STEVE INSKEEP, HOST:
Scientists have found World War II-era military weapons 3,000 feet beneath the waves off Los Angeles.
MICHEL MARTIN, HOST:
Eric Terrill of the Scripps Institution of Oceanography in San Diego helped lead a team mapping the ocean floor in the San Pedro Basin.
ERIC TERRILL: There was actually four different types of munitions. We found a type of pyrotechnic called a smoke float. This is essentially set up a smokescreen for ships to evade the enemy. And then we found two different types of depth charges. These are the type of munitions that are dumped over the side of a ship to essentially damage enemy submarines.
INSKEEP: Wow. They're just sitting there. Now, when they discovered these weapons, researchers were expecting to map something else - a debris field of chemical waste, traces of the insecticide DDT.
TERRILL: Early in the history of our country, we thought the oceans made a perfect dumping ground. With the environmental revolution in the '70s, I think we quickly realized that this was probably not such a great idea, even if it was out of sight, out of mind.
INSKEEP: Dumping munitions in the water was also common during and after World War II. Today, researchers are studying how all that ocean waste affects our food chain.
MARTIN: Sophia Merrifield is another Scripps oceanographer who co-led the mapping assignment. She says there is still a lot more mapping to do.
SOPHIA MERRIFIELD: Just understanding what the human footprint was in the ocean, going back historically, and then understanding what the impact of those dumping activities are on the marine food web presently, I think is a really important societal effort.
INSKEEP: Now, more than 300 hours of high-resolution images may help to map those effects. Transcript provided by NPR, Copyright NPR.