Change and Instability

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. Greater storms and droughts and other climate-related changes may make these worse.

Inadequate circulation and exchange with Bay waters have been problems almost since the park was created during the 1930s — as an afterthought to building a highway to the Bay Bridge. In the 1950s and 1960s, Berkeley came close to letting the lagoons be filled for industrial expansion. 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. Meanwhile, the city failed to maintain the pipes connecting lagoons and Bay.

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 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, with few obvious problems:

Dead Australian tube worm casings blocking Aquatic Park tide tube
In summer 2022, casings of dead Australian tube worms still blocked smaller connections and lined much of Aquatic Park’s main lagoon, although the worm cases were crumbling. Live worms may have died because of greater rise and fall of tides after the main tide tubes were cleared.
Dead native oyster shell bottoms
Native oysters that had lived for years along the shoreline also died. Only their shell bottoms cling to rocks.
Colorful "delicate lace" and "dead mans fingers" seaweed
By 2022, years of drought had made the lagoons almost as salty as the Bay, with colorful seaweeds like “delicate lace” and “dead man’s fingers.”
Spine of bat ray, probably feeding on mussels
Leopard sharks and bat rays feasted on abundant mussels that thrived along much of the shoreline. The photo shows a hunting bat ray’s sharp tail.
Dead leopark shark, Aquatic Park main lagoon
Long and heavy rainfall in winter 2022-23 turned the lagoons almost entirely fresh, with a heavy load of city pollutants and nutrients. Trapped in this water and weakened by a brain parasite, bat rays and leopard sharks suffered a mass die-off in February 2023. More than 60 carcasses were counted, like the leopard shark above and bat ray below. Many more must have died unseen.
Dead bat ray in Aquatic Park
Dead mussels, Aquatic Park
By late spring 2023, gaping shells showed that massive numbers of mussels also had died (above). Mussels are important in filtering out pollutants, and they can tolerate difficult conditions, but not extremely long stints in fresh water. Those nearest the tide gates, where saltier ay water flowed in and out, seem to have survived.
Algae and widgeon grass at north end of main lagoon
As spring 2023 turned to summer, algae and widgeon grass covered significant areas at the north (above) and south ends of the main lagoon, where circulation is limited.
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.
Yellow-green algae, bubbles, and invasive Asian date mussels

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 and speeded shallowing of the lagoons.

Boat cutting algae, Aquatic Park

Through a second rainy winter in 2023-4, 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). The city appeared to make no effort to keep polluted flows out of the lagoons.

Spring 2024, although unusually chilly, brought a massive bloom of slimy filamentous algae in the Model Yacht Basin/middle lagoon, covering large areas by early April. This was new. There was not yet any algae in the main lagoon, which saw massive blooms the previous year. There had been virtually no such algae in this smaller lagoon the previous summer, during those 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).

Such blooms are a sign of eutrophication, a process set off by too great a load of nutrients, such as those brought by urban runoff. In a vicious circle, in salt water it leads to depletion of oxygen, fish kills, acidification that weakens shellfish such as mussels that help purify water, support for types of algae that carry toxins. As the algae decays and sinks, it hastens the natural filling of ponds, which become marshes and then dry land. In the Model Yacht Basin, already largely filled in by sediment, the shallow water may warm rapidly in the sun, speeding up the process. None of this is being monitored.

Model Yacht Basin looking SE from western pipe-connection box on N shore
/Algae in Model Yacht Basin, looking east from W. pipe box on N. shore, April 8, 2024
Algae in Model Yacht Basin, April 2024, looking S. from western pipe box on N. shore.
Algae in Model Yacht Basin, looking S. from western pipe box on N. shore, April 8 2024.
Algae in Model Yacht Basin, April 8, 2024
Algae in Model Yacht Basin, April 8, 2024
Algae in Model Yacht Basin, April 8, 2024

Above: Filamentous algae typical of eutrophication in Model Yacht Basin/middle lagoon, April 8, 2024. There was virtually no such algae in 2023, and at this date there was no algae yet in the main lagoon. There may have been no such blooms in this lagoon for 20 years.