Decades-old industrial waste barrels dumped into the Pacific Ocean are still impacting the deep seabed off the coast of Los Angeles.
These barrels, often surrounded by mysterious white halos, may have leaked hazardous waste into the marine ecosystem, according to a recent study published on Tuesday in the Proceedings of the National Academy of Sciences Nexus.
Researchers noted that these barrels, observed in images from 2020, were filled with a variety of acidic wastes that had been dumped into the oceans between the 1930s and 1970s.
The study highlighted that DDT production not only created alkaline byproducts but that other industries, such as petroleum refining, also contributed significant alkaline waste. “One of the main waste streams from DDT production was acidic, but we didn’t actually put that in the barrels,” said Johanna Gutlben, a postdoctoral researcher at the Scripps Institute of Oceanography.
She raised an interesting point, asking, “What could possibly be worse than DDT acid waste that warranted being stored in barrels?”
Researchers found that the caustic waste leaking from these barrels transformed parts of the seabed into conditions similar to natural hydrothermal vents, which support specialized bacteria that thrive in extreme environments. However, the degree of impact varies based on the number of barrels and the chemicals they contain.
Interestingly, senior author Paul Jensen noted that he had expected the alkaline waste to break down quickly in seawater. However, he found that these contaminants persisted for over fifty years, suggesting a potential long-term environmental impact, comparable to DDT.
Though the exact number of barrels is unknown, the team used a remotely operated vehicle to gather sediment cores near five barrels. They then analyzed these samples for DDT levels, mineral content, and microbial DNA.
While they discovered elevated concentrations of chemicals near the barrels, their presence did not diminish with distance, leading researchers to conclude that DDT was not connected to the ongoing contamination.
In addition, they observed higher pH levels in the microbial DNA, indicating a strong presence of alkaline waste. The sediment deposits had lower bacterial diversity, comprised mainly of species suited to alkaline conditions, like those found in deep-sea hydrothermal vents.
Although the precise chemicals in the barrels remain unidentified, researchers are emphasizing the role of white halos in tracking the impact of alkaline waste.
Moreover, scientists are currently studying DDT-contaminated sediments from dump sites to find microorganisms capable of breaking down these toxic substances. “This adds to our understanding of the consequences of dumping these barrels,” Jensen remarked. “It’s surprising that even after more than fifty years, these effects are still apparent. While we can’t measure the full environmental impact without knowing how many of these halos exist, it’s clear they are affecting local microorganisms.”
