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theses

Estuaries play an important role in the biogeochemistry of the global ocean, particularly the cycling of nitrogen (N) and carbon from natural and anthropogenic sources. Delaware Estuary is a temperate coastal plain estuary with a significant economic and ecological value. In this study, a coupled three-dimensional physical and biogeochemical (BGC) modeling framework based on the Regional Ocean Modeling System (ROMS) was utilized to investigate hydrodynamic and BGC characteristics in Delaware Estuary. Freshwater dynamics, transport pathways, and dispersal time scales are presented in Chapter 2. The model simulated water level, velocity, salinity, and temperature with a minimum correlation coefficient of 0.78, and a maximum centered root mean squared difference of 72% of one standard deviation of the observations. We found that total transport and mean age of freshwater were more sensitive to discharge changes on the Delaware side than the New Jersey side. The mean flushing time (FT) of freshwater was estimated to be 40-125 days depending on discharge. A method introduced to estimate spatial FT highlighted increased FT on the lower NJ flank with higher discharge. In Chapter 3, the physical model was used to investigate a large oyster mortality event in the upper reaches of Delaware Bay following Hurricane Irene and Tropical Storm Lee in 2011. Monthly mortality rates of 10-55% were associated with a continuous low salinity (<7 psu) exposure for longer than 20 days. Population recovery projections predicted that recovery would take approximately 10 years. The configuration, parametrization, and evaluation of a process-based coupled BGC model are presented in Chapter 4. The simulation during 2009-2011 reproduced physical and BGC fields such as dissolved inorganic nitrogen (DIN), dissolved organic nitrogen, particulate organic nitrogen, and dissolved oxygen within one standard deviation of long-term mean values. In Chapter 5, major monthly and annual N fluxes were quantified with a positive net ecosystem production in the bay. Benthic processes (denitrification and N burial) accounted for 19-28% of the annual and 8-73% of the monthly DIN input in the budget. We found that up to 35% of excess DIN input during high discharge periods left the bay without being assimilated into organic N.

ETD_7866

Ph.D.

Includes bibliographical references

by Seyed Aboozar Tabatabai

doi:10.7282/T3SQ92TG

ETD doctoral

The author owns the copyright to this work.