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Abstract Coastal salt marshes store large amounts of carbon but the magnitude and patterns of greenhouse gas (GHG; i.e., carbon dioxide (CO2) and methane (CH4)) fluxes are unclear. Information about GHG fluxes from these ecosystems comes from studies of sediments or at the ecosystem‐scale (eddy covariance) but fluxes from tidal creeks are unknown. We measured GHG concentrations in water, water quality, meteorological parameters, sediment CO2efflux, ecosystem‐scale GHG fluxes, and plant phenology; all at half‐hour intervals over 1 year. Manual creek GHG flux measurements were used to calculate gas transfer velocity (k) and parameterize a model of water‐to‐atmosphere GHG fluxes. The creek was a source of GHGs to the atmosphere where tidal patterns controlled diel variability. Dissolved oxygen and wind speed were negatively correlated with creek CH4efflux. Despite lacking a seasonal pattern, creek CO2efflux was correlated with drivers such as turbidity across phenological phases. Overall, nighttime creek CO2efflux (3.6 ± 0.63 μmol/m2/s) was at least 2 times higher than nighttime marsh sediment CO2efflux (1.5 ± 1.23 μmol/m2/s). Creek CH4efflux (17.5 ± 6.9 nmol/m2/s) was 4 times lower than ecosystem‐scale CH4fluxes (68.1 ± 52.3 nmol/m2/s) across the year. These results suggest that tidal creeks are potential hotspots for CO2emissions and could contribute to lateral transport of CH4to the coastal ocean due to supersaturation of CH4(>6,000 μmol/mol) in water. This study provides insights for modeling GHG efflux from tidal creeks and suggests that changes in tide stage overshadow water temperature in determining magnitudes of fluxes.
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Atmospheric Ammonia Measurements Over a Coastal Salt Marsh Ecosystem Along the Mid‐Atlantic U.S.
Abstract Measurements of atmospheric ammonia (NH3) concentrations and fluxes are limited in coastal regions in the eastern U.S. In this study, continuous and high temporal resolution measurements (5s) of atmospheric NH3concentrations were recorded using a cavity ring‐down spectrometer in a temperate tidal salt marsh at the St Jones Reserve (Dover, DE). Micrometeorological variables were measured using an eddy covariance system which is part of the AmeriFlux network (US‐StJ). Soil, plant, and water chemistry were also analyzed to characterize the sources and sinks of atmospheric NH3. A new analytical methodology was used to estimate the average ecosystem‐scale diurnal cycle of NH3fluxes by replicating the characteristics of a chamber experiment. This virtual chamber approach estimates positive surface fluxes in continuing strongly stable conditions when mixing with the air above is minimal. Our findings show that tidal water level may have a significant impact on NH3emissions from the marsh. The largest fluxes were observed at low tide when more soil was exposed. While it is expected that NH3fluxes will peak when the air temperature maximizes, high tide occurred concurrently with midday peaks in solar irradiance led to a decrease in NH3fluxes. Furthermore, soil, plant, and water chemistry measurements underpinning the NH3concentrations and fluxes lead us to conclude that this coastal wetland ecosystem can act as either a sink or a source of NH3. Such measurements provide novel data on which we can base reliable parameterizations to simulate NH3emissions from coastal salt marsh ecosystems using surface‐atmosphere transfer models.
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- Award ID(s):
- 1652594
- PAR ID:
- 10360543
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 126
- Issue:
- 5
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Coastal salt marshes store large amounts of carbon but the magnitude and patterns of greenhouse gas (GHG; i.e., carbon dioxide (CO2</sub>) and methane (CH4</sub>)) fluxes are unclear. Information about GHG fluxes from these ecosystems comes from studies of sediments or at the ecosystem-scale (eddy covariance) but fluxes from tidal creeks are unknown. </div>This dataset includes GHG concentrations in water, water quality, meteorology, sediment CO2</sub> efflux, ecosystem-scale GHG fluxes, and plant phenology; all at half-hour time-steps over one year.</div></div>This study was carried out in the St. Jones Reserve, a component of the Delaware National Estuarine Research Reserve in Dover, Delaware, U.S.A. The study site is part of the following networks:</div></div>- AmeriFlux (https://ameriflux.lbl.gov/sites/siteinfo/US-StJ) </div>- Phenocam (https://phenocam.sr.unh.edu/webcam/sites/stjones/) </div></div>The GHG concentration and efflux sampling point was located at Aspen Landing within a microtidal (mean tide range of 1.5 m), mesohaline (typical salinity of 5-18 ppt) salt marsh (Delaware Department of Natural Resources and Environmental Control, 2006) tidal creek.</div></div>Main reference:</div> Trifunovic, B., Vázquez‐Lule, A., Capooci, M., Seyfferth, A. L., Moffat, C., & Vargas, R. (2020). Carbon dioxide and methane emissions from a temperate salt marsh tidal creek. Journal of Geophysical Research: Biogeosciences, 125, e2019JG005558. https://doi.org/ 10.1029/2019JG005558 </p> </div> </div> </div></div>more » « less
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