Decadal acoustic monitoring of toothed whales in the Gulf of Mexico post-oil spill

Shortly after the Deepwater Horizon oil spill began in April 2010, a
widely spaced passive acoustic monitoring array was deployed in the
northeastern Gulf of Mexico to document the impacts of this
unprecedentedly large and deep offshore oil spill on oceanic marine
mammals. The array was subsequently maintained for over a decade. Here we
document decadal density declines for seven of eight monitored species
groups, including sperm whales (up to 31%), beaked whales (up to 83%), and
small delphinids (up to 43%). Declines were observed both within and
outside of the surface oil footprint. Though not conclusively linked to
the oil spill, the broad spatial and temporal scale of these declines
observed for disparate marine mammal species is consistent with Deepwater
Horizon impacts. These declines have exceeded and outlasted post-spill
damage assessment predictions, suggesting that the offshore ecosystem
impacts of Deepwater Horizon may have been larger than previously thought.