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2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 28-41
Presentation Time: 9:00 AM-5:30 PM

VARIATIONS IN BIOGEOCHEMISTRY AND GREENHOUSE GAS EMISSIONS FOUND WITHIN DIFFERENT VEGETATION SITES IN A TIDAL MARSH LOCATED IN THE HUDSON RIVER ESTUARY


CORBETT, J. Elizabeth1, MARTIN, Isabella2, HO, Lauren2, SEVILLA, Laisa3, SUN, Eric2, ZHANG, Amy2, NEWTON, Robert4, VINCENT, Susan5 and PETEET, Dorothy M.4, (1)NASA, Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025, (2)Lamont-Doherty Earth Observatory, Palisades, NY 10964, (3)The Young Women's Leadership School, 105 East 106th Street, New York, NY 10029, (4)Lamont-Doherty Earth Observatory, 61 Route 9w, Palisades, NY 10964, (5)The Young Women's Leadership School of East Harlem, 105 East 106th Street, New York, NY 10029, laisas2406@tywls.org

Sites located within a tidal brackish marsh in the Hudson River Estuary were investigated to assess whether methane escape and biogeochemical patterns found within the porewater were influenced by vegetation differences. Porewater within the marsh was collected from 0–3 m at 50 cm intervals. The site dominated by invasive Phragmites australis was more inland and was found to have lower conductivity, higher sulfate, lower methane, and lower dissolved inorganic carbon (DIC) concentrations than sites dominated by either native mixed (Spartina patens, Scirpus americanus and Typha angustifolia), or native vegetation (Eleocharis palustris). Sulfate concentrations fell below 0.2 mM at 50 cm and 200 cm at the Eleocharis and mixed vegetation sites, respectively. In the Phragmites site, sulfate concentrations remained above 0.2 mM at all depths measured. For the Phragmites, Eleocharis, and mixed vegetation sites, average DIC concentrations with depth were found to be 9.77 ± 1.45, 26.58 ± 14.95, and 28.05 ± 15.11 mM respectively and average methane concentrations with depth were found to be 0.21 ± 0.09, 0.55 ± 0.26, and 0.50 ± 0.21 mM. DIC and methane concentrations increased with depth in both the Eleocharis and mixed vegetation sites, but remained constant in the Phragmites site. All porewater nitrate concentrations were low (0.0066 ± 0.0032 mM) and no significant differences were observed between sites. δ13C-CO2 values were found to be more depleted and δ13C-CH4 values were found to be slightly more enriched within the Phragmites site. Isotopic evidence of methane oxidation was found within the Phragmites porewater at 100 and 150 cm and in the mixed vegetation at 50 cm. These findings suggest that less methanogenesis and more nonfractionating respiration pathways such as sulfate reduction is occurring in sites dominated by Phragmites as compared to sites dominated by native vegetation.

Session No. 28--Booth# 88

Geochemistry (Posters)
Sunday, 1 November 2015: 9:00 AM-5:30 PM
Exhibit Hall (Baltimore Convention Center)
Geological Society of America Abstracts with Programs. Vol. 47, No. 7, p.94
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