AQUA‐Flux: An Inexpensive, Autonomous Floating Chamber for High‐Frequency, Long‐Term Monitoring of Greenhouse Gas Fluxes From Aquatic Ecosystems

Abstract Inland waters are a major global source of greenhouse gas emissions. Quantifying aquatic emissions at high spatiotemporal resolution is critical for understanding their biophysical drivers, constraining the global carbon budget, and improving climate projections. Current floating chamber techniques rely on labor‐intensive manual sampling or expensive infrared greenhouse gas analyzers, which limit the spatial and temporal sampling frequency. Here, we present an improved, inexpensive autonomous floating chamber design: AQUA‐Flux (autochamber for quantifying and understanding aquatic fluxes), which can capture diffusive and ebullitive methane (CH 4 ) and carbon dioxide (CO 2 ) fluxes on small freshwater bodies at high frequency. A solar‐power system enables long‐term deployment. We have successfully tested 12 AQUA‐Flux systems for up to six months in two environmental extremes—the Arctic tundra and Brazilian Amazon. Low‐cost sensors measure CH 4 and CO 2 concentrations within a closed chamber, and a linear actuator extends and retracts to vent the chamber headspace between flux measurements. Field‐based calibrations using an infrared gas analyzer indicate that these low‐cost sensors perform well, with average resolutions of 2–3 ppm for both CH 4 and CO 2 . We also show that sensors can be field‐calibrated using discrete samples collected manually for laboratory analysis (gas chromatography), providing a lower‐cost calibration method. The AQUA‐Flux is well‐suited for water bodies with high fluxes. We include detailed assembly instructions to enable others to create and improve the design. By developing inexpensive open‐source tools, we aim to democratize greenhouse gas flux measurements and ultimately improve global estimates of fluxes from aquatic environments.