Hydrographic characterization of two tidal creeks with implications for watershed land use,flushing times,and benthic production |
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Authors: | Christopher Buzzelli A Frederick Holland Denise M Sanger Paul C Conrads |
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Institution: | (1) Division of Water Quality: Aquifer Protection Section, NC Department of the Environment and Natural Resources, 127 Cardinal Drive Extension, Wilmington, NC 28405, USA;(2) Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403, USA;(3) Center for Marine Science, University of North Carolina Wilmington, 5600 Marvin K. Moss Lane, Wilmington, NC 28409, USA |
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Abstract: | Many coastal ecosystems are undergoing anthropogenic stress from large increases in population and urbanization. In many regions
changes in freshwater and material inputs to the coastal zone are altering the biogeochemical and biological capacities of
ecosystems. Despite increased watershed inputs, large tidal volumes and flushing indicative of macrotidal estuaries can modulate
the fate of introduced materials masking some of the symptoms of eutrophication. The Land Use Coastal Ecosystem Study (LU-CES)
examined linkages between land use and environmental properties of Malind and Okatee Creeks in South Carolina from 2001 to
2004. The objectives of this particular study were to assess the hydrography of the two macrotidal creek ecosystems, explore
differences in dissolved oxygen (DO), and develop a better understanding of the variations in primary and benthic secondary
production in southeastern creek ecosystems. Depth, pH, salinity, and DO were reduced and more variable in Malind Creek than
in Okatee Creek, although both creeks had strong semidiurnal frequencies in salinity time signatures. While time series analyses
of DO saturation in Malind Creek revealed a dominant semidiurnal pattern, Okatee Creek had a distinctly diel DO pattern. The
strongly semidiurnal fluctuations in DO and reduced flushing time indicated that biological processes were not fast enough
to influence DO in Malind Creek. The Okatee Creek system had a much greater storage volume, a wider marsh, and a dominant
25-h DO frequency. These attributes contributed to an estimated 8–10 times more phytoplankton-based carbon in Okatee Creek
and twice the annual benthic production. As expected from their proximity to the upland, low surface area, and high organic
content, both ecosystems were net heterotrophic. This fundamental understanding of tidal creek hydrography is being used to
help define linkages among differential watershed land uses, flushing characteristics, and levels of biological production
in coastal ecosystems of the southeastern United States. |
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