Fish Die-Off at Lake Merritt

From the ecological calamity at Lake Merritt in Oakland this morning … images of the huge fish die-off, likely related to the algal bloom on SF Bay. The cause hasn’t been confirmed, although the algae is at the top of the suspects list.

According to naturalist Damon Tighe who reported on the situation at the lake on Sunday, measurements of the water showed the lake to be anoxic — so depleted of oxygen, the numbers were less than one part per million. You can see an interview with Tighe in the video below, where he discusses his observations in more detail.

Walking the shore from the Lake Chalet to the Rotary Nature Center, we couldn’t fully count the number of dead and dying fish, rays, and other aquatic animals that lined the lake’s shore. It seemed endless. Tighe counted 39+ dead bat rays and 522+ dead striped bass. That doesn’t include the thousands of smaller fish and animals we saw lying at the lake’s edge, dead or dying in the muds of the receding tide.

Bearing witness to these events can feel inconsolable at times. The scene today was utterly heart crushing.

According to a piece in the SF Chronicle today, this is the largest algal bloom we’ve seen in the region, “dominated by a harmful species known as Heterosigma akashiwo.”

From the same article, Ian Wren, a scientist with San Francisco Baykeeper says:

“We’ve never seen this before and even the models that have been developed didn’t see this as being possible.”

Algal blooms are expected to increase with climate change and warming waters.

Among the dead fish were those still living which, in turn, drew a frenzy of pelicans, egrets, and cormorants to feed.

I hope the presence of active, live fish speaks to increased oxygen levels for the coming days, although that would be an optimistic vision. I don’t know how this bloom and its cascading effects will impact the birds, short term or long. Our fall and winter bird migrants will soon descend on these marshes and shores for their winter sustenance, and no one can say yet how significant the disruption will be to the Bay Area’s food chain. I hope it will be far less than what I fear.

Interview with biologist Damon Tighe, about the fish die-off, the algal bloom, and his observations at Lake Merritt