Embryos were exposed to 18 ppb TPAH.

Habitat Assessment After A Major Oil Spill

The Exxon Valdez oil spill in 1989 was a catastrophe that inadvertently created an un-planned “experiment” for long term study of the effects of an oil spill in a region where people and pollution had little prior environmental impact. Because of pending litigation between Exxon and the State/Federal governments on natural resource damages, both sides used a small army of scientists and contractors to investigate the damages to habitat and wildlife. In some cases, similar studies were conducted in parallel, on similar sites and species, but all of this information was held from the public because of the litigation. The initial settlement came in 1991 (approximately $1 billion to State/Federal governments for natural resource damages), and the information from the scientific studies began to flow. Since that settlement, scientists from both Exxon and the government have published a series of studies and often do not agree on the results. This is unfortunate, as the public is often at a loss to understand why there are differences between interpretation. For further information on these differences, see references [1-3].

The controversy continues to present day, fueled by lingering oil in PWS and continuing litigation. As of May 2007, two of three litigation issues remain unsettled, 18 years after the initial spill event. The stakes are high: the remaining two litigation efforts involve up to $100 million (between ExxonMobil and State/Federal governments) and up to $2 to 5 billion (civil litigation between Exxon-Mobile and local residents or fishermen impacted by the spill). Currently, the State and Federal governments have petitioned Exxon for an additional $92 million, under the ‘reopener’ clause in the 1991 settlement. State/Federal governments are seeking these additional funds to restore current damage caused by lingering oil; this additional damage was unexpected at the time of the 1991 settlement.

Response to Brannon et al. 2006 In their paper, Brannon et al. [4] attempted to replicate some of the pink salmon embryo experiments done by our laboratory [5,6,7,8,9] using exposure methods similar to ours. Our series of papers present evidence that concentrations in the low parst per billion PAH (1-20 ppb) can be very damaging to embryos and to populations of pink salmon and herring. The Brannon et al. paper is critical of our series of papers, and cites toxic exposure doses in their study that were several orders of magnitude greater than our exposure concentrations. Simply put, what distinguishes the Brannon et al. (2006) report from ours is that they base their interpretations on dose added (nominal oiling) instead of dose measured (aqueous TPAH concentration).

Download entire response (pdf): Response to Brannon et al. 2006

In a subsequent rebuttal, Brannon et al. [10] reanalyzed a small portion of our data for the presence of oil droplets using phytane as a surrogate indicator, again reaching the scientifically indefensible conclusion that microdroplets explain embryo toxicity. Brannon et al. [4,10] have presented no evidence of microdroplets as an agent of embryo mortality, whereas we have done so for PAHs [5-9] and we have definitively eliminated microdroplets as directly toxic [11] to fish embryos. The linked document provides the data in question so readers can evaluate the validities of conflicting conclusions based on identical observations.

Download conflicting interpretations (pdf): Response to Brannon et al. 2008

Key Publications to this Research

1. Peterson, C. H., L. L. McDonald, R.H. Green, and W.P. Erickson. (2001). "Sampling design begets conclusions: the statistical basis for detection of injury to and recovery of shoreline communities after the 'Exxon Valdez' oil spill." Marine Ecology Progress Series 210: 255-283.
2. Rice, S. D., J. W. Short, M.G. Carls, A. Moles, and R.B. Spies. (2006). The Exxon Valdez oil spill. Long-term ecological change in the northern Gulf of Alaska. R. B. Spies. Amsterdam, Elsevier: 413-514.
3. Rice, S. D., R. E. Thomas, M.G. Carls, R.A. Heintz, A.C. Wertheimer, M.L. Murphy, J. W. Short, and A. Moles. (2001). "Impacts to pink salmon following the Exxon Valdez oil spill: persistence, toxicity, sensitivity, and controversy." Reviews in Fisheries Science 9: 165-211.
4. Brannon, E. L., K. M. Collins, et al. (2006). "Toxicity of weathered Exxon Valdez crude oil to pink salmon embryos." Environmental Toxicology and Chemistry 25(4): 962-972.
5. Marty, G. D., J. W. Short, et al. (1997). "Ascites, premature emergence, increased gonadal cell apoptosis, and cytochrome P4501A induction in pink salmon larvae continuously exposed to oil-contaminated gravel during development." Canadian Journal of Zoology-Revue Canadienne De Zoologie 75(6): 989-1007.
6. Carls, M. G., S. D. Rice, et al. (1999). "Sensitivity of fish embryos to weathered crude oil: Part I. Low-level exposure during incubation causes malformations, genetic damage, and mortality in larval Pacific herring (Clupea pallasi)." Environmental Toxicology and Chemistry 18(3): 481-493.
7. Heintz, R. A., J. W. Short, et al. (1999). "Sensitivity of fish embryos to weathered crude oil: Part II. Increased mortality of pink salmon (Oncorhynchus gorbuscha) embryos incubating downstream from weathered Exxon Valdez crude oil." Environmental Toxicology and Chemistry 18(3): 494-503.
8. Heintz, R. A., S. D. Rice, et al. (2000). "Delayed effects on growth and marine survival of pink salmon Oncorhynchus gorbuscha after exposure to crude oil during embryonic development." Marine Ecology-Progress Series 208: 205-216.
9. Carls, M. G., R. A. Heintz, et al. (2005). "Cytochrome P4501A induction in oil-exposed pink salmon Oncorhynchus gorbuscha embryos predicts reduced survival potential." Marine Ecology-Progress Series 301: 253-265.
10. Brannon, E. L., J. S. Brown, J. M. Neff, K. R. Parker and W. A. Stubblefield 2008. Authors' Reply, Letter to the Editor. Environmental Toxicology and Chemistry.
11. Carls, M. G., L. Holland, M. L. Larsen, T. K. Collier, N. L. Scholz and J. P. Incardona 2008. Fish embryos are damaged by dissolved PAHs, not oil particles. Aquatic Toxicology 88: 121-127.

Habitat Program Manager
Jeep Rice
Auke Bay Laboratories
Alaska Fisheries Science Center, NOAA Fisheries

Ted Stevens Marine Research Institute
17109 Pt Lena Loop Rd
Juneau AK 99801
Jeep.Rice@noaa.gov