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Sediment oxygen demand and biochemical oxygen demand : patterns of oxygen depletion in tidal creek sites

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Tara A. Macpherson (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Daniel Baden

Abstract: Concerns about low dissolved oxygen levels in New Hanover County, North Carolina tidal creeks resulted in a study measuring rates of oxygen loss as water-column biochemical oxygen demand (BOD5) and sediment oxygen demand (SOD). Selected tidal creek sites were sampled monthly from July 2001 to August 2002 in collaboration with the New Hanover County Tidal Creeks monitoring project to identify any trends that may be evident concerning rates of oxygen loss. BOD5 rates ranged from 0.0 to 7.6 mg l-1 and were strongly correlated with chlorophyll a measurements. This indicates that conditions leading to algal blooms have the potential to cause increased BOD and thus contribute to hypoxia in tidal creeks. SOD rates ranged from –1.5 to 6.3 g O2 m-2 d-1. Both rates of oxygen uptake were seasonally dependent. Oxygen loss to sediments was greater and more variable than oxygen loss in the water column, indicating that SOD should be considered in all comprehensive water quality monitoring programs. Results indicate that sediment composition and the bioavailability of organic matter may be key elements in determining SOD. On-land processes that increase sedimentation of organic material may contribute to creek hypoxia incidents. Groundwater inputs decreased SOD rates at selected sites, thus recharge areas may be critical to tidal creek health. Correlation and principal component analyses were conducted using SAS statistical software to assess the effects of numerous variables on oxygen demand. The results suggest that BOD5 responds to a suite of environmental variables including temperature, salinity, chlorophyll a, total and organic suspended solids and rainfall while SOD responds to salinity and nutrients.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Keywords
Oxygen--Measurement, Rivers--North Carolina--New Hanover County
Subjects
Oxygen -- Measurement
Rivers -- North Carolina -- New Hanover County