When sea lions suffered seizures and birds and porpoises started dying on the California coast last year, scientists weren’t entirely surprised. Toxic algae is known to harm marine mammals.
But when researchers found enormous amounts of toxin in a pelican that had been slurping anchovies, they decided to sample fresh-caught fish. To their surprise, they found toxins at such dangerous levels in anchovy meat that the state urged people to immediately stop eating them.
The algae bloom that blanketed the West Coast in 2015 was the most toxic one ever recorded in that region. But from the fjords of South America to the waters of the Arabian Sea, harmful blooms, perhaps accelerated by ocean warming and other shifts linked to climate change, are wreaking more havoc on ocean life and people. And many scientists project they will get worse.
“What emerged from last year’s event is just how little we really know about what these things can do,” says Raphael Kudela, a toxic algae expert at the University of California, Santa Cruz.
It’s been understood for decades, for example, that nutrients, such as fertilizer and livestock waste that flush off farms and into the Mississippi River, can fuel harmful blooms in the ocean, driving low-oxygen dead zones like the one in the Gulf of Mexico. Such events have been on the rise around the world, as population centers boom and more nitrogen and other waste washes out to sea.
“There’s no question that we are seeing more harmful blooms in more places, that they are lasting longer, and we’re seeing new species in different areas,” says Pat Glibert, a phytoplankton expert at the University of Maryland. “These trends are real.”
But scientists also now see troubling evidence of harmful algae in places nearly devoid of people. They’re seeing blooms last longer and spread wider and become more toxic simply when waters warm. And some are finding that even in places overburdened by poor waste management, climate-related shifts in weather may already be exacerbating problems.
Fish kills stemming from harmful algal blooms are on the rise off the coast of Oman. Earlier this year, algae blooms suffocated millions of salmon in South America, enough to fill 14 Olympic swimming pools. Another bloom is a suspect in the death last year of more than 300 sei whales in Chile.
In the north, blooms are on the rise in places like Greenland, where some scientists suspect the shift is actually melting ice. Just this year, scientists showed that domoic acid from toxic algae was showing up in walrus, bowhead whales, beluga, and fur seals in Alaska’s Arctic, where such algae species weren’t believed to be common.
“We expect to see conditions that are conducive for harmful algal blooms to happen more and more often,” says Mark Wells, with the University of Maine. “We’ve got some pretty good ideas about what will happen, but there will be surprises, and those surprises can be quite radical.”