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Tiny Algae Bloom By The Billions To Threaten Northwest Salmon

Right now coastal waters in the Northwest are a bustle - salmon are running, killer whales are showing up, and so are algae. Sometimes massive blooms of algae show up in coastal waters of the region, making shellfish unsafe to eat. These algae have a little-known cousin that’s bad news for salmon.

Towards the bottom of the marine food chain you’ll find Heterosigma Akashiwo. They’re among the smallest creatures in the ocean. And most of the time, they’re harmless. But every year, in the spring and fall, these microscopic phytoplankton join forces and become the terror of the sea.

Vera Trainer: “It is a heterosigma soup at times and that is the only cell you’ll see, in the water. You’re talking square miles, you’re talking about millions of cells per liter. The numbers are just amazing.”

Vera Trainer is the lead investigator with the National Oceanic and Atmospheric Association’s ECOHAB project. The research team is here on San Juan Island, trying to figure out what causes spikes in the population of heterosigma – which is lethal to salmon.

But to do that, they need to get up close and personal with this tiny critter in the lab.

Ashley Ahearn / KUOW
The ECOHAB team takes water samples near Orcas Island, in search of Heterosigma Akashiwo.

Vera Trainer: “And then over here is where we have our gill cells exposed to a number of heterosigma treatments.”

But why gill cells?

Vera Trainer: “If you look at a normal fish and a heterosigma-treated fish, the gills are essentially destroyed and they’re basically suffocating.”

Fish exposed to heterosigma often leap out of the water, gasping for breath.

Ok, so dead fish and toxic reddish algae soup in the water are the symptoms, but let’s look at the root of the problem.

In another room, Mark Wells shows me heterosigma under the microscope. Wells is a professor at the University of Maine, and a member of the ECOHAB team.

Ashley Ahearn: “Oh wow, they’re just kinda swimming around. They’re so cute! Wells: Cute? They are! They look a little bit like Slimer from the Ghostbusters.

Mike O'Connell manages of the Glenwood Springs Salmon Hatchery.

Ashley Ahearn / KUOW

Heterosigma kind of have Slimer beat though. These green single-celled organisms are a sort of “super bug” – a monster cross that combines photosynthesis with self-propelled movement. They have two little whip-like tails, or flagella, that propel them through the water column in search of nutrients.

During the winter months Heterosigma lie dormant as cysts on the ocean floor. When warmer weather arrives and the spring rains flush fresh water filled with nutrients into the ocean, they go crazy.

Charles Trick is a professor at Western Ontario University and a member of the ECOHAB team. He says there’s probably a connection between human activity and increased heterosigma blooms in the past 20 years.

Charles Trick: “Whether it’s putting fertilizer down, maybe aquaculture, some sort of land use that seems to be causing these species to be more prevalent in our waters now.”

Ashley Ahearn / KUOW
Vera Trainer and Mark Wells head out to collect water samples.

Research suggests that human inputs combined with warming ocean waters may be making conditions extra comfortable for harmful algal blooms.

The weird thing about heterosigma is that even though they’re almost always found in water samples this time of year, they’re not always toxic.

Charles Trick: “No that’s the secret. As longs as they’re growing fast and they’re happy they’re not making much toxin. It’s when their growth is slowing down, they’re starting to compete for other nutrients in the water and that makes them toxic at that stage - sort of that last man standing scenario.”

Heterosigma are scavengers and Trick says secreting a toxin into the water is a way for them to kill the competition for food.

But it’s the big fish - often salmon - that are accidental victims of heterosigma’s destructive quest for nutrients.

Near neighboring Orcas Island, the researchers collect water samples and then stop by to visit Mike O’Connell and Guinness, his big chocolate Lab.

O’Connell manages the Glenwood Springs Salmon Hatchery. We walk up from the dock to where his red pickup is parked next to a large pool teeming with juvenile chinook salmon.

Mike O’Connell: “They’ll be coming through here as they are right now, and down the fish ladder and out to sea.”

O’Connell says for several years returning salmon numbers were down and he didn’t know why. Then he heard about Vera Trainer’s work with harmful algal blooms and started releasing the young salmon earlier in May, before the heterosigma population spiked.

Mike O’Connell: “And we did see a huge number of fish return to our hatchery last year. Over 700, over our average, so we were very happy to see that take place and hopefully that will continue in the future.”

Heterosigma is bad news for wild and farmed salmon alike. Research on sockeye salmon in British Columbia’s Fraser River shows that in years when big heterosigma blooms occur, returning salmon numbers decrease by about 60 percent. Fish farmers lose between 2 and 6 million dollars worth of salmon with each heterosigma bloom

The ECOHAB researchers want to develop a test that will allow them to figure out immediately whether a bloom is hazardous, and then alert folks who work with salmon. That way hatchery managers like Mike O’Connell will know to release their salmon early, and fish farmers can have some extra notice to harvest their penned salmon before the blooms turn toxic.