President Trump is pushing to allow oil and gas companies to use seismic gun blasts while surveying the Atlantic seafloor, a practice that is estimated to harm or kill tens of thousands of marine animals.

On Friday, NOAA Fisheries took a crucial step toward the Trump administration’s goal by implementing “incidental take authorizations,” which are special provisions in the Marine Mammal Protection Act (MMPA) that allow companies to “incidentally, but not intentionally, harass marine mammals,” according to a NOAA statement.

These seismic surveys involve shooting high-pressure airguns from the bottom of ships, producing acoustic shock waves that bounce off the ocean floor. The rebounding signals, captured by ship sensors, are used to map out the topography of the seafloor to assess its potential for offshore drilling.

As you might imagine, this technique is incredibly noisy for marine life, producing sonic disruptions that can travel over 300,000 square kilometers. The blasts raise background noise levels 100-fold, about the same decibel level as a jet takeoff, and often continue for weeks or months.

According to a 2014 study from the US Bureau of Ocean Energy Management, Atlantic seismic surveys would disturb at least 100,000 marine mammals. Large animals close to the blast radius could suffer hearing loss, injuries, and death. Moreover, a 2017 study in Nature Ecology & Evolution found that seismic surveys tripled the mortality rate of zooplankton, the tiny organisms that form the bedrock of ocean food webs.

Read More: Trump Wants to Open Nearly All US Offshore Waters to Drilling

It has been more than 30 years since any offshore oil and gas exploration has been permitted in Atlantic waters. Though oil and gas companies have obvious interests in resuming offshore drilling, commercial fisheries could be negatively affected by seismic surveys because the airguns can reduce catch rates. The tourism industry on the US East Coast is also opposed to any offshore drilling developments in the Atlantic.

Several Congressional leaders voiced their disagreements with the decision on Friday, including New Jersey Representative Frank Pallone, New Jersey Senator Cory Booker, Massachusetts Senator Ed Markey, Virginia Representative Donald McEachin, and Florida Representative Lois Frankel.

Despite these concerns, the newly released authorizations from NOAA Fisheries allow companies interested in Atlantic seismic exploration, such as TGS-NOPEC Geophysical Company ASA and WesternGeco, Ltd., to pursue permits from the Interior Department's Bureau of Ocean Energy Management.

If they are approved, they may begin conducting seismic surveys off the US eastern seaboard, from Delaware to Florida.