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Heterotrophic aquatic metabolism and sustained carbon dioxide emissions in a mineral-soil wetland restored with treated effluent
Ist Teil von
The Science of the total environment, 2023-08, Vol.884, p.163584-163584, Article 163584
Ort / Verlag
Netherlands: Elsevier B.V
Erscheinungsjahr
2023
Quelle
MEDLINE
Beschreibungen/Notizen
Wetlands are economically valuable ecosystems, in part because they purify wastewater by retaining and processing nutrients, organic matter (OM), and other pollutants. While natural wetlands are highly productive and sequester large pools of carbon (C), it is unclear whether the C cycle of restored treatment wetlands is functionally consistent with natural systems. This knowledge gap limits our appreciation for the role that wetland restoration can play as a natural solution to climate change. Here, we quantified metabolic and C cycling patterns of a restored, multi-basin wetland (Frank Lake, Alberta, Canada) receiving municipal and beef processing plant effluents rich in nutrients and OM. We conducted metabolic measurements in all three basins using dissolved oxygen sensors deployed under ice and in open water. Extreme production and respiration indicated that effluent was largely mineralized and replaced with wetland OM in transit. The heterotrophic status of all basins aligned with a published mass budget demonstrating the aquatic habitat of the wetland was an OM sink under current drought conditions that lengthen effluent processing time. Floating chamber measurements in open water zones confirmed that the wetland was a source of CO2 to the atmosphere. From input to outflow, sustained emissions led to declining pCO2 and a decline in the ratio of dissolved inorganic to organic C. Over 30 years post-restoration, the open water habitats in Frank Lake remain heterotrophic and a net source of CO2, suggesting that the trajectory of aquatic C cycling may be distinct from wetlands restored with non-effluent water sources.
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•The Frank Lake wetland has received municipal and slaughterhouse effluent since 1989.•We measured wetland metabolism and carbon cycling in ice free seasons and under ice.•Open water zones were heterotrophic and a sink for effluent organic matter.•The ratio of dissolved inorganic to organic carbon decreased from in- to outflow.•Sustained aquatic CO2 emissions may limit wetland carbon sequestration potential.