Summer Algal Bloom and Aquatic Grass Growth Forces Boats Off the Water in Berkeley’s Aquatic Park

July 27, 2017

The final approach to the dock at the Berkeley Paddling and Rowing Club at Berkeley’s Aquatic Park usually takes Ellen Braithwaite about 30 seconds to row. But on the 4th of July, it took her nearly 20 minutes. The reason? Dense grasses accompanying a summer algal bloom.

The Aquatic Park lagoon has been covered with algae since late June, and while blooms there are typical this time of year, Braithwaite, who is on the club’s board of directors, says this summer’s algae and aquatic growth seems heavier than usual. It’s easily visible from the Eastshore Freeway, a two-inch thick yellow-brown blanket rolled over the lagoon. “It’s lasted longer, it seems to be thicker,” Braithwaite said. “It’s been almost impossible to leave the dock.”

Susan Ferrera, the superintendent of parks for the city of Berkeley, agreed this year’s bloom is bigger than it has been in recent years, with more algae and denser widgeon grass, an aquatic plant that thrives in brackish water like the lagoon. The city typically times its yearly maintenance of the lagoon to coincide with the full bloom of the widgeon grass, and in recent days, the parks division has been out on the water with a harvester that cuts the plants just below the water level and picks up dead grass and algae.

The harvester won’t clear all of the growth, but Ferrera said the goal is to allow for recreational use of the water, so that groups like the rowing club and the Berkeley Water Ski Club can return to the water. They’re also hoping to clear enough of the water so that candlelight lanterns can be floated across the lagoon during Berkeley’s annual peace lantern ceremony on August 5.

But the grass and algae will return. “It grows back every year,” said Ferrera.

Brownish yellow algae on the surface of Aquatic Park.
Brownish yellow algae on the surface of Aquatic Park.

Algal blooms have been on the rise in California. Last year, 40 different bodies of water in California tested positive for harmful algae, setting a new state record. Drought conditions, like stagnant water and warmer temperatures, can exacerbate blooms, said Ali Dunn, an environmental scientist with California’s Water Resources Control Board. But periods with more rainfall, like this last winter, can also cause algae blooms that are larger than usual, as elements like nitrogen and phosphorus wash into lakes and ponds, changing the nutrient profile of the water. These factors can also promote other aquatic growth, like widgeon grass.

Aquatic Park isn’t the only body of water in the East Bay experiencing a bloom this summer. Lake Temescal in Oakland and Fremont’s Quarry Lakes are both currently closed to swimmers because of blooms. The specific growth in both of those bodies of water is cyanobacteria, a particular organism that is not technically algae — although it’s often referred to as “blue-green algae” — that can produce toxins that are harmful to wildlife and humans. The rate of cyanobacteria growth is particularly sensitive to warmer water temperatures and can edge out other non-toxic algae growth.

The state launched a California Harmful Algal Blooms portal last summer, which includes an interactive map of voluntarily reported blooms, along with information on environmental and health effects. (The map does not include the Aquatic Park bloom.) The bloom in Aquatic Park is not cyanobacteria and is not being tested for toxins, but Dunn said that even non-toxic blooms can be harmful to the environment. Algae can bring about a loss of water clarity, and the same nutrient density that encourages algal growth depletes oxygen in the water, which can lead to fish kills. “Everything’s interrelated in these systems,” she said. “If one thing is out of whack, there are repercussions for the whole system.”

Ferrera said that the city had not received any reports of problems with fish or other wildlife. “The main impact is materials on the surface are making it difficult for boaters on the water to row,” she said.

Braithwaite, of the Berkeley Paddling and Rowing Club, agreed. Most members of the club are keeping their boats out of the water, especially after a few intrepid paddlers wound up with their oars entangled in the growth and tipped their boats over. The bloom is starting to clear away from the dock and Braithwaite said they’re hoping for greater access to the lagoon as the city continues its harvesting process. But, she said, while the bloom has been a nuisance, they’ll be happy to just get back out on the water. “We’re lucky to have a lagoon at all,” she said.

Sonner Kehrt is a freelance reporter and second-year graduate student at UC Berkeley’s Graduate School of Journalism.

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