Impoundment increases methane emissions in Phragmites-invaded coastal wetlands
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- More information: Publisher Index Page (via DOI)
- Data Releases:
- USGS data release - Carbon dioxide and methane fluxes with supporting environmental data from coastal wetlands across Cape Cod, Massachusetts (ver 2.0, June 2022)
- USGS data release - Static chamber gas fluxes and carbon and nitrogen isotope content of age-dated sediment cores from a Phragmites wetland in Sage Lot Pond, Massachusetts, 2013-2015
- USGS data release - Continuous Water Level, Salinity, and Temperature Data from Coastal Wetland Monitoring Wells, Cape Cod, Massachusetts (ver. 2.0, August 2022)
- Open Access Version: External Repository
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Abstract
Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate-rich seawater. Yet, widespread management of coastal hydrology has restricted tidal exchange in vast areas of coastal wetlands. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites, that affect ecosystem carbon balance. Understanding controls and scaling of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here, we (1) examine how carbon fluxes vary across a salinity gradient (4–25 psu) in impounded and natural, tidally unrestricted Phragmites wetlands using static chambers and (2) probe drivers of carbon fluxes within an impounded coastal wetland using eddy covariance at the Herring River in Wellfleet, MA, United States. Freshening across the salinity gradient led to a 50-fold increase in CH4 emissions, but effects on carbon dioxide (CO2) were less pronounced with uptake generally enhanced in the fresher, impounded sites. The impounded wetland experienced little variation in water-table depth or salinity during the growing season and was a strong CO2 sink of −352 g CO2-C m−2 year−1 offset by CH4 emission of 11.4 g CH4-C m−2 year−1. Growing season CH4 flux was driven primarily by temperature. Methane flux exhibited a diurnal cycle with a night-time minimum that was not reflected in opaque chamber measurements. Therefore, we suggest accounting for the diurnal cycle of CH4 in Phragmites, for example by applying a scaling factor developed here of ~0.6 to mid-day chamber measurements. Taken together, these results suggest that although freshened, impounded wetlands can be strong carbon sinks, enhanced CH4 emission with freshening reduces net radiative balance. Restoration of tidal flow to impounded ecosystems could limit CH4 production and enhance their climate regulating benefits.
Study Area
Publication type | Article |
---|---|
Publication Subtype | Journal Article |
Title | Impoundment increases methane emissions in Phragmites-invaded coastal wetlands |
Series title | Global Change Biology |
DOI | 10.1111/gcb.16217 |
Volume | 28 |
Issue | 15 |
Year Published | 2022 |
Language | English |
Publisher | Wiley |
Contributing office(s) | Woods Hole Coastal and Marine Science Center |
Description | 19 p. |
First page | 4539 |
Last page | 4557 |
Country | United States |
State | Massachusetts |
City | Falmouth, Truro, Wellfleet |
Other Geospatial | Cape Cod, Cape Cod National Seashore, Herring River, Sage Lot Pond, Waquoit Bay National Estuarine Research Reserve |
Google Analytic Metrics | Metrics page |