Scientists aboard the research vessel Reuben Lasker were conducting surveys of marine life off the Southern California coast in early January when ash from the Los Angeles wildfires began to rain down on the ship. "It's like a winter day with big, fluffy snowflakes falling around you, except these weren’t snowflakes,” said oceanographer Rasmus Swalethorp. "It didn’t smell like burned wood; it smelled very synthetic, like burned electronics.”
Being in "the right place at a horrible time,” said Swalethorp, has given researchers a rare opportunity to collect real-time data on catastrophic urban wildfires’ effects on ocean ecosystems and commercially valuable fisheries. Even as climate change-driven wildfires burn ever-larger swathes of California, their impact on the ocean remains little studied. Increasingly fast-moving infernos can burn tens of thousands of acres within hours, but it can take months to launch expensive ocean-going scientific expeditions.
The few existing studies mainly focus on marine effects from forest fires that combust organic matter. One paper on the 440-square mile (1,140 square kilometer) Thomas Fire in Southern California found that woodland ash that fell in the Santa Barbara Channel in 2017 promoted the growth of plankton. The more than 15,000 structures that burned in the LA fires, on the other hand, incinerated unknown amounts of plastic, pesticides, asbestos, herbicides and lithium-ion batteries, releasing carcinogenic clouds of ash that blew far out to sea.
"These fires are bringing tons of toxic compounds into marine ecosystems,” said Julie Dinasquet, an associate project scientist at the Scripps Institution of Oceanography at the University of California at San Diego. "We want to find out if these toxins are going to be mixed up in the food web and then start accumulating in the fish that people eat.”
Dinasquet is leading an investigation into LA wildfire impacts by scientists at Scripps and the National Oceanic and Atmospheric and Administration (NOAA). When the wildfires ignited, the Reuben Lasker, a 209-foot-long NOAA ship, had just embarked on a quarterly expedition along the California coast. It was one of the California Cooperative Oceanic Fisheries Investigations (CalCOFI) surveys that have been conducted continuously since 1949.
"Since every fire is different and every coastal ecosystem is different, it is really important to keep monitoring the effects of wildfire ash and smoke across fires and coastal ecosystems,” said Sasha Kramer, a postdoctoral fellow at the Monterey Bay Aquarium Research Institute who co-authored another study on the 2017 Thomas Fire.
Every year, CalCOFI research vessels travel from San Diego to San Francisco, moving in transects from coastal waters to 300 miles offshore as they collect data on ocean chemistry and marine life, from plankton to whales. On Jan. 8, the Reuben Lasker’s 39 scientists and crewmembers were about 140 miles offshore when they spotted huge plumes of yellow smoke in the sky. As the ship traveled toward the coast, they saw ash and debris littering the water.
About four miles offshore of the Los Angeles County community of Manhattan Beach, the ship deployed a net below the surface to collect plankton, tiny organisms that form the basis of the marine food web. "This net is usually white, but when it comes up, it's completely black, and the sample inside the net is also completely full of ash and debris,” said Swalethorp, director of ship operations and an associate project scientist at Scripps.
Scientists continued to catch ash and debris in their nets as far as 100 miles from the coast. They collected samples down to a depth of 140 meters (460 feet), and when the ship stopped in port on Jan. 18, researchers brought aboard equipment to take air samples and identify metals in the ash that could be used to trace the movement of toxins through the marine environment and the food chain.
One worry: California anchovies were spawning as the wildfires erupted. They’re a crucial food for seabirds, salmon, tuna, sea lions and whales. "We saw a lot of anchovy eggs in the water, so if you introduce a lot of toxins to the water, that could impede the development of these eggs, and they may turn out to be nonviable,” said Swalethorp.
Winter rains will magnify such threats as toxic-contaminated ash and soil wash into coastal waters. Last week, another Scripps scientist, Dante Capone, began taking water samples from nearshore areas, hitching a ride on a sanitation district boat.
"The concentration of anthropogenic pollutants that might be entering the water is completely different than those from wildland fires, and we expect there'll be more ecotoxic effects,” said Capone, a PhD student whose dissertation focuses on wildfire impacts on the coastal environment.
Next week, Capone is set to sample the waters around Santa Monica Bay and is planning another expedition farther up the coast. The next CalCOFI cruise departs March 20, presenting another opportunity to measure the ramifications of the wildfires, according to Swalethorp.
"This is the first chance that we really have to study the impacts when all of these things that we keep in our homes burn and then get deposited into the ocean,” he said.
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