Establishing nearshore marine injuries for the Deepwater Horizon natural resource damage assessment using AQUATOX

•AQUATOX was used to calculate NRDA injury following Deepwater Horizon Oil Release.•Post-oiling model results were compared to simulations with background Total PAH.•Injuries to secondary and tertiary productivity for multiple habitats were calculated.•The use of a food-web model for NRDA will estimate comprehensive injury estimates.

The Oil Pollution Act of 1990 (OPA) requires that the responsible party make the public whole for natural resource injuries attributable to an oil spill incident. We have presented our approach at establishing natural resource baseline conditions for multiple habitats in Coastal Mississippi and Alabama. This paper presents the subsequent steps that were taken to estimate natural resource injuries for the Deepwater Horizon Oil release (DWH) using AQUATOX Release 3.1 NME (Nearshore Marine Environments). TPAH (Total polycyclic aromatic hydrocarbon) exposure matrices in water and sediment were estimated over a spatial gradient based on observed data in Mississippi and Alabama. Bioaccumulation parameters were derived from literature and reasonable bioaccumulation calibration was verified using site specific data when available. TPAH was segregated into six different analyte groups, binned by Kow, based on observed sediment data. Toxicity data from NOAA and literature were used to estimate effects of TPAH and individual analytes on species observed on site. Combining each of these analyses, total injuries could be estimated for Mississippi and Alabama ranging from 0.2% to 4.2% of secondary and tertiary productivity lost over three years, depending on the habitat investigated and its spatial location in the study area. The analysis demonstrates the effectiveness of the AQUATOX model as a tool to quantify levels of injury by comparing the results of a baseline ecological model, calibrated and verified with pre-oiling observations, with post-oiling results. This alternative approach to injury assessment can be used to validate single-species approaches and also to evaluate the injury to, and recovery of, an integrated ecosystem.