Berkeley Marina Mussel Death
Seagulls pick at mussels on the Berkeley Marina dock. Credit: Supriya Yelimeli

On Monday afternoon, Paul Kamen kayaked in the Berkeley Marina harbor. The sky was blue, the sun bright, and the sea breeze gentle. But one thing was amiss: the water had turned a red-brown, almost chocolatey hue. 

Paul Kamen. Credit: Ximena Natera, Berkeleyside, CatchLight

“I’ve been coming here since 1973,” said Kamen, a longtime Berkeley sailor, consulting naval architect, and former Waterfront commissioner. “I’ve never seen anything like it.”

Then there was the stench, or as one Berkeleyside reader put it: a “distinctive porta-potty smell” coming from the water. Several docks had been turned into a makeshift seafood buffet by the gulls, which hopped around merrily and feasted on the piles of dead and dying mussels, occasionally picking up shells bigger than their beak. 

Scientists say these mussel deaths are likely connected to a red tide of Heterosigma akashiwo, microscopic algae that have been observed in the Bay since at least July, from Fremont to San Pablo Bay. According to the environmental group SF Baykeeper, “a bloom of this magnitude has not occurred in the region since 2004.” 

While toxicity to humans or pets has not been documented in the scientific literature, some local jurisdictions are warning residents to avoid water contact on a precautionary basis. Berkeley spokesperson Matthai Chakko said the city is waiting on guidance from state and regional water board agencies. 

Berkeley Marina Mussel Death
Don’t worry about the gulls, says Jonathan Shurin, an ecology professor at UC San Diego. “They eat garbage all the time.” Credit: Supriya Yelimeli

Like other affected marine life, the mussels are probably dying because they can’t breathe.

When high temperatures coincide with water high in nutrients, the algae proliferates and then dies off. As bacteria digest the algae, they consume large amounts of oxygen from the water, causing fish and other lifeforms to suffocate. Jonathan Shurin, an ecology professor at UC San Diego, likened it to overfeeding fish in a fish tank: “If you overfeed your fish in your fish tank, it can die, and it’s not because they eat too much. It’s because you’re overfeeding the bacteria in the water, and it uses up all the oxygen … and then the fish suffocate.”

This could be what’s driving the die-off. Or the algae itself could be toxic. Or both. Scientists still aren’t sure. What’s unlikely is that it’s heat alone, since there hasn’t been a major heat wave along the coast this month. 

The Berkeley Marina hasn’t seen the sort of apocalyptic mass fish death seen in Oakland’s Lake Merritt. Its position next to open water allows some species to swim out of the way of the algae and into deeper waters, where they can breathe.

Mussels aren’t so lucky. They are sessile, meaning they, much like trees, are dispersed as larvae and find a place to settle, where they grow into adulthood.

Mussel beds are “sort of like coral reefs,” Shurin said, in that they are habitats for other species. “If the mussel bed is completely gone for some period of time, then all those other species may suffer.”

The gulls eating the decaying mussels will be fine, though, he added. “They eat garbage all the time.”

Where did the algae come from?

Berkeley Marina Mussel Death
On the Berkeley Marina dock. Credit: Supriya Yelimeli

The bloom of Heterosigma akashiwo is natural and occurs every few years, but rarely in such incredible abundance. 

Damon Tighe is looking for more volunteers to help document the wildlife impacts of the algal bloom. No experience in identifying species is needed — just a phone camera. 

Damon Tighe, a community naturalist who documents wildlife at Lake Merritt, explained that this organism is always present in the water, but it spends part of its life in a “cyst” form, similar to a seed that floats or rests in the sediment, waiting until the conditions are right to grow, bloom, and reproduce.

For a variety of reasons we don’t yet fully understand, the conditions are great right now for Heterosigma akashiwo to grow. We do know that the algae need nitrogen and phosphorus to feed on. Some have speculated that wastewater outflows into the Bay from the many sewer districts where human and industrial waste flow could be providing these nutrients. 

A study of a red tide that killed fish in Florida last year showed that wastewater worsened the deadly event for fish and other wildlife. Others wonder if there was excessive runoff from agricultural fields in the Central Valley this year.

Iris Kwok covers the environment for Berkeleyside through a partnership with Report for America. A former music journalist, her work has appeared in the San Francisco Chronicle, KQED, San Francisco Examiner...

Before joining The Oaklandside as News Editor, Darwin BondGraham worked with The Appeal, where he was an investigative reporter covering police and prosecutorial misconduct. He has reported on gun violence...