555
2016. Depending on their maximum depth, polygons were subdivided into up to six
water column layers (0–10 m, 10–20 m, 20–50 m, 50–200 m, 200–2000 m, and
2000–4000 m), plus a sediment layer.
32.2.2 Hydrographic Data
Hydrodynamic data were obtained from the American Seas (AMSEAS) ocean prediction system operated by the USA Naval Oceanographic Office (NAVOCEANO)
and based on the Navy Coastal Ocean Model (NCOM) developed by the Naval
Research Laboratory (Martin et al. 2009). AMSEAS estimates ocean temperature,
salinity, and eastward and northward currents on a regular latitude/longitude grid
with a resolution of 1/36 degree. A 1-year AMSEAS data series with 12-hour steps
was integrated over the Atlantis polygons using the Ocean Model Slicer tool created
by the National Oceanographic and Atmospheric Administration (NOAA) National
Coastal Data Development Center (Ainsworth et al. 2018). The resulting dataset
included average temperature, salinity, and net water flux for each polygon and
depth layer every 12 hours (Ainsworth et al. 2015). Initial conditions of nitrates,
dissolved oxygen, and silicate concentrations correspond to climatological means
obtained from NOAA’s Gulf of Mexico Data Atlas (http://gulfatlas.noaa.gov/
catalog/).
32.2.3 Functional Groups
Atlantis simulates essential ecosystem dynamics using functional groups of species
aggregated by life history, habitat, and trophic similarities. Species of high fisheries
importance or conservation interest are represented by single species groups. The
SGoM model uses 91 functional groups, including primary producers (8 groups),
nutrient cycle (5), structural species (4), filter feeders (3), pelagic invertebrates (4),
macrobenthos (6), octopus (1), shrimp (4), elasmobranchs (6), forage fish (4), reef
fish (11), demersal fish (12), pelagic fish (14), sea turtles (3), seabirds (2), and mammals (4). The model tracks flow of nitrogen as it passes between functional groups
through the food web. Fish abundance data was obtained from the Southeast Area
Monitoring and Assessment Program (Rester 2011; Ainsworth et al. 2015). Spatial
distribution of biomass was based on estimates from generalized additive models
(Drexler and Ainsworth 2013), and the diet matrix was determined using gut content and statistical analysis (Masi et al. 2014; Tarnecki et al. 2016). Vertebrates (fish,
turtles, birds, and mammals), shrimp, and octopus groups are age-structured and
tracked by number of individuals per polygon, structural nitrogen weight per individual (mg sN/individual), and reserve nitrogen weight per individual (mg rN/individual). Structural nitrogen represents hard body part such as bones and teeth, while
reserve nitrogen represents somatic and gonadal soft body tissue. Invertebrates and
32 Comparing Ecosystem Model Outcomes Between Ixtoc 1 and Deepwater...
2016. Depending on their maximum depth, polygons were subdivided into up to six
water column layers (0–10 m, 10–20 m, 20–50 m, 50–200 m, 200–2000 m, and
2000–4000 m), plus a sediment layer.
32.2.2 Hydrographic Data
Hydrodynamic data were obtained from the American Seas (AMSEAS) ocean prediction system operated by the USA Naval Oceanographic Office (NAVOCEANO)
and based on the Navy Coastal Ocean Model (NCOM) developed by the Naval
Research Laboratory (Martin et al. 2009). AMSEAS estimates ocean temperature,
salinity, and eastward and northward currents on a regular latitude/longitude grid
with a resolution of 1/36 degree. A 1-year AMSEAS data series with 12-hour steps
was integrated over the Atlantis polygons using the Ocean Model Slicer tool created
by the National Oceanographic and Atmospheric Administration (NOAA) National
Coastal Data Development Center (Ainsworth et al. 2018). The resulting dataset
included average temperature, salinity, and net water flux for each polygon and
depth layer every 12 hours (Ainsworth et al. 2015). Initial conditions of nitrates,
dissolved oxygen, and silicate concentrations correspond to climatological means
obtained from NOAA’s Gulf of Mexico Data Atlas (http://gulfatlas.noaa.gov/
catalog/).
32.2.3 Functional Groups
Atlantis simulates essential ecosystem dynamics using functional groups of species
aggregated by life history, habitat, and trophic similarities. Species of high fisheries
importance or conservation interest are represented by single species groups. The
SGoM model uses 91 functional groups, including primary producers (8 groups),
nutrient cycle (5), structural species (4), filter feeders (3), pelagic invertebrates (4),
macrobenthos (6), octopus (1), shrimp (4), elasmobranchs (6), forage fish (4), reef
fish (11), demersal fish (12), pelagic fish (14), sea turtles (3), seabirds (2), and mammals (4). The model tracks flow of nitrogen as it passes between functional groups
through the food web. Fish abundance data was obtained from the Southeast Area
Monitoring and Assessment Program (Rester 2011; Ainsworth et al. 2015). Spatial
distribution of biomass was based on estimates from generalized additive models
(Drexler and Ainsworth 2013), and the diet matrix was determined using gut content and statistical analysis (Masi et al. 2014; Tarnecki et al. 2016). Vertebrates (fish,
turtles, birds, and mammals), shrimp, and octopus groups are age-structured and
tracked by number of individuals per polygon, structural nitrogen weight per individual (mg sN/individual), and reserve nitrogen weight per individual (mg rN/individual). Structural nitrogen represents hard body part such as bones and teeth, while
reserve nitrogen represents somatic and gonadal soft body tissue. Invertebrates and
32 Comparing Ecosystem Model Outcomes Between Ixtoc 1 and Deepwater...