Community Update: Lake Merritt algae bloom and fish die-off

This message was first posted on Aug. 5, 2022, and updated Aug. 30, 2022, to respond to community inquiries. Check here for updates from the City of Oakland on the potential harmful algae bloom at Lake Merritt. Tags: Algal bloom, red tide, fish kill, fish die-off

Updated 9/8/22, 9:00pm:

The City received recently the results of algae monitoring tests performed on Aug. 22, 2022. The tests continued to show low levels of contaminants associated with harmful algae blooms, which remains consistent with the level of caution the City has posted for community awareness at the lake since May 2022. The City and its partner agencies will continue to monitor conditions at the lake and provide updates.

Over the Labor Day weekend, staff produced additional signage advising visitors to exercise caution and avoid touching the water as well as any algae or scum -- as well as advising visitors not to touch any dead fish or aquatic life they might find at the lake. These may be reported to OAK311 to request cleanup services.

An example of caution signage posted at Lake Merritt, September 2022
An example of caution signage posted at Lake Merritt, September 2022

The City has received community inquiries about the manner of disposal for the dead fish and aquatic wildlife that was removed from the shoreline and lake surface. In an abundance of caution, the material was collected and inspected, and disposed of in a landfill. After the initial clean up, the City's clean-up contractor consulted with the compost facility operator and it was determined that the material was not suitable for composting -- because the collection method captured other materials not suitable for composting, and because some of the fish had begun to decompose anaerobically, which is problematic in an aerobic composting facility. It's important to note that composting is not a means of disposal; rather it is a manufacturing process to produce a specified agricultural product.

Updated 9/2/22, 10:30am:

As announced Thursday night, on Friday morning the Lake Merritt cleanup operation shifted from the shoreline to focus on cleaning floating material from the water's surface. This work will continue through the weekend.

Photo of aquatic surface cleanup underway at Lake Merritt, morning of 9/2/22
Photo of aquatic surface cleanup underway at Lake Merritt, morning of 9/2/22

The City has received community inquiries about the fountains in the lake. There are two functional fountains: Glen Echo Fountains and Embarcadero Fountain. The Glen Echo fountain was repaired earlier this week, but requires additional repair work today -- that work is underway now with a goal to resume operation later today. The Embarcadero fountain was operational earlier this week but crews have discovered a broken component that has been sent to the manufacturer for repair. Additionally the Embarcadero location is an aeration fountain that can only function when the tide is high. When water is too shallow, aeration fountains cannot work. The fountains help oxygenate the lake's water and support a healthier environment for fish and wildlife. However, at the scale of the current bloom and die-off issues their aerating effects are not anticipated to significantly impact current conditions.

The San Francisco Bay Regional Water Quality Control Board has posted a page of Frequently Asked Questions about the San Francisco Bay Harmful Algal Bloom (which is what is affecting Oakland and Lake Merritt) at this link.

Updated 9/1/22, 7:00pm:

Crews completed a second 10-hour day Thursday removing dead fish and aquatic life from the lake shoreline. The shoreline work has concluded for now, and the largest contributor to the public nuisance and odor has now been removed. It might take some time for the odors to dissipate. Work on Friday will transition to removing floating material from the surface of the lake, which will continue throughout the weekend. Oakland Public Works (OPW) will continue monitoring the lake shoreline for changes as tidal shifts and other factors might produce evolving conditions. We encourage community members to continue reporting cleanup needs to the City by contacting OAK311.

The Oakland and Lake Merritt shorelines remain part of a much larger natural phenomenon, with algae blooms and fish die-offs reported for many miles to the north and south along the coastline. OPW is working overtime to treat the unpleasant symptoms of this phenomenon to provide a comfortable and welcoming space around Lake Merritt.

The City continues to advise caution to avoid touching the water, algae, and scum that remains in parts of the lake, particularly for children and pets. Boating activity remains allowed in the lake, and visitors are welcome to enjoy the lake's shoreline and parks over the long weekend.

