Periodic CH₄ Fluxes at Dutch Slough

Biomet Lab’s

Active Delta Flux Sites

Agricultural Sites (Gold):

• Bouldin Alfalfa (Since 2016)
• Bouldin Corn (Since 2017)

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Impounded Wetlands (Red):

• Mayberry (Since 2010)
• West Pond (Since 2012)
• East End (Since 2013)

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Tidal Wetlands (Blue):

• Hill Slough (Since 2021)
• Dutch Slough (Since 2021)

Eddy Covariance

Slide Credit: Carlos Wang

Dutch Slough

-850 gC m^-2 y^-1

Histogram of Annual

Net Ecosystem Carbon

Exchange, World-Wide

Via Fluxnet

The Magnitude of the

Carbon Sink at Dutch

Slough is in the

Top 1 Percentile Worldwide

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Slide Credit: Dennis Baldocchi

# of Sites Worldwide

80%

Flux Footprint

Gilbert Tract CH4 Flux 2022-2024

Methane Flux (nmol/m^2/second)

~2 Weeks

Bimodal Distribution During Noon High Tide

Peak In Methane Shifts Later With Daytime Low Tide

New Peak Starts in AM Hours

Gilbert Tract CH4 Flux 2022-2024

Methane Flux (nmol/m^2/second)

Gilbert Tract CH4 Flux 2022-2024

Methane Flux (nmol/m^2/second)

GT

GT

GT

Direct Measurement: �Floating Chambers

(Many thanks to Kuno Kasak)

Hill Slough Vs Dutch Slough�Three Years After Breach

Photo Credit: Mel Baldino, UCB

HS

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CH4 Periodicity: What are the Mechanisms?

• Methane emissions avoided during the day are not released in full the following night, meaning it is not purely due to transport

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• Air Temperature is a driving factor, but is coincidental with direct solar heating and plant productivity

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• Addition of Nitrate with tidal influx may inhibit CH4
• Simultaneously, Methanotrophy is present within the water column, which is removed at low tide

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• Evaporation of CH4-laden water may release it to the atmosphere

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Thanks for Your Attention