The purpose of this thesis is to explore the connections between agricultural runoff
influx, oil influx, and oxygen levels in a near-coastal marine environment. The creation
of oxygen deficient conditions is investigated through the use of a stoichiometric
modeling approach that utilizes a system of ordinary differential equations. Agricultural
runoff is modeled as a source of a limiting nutrient for algae. Oil influx is modeled as a
carbon source for bacterial consumption. The investigation is motivated by the Gulf of
Mexico-ecosystem in the wake of the Deepwater Horizon oil rig incident of 2010, which
contributed large amounts of oil (carbon) to the Gulf system. The model consists of an
algal class with flexible stoichiometry that utilizes the nutrient for growth and a bacterial
class with fixed stoichiometry that assimilates the carbon. A consumer class with fixed
stoichiometry that is dependent upon the oxygen present in the system is modeled and is
used to indicate oxygen deficient conditions. Equilibrium, time series, and stability
analysis of this five-dimensional system are presented. Through the analyses presented
and simulations, it is found that this model reproduces the behavior of the biological
processes associated with nutrient enrichment and the creation hypoxic areas, or ‘dead zones'.
University of Minnesota M.S. thesis. July 2012. Major: Applied and computational mathematics. Advisor:Harlan Stech. 1 computer file (PDF); vi, 130 pages, appendix p. 73-130.
Pollesch, Nathan L..
Stoichiometric modeling of nutrient and biomass flux in the Gulf of Mexico..
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