Scientists Find Ash, Debris From LA Fires 100 Miles Offshore

Ash collected from a Manta plankton net, which samples the top six inches of the ocean. Initially, the ash floats on the surface, but once mixed with the water, it sinks rapidly, scientists with the Scripps Institution of Oceanography and NOAA reported on Jan. 20, 2025. Rasmus Swalethorp, Scripps Institution of Oceanography, UC San Diego

Ash and debris from the massive Los Angeles wildfires burning since Jan. 7 have been found in waters 100 miles off the coast of California, according to researchers.

Ocean researchers testing water near a military testing range on San Nicolas Island found ash and debris from the fires just one day after they erupted, according to a report published on Jan. 20.

A crew on the National Oceanic and Atmospheric Administration (NOAA) research ship Reuben Lasker was conducting testing near a sampling station past the island on Jan. 8, shortly after the fires started.

Two of the larger fires—Palisades and Eaton—have resulted in at least 27 deaths, and destroyed more than 16,000 structures in Pacific Palisades and Altadena, according to local and state officials. The cause of the fires is still under investigation.

The team knew about the fires from the news and could see large smoke plumes in the sky extending far offshore when they were near Catalina Island, according to the report from the Scripps Institution of Oceanography and NOAA.

“Seeing it snowing, but knowing it wasn’t snow but ash, was really eerie,” biological oceanographer Rasmus Swalethorp, director of ship operations for the Scripps Institution, said. “It seemed apocalyptic. I can only imagine how it must have been on land.”

The ship and its crew collected samples of the ash from the surface and from about 330 feet deep in the surrounding waters.

San Nicolas Island is one of eight Channel Islands off the Southern California coast. It is now owned by the U.S. Navy and used for weapons testing and training. It has served as a launch site for military research rockets.

It was also the setting for “Island of the Blue Dolphins,” a classic work of historical fiction based on the life of an American Indian woman who spent 18 years in isolation on the island.

The island is closed to the public.

NOAA adjusted the ship’s course to track any effects that the ash and debris might have on the marine ecosystem.

The source of the ash and debris gives scientists a “rare opportunity” to sample the fallout of ash from urban sources that contain household chemicals, building materials, and other substances, according to researchers.

“We’re positioning ourselves to answer the question, ‘What does this mean for West Coast fisheries and the food web that we all depend on?” Nicolas Concha-Saiz, NOAA Fisheries’ chief scientist for the investigation, said.

The scientists plan to also monitor for toxic substances that could affect one of the county’s most productive marine ecosystems, which supports commercial and recreational fisheries, according to the report.

The ship left San Diego on Jan. 3 for routine testing. After visiting the Port of San Luis Obispo along the central California coast on Jan. 18, crew members brought aboard specialized equipment to capture and test the ash particles in the water and to preserve them for trace metals and other analyses.

The ship returned to the site to resample the most affected area, located in and just off Santa Monica Bay.

The amount of debris observed and its source are concerning, according to project leader Julie Dinasquet of Scripps Oceanography.

“These fires are not only consuming vegetation but also massive amounts of urban infrastructure,” she said.

This introduces to the wildfire source “urban ash” that is filled with exceptionally toxic materials such as lead, arsenic, and asbestos fibers, and microplastics, which can pose significant threats to humans and the ecosystems, according to Dinasquet.

NOAA Fisheries’ scientists will monitor the ocean for the fires’ potential effects on fisheries and marine life, including how the ash might affect the anchovy eggs that are abundant in the water downwind of the fires.

The crew collected samples before and after the eggs were exposed to ash and other debris, to record any change in the number of eggs and the fires’ effect on early development, the report stated.

“We have painstakingly saved archives of samples with treasure troves of information,” Noelle Bowlin, a NOAA Fisheries’ director in California, said. “Any time there is a question, we can turn to the samples and see what changed.”

Seawater collected off the California coast by the Scripps Institution of Oceanography and NOAA will be tested for effects of ash and debris falling from the recent Los Angeles County fires. Rasmus Swalethorp, Scripps Institution of Oceanography, UC San Diego

Additional testing will look for traces of toxic materials in the tissues of plankton and larger fish, according to the report.

Scientists expect the ash and debris to be more harmful to the environment and ecosystem than the 2020 LNU Lightning Complex fires that sent ash falling into Monterey Bay, according to oceanography doctoral student Dante Capone, who studied the fallout from those fires. The LNU Lightning Complex fires are considered to be among the the largest wildfires in the state’s history.

On Jan. 22, NOAA Chief Survey Technician Jaclyn Mazzella uploaded a video of the ash seen floating in the seawater.