Another struggle after the Maui fires: keeping toxic runoff out of the ocean

With more than 2,200 homes and buildings destroyed in Lahaina, Maui, the rubble and ash will take months to clean up. The process has yet to begin, and another challenge is looming: keeping the toxic fire debris from pouring into the ocean.

Coral reefs sit just offshore from the town's razed waterfront, an ecosystem that's highly vulnerable to runoff. Residents who are sifting through the wreckage of their community don't want to see more damage done.

"The rain is going to wash everything away, and then our ocean is going to be dead," says Travis Cabanilla Okano, who lost his home in the fire. "Our reef – that's what my family lives on. We do fishing, diving. Everything we do is with the water."

State and federal agencies are now installing barriers to catch debris, as well as putting monitoring equipment in the ocean to measure the impact on the ecosystem. The toll the runoff could take is unknown, since there are few examples of such an extreme fire burning so close to a tropical reef.

With ocean temperatures also expected to be hotter than normal this year as the climate pattern El Niño continues, marine experts worry the reefs will decline.

"Coral reefs support the economies of coastal communities, not only through tourism and recreation fisheries, but also as first line defense against storm-driven flooding," says Curt Storlazzi, a research geologist who works on coastal hazards with the U.S. Geological Survey. "The runoff from these fires and upcoming rainstorms really has the ability to negatively impact those adjacent coral reefs and in turn, reduce their ability to protect the coastal communities."

Barriers being installed around storm drains

As the fire hit wood buildings in downtown Lahaina, high winds stoked flames that reached extreme temperatures. The resulting wreckage holds a vast amount of chemicals and metals.

"You've got a car and heavy metals in the catalytic converters," Storlazzi says. "But then you've also burned the fuel in the gas tank and the rubber tires. There's such a wide range of chemicals in there. Same thing in a house."

While Lahaina is located on the drier side of Maui, rainstorms could cause soot and debris to pour into storm drains, which empty into the ocean.

County workers have been installing barriers around storm drain openings, using long sausage-like tubes of organic material. They're designed to both catch large debris and filter some of the water passing through them. The U.S. Coast Guard is also putting absorbent booms in the ocean around the stormwater outlets, which capture oil.

"We're hoping to restrict any oil or hazardous material from entering into the water," says U.S. Coast Guard Lt. Trenton Brown. "Unfortunately I don't think we'll be able to stop it all, but we'll do our best."

To assess what contaminants do reach the reef, Hawaii state agencies are working with the U.S. Geological Survey to place monitoring equipment in the water. A sediment trap will collect larger particles for analysis, while special membranes absorb contaminants from the water itself. The hope is that the data will show which reefs may need urgent restoration or rehabilitation.

"It's an incredibly tragic incident, but these kinds of things are projected to occur in greater frequency and magnitude in the future," Stolazzi says. "So anything that we can learn now will allow us to provide better, impartial, sound scientific information in the future to hopefully avoid impacts and really increase the resiliency of these coastal communities."

Coral reefs become less resilient

Metals and contaminants from the fire could enter the bottom of the food chain in the ocean, which then become concentrated in fish as they eat those smaller animals. The runoff could also stress the coral, causing disease or even death. Even water that's clouded by dust could have an impact.

"What that does is it blocks the sun reaching corals, and corals are photosynthetic organisms so they need light to produce energy and therefore survive," says Jamison Gove, research oceanographer with the National Oceanic And Atmospheric Administration.

Ocean temperatures are already high across the globe, a result of both the El Niño weather pattern and rising temperatures from climate change. Marine heat waves cause corals to bleach, where they lose the algae in their tissue that they need to survive.

While corals can recover from bleaching events, research shows they're less likely to bounce back if they're already stressed by urban runoff.

"The resilience of those reefs to changing ocean temperatures is really important," Gove says. "So when we chronically impact reefs, like with coastal runoff in urban areas, we make them more susceptible to the impacts of climate change."

With the risk that some heavy metals and toxins could last in the environment for some time, health officials and scientists will need to monitor the lasting impact these fires could have.