Chile's Record Toxic Tides May Have Roots in Dirty Fish Farming

A red tide crisis has stirred fishermen to unrest and may be at least partially linked to controversial aquaculture practices, while El Niño is also to blame.

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Shellfish divers protest against the Chilean government on Chiloé Island May 12, after toxic tides have ruined their catch.


Images of death have been arriving from southern Chile for weeks, each one seemingly more apocalyptic than the last. First there were thousands of dead salmon in aquaculture cages. Then there were rafts of dead sardines floating along the coast. Next, beached clams covered miles of shoreline. Then there were die-offs of jellyfish, birds, and even mammals.

So much death has sown panic among the public. Worried that their livelihoods are at risk, fishermen have taken to the streets, blocking roads and sowing unrest.

"People don’t dare to eat our fish because they're afraid it is contaminated, so we are all affected on the island," says Marcos Salas, president of the Fishermen's Union of Quellón, one of the main towns on the Chilean island of Chiloé. 

"We lost our labor source and now we have no way to bring sustenance to our families," says Salas. 

The Chilean government officially blames the marine mortality on blooms of toxic microalgae that are popularly known as red tide and says the root cause is likely warming of the Pacific Ocean thanks to this year's strong El Niño. It's the worst case of toxic blooms on record in the country. In response, the government has declared a state of disaster for the southern part of the country and is paying 100,000 Chilean pesos (about U.S. $150) to each impacted family.

But many fishermen say that's not enough. What's been happening in southern Chile is far worse than a "normal" red tide, they say, and it may be at least partially caused by poor regulation of the country's booming aquculture trade. Protestors have even blocked access to Chiloé, demanding answers and help from their government.

Unraveling the complex causes of the toxic blooms isn't easy, scientists warn. It is particularly difficult in Chile, where scientific monitoring hasn't been as rigorous or well supported as it should be, says Barbara Saaavedra, an ecologist who is the director of the Wildlife Conservation Society in Chile.

"Sufficient resources have not been allocated to study the problem," says Saaavedra.

Niño "Godzilla" or Salmon?

At the root of the problem are the microalgae. They are photosynthetic microorganisms that normally are a vital link in the ocean food chain, serving as sustenance to filter-feeding mollusks and other animals. But occasionally, the microalgae explode in numbers to form blooms. The exact conditions needed may vary but are probably related to water temperature, nutrients, salinity, light, and currents.

In some cases, the type of microalgae involved can produce a toxin that can be harmful to people. Sometimes the water is also stained red, leading to the common term "red tide." Filter-feeding mollusks can concentrate the toxins in their tissues. When people or animals eat the mollusks it can lead to severe illness or even death. 

Globally, microalgae blooms have been more prevalent this year, with scientists pointing to warmer waters from El Niño as a likely culprit. In fact, this year's cycle has been so powerful that some have dubbed it Niño Godzilla. 

"Chile had never seen such a peak in blooms, in terms of geographical extent, level of growth, and duration," reports the country's Association of Marine Biologists.

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Dead sardines blanket Tolten Beach in Temuco, Chile, on May 15.


From February to March this year, one of these blooms killed 25 million salmon in 45 farming centers in Chile. What happened next would prove to be controversial.

About thirty percent of the dead fish were taken to landfills. But the rest were thrown into the sea, about 80 miles (130 kilometers) from Chiloé island. That operation was authorized by the Chilean Navy and the fisheries managers.

A few weeks later, a wave of more dead sealife washed up on Chiloé. While the government has blamed El Niño, many on the island suspect the dumping of the dead salmon might have had something to do with it. It's one more example of the lax regulations of the country's aquaculture industry, they say, which has exploded since the 1970s, making Chile the world's second largest exporter of salmon.

Environmentalists have complained for years that Chile's aquaculture industry has polluted the water through feces and unfinished food, which may build up on the seafloor. 

It's hard to say whether the dead salmon can really be blamed for the red tide but it's possible they contributed to it, says Victor Marin, an oceanographer who works with the University of California and University of Chile.

"The dumping occurred at the same time there were ideal conditions for the bloom, namely: high amounts of nutrients in the area, optimal temperature, and other variables," says Marin. "It would be difficult to argue the salmon industry has not increased the amount of nutrients in the water, but our society also throws a lot of other stuff into the ocean, so there may be a synergistic effect."

An Uncertain Future

One problem with toxic blooms is that they take a while to clear out. Chiloé will likely have to wait several months before mollusks and other natural processes detoxify the water and make it safe enough for people to eat products form the area, says Patricia Gomez, a biologist at the University of Concepcion.

"It is expected that [bloom] events will decline as temperatures drop soon," she says.

However, some of the toxic microalgae species, such as Alexandrium catenella, can form tough cysts that are deposited on the seabed once the bloom ends. They can remain dormant for years, waiting for ideal conditions for proliferation. And scientists like Gomex warn that its hard to predict. 

The recent toxic blooms should encourage governments, the fishing industry, and the public to take a closer look at how our collective actions impact the health of the ocean, particularly as the climate changes, says Saaavedra.

"We need to better protect and manage ecosystems and contribute to the resilience of the ocean," says Saavedra. "Otherwise more communities may face apocalyptic situations."

Evelyn Pfeiffer is a journalist in Chile. Follow her on Twitter.

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