Integrating Ecosystem Patch Contributions to Stream Corridor Carbon Dioxide and Methane Fluxes

Abstract

As water moves carbon through watersheds and across ecosystem boundaries, stream corridors collect and integrate landscape-scale signals of carbon cycling. Streams metabolize organic carbon and emit carbon dioxide (CO 2 ) and methane (CH 4 ) derived from internal metabolism and external sources (Hotchkiss et al., 2015;Stanley et al., 2016). The rates at which streams emit carbon to the atmosphere reflects their importance in local and global carbon cycling. Streams emit CO 2 globally at a rate that surpasses the terrestrial and oceanic carbon sinks (Webb et al., 2018) and emit approximately 5% of yearly global CH 4 to the atmosphere (Flury & Ulseth, 2019;Stanley et al., 2016). As global concentrations of atmospheric greenhouse gases continue to rise, quantifying the relative contributions of different sources and sinks of CO 2 and CH 4 grows ever more important.

Greenhouse gas dynamics in river networks fragmented by drying and damming

“…In a synthesis of CO 2 fluxes from dry inland waters, dry sediment fluxes were higher than those from lentic waters, and more similar to fluxes reported from lotic waters (Marcé et al, 2019). In some cases, the CO 2 flux from IRES dry sediments is comparable to riparian soil fluxes (Bretz et al, 2021;Gómez-Gener et al, 2016;von Schiller et al, 2014). Similar to observations in dry riverbeds, CO 2 fluxes from reservoir drawdown areas…”

Carbon Biogeochemistry and Export Governed by Flow in a Non‐Perennial Stream

“…We took discrete samples of dissolved CO 2 from four persistent pools along the lower 1,000 m of the stream, including the sensor deployment pool above the Beast‐Poverty confluence. We used discrete stream dissolved CO 2 concentrations measured from the sensor deployment pool to calibration‐correct the sensor measurements, assuming linear drift occurred during deployment (as in Bretz et al., 2021). We sampled stream water for CO 2 using the syringe headspace method (Halbedel, 2015), approximately monthly in fall and winter, and twice per month in summer, at the downstream sensor monitoring site.…”

“…We took triplicate samples at each site, drawing 80 mL of bubble free water and 40 mL of ambient air into a 120 mL syringe (JMS JS‐S00L) fitted with a 3‐way stopcock valve (Kimble). We shook each sample vigorously for 3 min, then pushed the water out of the syringe and injected the headspace into sealed 20 mL vials (Wheaton MicroLiter 20 mm), displacing ambient air with sample volume using a vent needle (Bretz et al., 2021). We measured the headspace concentrations of CO 2 on a gas chromatograph (Shimadzu Nexis GC‐2030) fitted with a thermal conductivity and flame ionization detector.…”

Large-scale sampling of the freshwater microbiome suggests pollution-driven ecosystem changes

“…It is likely that these differences also extend to prokaryotes and thus influence microbial production and mineralization. Freshwater ecosystems are a significant source of microbially mediated CO 2 and CH 4 (Raymond et al, 2013;Tranvik et al, 2009) and transform a large amount (up to 5.1 Pg C y − 1 ) (Bretz et al, 2021) of the terrestrial carbon sink. In addition to water-column processes of the plankton, microorganisms living in sunlit (i.e., euphotic) sediments are important for the assimilation of CO 2 through photosynthesis and the release of CO 2 and CH 4 through mineralization (i.e., primary production and respiration).…”

“…In addition to water-column processes of the plankton, microorganisms living in sunlit (i.e., euphotic) sediments are important for the assimilation of CO 2 through photosynthesis and the release of CO 2 and CH 4 through mineralization (i.e., primary production and respiration). CO 2 concentration in freshwaters can also be influenced by the import of carbon from the adjacent landscape (Bretz et al, 2021). CH 4 is mainly produced by methanogenic archaea in sediments as an end product of anaerobic decomposition of organic matter.…”