551
© Springer Nature Switzerland AG 2020
S. A. Murawski et al. (eds.), Deep Oil Spills,
https://doi.org/10.1007/978-3-030-11605-7_32
Chapter 32
Comparing Ecosystem Model Outcomes
Between Ixtoc 1 and Deepwater Horizon Oil
Spills
Joel G. Ortega-Ortiz, Cameron H. Ainsworth, and Adolfo Gracia
Abstract A spatially explicit biogeochemical Atlantis ecosystem model of the
southern Gulf of Mexico was developed to simulate impacts from the Ixtoc 1 oil
spill. Oil dispersion and concentration were estimated from satellite imagery and
reported flow rates and a dose-response model applied to estimate impact on fish
growth and mortality rates. Effects estimated for the Ixtoc 1 spill were compared
with previously reported Atlantis ecological model simulations of the Deepwater
Horizon (DWH) effects on the biomass of eight fish guilds. Biomass decreased
sharply after the oil spill in both scenarios, compared to no-oil simulations, reaching
minimum values within less than 2 years for most fish guilds. At the end of the
37-year simulation period, all fish guilds recovered to within 95% of the biomass of
no-oil simulation for DWH, while all but one guild in the Ixtoc 1 simulation reached
new equilibrium at less than 95% of the no-oil biomass. Comparison of the two oil
spill simulations highlighted the important roles of starvation and juvenile mortality
on fish stock biomass decrease.
Keywords Atlantis ecosystem model · Ixtoc 1 · Fish mortality · Fish biomass
32.1 Introduction
The blowout of the Macondo well and explosion of the Deepwater Horizon (DWH)
drilling rig started the largest oil spill in the Gulf of Mexico on April 20, 2010. By
the time the well was shut 87 days later, at least five million barrels of oil had been
discharged into the Gulf (McNutt et al. 2012a). The DWH disaster generated a massive scientific and engineering response, including several studies to document
J. G. Ortega-Ortiz (*) · C. H. Ainsworth
University of South Florida, College of Marine Science, St. Petersburg, FL, USA
e-mail: jortegaortiz@mail.usf.edu; ainsworth@usf.edu
A. Gracia
Universidad Nacional Autónoma de México, Instituto de Ciencias del Mar y Limnología,
Ciudad de México, Mexico
e-mail: gracia@unam.mx
© Springer Nature Switzerland AG 2020
S. A. Murawski et al. (eds.), Deep Oil Spills,
https://doi.org/10.1007/978-3-030-11605-7_32
Chapter 32
Comparing Ecosystem Model Outcomes
Between Ixtoc 1 and Deepwater Horizon Oil
Spills
Joel G. Ortega-Ortiz, Cameron H. Ainsworth, and Adolfo Gracia
Abstract A spatially explicit biogeochemical Atlantis ecosystem model of the
southern Gulf of Mexico was developed to simulate impacts from the Ixtoc 1 oil
spill. Oil dispersion and concentration were estimated from satellite imagery and
reported flow rates and a dose-response model applied to estimate impact on fish
growth and mortality rates. Effects estimated for the Ixtoc 1 spill were compared
with previously reported Atlantis ecological model simulations of the Deepwater
Horizon (DWH) effects on the biomass of eight fish guilds. Biomass decreased
sharply after the oil spill in both scenarios, compared to no-oil simulations, reaching
minimum values within less than 2 years for most fish guilds. At the end of the
37-year simulation period, all fish guilds recovered to within 95% of the biomass of
no-oil simulation for DWH, while all but one guild in the Ixtoc 1 simulation reached
new equilibrium at less than 95% of the no-oil biomass. Comparison of the two oil
spill simulations highlighted the important roles of starvation and juvenile mortality
on fish stock biomass decrease.
Keywords Atlantis ecosystem model · Ixtoc 1 · Fish mortality · Fish biomass
32.1 Introduction
The blowout of the Macondo well and explosion of the Deepwater Horizon (DWH)
drilling rig started the largest oil spill in the Gulf of Mexico on April 20, 2010. By
the time the well was shut 87 days later, at least five million barrels of oil had been
discharged into the Gulf (McNutt et al. 2012a). The DWH disaster generated a massive scientific and engineering response, including several studies to document
J. G. Ortega-Ortiz (*) · C. H. Ainsworth
University of South Florida, College of Marine Science, St. Petersburg, FL, USA
e-mail: jortegaortiz@mail.usf.edu; ainsworth@usf.edu
A. Gracia
Universidad Nacional Autónoma de México, Instituto de Ciencias del Mar y Limnología,
Ciudad de México, Mexico
e-mail: gracia@unam.mx