Date of Award

Spring 2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Civil & Environmental Engineering

Committee Director

Jaewan Yoon

Committee Member

Russell Burke

Committee Member

Sandeep Kumar

Abstract

Due to several anthropogenic influences, the Chesapeake Bay has experienced a marked decrease in water quality since the colonists arrived at the Jamestown settlement in Virginia during the 1600s. Higher concentrations of nitrogen and phosphorus have enriched the estuaries and coastal waters via point sources (sewage treatment plants and industrial wastes), nonpoint sources (agricultural run-off and septic tank discharges) and the atmosphere (Newell et al., 2005). Restoring oyster beds is considered a Best Management Practice (BMP) to improve water quality as well as provide physical habitat for aquatic species and a healthier estuarine system (USACE Native Oyster Restoration Master Plan, 2012). Efforts to assist water quality improvement in conjunction with the fisheries include declaring sanctuaries for brood-stocks, supplementing hard substrate on the bottom and aiding natural populations with the addition of hatchery-reared and disease-resistant stocks in most of the coastal states in United States (Coen & Luckenbach, 2000). An economic assessment of oyster reefs suggests that restoring the ecological functions will improve water quality, stabilize shorelines, reduce predation (Grabowski, 2004) and establish a habitat for breeding grounds that outweighs the importance of harvestable oyster production (Luckenbach et al., 2005). Statistical models to investigate factorial multicolinearities between water quality and oyster restoration activities were developed in this research to evaluate productivity levels of oyster restoration on multiple substrates, as well as the physical, chemical, hydrological and biological site characteristics, so that the greatest contributing factors were systematically identified. Findings from the factorial models were then further utilized to propose and develop a number of in situ water quality improvement design in forms of Total Maximum Daily Loads (TMDLs) and Best Management Practices (BMPs). A factorial model evaluates the relationship among the dependent variable, oyster biomass, and treatment levels of temperature (which includes seasonal variability), as well as salinity, TSS (total suspended solids),Escherichia coli/Enterococcus bacterial counts, depth, dissolved oxygen levels (DO) and nutrients such as nitrogen, phosphorus and chlorophyll a, and the block levels designated for the model such as alternative substrates (oyster shells versus riprap, granite, cement, cinder blocks, limestone marl or combinations). The different scenarios are analyzed utilizing the Factorial Model along with a Multiple Means Comparison (MMC) to compare the production rates and evaluate which combination of variables produces the highest biomass of oysters. Once the variables of greatest impact are identified, BMPs and TMDLs will be identified to aid in lowering the existing levels and develop future plans for maintaining them. In summary, this model is being developed for maximizing the likelihood of successful oyster reef restoration in an effort to establish a healthier ecosystem and to improve overall estuarine water quality in the Chesapeake Bay estuaries.

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DOI

10.25777/mh94-wm09

ISBN

9781303219764

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