"Anyone who lives in Oakland has probably seen the insane amount of dead fish accumulating on the shores of Lake Merritt. But why are they there?" -- Callie Frederick, 8th Grade
Discolored water in Lake Merritt due to the harmful algal bloom Anyone who lives in Oakland has probably seen the insane amount of dead fish accumulating on the shores of Lake Merritt. But why are they there? The simple answer: Algae. A harmful algal bloom, or HAB, began wreaking havoc on the Bay Area—especially Lake Merritt—in late July, when residents and scientists noticed that the bay and bodies of water connected to it were turning an unpleasant rusty color. Fish started dying off, and water testing determined that a highly toxic species of algae known as Heterosigma akashiwo was behind the bloom.
Nobody can really be positive about what is causing the HAB, and it’s likely a mix of factors, but likely contributors are the recent heat wave and the excessive flow of nitrogen and phosphorus (from sources such as sewage plants) into the bay. Algae thrives on heat and these nutrients, so the bloom is getting less severe as it gets cooler and the algae burns through all of the nitrogen and phosphorus.
Nobody can really be positive about what is causing the HAB, and it’s likely a mix of factors, but likely contributors are the recent heat wave and the excessive flow of nitrogen and phosphorus (from sources such as sewage plants) into the bay. Algae thrives on heat and these nutrients, so the bloom is getting less severe as it gets cooler and the algae burns through all of the nitrogen and phosphorus.
A snowy egret eating a dead fish at Lake Merritt
The amount of fish killed by this algae bloom was completely unprecedented, even though researchers have been expecting a major HAB for years. According to a KQED interview with Dr. Jon Rosenfield, a senior scientist at the San Francisco Baykeeper, the number of fish washing up on the shore might not even come close to the actual amount of casualties. “What you see is just the hint of what's actually happening further beneath the water's surface and in places you're not getting to on the shoreline,” said Dr. Rosenfield. “So it's really an uncountable number.”
The variety of marine life dying at Lake Merritt is also highly alarming. Everything from the tiniest anchovies to the most gigantic bat rays are washing ashore dead, and it’s clear that almost every species in the lake is affected by Heterosigma akashiwo. Striped bass, northern anchovies, yellowfin gobies, flounder, bat rays, and even crabs have been found dead.
Cleanup crews removing dead fish from Lake Merritt's shore
People stop to look at the dead fish in the lake The algae bloom at Lake Merritt has had a big effect on not only fish but also Oakland residents, who were unable to even walk around the lake because of the putrid dead fish smell. Zanthe Jones-Gerachis (she/her), a seventh grader at OSA, said that the algae bloom has affected her daily life, especially at school. “Well, I mean, obviously the algae bloom has affected P.E., because of having to run around that lake with the horrible stench and just breathing that toxic air in,” said Jones-Gerachis. Zara Quiter (all pronouns), an OSA student in sixth grade, said that their mom often runs by the lake and the HAB meant she couldn’t anymore. “It might be really stinky during my mom’s race,” said Quiter. “That would be annoying because she was really looking forward to it.”
While we can all hope that there will never be another HAB of this enormity, scientists are beginning to expect that this might become the grim new normal for the bay, with the planet heating up, causing frequent mass heat waves, and more and more waste being dumped into the bay. This algae bloom should be taken as a massive reminder that we will start to see more and more extreme consequences of climate change every year we do nothing. Calliope Dean (she/her), an OSA eighth grader, said that seeing the algae bloom’s effects really made an impact on her. “When I was at Lake Merritt I was just like, looking at all the dead fish and I thought, wow, this looks like the start of the apocalypse,” said Dean. “It was insane that all these fish are dying, and climate change is happening, and it’s really, really bad.”
