Controls on spatial variation in porewater methane concentrations across United States tidal wetlands

Tidal wetlands can be a substantial sink of greenhouse gases, which can be offset by variable methane (CH4) emissions under certain environmental conditions and anthropogenic interventions. Land managers and policymakers need maps of tidal wetland CH4 properties to make restoration decisions and inv...

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Published in:	The Science of the total environment Vol. 957; p. 177290
Main Authors:	Koontz, Erika L., Parker, Sarah M., Stearns, Alice E., Roberts, Brian J., Young, Caitlin M., Windham-Myers, Lisamarie, Oikawa, Patricia Y., Megonigal, J. Patrick, Noyce, Genevieve L., Buskey, Edward J., Derby, R. Kyle, Dunn, Robert P., Ferner, Matthew C., Krask, Julie L., Marconi, Christina M., Savage, Kelley B., Shahan, Julie, Spivak, Amanda C., St. Laurent, Kari A., Argueta, Jacob M., Baird, Steven J., Beheshti, Kathryn M., Crane, Laura C., Cressman, Kimberly A., Crooks, Jeffrey A., Fernald, Sarah H., Garwood, Jason A., Goldstein, Jason S., Grothues, Thomas M., Habeck, Andrea, Lerberg, Scott B., Lucas, Samantha B., Marcum, Pamela, Peter, Christopher R., Phipps, Scott W., Raposa, Kenneth B., Rovai, Andre S., Schooler, Shon S., Twilley, Robert R., Tyrrell, Megan C., Uyeda, Kellie A., Wulfing, Sophie H., Aman, Jacob T., Giacchetti, Amanda, Cross-Johnson, Shelby N., Holmquist, James R.
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 20-12-2024
Online Access:	Get full text
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Summary:	Tidal wetlands can be a substantial sink of greenhouse gases, which can be offset by variable methane (CH4) emissions under certain environmental conditions and anthropogenic interventions. Land managers and policymakers need maps of tidal wetland CH4 properties to make restoration decisions and inventory greenhouse gases. However, there is a mismatch in spatial scale between point-based sampling of porewater CH4 concentration and its predictors, and the coarser resolution mapping products used to upscale these data. We sampled porewater CH4 concentrations, salinity, sulfate (SO42−), ammonium (NH4+), and total Fe using a spatially stratified sampling at 27 tidal wetlands in the United States. We measured porewater CH4 concentrations across four orders of magnitude (0.05 to 852.9 μM). The relative contribution of spatial scale to variance in CH4 was highest between- and within-sites. Porewater CH4 concentration was best explained by SO42− concentration with segmented linear regression (p < 0.01, R2 = 0.54) indicating lesser sensitivity of CH4 to SO42− below 0.62 mM SO42−. Salinity was a significant proxy for CH4 concentration, because it was highly correlated with SO42− (p < 0.01, R2 = 0.909). However, salinity was less predictive of CH4 with segmented linear regression (p < 0.01, R2 = 0.319) relative to SO42−. Neither NH4+, total Fe, nor relative tidal elevation correlated significantly with porewater CH4; however, NH4+ was positively and significantly correlated with SO42− after detrending CH4 for its relationship with SO42− (p < 0.01, R2 = 0.194). Future sampling should focus on within- and between-site environmental gradients to accurately map CH4 variation. Mapping salinity at sub-watershed scales has some potential for mapping SO42−, and by proxy, constraining spatial variation in porewater CH4 concentrations. Additional work is needed to explain site-level deviations from the salinity-sulfate relationship and elucidate other predictors of methanogenesis. This work demonstrates a unique approach to remote team science and the potential to strengthen collaborative research networks. [Display omitted] •Methane variance was highest along environmental gradients and between sites.•Sulfate was negatively and non-linearly correlated with methane concentration.•Salinity was a significant, but weaker proxy for methane concentration.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0048-9697 1879-1026 1879-1026
DOI:	10.1016/j.scitotenv.2024.177290