Surface and small-scale processes of biogeochemical cycling of organic matter in tidal sediments
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Gwendolyn A. Shaughnessy (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Courtney Hackney
Abstract: Despite their exceptionally high productivity, freshwater and oligohaline tidal marshes
are rarely studied in terms of their biogeochemistry because of their highly variable and diverse
conditions. Such environments are particularly interesting because they experience salinity
variations that can dramatically alter biogeochemical processes. Sediment cores were collected
on a monthly basis over the course of one year from three substations (intertidal mud flat, marsh,
and marsh/upland edge) of an oligohaline tidal marsh in the Cape Fear River Estuary, North
Carolina. Depth profiles of redox-active remineralization products (O2, Fe2+, Mn2+, and HS-)
were generated with microelectrode-based voltammetry, allowing for high-resolution (millimeter
scale) assessment of small-scale microbial processes often overlooked in biogeochemical studies.
Oxygen (and attendant aerobic respiration), when present, was limited to less than 7 mm below
the sediment-water interface at all three substations. Low quantities of labile organic matter
limited remineralization processes to Mn reduction in the upper 10 cm of the intertidal mud flat
sediments; Fe reduction and sulfate reduction play apparently minor roles. While Mn reduction
has previously been shown to dominate organic matter remineralization in some coastal marine
sediments, this study demonstrates that this process is also important in intertidal mud flat
sediments. Seasonal trends emerged in the biogeochemistry of the marsh substation due to
sediment-root interactions, in which sulfate reduction dominated in spring and summer, Mn
reduction in fall, and methane production in winter. Marsh/upland edge sediments were highly
influenced by subsurface hydrology and plant physiology, resulting in a biogeochemical mosaic
of overlapping microenvironments dominated by different remineralization pathways (Mn
reduction, Fe reduction, sulfate reduction, methanogenesis). Biogeochemistry at this substation
reflects changes in environmental conditions on short time scales due to subsurface hydrology, tidal inundation, plant physiology, rainfall, and labile organic matter content. These sites and
their varied biogeochemistry are likely to represent transitional environments expected to result
from sea level rise. The great complexity of these environments, as demonstrated in this study,
creates challenges for predicting the role that transitional wetlands will play in carbon storage
and the release of greenhouse gases.
Surface and small-scale processes of biogeochemical cycling of organic matter in tidal sediments
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Created on 1/1/2009
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
- Language: English
- Date: 2009
- Keywords
- Biogeochemical cycles, Biological systems, Water quality--Environmental aspects
- Subjects
- Biogeochemical cycles
- Water quality -- Environmental aspects
- Biological systems