Global CO2 emissions from dry inland waters share common drivers across ecosystems

Abstract

Many inland waters exhibit complete or partial desiccation, or have vanished due to global change, exposing sediments to the atmosphere. Yet, data on carbon dioxide (CO 2) emissions from these sediments are too scarce to upscale emissions for global estimates or to understand their fundamental drivers. Here, we present the results of a global survey covering 196 dry inland waters across diverse ecosystem types and climate zones. We show that their CO 2 emissions share fundamental drivers and constitute a substantial fraction of the carbon cycled by inland waters. CO 2 emissions were consistent across ecosystem types and climate zones, with local characteristics explaining much of the variability. Accounting for such emissions increases global estimates of carbon emissions from inland waters by 6% (~0.12 Pg C y −1). Our results indicate that emissions from dry inland waters represent a significant and likely increasing component of the inland waters carbon cycle.

Biogeochemical characteristics and hydroperiod affect carbon dioxide flux rates from exposed high‐elevation pond sediments

“…Ponds of varying hydroperiods had significantly different sizes and area-specific flux over the course of a season, so scaling to entire pond areas involved a clear interplay between pond areas and tendency to dry down (Supporting Information Table 2). These high flux rates from exposed pond sediments are consistent with site-specific studies that have considered exposed pond sediments (Catalán et al 2014;Obrador et al 2018) and in range of recently globallycompiled rates of pond sediment CO 2 flux, which had a mean of 267 AE 221 mmol m −2 d −1 (mean AE SD, Keller et al 2020).…”

Attributes of Drying Define the Structure and Functioning of Microbial Communities in Temperate Riverbed Sediment

“…In this sense, microbes would have quickly reduced their metabolic activity as a strategy to overcome drying, allowing them to maintain their community abundance, diversity and composition for a few days, but with immediate consequences for CO 2 production. Further, the parallel decline in sediment moisture and CO 2 production with increasing drying time confirmed that moisture is the main controlling factor for sediment CO 2 production (Keller et al, 2020). Similar moisture declines subsequent to drying have been observed in previous studies simulating drying events in Mediterranean (Amalfitano et al, 2008;Timoner et al, 2012) and temperate (Pohlon et al, 2013) rivers.…”

“…Temporary drying of river channels can significantly compromise the function and structure of the riverbed microbial community ( Junk et al, 1989 ; Humphries and Baldwin, 2003 ; Datry et al, 2014 ), which is responsible for a large proportion of the carbon and nutrient processing in river systems ( Cole et al, 1988 ; Duarte and Prairie, 2005 ). Dry riverbeds are, in general, sources of CO 2 fluxes to the atmosphere ( Keller et al, 2020 ). However, the duration of non-flow periods and the intensity of drying are known factors influencing microbial community assembly and C-transformation in riverbeds ( Marxsen et al, 2010 ; Gionchetta et al, 2020 ).…”

Regulation of CO2 fluxes along gradients of water saturation in irrigation canal sediments

“…It is possible that without additional C inputs the CO 2 fluxes would tend to decrease along with the duration of the air exposure, as the supplies of readily decomposable C are exhausted, resulting in lower CO 2 emission from sediments. This is also likely The weakly negative and positive effect of net potential nitrification and denitrification rate on the CO 2 emissions we found is expected as nitrification is a chemoautotrophic process where CO 2 is incorporated during microbial growth (Kinsbursky and Salzman 1990;Denecke and Liebig 2003), acting as CO 2 sink, while denitrification is a microbial respiration carried out by heterotrophic bacteria that use organic matter as substrate, acting as CO 2 sources (Jalota et al 2018). Nitrification rates in aquatic and terrestrial ecosystems are extremely variable (from a few up to some hundreds µmol N m −2 h −1 ) and they are regulated by pH and temperature and by the availability of NH 4 + and O 2 (Prosser 2005).…”