The Reuben Lasker was about four miles off the coast of Manhattan Beach when ash began to rain upon the sea — first in delicate flurries, then in noxious clouds.

The fisheries research vessel had set sail days earlier for a coastal survey. It was supposed to be a routine voyage, the kind that the California Cooperative Oceanic Fisheries Investigations (CalCOFI) program embarks upon four times a year as part of the world’s longest-running marine ecosystem monitoring effort.

But when the Palisades and Eaton fires broke out, scientists aboard the National Oceanic and Atmospheric Administration ship inadvertently became the first investigators on the scene of a brewing disaster that could upend life underwater.

The smoke that has choked Los Angeles, the debris piled up along decimated streets, the charred and toxic remnants of thousands of destroyed homes, businesses, cars and electronics — nearly all of it, eventually, will come to rest in the ocean.

There is no precedent for how an urban fire of this magnitude could change the ecosystem that countless species, including our own, rely on for food and sustenance.

Scientists on board the Reuben Lasker wear goggles and masks to shield themselves from smoke while observing seabirds and marine mammals.

(Rasmus Swalethorp/Scripps Institution of Oceanography)

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But there’s also no team better equipped to understand how the fires that transformed Los Angeles will affect life in the sea.

Unlike the smoke that emanates from rural wildfires, the charred material now entering the ocean is the stuff of “people’s homes: their cars, their batteries, their electronics,” said Rasmus Swalethorp, a biological oceanographer at UC San Diego’s Scripps Institution of Oceanography. “It’s certainly going to contain a lot of things that we ideally don’t want to see in our oceans — and in our soils, for that matter, and our water streams, and certainly not on our dinner plates.”

CalCOFI was formed in 1949 to study the collapse of the sardine industry, in a joint effort by Scripps, NOAA Fisheries and state fish and wildlife officials.

But scientists quickly realized that question could only be answered by studying the interconnected layers of the broader marine ecosystem.

CalCOFI began to methodically collect detailed ocean samples from the same 113 locations multiple times a year, along a systematic grid that spans the California coast. Millions of samples of plankton, fish eggs and marine animals have since been preserved in its archives, providing invaluable snapshots of the ocean over time.

Since 1949, scientists at Scripps and NOAA have systematically collected samples from more than 100 stations across the California coast.

(CalCOFI)

As this month’s fires raged on land, the Reuben Lasker continued that orderly lawnmower-style route through the sea. Its researchers from Scripps and NOAA’s Southwest Fisheries Science Center donned goggles and masks. Wildlife counts were temporarily suspended when the smoke became too thick to make out seabirds and marine mammals.

Fire debris clouded the ocean’s surface as far as 100 miles offshore. Once-white collection nets came up blackened with soot and charred detritus. As the team hauled up samples of ash-filled seawater, Swalethorp recoiled at the odor, which was unlike that of any wildfire smoke he’d encountered before.

“It didn’t have your typical bonfire smell to it,” said Swalethorp, who runs CalCOFI’s ship operations. “The first thing that sprang to my mind when I smelled it, and immediately pulled away, was: this smells like burned electronics.”

A typical CalCOFI cruise collects data on everything from water clarity to local plant and animal species. The program’s decades-long data archives make it ideal for studying long-term changes to marine ecosystems.

“I don’t think there’s a precedent for this kind of input into the ocean ecosystem,” NOAA Fisheries’ CalCOFI Director Noelle Bowlin said of the fires. But with 76 years of data to measure against, “we can provide the context needed to answer the question of, how big of a perturbation is this event?”

CalCOFI researchers hold up once-white nets blackened by soot and charred debris. His first reaction to pulling up the nets, one team member said, was: “This smells like burned electronics.”

(Rasmus Swalethorp/Scripps Institution of Oceanography)

The samples collected at the start of the fires can help provide much-needed answers on whether higher concentrations of toxic metals, PCBs, PFAS and other forever chemicals will wind up in the ocean — and for how long, said Mark Gold, an environmental scientist at the Natural Resources Defense Council.

“It’s so serendipitous, having CalCOFI being there literally during the catastrophe and being able to collect such extensive samples,” Gold said.

Among the most immediate concerns is ocean water contamination. In addition to the already-massive footprint of ash offshore, Gold noted that runoff from the first few rainstorms is a huge concern. He’s had a flurry of conversations with city, county and state officials, who have been trying to proactively limit the amount of fire pollution going into the ocean.

Imagine Los Angeles County, framed by foothills and mountains, as a giant bowl tilted toward the sea. Whenever it rains, water rushes off rooftops and down streets and sidewalks, picking up any pesticides, trash, car tire residue and other contaminants in its way.

Unlike the region’s sewage, which is filtered through treatment facilities before it’s discharged, this mix of rainwater and debris usually flushes straight into the ocean through a massive network of storm drains and concrete-lined rivers.

CalCOFI researchers found ash and debris on the ocean’s surface as far as 100 miles offshore.

(Rasmus Swalethorp/Scripps Institution of Oceanography)

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The rain this week was the first significant precipitation in the region since May. In addition to the fires’ ash and chemical residue, it was also the first flush of nine months’ worth of daily pollution into the sea.

Local environmental groups like Heal the Bay have urged beachgoers to avoid water contact at any beaches from Malibu’s Surfrider Beach down to Dockweiler State Beach near L.A. International Airport.

The Los Angeles County Department of Public Health has issued similar ocean precautions and even beach closures, along with a map of closed or contaminated beaches.

Public health officials cautioned that even the sand may contain toxic or carcinogenic chemicals, advising beachgoers to avoid any fire debris and any runoff that may flow onto or pond on the beach sand. Gold, as an extra precaution, added that he wouldn’t swim or surf in the water for at least two or three weeks after it rains.

Longer term, there are serious questions about whether contaminants released by the fire will penetrate the food chain.

Ash from forest fires can sometimes boost the growth of phytoplankton, the microscopic algae at the base of the marine food web, thanks to the infusion of nutrients from burned plants. No one yet knows how a massive infusion of ash from urban fires — with its mix of asbestos, lead, microplastics and heavy metals — will affect our food supply.

The CalCOFI team collected samples of seawater contaminated with fire debris.

(Rasmus Swalethorp/Scripps Institution of Oceanography)

“Is it going to be having an impact on all the food web interactions, starting with the base of the food chain, the phytoplankton and the microbes, and then slowly accumulating … all the way up to the fish that we are eating?” said project leader Julie Dinasquet, a Scripps marine ecologist. “Maybe in a few months to a year, people are going to realize that there’s a bioaccumulation of heavy metals in [these fish], or something else from these fires.”

L.A.’s devastating fires are only the latest episode in which the ocean has served as an unappreciated receptacle for trash and hazards originating on land.

A series of Times reports in recent years have unraveled a haunting history of how the nation’s largest manufacturer of DDT had once dumped its waste at sea, just off the coast of Los Angeles. Further research has since uncovered that this part of the ocean had also served as a dumping ground for military munitions and radioactive waste.

“To me, the circumstances and the magnitude of these fires have shown that the L.A. region is not climate resilient at all,” Gold said. “One of the consequences of not being climate resilient … is that the ocean once again becomes a dumping ground, whether it’s intentional or not.”