Both the long- and short-term effects of the oil spill have been studied comprehensively.^[18] Thousands of animals died immediately; the best estimates include 100,000 to as many as 250,000 seabirds, at least 2,800 sea otters, approximately 12 river otters, 300 harbor seals, 247 bald eagles, and 22 orcas, as well as the destruction of billions of salmon and herring eggs.^[5][19] The effects of the spill continued to be felt for many years afterwards. Overall reductions in population have been seen in various ocean animals, including stunted growth in pink salmon populations.^[20] Sea otters and ducks also showed higher death rates in following years, partially because they ingested prey from contaminated soil and from ingestion of oil residues on hair due to grooming.^[21]

Almost 20 years after the spill, a team of scientists at the University of North Carolina found that the effects are lasting far longer than expected.^[20] The team estimates some shoreline Arctic habitats may take up to 30 years to recover.^[5] Exxon Mobil denies any concerns over this, stating that they anticipated a remaining fraction that they assert will not cause any long-term ecological impacts, according to the conclusions of 350 peer-reviewed studies.^[21] However, a study from scientists from the NOAA concluded that this contamination can produce chronic low-level exposure, discourage subsistence where the contamination is heavy, and decrease the "wilderness character" of the area.^[16]