The study, published Monday in the Proceedings of the National Academy of Sciences, found that animal populations—including octopus, krill, squid, and shrimp—declined by 60 to 85 percent in the three and a half years after the spill, with few signs of recovery since. Krill and lanternfish, both foundational species in the Gulf’s food web, were among the hardest hit. The findings also suggest that the die-off is causing genetic bottlenecks that could further hinder ecosystem recovery.