Temperature and sediment properties drive spatiotemporal variability of methane ebullition in a small and shallow temperate lake

Abstract

Ebullition is a major pathway of methane (CH4) fluxes from lakes to the atmosphere. Small and shallow lakes can have high emissions but have only recently gained more attention. We studied the quantity and spatiotemporal variability of CH4 ebullition from a small (1.4 ha) and shallow (max 1.5 m) temperate lake in Germany during 2017 and 2018. We found a high range of fluxes (0–872 mg m−2 d−1) and > 90% of the fluxes were emitted between May and August. Fluxes in early spring and late autumn were below 4 mg m−2 d−1. Also, on a spatial scale, fluxes varied distinctly and generally increased from the shore to the center of the lake. To identify drivers of observed emissions patterns, we measured temperature and air pressure, the quantity and quality of the sedimented organic matter (OM) as well as chemical and physical properties of the sediment. Generalized linear models identified temperature, sediment porosity and organic matter content as the best predictors for the observed spatiotemporal differences, whereas temperature was accountable for the observed temporal, and porosity and organic matter content for the spatial variability. We suggest that in small lakes, temperature could serve as master variable to predict site-specific CH4 ebullition while spatial within-lake differences are determined by varying physical sediment properties more than quantity or quality of the OM.