537
31.1 Introduction
The Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GoM) triggered the
largest response to a spill in US history (Levy and Gopalakrishnan 2010; Barron
2012; Lubchenco et al. 2012, Colwell et al. 2014). The cumulative research from
this response has resulted in hundreds of publications describing the range of
impacts from the DWH event on various components of the system. An ecosystembased approach to assessing the consequences of the DWH oil spill can help to
address non-linear and ecosystem-level interactions (reviewed by Curtin and
Prellezo 2010) and would be a key step toward integrating the knowledge gained
from research efforts. Whereas Ainsworth et al. (2018) tested top-down effects of
the oil spill on fish abundance and mortality, this chapter represents a synthesis of
bottom-up and top-down effects across a broader range of taxa. Bottom-up effects
relate to the accumulation of detrital biomass and oil on the seafloor as a result of
marine oil snow sedimentation and flocculent accumulation (MOSSFA).
Additionally, understanding of the cumulative effects of various human stressors
on fish populations has been identified as a major gap in our knowledge (Pew Ocean
Commission 2003; U.S. Commission on Ocean Policy 2004; Crain et al. 2008,
2009). In particular, Crain et al. (2008) note that the absence of controlled studies
assessing the combined effects of fishing and other stressors on fish populations is a
particular concern. Controlled field experiments of this type are inherently difficult
to perform, requiring that they be addressed using a different means (Crain et al.
2009). For instance, by using established ecosystem-based modeling efforts, not
only could the potential cumulative effects of fishing and an oil spill on fish populations be identified, but the synergistic effects of multiple stressors across a community of fished populations could be elucidated, providing critical insights for both
scientists and managers. This chapter will address the combined effects of fishing
mortality and an oil spill, using an Atlantis ecosystem-based fishery model.
31.2 Methods
31.2.1 Atlantis
Atlantis is a deterministic, end-to-end ecosystem model with a spatially explicit
three-dimensional framework (Fulton 2001; Fulton et al. 2004a, 2004b, 2005,
2007). It operates at 12-hour time steps. Atlantis uses an irregular polygon structure
reflecting bioregional features and political and regulatory boundaries. Each polygon has a sediment layer and up to six water column layers, depending on depth of
the area described by the polygon. Depth strata are consistent across polygons
(z-coordinate system).
Atlantis is also coupled to a hydrodynamic model that includes currents, temperature, and salinity per polygon and depth layer. For the GoM Atlantis model, the
31 A Synthesis of Top-Down and Bottom-Up Impacts of the Deepwater Horizon Oil…
31.1 Introduction
The Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GoM) triggered the
largest response to a spill in US history (Levy and Gopalakrishnan 2010; Barron
2012; Lubchenco et al. 2012, Colwell et al. 2014). The cumulative research from
this response has resulted in hundreds of publications describing the range of
impacts from the DWH event on various components of the system. An ecosystembased approach to assessing the consequences of the DWH oil spill can help to
address non-linear and ecosystem-level interactions (reviewed by Curtin and
Prellezo 2010) and would be a key step toward integrating the knowledge gained
from research efforts. Whereas Ainsworth et al. (2018) tested top-down effects of
the oil spill on fish abundance and mortality, this chapter represents a synthesis of
bottom-up and top-down effects across a broader range of taxa. Bottom-up effects
relate to the accumulation of detrital biomass and oil on the seafloor as a result of
marine oil snow sedimentation and flocculent accumulation (MOSSFA).
Additionally, understanding of the cumulative effects of various human stressors
on fish populations has been identified as a major gap in our knowledge (Pew Ocean
Commission 2003; U.S. Commission on Ocean Policy 2004; Crain et al. 2008,
2009). In particular, Crain et al. (2008) note that the absence of controlled studies
assessing the combined effects of fishing and other stressors on fish populations is a
particular concern. Controlled field experiments of this type are inherently difficult
to perform, requiring that they be addressed using a different means (Crain et al.
2009). For instance, by using established ecosystem-based modeling efforts, not
only could the potential cumulative effects of fishing and an oil spill on fish populations be identified, but the synergistic effects of multiple stressors across a community of fished populations could be elucidated, providing critical insights for both
scientists and managers. This chapter will address the combined effects of fishing
mortality and an oil spill, using an Atlantis ecosystem-based fishery model.
31.2 Methods
31.2.1 Atlantis
Atlantis is a deterministic, end-to-end ecosystem model with a spatially explicit
three-dimensional framework (Fulton 2001; Fulton et al. 2004a, 2004b, 2005,
2007). It operates at 12-hour time steps. Atlantis uses an irregular polygon structure
reflecting bioregional features and political and regulatory boundaries. Each polygon has a sediment layer and up to six water column layers, depending on depth of
the area described by the polygon. Depth strata are consistent across polygons
(z-coordinate system).
Atlantis is also coupled to a hydrodynamic model that includes currents, temperature, and salinity per polygon and depth layer. For the GoM Atlantis model, the
31 A Synthesis of Top-Down and Bottom-Up Impacts of the Deepwater Horizon Oil…