Aquatic Park’s lagoons look peaceful, but like most human-created lagoons, they undergo quick changes that can devastate plant and animals and disturb visitors’ enjoyment. Climate-related changes including more-severe storms and droughts, as well as gradual filling of the lagoons by polluted runoff from much of Berkeley, may increase the problems,.
Aquatic Park’s human-made lagoons grew out of building the Bay Bridge, the Bay Area’s largest public works project of the Great Depression. To get cars to the bridge without massive traffic jams, the federal government built Eastshore Highway (then Highway 40, now I-80) as a straight feeder road from the north. Through Emeryville and South Berkeley, this meant building just offshore, west of the railroad tracks along the shoreline. Since both industrial waste and domestic sewage emptied here, the long cut-off finger of tideflat and shallow Bay cut off would have become a cesspool. Emeryville filled its share. Berkeley got a federal grant to dredge its part to create a recreational lagoon, with pipes exchanging water with the Bay. The same grant paid to dredge the Berkeley Yacht Harbor. The material dredged was used to support the highway and bridge, but this was Berkeley’s first gesture toward encouraging people to enjoy the waterfront. When it opened in 1937, the park was immediately a site for big celebrations like July 4. There were small-boat rentals, and swimming was allowed at first.
Fish die-offs and smelly algae, however, began in the 1940s. In the 1950s, the Santa Fe Railroad filled its tidelands to the west, blocking the main lagoon’s north outlet pipe and reducing circulation. Berkeley increased the amount of stormwater sidetracked from the big Potter Drain into the park’s Model Yacht Basin (middle lagoon), so that flows would not back up into low-lying West Berkeley. There was talk of selling the park so that the heavy industry just east of the railroad could expand. This was twice cut off — the second time with credit given to Florence Minard, a longtime art teacher at Mills College. The first time, a big turnout of service clubs and children at a meetine quashed the idea. The second time, credit is widely given to Florence Minard, a longtime teacher of art at Mills College. In 1962, in her 70s, became one of Berkeley’s pioneering environmental activists, organizing Friends of Aquatic Park and insisted on better maintenance, especially cleaning the pipes.
As environmental awareness grew, pollution, smells, algae, and repeated die-offs led to increasingly expensive studies, all recommending reducing polluted runoff from the city and improving circulation and exchange. None of these studies led to significant action, and the pipes went uncleaned.
By 2020, invasive Australian tube worms (Ficopomatus enigmaticus) had all but blocked the tide tubes between the Bay and the main lagoon. The city used bond funds meant for capital improvements to clean the main tide gates and tubes, restoring some rise and fall of tides.
An excellent 2020 YouTube video on the worms is here (this will open in a new tab)
Two years of drought followed the cleaning, with few obvious problems:
Though not toxic, this dense algal growth can shade out sunlight and leave water without oxygen, killing other life. Widgeon grass is a native aquatic flower plant that ducks love. But it hinders boaters.
Below: Thousands of tiny Asian date mussels, an invasive species, rested on the algae dense algae.
These blooms are now new. As in the past, the city paid a harvest boat, visible in the background below, to cut the algae and wigeon grass and haul it ashore. Otherwise, the mass would stink before it sank — speeding the shallowing of the lagoons.
Through a second rainy winter in 2023-4, and a cool, late spring, massive quantities of urban runoff as well as salt Bay water at high tides flowed into the lagoons via the Potter Street storm drain edging the Model Yacht Basin and the Strawberry Creek connection at the north end of the main lagoon (see Connections and Circulation).
April 2024 brought a brief, massive bloom of slimy filamentous algae, typical of eutrophication, in the Model Yacht Basin/middle lagoon, covering large areas in early April before disappearing almost overnight. It did not recur all summer. This bloom seemed to be new. There was no such algae in the main lagoon, and there had been virtually no such algae in this smaller lagoon the previous summer, during the main lagoon’s massive blooms. No one seems to remember this kind of bloom in this pond before in any season. (If you remember or know about such blooms, please email f5creeks@gmail.com).
This lagoon seems to be filling in, with much of it shoal at lowest tides. Sunlight through shallow water could promote the growth of algae, but cold, cloudy Bay water flooding in from the huge Potter drain at high tides may limit this growth.
In summer 2024, there was almost no surface scummy algae, perhaps due to late rains, relatively cool temperatures, or an overall lack of deluges or heat waves. In the main lagoon, however, the bottom visible from shore tended to be dense with scummy, thready algaes, especially at the north and south ends. Along with them came seaweeds that have spread worldwide, thriving in shallow, muddy estuaries with sharply changing temperature and salinity and high levels of nutrients from land runoff.
These can be signs of eutrophication, a vicious circle: Too great load of nutrients promotes growth of algae and other plants. Although these can provide habitat and food, they also can deplete oxygen, kill fish, acidify water weakening shellfish, and promote algae that carry toxins. Loss of mussels and other filter-feeders means they no longer purify water. As the algae decays and sinks, it hastens the natural filling of ponds, which become marshes and then dry land.
On the positive side, mussels showed signs of making a comeback. There were some large crabs, including the voracious, invasive European green crab, along with tentative first sightings of sharks and bat rays since the die-off in the winter of 2022-23. For more on animals in the park, see the page Hidden Creatures of the Lagoons.
