One year ago when a harmful algae bloom spread to Lake Merritt, killing thousands of fish and other creatures, the fountain that used to spray a pleasant cone of water high into the air near the Pergola and Colonnade wasn’t running. The fountain—which could have been activated to churn oxygen into the water, perhaps saving some fish—had been pulled from the water because it was clogged with silt, algae, and other debris.
Last week, the city finally installed a new fountain in the same place, although the device isn’t really considered a fountain by water-quality experts: Technically, it’s a “surface aerator” that’s designed to agitate the top of the lake so more oxygen is dissolved into the water.
Eli Kersh of LakeTech, an Oakland-based company that helped install the fountain, said the aerator is “simple to maintain and low-cost,” and best of all, it should help lake-dwelling creatures survive if another algae bloom depletes Lake Merritt’s oxygen levels.
“The fish like the currents these things generate,” said Kersh about the new aerator. “They swim in place and the food comes to them.”
The five-horsepower aerator has another advantage over the old fountain: Because it floats, it’s less likely to suck in muck and debris off the lake bottom and become clogged.
The device is the first of what lake stewards hope will be several interventions to improve water quality and create tiny safe havens where fish, crustaceans, mollusks, worms, and other aquatic life can survive during red tides. Kersh and others have been working for almost a year to gather data about oxygen levels and other environmental fluctuations in the lake. They’ve used this information to devise a pilot project to improve water quality throughout the year—but especially during red tides.
James Robinson, the executive director of the Lake Merritt Institute, a nonprofit that helps look after the lake, said the new aerator is just as pleasing to the eyes as the old fountain—and it already appears to be attracting more wildlife.
“I walked by it the last couple of days and there were lots of brown pelicans,” said Robinson. “There’s a lot of fish that hang out around the [aerator].”
Robinson said some of the small fish schooling in the circulating water might be smelt. When smelt swim near the surface and turn quickly on their sides, often to devour a morsel of plankton or a tiny crustacean, their sides give off a silvery flash. This is a signal to the brown pelicans hovering overhead. The birds dive-bomb and trap the fish in their billowing gullets before gulping them down.
Kersh said the next device that will go into the lake won’t be as noticeable, but it has much greater potential to improve water quality.
In September, Kersh and the city are hoping to install a pair of seven-foot plastic cylinders at the bottom of the lake’s Glen Echo arm, near Children’s Fairyland. Under pressure inside the cylinders, the cold salty water pulled in from the bottom of the lake will be injected with the gas supplied from tanks on shore. Once oxygen levels inside the cylinders are two to three times higher than what’s in the lake, the tubes will release the water, which will spread under the surface layer. This could create a modest, deepwater refuge for fish if the lake’s overall oxygen levels plummet to dangerous levels.
“This is really cutting edge,” Kersh said about the technology.
Robinson said he hasn’t noticed any sign of the Heterosigma akashiwo algae in the lake that caused last year’s fish kill. He investigated a report of dead fish last week near the channel to the Bay but didn’t find anything. “Luckily, Lake Merritt hasn’t been affected yet,” he said.
The algae has been detected in the Bay near Berkeley and Emeryville’s shorelines. Researchers have asked the public to report any signs of dead fish or other marine life.
“I think we dodged a bullet,” said Kersh about the apparent absence of harmful algae in the lake so far. “We’re all very fortunate for that.”
But Kersh and Robinson both said it only takes a few days for algae to flow into the lake and bloom to dangerous levels, and more research and new interventions are needed to prevent another massive marine life die-off.
