Unravelling a scientific mystery: Could wildfire ash end up in our fish dinner?
Researchers hope what they're finding in California waters could help Canada's coastal communities
Together, the two creatures lurking in the depths weigh as much as a thousand average humans. But the only hint of their presence is the ring of bubbles forming at the surface of the ocean. Moments later, two gaping, barnacled mouths explode through the waves and take a school-bus-sized gulp of fish and water.
Kelsey Bisson may be a marine biologist, but even she gasps at the sight of humpback whales lunge-feeding near her research vessel.
"That was awesome!" says Bisson. "I've never seen humpback whales that close before in my life!"
The humpbacks may be awesome, but they're not the sea creatures Bisson is hunting for. To see her quarry, she needs a microscope. And her "harpoon," which she launches repeatedly off the stern of the research vessel Shearwater, collects them by the millions.
Bisson is on a mission that, to her knowledge, has never been attempted before: to find out how microscopic marine plants, animals and bacteria have been directly affected by wildfire.
Last December, Bisson, a graduate student at UC Santa Barbara, had planned a research expedition off the Santa Barbara coast to study the local microorganisms. But shortly before her trip, an unprecedented wildfire broke out in nearby Ventura County. The Thomas Fire devastated several coastal communities around Santa Barbara, eventually becoming the worst blaze in California's recorded history.
Then and there, she decided to switch the focus of her research and examine how these clouds of ash might affect creatures along the ecologically sensitive Santa Barbara Channel.
"It gave us a chance to leverage our resources and just kind of pivot our goals a little bit to try to accomplish something," Bisson says.
'A big question mark'
In California, wildfire is an inexorable stage in nature's cycle, and scientists already know that volcanic ash that ends up in the ocean often provides nutrients for marine organisms.
"When these things are put into the air, knowing how they're going to react with seawater is a big question mark," Bisson says. "It's human and man-made materials that are being combusted at high temperatures, and having those interact with the ocean is a different question."
To answer that question, Bisson and her colleagues take to the waters of the Santa Barbara Channel. They stop at several locations up to 40 kilometres off the coast, then use a winch to lower a mechanism called a CTD (which stands for conductivity, temperature and depth) into the ocean.
Researchers filter the samples collected by the CTD in a makeshift lab aboard the boat, which Bisson studies later on land.
"We'll be able to do different analyses like DNA extraction and things like that to say what exactly is in the water, at what depth and what does that indicate about the ecosystem," Bisson says.
'It was really intriguing'
Bisson says she wasn't surprised on that first trip in December 2017 to find plenty of ash particles floating in the water she analyzed. But she never imagined how far down the ash would settle.
"We were able to see microscopic shards of ash in water samples that are both in the surface ocean and also ones that were at 400 metres deep," Bisson says.
"We saw things in the ocean from a biologic micro-organism point of view that we hadn't expected to find in December," Bisson says. "It was really intriguing. We think that maybe their presence in the water was spurred by the fire. And that's a running hypothesis right now that we're testing."
Three months after the Thomas Fire, Bisson is again aboard the Shearwater, operated by the National Oceanic and Atmospheric Administration. Again and again, the CTD plunges to various depths, measuring the ocean conditions and bringing back samples teeming with invisible marine life that has possibly been altered by far away events on land.
"When there's big, big rains like the ones that we're having right now, it's basically flushing all of the valleys that at this point now have a ton of ash in them," Bisson says.
The fact that she found ash near the bottom of the ocean suggests it could have a lasting effect on the food chain.
"The toxicity has a residence time, and it lingers and it stays, and that can then be carried from a very small microscopic level up to a level that we can see like in fish," Bisson says.
Fire-derived ash in seawater hadn't been studied before, but once news of Bisson's research became public, she says she was contacted by scientists asking for water samples.
"I think their research is truly cutting edge," says B. B. Cael, who studies ocean physics at MIT and the Woods Hole Oceanographic Institution. "The question they are asking – how do wildfires affect nearby marine ecosystems – is not only an important one given that wildfires are projected to increase in size and frequency, but also one for which virtually no data exist today... I expect it will provide novel insights for our understanding of the total environmental impact of these wildfires."
As housing development in areas adjacent to wilderness has increased, so has the number and size of mega-fires. Understanding their effects across the entire ecosystem, she says, may eventually play a role in mitigating the long-term damage.
"Ideally, what we'll be able to have and share with the community will be applicable at a global and broader scale," Bisson says. "Our hope is that whatever we can find and what things that we can learn can help inspire people to be better stewards of their environment and better community citizens."
As the Shearwater returns to port, Bisson acknowledges that the data she has collected on these recent expeditions is still just raw research, and that she still has plenty of work to do before she can publish any results. But if Bisson had any doubts about the importance of her research, she says all she has to do is look down at the dolphins surfing in the boat's wake.
"Sometimes when we look through microscopes all the time, our view of oceanography sometimes is very focused," Bisson says. "Any time we can get out here, we feel excited and grounded in what we're doing... and why we're doing it in the first place."