What the heck is that green stuff in the Russian River?

Like clockwork, Sonoma County residents received warnings this summer about toxic algae blooms cropping up in laced mats along the Russian River.

“Where is it?”

“Is my dog going to die? What do I do if he drank the water?”

“Is there any place to go this summer?”

This year, questions of despair have been peppered with queries of curiosity, especially on social media.

“Does toxic algae have flowers?”

“Someone said you could eat the algae in the River? Isn’t it toxic?”

“Can I make biofuel from the algae in the River?”

The answers to the questions above, according to one of Sonoma Water’s resident botanists, Keenan Foster: “No, yes, yes/no and yes-ish.”

The bottom line is, “no matter what, we’re going to have algal blooms,” Foster said.

What type of algal bloom depends on a handful of factors, Foster said.

Historically, the algae growth in Sonoma County’s Russian River follows cycles of booms and busts. Algae, Foster explained, loves phosphorus and agricultural runoff into the river is typically rich in the mineral.

Algae feeds on the substrate of the river. Plankton grow out in water columns and love to eat the algae. Sometimes the algae have a head start and the plankton, despite their best effort, can’t keep up.

“It has to do with the winter before,” Foster said. “Was there good scouring? Good flow? If not, you’re starting a build-up already.”

Since 2014, Foster said, green algae have been coming back strong in the river.

“Every year, by mid-July or August, we start to see the blue-green algae on the edge of the river,” Foster said. “This is the algae that releases toxins that can be hazardous to animals and young children.”

This year, along with duckweed – an aquatic flowering plant – the Russian River is being blanketed with Azolla, an aquatic fern that’s part of the Salvinia family, the class of plants that includes all ferns. Foster describes it as a fluffy, pleated plant, versus duckweed’s lighter green appearance. According to Foster, Azolla’s presence has been on the rise in the Russian River over the past decade or so.

“We as a species haven’t see it a ton,” Foster said. “But it’s also kind of a canary in the coal mine.”

That’s because Azolla, Foster said, has historically experienced blooms during ecologically unstable periods.

A rather important, theorized unstable period in which Azolla thrived occurred between 50 and 90 million years ago, when blooms of Azolla were thought to have exploded in the Arctic Ocean. As it sank to the sea floor and incorporated into the sediment, the Azolla drew down an enormous amount of carbon dioxide, helping transform the planet into a so-called greenhouse state that enabled turtles and palm trees to establish themselves at the poles.

The Russian River’s Azolla bloom could be a mini-version of the Arctic Ocean event, Foster noted.

“This is my personal theory,” he said. “It’s tied to the elevated CO2 and the plant is hugely adaptable.”

He expects to see more of it.

As for what River goers should do?

“Leave it alone or completely get it out of the River,” Foster said.

The last thing people should do is haul to the riverbank to fester.

“It’s natural for us to want to take green stuff out of the River,” Foster said. “But bringing it to the shore on the edge gives it more food and substrate to feed on. That’s when it can become toxic.”

If you do remove Azolla or its cousin (by appearance only) Duckweed, Foster encourages residents to compost it.