Del Mar Times |

Scripps researchers’ surprising find scanning the ocean floor: Thousands of WWII-era munitions and whale skeletons

New research from the Scripps Institution of Oceanography has revealed numerous discarded World War II-era munitions off the Southern California coast — the latest discovery in the team’s efforts to better understand industrial waste dumping in Southern California waters.

Friday’s unveiling of those findings follows a sea floor survey the researchers conducted in April, their second of two undersea dump sites in a stretch of ocean between Long Beach and Santa Catalina Island.

The work is part of a larger project with researchers across the region to assess the San Pedro Basin sites, where decades of dumping chemicals like DDT and other pollutants have raised environmental and human health risks.

After a 2021 survey showed thousands of barrel-sized objects on the sea floor, the researchers returned to the sites last year with more advanced technology — including higher-resolution acoustic sonar imaging techniques — and the ability to classify objects with video imaging.

Most of those objects, they learned, appear to be military munitions and pyrotechnics discarded roughly 80 years ago.

Scripps oceanographers Sophia Merrifield and Eric Terrill led the latest study using a deep-water autonomous vehicle with sonar capabilities and a remotely-operated vehicle with an high definition video camera, which can work in depths of 6,000 meters, or 19,600 feet.

With these tools, they were then able to map 135 square miles of seafloor and capture more than 300 hours of video footage, Scripps said.

“Because there are so few large-area, deep ocean surveys that have happened anywhere in the world, this concerted effort, including active acoustics and visuals, as well as chemical and biological analysis, really is a unique broad area survey effort,” said Brice Semmens, a Scripps marine biologist and the lead investigator on the overarching research project, at a press briefing on Friday.

The project, backed by $5.6 million in federal funding, aims to characterize and research potential environmental impacts of the DDT dumpsite. Another $6 million was awarded in September to further evaluate contamination and assess mitigation strategies.

From the 1930s to the 70s, the two sites were commonly used as dumping grounds for industrial waste, including byproducts from DDT manufacturing, a chemical used as an insecticide that was banned in 1972.

The presence of DDT in California and off its coast has had a lasting environmental impact: Significant amounts have been found in endangered California condors, and the chemical has been linked to cancer in sea lions.

But chemicals weren’t the only waste items dumped in the San Pedro Basin. In the mid-20th century, the U.S. Navy was also approved to dispose of munitions in this area when naval vessels returned to U.S. ports.

In this survey, the Scripps researchers identified munition boxes, Hedgehog and Mark 9 depth charges and Mark 1 smoke floats, chemical smoke munitions used to conceal a ship’s movement or mark locations.

The researchers cannot say precisely how many munitions were found — only that most of the roughly 25,000 barrel-like objects spotted in 2021 are munitions.

Scripps said in a statement that the Navy would “be reviewing the findings to determine the best path forward to ensure that the risk to human health and the environment is managed appropriately and within applicable federal and state laws and regulations.”

The Scripps research expedition was done in partnership with the Navy’s Supervisor of Salvage and the Office of Naval Research.

Along with the discovery of discarded munitions, the researchers also identified what appeared to be more than 60 whale falls — sunken whale carcasses — with sonar data. They were able to confirm seven of them with the video imagery.

The whale falls are located about 900 meters — or 3,000 feet — below the ocean’s surface, according to Greg Rouse, a marine biologist at Scripps. At such depths, the low levels of oxygen can impact the rate at which skeletons decompose.

That means more research is required to determine when and why the whales died.

But Craig Smith, a benthic ecologist at the University of Hawai’i at Manoa, said the revelation of the carcasses alone roughly doubles the number of whale falls known to exist in the worlds’ ocean. About 50 natural whale falls have been studied globally.

“It’s a remarkable find,” Smith said. “It also provides the first opportunity to really study in detail whale falls under low-oxygen conditions to document how things may change.”