560
32.2.7 Analysis
Simulations for the SGoM model were run for 37 years, from January 1, 1979, to
December 31, 2013. For comparison purposes, we followed the approach by
Ainsworth et al. (2018) and aggregated results from Atlantis fish functional groups
into eight “guilds’: snappers (family: Lutjanidae), groupers (family: Serranidae),
Sciaenidae, elasmobranchs, large pelagic fish, small pelagic fish, small demersal
and reef fish, and large demersal fish.
32.3 Results
A sharp decrease in biomass relative to no-oil spill simulations followed by a gradual increase (i.e., recovery) was observed on all fish guilds for both the Ixtoc 1 and
DWH oil spill scenarios (Fig. 32.3). The biomass decrease was higher for the DWH
scenario, with average minimum biomass of 40.2% relative to no-oil simulation,
compared 70.2% for the Ixtoc 1 scenario (Table 32.1). Despite the larger decrease,
all the fish guilds in the DWH scenario recovered to within 95% of the no-oil scenario biomass, while only half of the fish guilds in the Ixtoc 1 scenario recovered up
to that threshold. Indeed, except for large pelagic fish, biomass for fish guilds in the
Ixtoc 1 spill became asymptotic at values lower than the no-oil scenario toward the
end of the 37-year simulation (Fig. 32.3). On the DWH scenario, only the grouper
guild showed a similar biomass equilibrium at 94.8% of the no-oil simulation after
37 years. The magnitude of biomass decrease estimated in the Ixtoc 1 simulation
was comparable to results from Ainsworth et al. 2018 in the southwest region of the
Gulf. For example, the grouper guild had a decrease of about 5 t·km
−2
in the
Campeche Bay region in both simulations (Fig. 32.4). However, condition factor
decreased in the DWH simulations.
In contrast to results from the DWH simulation described by Ainsworth et al.
(2018), no meaningful changes in condition factor (Fig. 32.5) or shifts in age composition pre- and post-spill were observed in the Ixtoc 1 simulations (Fig. 32.6).
32.4 Conclusion
While it is practically impossible to determine the precise distribution and concentration of oil spilled from the Ixtoc 1 well, satellite imagery and flow rate estimates
provide a reasonable scenario to use in the ecological model simulations. Differences
in the depth of the wells and the use of oil dispersants at depth during the DWH spill
may have resulted in more effects on the continental shelf during Ixtoc 1 and over
the continental slope and abyssal region during DWH.
J. G. Ortega-Ortiz et al.
32.2.7 Analysis
Simulations for the SGoM model were run for 37 years, from January 1, 1979, to
December 31, 2013. For comparison purposes, we followed the approach by
Ainsworth et al. (2018) and aggregated results from Atlantis fish functional groups
into eight “guilds’: snappers (family: Lutjanidae), groupers (family: Serranidae),
Sciaenidae, elasmobranchs, large pelagic fish, small pelagic fish, small demersal
and reef fish, and large demersal fish.
32.3 Results
A sharp decrease in biomass relative to no-oil spill simulations followed by a gradual increase (i.e., recovery) was observed on all fish guilds for both the Ixtoc 1 and
DWH oil spill scenarios (Fig. 32.3). The biomass decrease was higher for the DWH
scenario, with average minimum biomass of 40.2% relative to no-oil simulation,
compared 70.2% for the Ixtoc 1 scenario (Table 32.1). Despite the larger decrease,
all the fish guilds in the DWH scenario recovered to within 95% of the no-oil scenario biomass, while only half of the fish guilds in the Ixtoc 1 scenario recovered up
to that threshold. Indeed, except for large pelagic fish, biomass for fish guilds in the
Ixtoc 1 spill became asymptotic at values lower than the no-oil scenario toward the
end of the 37-year simulation (Fig. 32.3). On the DWH scenario, only the grouper
guild showed a similar biomass equilibrium at 94.8% of the no-oil simulation after
37 years. The magnitude of biomass decrease estimated in the Ixtoc 1 simulation
was comparable to results from Ainsworth et al. 2018 in the southwest region of the
Gulf. For example, the grouper guild had a decrease of about 5 t·km
−2
in the
Campeche Bay region in both simulations (Fig. 32.4). However, condition factor
decreased in the DWH simulations.
In contrast to results from the DWH simulation described by Ainsworth et al.
(2018), no meaningful changes in condition factor (Fig. 32.5) or shifts in age composition pre- and post-spill were observed in the Ixtoc 1 simulations (Fig. 32.6).
32.4 Conclusion
While it is practically impossible to determine the precise distribution and concentration of oil spilled from the Ixtoc 1 well, satellite imagery and flow rate estimates
provide a reasonable scenario to use in the ecological model simulations. Differences
in the depth of the wells and the use of oil dispersants at depth during the DWH spill
may have resulted in more effects on the continental shelf during Ixtoc 1 and over
the continental slope and abyssal region during DWH.
J. G. Ortega-Ortiz et al.