Title

Impacts of the Deepwater Horizon Oil Spill Evaluated using an End-to-End Ecosystem Model

Document Type

Article

Publication Date

1-2018

Digital Object Identifier (DOI)

https://doi.org/10.1371/journal.pone.0190840

Abstract

We use a spatially explicit biogeochemical end-to-end ecosystem model, Atlantis, to simulate impacts from the Deepwater Horizon oil spill and subsequent recovery of fish guilds. Dose-response relationships with expected oil concentrations were utilized to estimate the impact on fish growth and mortality rates. We also examine the effects of fisheries closures and impacts on recruitment. We validate predictions of the model by comparing population trends and age structure before and after the oil spill with fisheries independent data. The model suggests that recruitment effects and fishery closures had little influence on biomass dynamics. However, at the assumed level of oil concentrations and toxicity, impacts on fish mortality and growth rates were large and commensurate with observations. Sensitivity analysis suggests the biomass of large reef fish decreased by 25% to 50% in areas most affected by the spill, and biomass of large demersal fish decreased even more, by 40% to 70%. Impacts on reef and demersal forage caused starvation mortality in predators and increased reliance on pelagic forage. Impacts on the food web translated effects of the spill far away from the oiled area. Effects on age structure suggest possible delayed impacts on fishery yields. Recovery of high-turnover populations generally is predicted to occur within 10 years, but some slower-growing populations may take 30+ years to fully recover.

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Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Was this content written or created while at USF?

Yes

Citation / Publisher Attribution

PLoS ONE, v. 13, issue 1, art. e0190840

S1Fig.pdf (275 kB)
Sediment PAH vs water column PAH. Sediment PAH concentration measured in C-IMAGE sediment sampling (Romero and Hollander, unpublished data) versus time- and depth- integrated water column PAH concentrations from the Coastal Modeling System. Dotted lines show sediment:water column ratios for reference. https://doi.org/10.1371/journal.pone.0190840.s001

S2Fig.pdf (155 kB)
Relative biomass changes caused by fishery closures and recruitment impacts. Fishery closures (top); recruitment impacts (bottom); no oil effects are incorporated. https://doi.org/10.1371/journal.pone.0190840.s002

S3Fig.pdf (220 kB)
Commercial catch of large pelagic fish. Catch is shown for species constituting the large pelagic guild before the oil spill (dark grey bars: average of 2007–2010) and after the oil spill (light grey bars: average of 2010–2014). Source: ICCAT and NMFS. https://doi.org/10.1371/journal.pone.0190840.s003

S4Fig.pdf (203 kB)
Age composition changes. Differences in age composition between no-oil (dark gray) and oiled (light grey) scenarios. Condition is shown for October 2010 for a subset of polygons that experienced the greatest oil impacts. Represents oil simulation [K1000 β363]. Relative proportion is shown. https://doi.org/10.1371/journal.pone.0190840.s004

S5Fig.pdf (198 kB)
Biomass of immature and mature cohorts before and after spill. Biomass in immature age classes and mature age classes for species assessed by SEDAR since 2012. Pre-spill shows average of 2009 and 2010, post-spill shows average of 2011 and 2012. The immature/mature age division is consistent with the juvenile/adult division used in Atlantis. References and notes provided in S3 Table. https://doi.org/10.1371/journal.pone.0190840.s005

S6Fig.pdf (618 kB)
Mature-to-immature numbers ratio. No-oil scenario (dotted line); oiled scenario (solid line) Represents oil simulation [K1000 β363]. https://doi.org/10.1371/journal.pone.0190840.s006

S7Fig.pdf (291 kB)
Absolute biomass reduction for no oil versus oil scenario. Biomass minima is shown occurring 7–16 months (median 10 months) after the oil spill. The areas of major impact typically occur on the continental shelves far from the oil plume, where concentrations of the affected populations occur. Represents oil simulation [K1000 β363]. https://doi.org/10.1371/journal.pone.0190840.s007

S8Fig.pdf (265 kB)
Per capita consumption rate on prey by guild. Area of circle is proportional to the per capita consumption rate. Both predator and prey are presented at aggregated guild level. Only prey items constituting >1% of the diet are presented. Large demersal fish (LDF), Sciaendiae (SCI), Elasmobranchs (ELA), Large pelagic fish (LPF), Groupers (GRP), Snappers (SNP), Small demersal and reef fish (SDR), Small pelagic fish (SPL), other prey items (OTH). No oil scenario and oiled scenario both show day 300 of the simulation (Oct 28, 2010) when biomass impacts were pronounced. https://doi.org/10.1371/journal.pone.0190840.s008

S9Fig.pdf (171 kB)
Condition factor of fish represented as reserve:structural nitrogen ratio. Reserve represents soft body tissue that can be reabsorbed (e.g. muscle, fat, gonads), structural represents hard tissues and structures (e.g., bone). High rN/sN indicates good body condition. Dotted line: no oil scenario, solid line: oiled [K1000 β363]. Seasonal saw-toothed pattern (present in both scenarios) reflects gonadal tissue loss in spawning. https://doi.org/10.1371/journal.pone.0190840.s009

S10Fig.pdf (269 kB)
Ecosystem indicators for no-oil and oiled scenario. Oil (dotted line); no-oil (solid line). Mean trophic level of ecosystem, pelagic-to-demersal biomass ratio for fish, piscivorous-to-planktivorous biomass ratio for fish, and Shannon biodiversity. Represents oil simulation [K1000 β363]. https://doi.org/10.1371/journal.pone.0190840.s010

S11Fig.pdf (273 kB)
Change in catch for the entire GOM due to fishery closures. No oil effects are included. https://doi.org/10.1371/journal.pone.0190840.s011

S12Fig.pdf (172 kB)
Comparison of fish count density data from remotely operated vehicles with numbers of fish from Atlantis. ROV data have been aggregated by species into Atlantis functional groups. Gray circles show densities measured at each site and sampling date (median value: dotted lines). The Atlantis numbers (solid lines) have been scaled so that median matches ROV data.

S13Fig.pdf (231 kB)
Fish body size predicted from the model versus ROV reef surveys. Model (red dotted line); laser-scaled fish size estimates from ROV surveys (black line: median; bars: lower and upper quartiles, whiskers: ±2*interquartile range, dots: outliers). ROV data have been converted to individual body weight using a length-weight relationship. https://doi.org/10.1371/journal.pone.0190840.s013

S1 Table.pdf (146 kB)
Composition of guilds and functional group-level data. Recovery to 99% of pre-spill biomass. See Ainsworth et al. [17] for species memberships in Atlantis functional groups. Note that the Atlantis model contains 91 functional groups in total. DNR: Did not recover. Represents oil simulation [K1000 β363]. https://doi.org/10.1371/journal.pone.0190840.s014

S2 Table.pdf (188 kB)
Sensitivity analysis of biomass. Shows smallest observed biomass for various guilds relative to no-oil scenario. Biomasses are summed across all functional groups within these guilds. Biomass minima occur 7–16 months (median 10 months) after the oil spill. Parameters varied are sediment:water column concentration factor (K) and threshold for oil impacts (β). Red and blue cells represent greatest and least potential impact, respectively. https://doi.org/10.1371/journal.pone.0190840.s015

S3 Table.pdf (261 kB)
References for SEDAR age structure data. https://doi.org/10.1371/journal.pone.0190840.s016

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