Salinity-driven patterns in sediment geochemistry and microbial activity in Georgia coastal estuaries. Kimberley Hunter1, Meaghan Bernier1, Christopher Craft2 and Samantha Joye1 1Department of Marine Sciences, University of Georgia; 2School of

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Salinity-driven patterns in sediment geochemistry
and microbial activity in Georgia coastal
estuaries. Kimberley Hunter1, Meaghan
Bernier1, Christopher Craft2 and Samantha Joye1
1Department of Marine Sciences, University of
Georgia 2School of Public and Environmental
Affairs, Indiana University
AcknowledgementsField or Lab Assistance Jon
Shelby, Josh Frost (Indiana) Daniel Saucedo,
Catarina Teixeira (UGA)Funding EPA (grant
number RD-83222001)
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How will changes in sea-level and climate alter
critical biogeochemical functions of coastal
wetlands ?
From KL McKee
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Biogeochemistry Goals samples obtained at two
tidal freshwater, brackish, marine sites of
Altamaha, Ogeechee Satilla rivers (6 sites
per river marsh and levee habitats at each
site) ? Document pore water biogeochemistry ?
Quantify rates of denitrification and
methanogenesis -future measure N2O, CH4 CO2
fluxes at Altamaha river sites total
metabolism in incubations
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Biogeochemistry Methods ? pore water geochemical
variables NO3-, NH4, PO43-, H2S, SO42-,Cl-,
DIC, DOC, Fe2, CH4, N2O ? pore water
inventories calculated to compare data between
sites ? potential CH4 and N2O fluxes estimated
from measured pore water gradients ? rates of
denitrification and methanogenesis
were determined in separate sub-samples
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Pore Water Biogeochemisty salt (Cl-)
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Pore Water Biogeochemisty DIC
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Pore Water Biogeochemisty H2S
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Pore Water Biogeochemisty NH4
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Pore Water Biogeochemisty PO43-
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Pore Water Biogeochemisty NP ratio
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Microbial Metabolism Denitrification
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Microbial Metabolism Methanogenesis
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Microbial Metabolism Methanogenesis
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Microbial Metabolism Methanogenesis
n.d.
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Microbial Metabolism CH4 fluxes
170
94
130
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Conclusions ? Surprisingly, denitrification
rates in August 2006 were highest marine and
brackish sediments. High rates of nitrate
removal may have contributed to the low observed
NP ratios in pore waters. ? Methane production
rates and fluxes were highest at freshwater
sites. Increases in salinity will likely both
reduce rates of CH4 production and increase rates
of methane oxidation coupled to sulfate
reduction, leading to decreased fluxes of CH4 but
increased fluxes of CO2.
Thanks again to the EPA for funding this work