tl;dr: A new PNAS study finds that deep-sea populations of octopus, squid, krill, shrimp, and lanternfish in the Gulf of Mexico dropped by at least 60% after the 2010 Deepwater Horizon spill and have shown little recovery 16 years later. Researchers also detected reduced genetic diversity and found oil-related compounds in deep-sea species, which can impair reproduction and development. While not definitively proven, the spill is described as "the most parsimonious explanation" for what they call the fastest, most severe decline ever documented in this ocean layer.