In Brief:
Scientists analyzed coastal water quality in the months following a major Southern California wildfire. Their results were eye-opening.
The November 2018 Woolsey Fire in Southern California’s Los Angeles and Ventura counties left more than a nearly 100,000-acre burn scar behind: It also left the adjacent coastal waters with unusually high levels of fecal bacteria and sediment that remained for months.
For a new study, published in Nature Scientific Reports, scientists combined satellite imagery, precipitation data, and water quality reports to assess two standard parameters for coastal water quality after the fire: the presence of fecal indicator bacteria and the turbidity, or cloudiness, of the water.
Fecal indicator bacteria originate from the gastrointestinal tracts of humans and other warm-blooded animals. While they’re not harmful, they indicate the presence of other bacteria and pathogens found in feces that can be. Turbidity has other implications: Cloudy, murky water results in less sunlight reaching marine life – like kelp and phytoplankton – that rely on it to survive.
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When it rains, runoff typically carries some bacteria and sediment from the land to coastal waters. But the huge spike in both following the fire was anything but typical.
“Post-fire, we saw drastic water quality changes, particularly at beaches draining the burned area,” said the study’s lead author, Marisol Cira, a UCLA Ph.D. candidate and an intern at NASA’s Jet Propulsion Laboratory in Southern California. “In those areas, both total coliform bacteria and enterococcus were far greater than pre-fire levels, as was turbidity plume size.”
The …