The type of algae that killed thousands of fish in Lake Merritt and parts of the San Francisco Bay last year has been detected again in waters off the Berkeley Marina. While it’s too early to tell if this will grow into a similar harmful algae bloom, biologists and researchers are already springing into action.

And they want your help.

How to participate

Create an iNaturalist account and sign up to take part in the SF Bay Harmful Algae Bloom 2023 project.

When you join the project, be sure to adjust your settings so the researchers can see the exact geographic coordinates of your observations. For the data to be useful, researchers need to know exactly where you found a dead fish or crab.

The state Department of Fish and Wildlife has set up a project on iNaturalist to crowdsource observations of dead marine life in the Bay and Lake Merritt over the coming weeks and months. The goal is to track how the algae bloom might be affecting fish, bivalves like clams and mussels, crustaceans like crabs and shrimp, and other aquatic lifeforms. Researchers believe that the overgrowth of algae consumes too much of the oxygen in water, suffocating fish and other creatures.

“Taking part in this project will allow us to understand the impact of the harmful algae bloom in the Bay and inform policy to help us get to a point where we’re not having these as frequently,” said Damon Tighe, a naturalist who helped the Department of Fish and Wildlife set up the data-gathering project. 

Tighe organized on his own a similar effort last year to track the red tide’s impact, logging over 4,000 observations on iNaturalist of creatures like sturgeon, razor clams, and marine worms.

“It was a really valuable experience in citizen science,” Jim Hobbs of the California Department of Fish and Wildlife said about Tighe’s 2022 crowdsourcing effort. “The department couldn’t have responded to this quickly enough to survey that much shoreline.”

Hobbs said the Department of Fish and Wildlife combined data from last year’s iNaturalist observations with data from other sources to come up with mortality counts of specific fish species like white sturgeon. The numbers will eventually inform a report on the 2022 red tide event. They’ll also be used by state agencies to inform policies, like whether or not to allow people to harvest sturgeon and other fish, or how to better regulate the nutrient runoff into the Bay from waste treatment plants. It’s the nutrients — mainly nitrogen and phosphorus — in wastewater emissions that algae feed on, allowing enormous blooms that can result in oxygen depletion in the water, and sometimes the production of toxins that kill wildlife.

Fish and Wildlife was quick this year to set up the new project, knowing how valuable the data is.

Katie Noonan of Rotary Nature Center Friends, a group that educates the public about Lake Merritt, said she thinks the tracking effort is important. The species of algae responsible for the fishkills, Heterosigma akashiwo, will almost certainly find its way into Lake Merritt from the Bay. “If the conditions are prime in Lake Merritt, it’ll bloom there.”

Noonan said she hasn’t seen any sign of the algae during her recent water quality tests. She sampled lake water on Tuesday and found no traces of Heterosigma akashiwo. She also sent water samples to a lab in Sacramento for more precise testing.

There’s been one small fish kill event in the lake this year, according to Noonan. It happened on July 5 along Lakeshore Avenue when a group of anchovies washed up dead. Noonan said a cause was never identified, but she noted there were lots of discarded, burned-out fireworks nearby from the Fourth of July celebrations.

James Robinson, executive director of the Lake Merritt Institute, said if the red tide blooms in the lake again and kills marine life, it’ll be a “one-two punch” to the ecosystem.

“I’ve been seeing fish come back. So this would be a bummer for it to hit right after the catastrophic red tide last year. It’s not just marine life. It’ll affect the birds that come here.” he said.

The Lake Merritt Institute, the city, and other stakeholders have been working to replace several of the old fountains in the lake with new fountains that could provide better shelter for fish and other aquatic life by oxygenating small patches of water during algae blooms. The old fountains look nice, but according to experts, they aren’t very good at mixing oxygen into the water. Robinson said the new fountains haven’t been installed yet and that there’s only one of the older types currently in place in the Glen Echo arm near Children’s Fairyland.

A Chinook salmon recently washed ashore near the Berkeley Marina, documented by jfmclaughlin92 for the SF Bay Harmful Algae Bloom 2023 project. Credit: jfmclaughlin92/

Among the handful of observations added to the new iNaturalist project Tighe pointed out that one of the dead fish is what’s commonly known as a shovelnose guitarfish, a type of ray that’s considered “near threatened” by the International Union for the Conservation of Nature, a global organization that advocates for the protection of biodiversity. A dead Chinook salmon was also recently spotted washed up near Berkeley.

Although it’s not possible to say whether these fish’s deaths were linked to the emerging harmful algae bloom, the observations will be of value for researchers thinking about whether or not to close a particular fishery next year, or whether or not sewage treatment facilities should be required to further reduce the algae-producing nutrient loads in wastewater they pump into the bay.

Before joining The Oaklandside as News Editor, Darwin BondGraham was a freelance investigative reporter covering police and prosecutorial misconduct. He has reported on gun violence for The Guardian and...