Breaking Coastal Hypoxia: Destratification of Gulf of Mexico Deadzone Through Artificially Enhancing Oxygen Transport Downwards to Maintain Marine Faunae

Veda Thipparthi, Louisiana State University, Chemical Engineering, Baton Rouge, LA, United States, Louis J Thibodeaux, Louisiana State Univ, Baton Rouge, LA, United States and David W Constant, Louisiana State University, Baton Rouge, LA, United States
As a consequence of seasonal eutrophication and human input, a vast hypoxic area termed “The Dead-zone” develops every year in the Gulf of Mexico during summer along the Louisiana coastline characterized by a heavy density-stratification of seawater and oxygen concentrations less than 2 mg.l-1. It poses a threat to bottom-dwelling faunae and their environment which has negative ecological and economic consequences. This project aims to mitigate hypoxia by employing mechanical impellers placed at strategic depths and locations in the Gulf, enhancing the transport of oxygen by mixing oxygen-enriched seawater at the surface, downward into the deeper oxygen-depleted Dead-zone water.
This is substantiated by laboratory experiments involving the mixing of targeted water layers below the water surface using a lab-scale impeller in a standard aquarium containing simulated density-stratified water. The position of the impeller is determined by Constant Flux Model, which is derived from the classical advection-diffusion principle and follows a strict chemical-engineering-based approach based on the idea that oxygen flux remains constant in the individual layers and throughout the water column. It is a modification of the traditional eutrophication-type mathematical model for use in the Gulf-shelf and when combined with the field-measured oxygen profiles, it can identify specific “choke points” contributing to the resistance of vertical oxygen transport.
The aquarium experiments resulted in the disruption of the density stratification, thereby facilitating vertical transport throughout the water column. On average, mixing for 30 minutes at an rpm of 70 resulted in a more or less uniform oxygen concentration profile in the column.
The constant flux model is a good benchmark in developing the proposed solution to hypoxia and shows promise in reducing it by targeting oxygen choke points. Once the proof-of-concept is completed, the results would be used in a future development phase to guide the design of a proposed field study site demonstration. This includes determining locations and depths in the Gulf to install impellers, spacing between and run-time for each, energy loads, and cost effectiveness.