On Thursday, June 5, James Robinson, Director of the Lake Merritt Institute (LMI), received a message from the City of Oakland and the San Francisco Regional Water Quality Control Board: reports of dead fish and shrimp had surfaced near the Rotary Nature Center and Sailboat House.
Robinson grabbed the Institute’s handheld dissolved oxygen (D.O.) meter and rushed to the scene. What he discovered confirmed his worst fears.
“The bottom D.O. levels were critically low,” Robinson said. “And there were dead fish and shrimp scattered across the lakebed. It was already too late for many.”
There were no signs of the harmful “red tide” algal bloom that devastated marine life in 2022. This time, something else was driving the oxygen crash.
By Saturday morning, June 7, the situation had worsened. Alfredo Sanchez, another staff member with LMI—a nonprofit environmental organization dedicated to improving Lake Merritt’s water quality—witnessed a grim sight: fish flinging themselves out of the water in distress.
“Fish were gasping for air near the boathouse dock,” Sanchez reported. “The oxygen levels may have crashed again.”
LMI immediately notified city officials and the regional water board, then reached out to Dr. Richard L. Bailey, marine biologist and founder of the Lake Merritt Institute. A pioneer in water quality monitoring at Lake Merritt, Dr. Bailey has studied the lake for over 30 years.
Dr. Bailey elaborated on the possible causes of the collapse. “You had reduced tidal exchange for nearly two weeks during warm weather, extended daylight, and high algae growth,” he explained. “That’s the perfect storm for an oxygen collapse.”
Dr. Bailey reviewed data from the LakeTech buoys, which provide continuous real-time monitoring of dissolved oxygen levels. “This is classic low D.O.,” he explained. “We’ve seen localized fish kills like this before, but what’s alarming is the duration. Eleven days of limited circulation is extreme.”
Lake Merritt, a tidal lagoon and one of the nation’s oldest wildlife refuges, depends on daily tidal flushing to deliver oxygenated water into the basin. When that flow is interrupted—especially in warm, nutrient-laden conditions—the bottom waters become hypoxic or even anoxic, creating zones where aquatic life cannot survive.
What’s most frustrating, Bailey noted, is that this event was avoidable. “We’ve been sounding the alarm for decades,” he said. “The difference now is we have real-time data—proof of the problem. And yet, these events continue.”
Some of the most recent events are documented on the Lake Merritt Commons Facebook page, underscoring the frequency and severity of the lake’s oxygen problems. These recurring events are why Lake Merritt is federally listed as an impaired water body under Section 303(d) of the Clean Water Act.
The San Francisco Regional Water Quality Control Board has launched a study to address the lake’s chronic low-oxygen conditions. However, formal recommendations aren’t expected until 2027.
Lake Merritt remains a symbol of Oakland’s natural beauty and civic pride. But for the fish, shrimp, and those dedicated to protecting them, it’s also a battleground—where every oxygen crash tells a story of survival, science, and the urgent need for action.
We encourage our Lake Merritt community to review the proposed plan by State Water Board, and submit your comments for the future TMDL public meeting. Your input is important to the health of Lake Merritt.
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