A mechanistic dissolved oxygen model of Corpus Christi Bay to understand critical processes causing hypoxia

Abstract

Corpus Christi Bay (TX, USA) is a shallow wind-driven bay which experiences hypoxia (dissolved oxygen<2 mg/L) during the summer months in the southeast region of the bay. We have developed and installed real-time monitoring systems in the bay to measure various water quality, meteorological and hydrodynamic parameters. These systems can aid in determining the extent and frequency of hypoxic events in this energetic bay. A three-dimensional mechanistic dissolved oxygen model has been developed in this study to investigate the key processes that induce hypoxia in Corpus Christi (CC) Bay. This model includes variable advection and dispersion coefficients so that it can be driven by real-time monitoring hydrodynamic data. The results from model simulations indicate that hypoxia may occur at the lower depths of the bay when both stratification and higher biological activity conditions exist. The water column in the south-east part of the bay becomes stratified during calm wind conditions when there is inflow of hyper-saline water from the neighboring Laguna Madre waterbody. This condition, when combined with higher biological activity during the summer months, induces hypoxia at the lower depths of the bay. The simulation results also point out that physical transport processes have more pronounced effect on the DO distribution within the water column than the effects of biological activity. Therefore, it is necessary to develop suitable sampling strategies that will measure hydrodynamic data at greater spatial and temporal resolution. The integration of this data with our developed model will provide a useful tool to the stakeholders to assess the water quality of the bay in real time.