Photo of Lake Merritt shoreline along Lakeshore Avenue after cleanup work on 9/1/22
Photo of Lake Merritt shoreline along Lakeshore Avenue after cleanup work on 9/1/22
Photo of Lake Merritt shoreline along Lakeshore Avenue after cleanup work on 9/1/22
Photo of Lake Merritt shoreline along Lakeshore Avenue after cleanup work on 9/1/22


Updated 8/31/22, 5:30pm:

Crews made major progress Wednesday, removing 1200 pounds of dead fish and aquatic life from the lake shoreline. These crews will return on Thursday.

City-contracted crews perform cleanup at Lake Merritt shoreline on 8/31/22
City-contracted crews perform cleanup at Lake Merritt shoreline on 8/31/22
A stretch of the Lake Merritt shoreline PRIOR to City cleanup, 8/31/22
A stretch of the Lake Merritt shoreline PRIOR to City cleanup, 8/31/22
City-contracted crews perform cleanup on the Lake Merritt shoreline, 8/31/22
City-contracted crews perform cleanup on the Lake Merritt shoreline, 8/31/22
A stretch of the Lake Merritt shoreline AFTER City-contracted cleanup, 8/31/22
A stretch of the Lake Merritt shoreline AFTER City-contracted cleanup, 8/31/22

Updated 8/30/2022, 3:45pm:

The City of Oakland Public Works (OPW) is aware of large numbers of fish and other wildlife observed dead across the Lake Merritt shoreline beginning Sunday, Aug. 28, consistent with reports of fish die-off observed throughout the Bay Area.

OPW staff is working in conjunction with regulatory agencies, including the California Department of Fish and Wildlife and the San Francisco Bay Regional Water Quality Control Board, to identify appropriate options to treat the area. The department's immediate next steps will be to facilitate clean-up of the lake's shoreline, removing the dead wildlife to mitigate the odor and public nuisance ahead of forecasted hot weather. Contracted cleanup crews are scheduled to begin this work on the morning of Wednesday, Aug. 31. Crews will wear protective gear in an abundance of caution. Community members are asked to watch for signage and work crews/vehicles to enable these crews to perform this work.

Additionally, OPW is anticipating results from water testing performed at the lake by the Water Board on Aug. 22. OPW will share those results as they become available.

Recent media coverage of this event has included speculation that the cause of the fish die-off and/or the algae blooms might be increased sewer overflows into the lake. However, OPW has made significant progress in recent years improving sewer system infrastructure affecting the area and there have been no major recent overflow incidents affecting the lake.

Additionally, harmful algae blooms have recently been reported across the Bay Area, including along the Oakland shoreline and estuary, and for several miles in either direction along the coast.

OPW and the Water Board first detected low levels of contaminants associated with harmful algae blooms in May 2022, and OPW promptly posted warning signage to alert and advise lake visitors. These caution signs alert the public that harmful algae may be present in the water and to stay away -- and keep children and pets away -- from the algae, scum, and water.

What causes harmful algal blooms at the Lake: Generally, increased inputs of nutrients like nitrogen and phosphorus (from fertilizers and human or animal wastes), low water flows, stagnant water, increased intensity and duration of sunlight, and sustained high temperatures create the ideal conditions for these blooms. Current research suggests that the rising temperatures and changing precipitation patterns caused by climate change are a catalyst for their growth.

How you can help: We can all play a part in keeping the Lake safer for everyone. For example, property owners can avoid over-irrigation of landscapes (such as overwatering lawns) to prevent excess nutrients from entering waterways. And we all need to continue working to keep Lake Merritt clean – littering, especially food and food containers, may contribute nutrients to the Lake that feed these harmful algal blooms.

It is also important to note that algae is a normal and regularly occurring organism in Lake Merritt. Most summers the City employs an algae skimmer to harvest the larger concentrations of algae from the lake.

State of California information about harmful algae blooms, including the signage OPW has posted, is available online at the State's My Water Quality web page. This site also includes a Harmful Algal Bloom (HAB) Incident Reports Map where community members can learn about all nearby bloom reports.


Tagged with: Public Works

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Posted: August 30th, 2022 7:00 AM

Last Updated: September 8th, 2022 9:17 PM

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