gomes Da Silva, University of Texas- Rio Grande Valley  (marcelo.gomezdasilva@utrgv.edu)

Nathan Barros, Federal University of Juiz de Fora  (Nathan.barros@ufjf.edu.br)