Fish in the Bay – August 2022, RED TIDE ALERT!

Folks, the Red Tide continues to sweep across portions of North and Central San Francisco Bay.  Areas affected by dark chocolate brown water (it generally looks more dark brown than red) and dead fish include Alameda and Oakland, Lake Merritt in Oakland, and Oyster Point just south of San Francisco on the Peninsula.  

  • Most recently, on Thursday and Friday, August 25th and 26th, brown water and three dead Sturgeon were spotted at the Dumbarton Bridge, and
  • Red Tide algae was detected near the mouth of Coyote Creek in Lower South Bay!



San Francisco Estuary Institute (SFEI) in collaboration with Baykeeper and UC Davis, set up a citizen-science webform to track fish mortality.

If you observe dead fish in Bay waters or along the shoreline, upload photo(s), and provide other relevant information about what you observe at the links below.   

Full link to reporting form is here: 

Quick links:


This photograph of Red Tide (brown water) was posted in “Everything South City” on August 17th   

If you see water that looks like this, PLEASE REPORT!


This is one of several photos provided by Rachel Tertes, a wildlife biologists with USFWS, on Friday, 26 August.  This dead Sturgeon washed up on a beach near Dumbarton Bridge. Rachel and her coworkers spotted 3 dead Sturgeon and 50 dead fish that included Striped Bass on Thursday and Friday.


Rachel also provided this photo of chocolate brown water under Dumbarton Bridge.


Another photo of dark brown water under Dumbarton Bridge from Rachel.


2. History of this current Red Tide.

This current Red Tide condition was first reported in San Francisco Bay on July 16th.  It has since spread considerably. Red Tides are rare in the Bay.  The last reported major events like this were in 2004 and 2002.

An excellent video was posted on YouTube on Sunday, August 28th: “Harmful Algal Bloom San Francisco Bay 2022 – Heterosigma akashiwo.”   


Screenshot from Lasphotos YouTube video titled: “Harmful Algal Bloom San Francisco Bay 2022 – Heterosigma akashiwo.”

The video creator, Lasphotos, misidentifies H. akashiwo as a dinoflagellate. That is almost correct:  H. akashiwo has been reclassified as a raphidophyte in recent years.  He claims to have first observed this chocolate brown H, akashiwo bloom at Sea Plane Lagoon in Alameda on July 16th, 2022.  Drone footage of the bloom is shown at around the 4-minute mark.  


Lorien Fono, Executive Director of the Bay Area Clean Water Agencies (BACWA), led a joint BACWA/SFEI fact-finding expedition on Sunday, August 28th.  She provided this photo of Brown and White Pelicans feasting on dead and dying fishes in Oakland’s Lake Merritt.


3. Heterosigma akashiwo is a single-celled organism that is neither plant nor animal.

There are at least several single-celled organisms that are well known to cause Red Tides around the world.  Most of these are Dinoflagellates from the genus Gymnodinium (aka the “naked” or “unarmored” dinoflagellates).  Some of the well known species include:  Gyrodinium, Akashiwo (not H. Akashiwo we are currently experiencing!), Karenia, Karlodinium, and Katodinium

Interestingly, San Francisco Bay is currently under attack from a similar organism that has an entirely different lineage.  Heterosigma akashiwo looks like a dinoflagellate, acts like a dinoflagellate, is also unarmored like the Gymnodinium dinoflagellates, and creates red tides as well.  BUT, H. akashiwo is NOT a dinoflagellate.  Instead, modern genetic analysis assigns H. akashiwo to the raphidophytes in the Stramenopile branch of the eukaryotic tree of life.

To most of us, it makes no difference whether H. akashiwo is a dinoflagellate or a raphidophyte.  Even under a microscope, they look and act very similar.  But, there is perhaps one major exception: Dinoflagellates that cause Red Tides also produce toxins that kill fish.  H. akashiwo also kills fish, but it is believed that the killing mechanism may be asphyxiation rather than toxin.  There are many other microscopic differences, but the lack of a known killing toxin is biggest one.  (Hopefully, the result is less risk to pelicans, ospreys, and other birds that may eat some of these dead fishes.)


Figures 2 & 3 show H akashiwo cells from Chile.  Figs 6 and 7 show cells from France.   Figures from Gomez et al 2021.


A photo of thousands of dead small fishes in Lake Merritt on Sunday – by Lorien Fono.


4. The word “Algae” is very misleading in describing these Red Tide creatures.

(Personal rant.  Feel free to ignore.) Centuries ago, scientists named living things that photosynthesize either “plants” or “algae.”  When the microscope was invented in the 1600s “Algae” became the catch-all term for all the newly discovered “animalcules” (tiny animals – ) that appeared to have chloroplasts.  Thus, Cyanobacteria were identified as “blue-green algae,”  Chrysophytes became “golden algae,”  and most single-celled organisms that looked green became “green algae” or Chlorophytes.

In human terms, an alga is a much larger plant-like organism that is either rooted to a rock or the ground by a holdfast, or it may be a free-floating fiberous mass on the water surface.  (I can accept that many types of cyanobacteria are very algae-like.) “Seaweeds” are correctly identified as green, red, or brown algae, IMO.

But, to call these whirling microscopic organisms an “Algae” as in Harmful “Algal” Bloom (HAB) conjures a completely mistaken image.  

  • They bear little relation to any green plant or seaweed in the way most normal people conceive.
  • These microscopic whirling dynamos swim up and down in the water column.
  • They photosynthesize, but they also chase prey when they get hungry.
  • The unarmored varieties are highly nutritious. They are critical food for larval Anchovies and probably every other larval fish in this system as well.
  • When they get angry, they turn red and start wrecking the place.
  • We must NOT make them angry! (end rant.)   

See: Gomez et al 2021  “Comparison of a Chilean strain of the ichthyotoxic phytoflagellate Heterosigma akashiwo (Raphidophyceae) with strains from France, Spain and New Zealand.”  

“The marine raphidophyte Heterosigma akashiwo is a bloom-forming planktonic species distributed worldwide which has been implicated in fish kill events in China (Tseng et al. 1993), Japan (Honjo 1992), New Zealand (Chang et al. 1990), Canada (Taylor & Haigh 1993) and the United States (Kempton et al. 2008; Rensel et al. 2010). Diel vertical migration capabilities of vegetative cells (Kohata & Watanabe 1986) as well as sinking of cysts (Powers et al. 2012) are some of the adaptive eco-physiological traits that explain the increasing distribution and blooming capacity of H. akashiwo.”


Many of these dead fish from Lake Merritt were identified as Yellowfin Gobies.  Photo by Lorien Fono.

It is equally misleading to refer to Dinoflagellates or Raphidophytes as microscopic “animals.”  They are completely different life forms.

See:   Raphidophytes are a small group of eukaryotic algae [Ugg! That word again!] that includes both marine and freshwater species. All raphidophytes are unicellular, with large cells but no cell walls. Raphidophytes possess a pair of flagella, organized such that both originate from the same invagination. One flagellum points forwards and is covered in hair-like mastigonemes, while the other points backwards across the cell surface, lying within a ventral groove. Raphidophytes contain numerous ellipsoid chloroplasts, which contain chlorophylls a, c1 and c2. They also make use of accessory pigments including β-carotene and diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the photoreceptive organelle typical of this group. In terms of ecology, raphidophytes occur as photosynthetic autotrophs across a range of aquatic systems. Freshwater species are more common in acidic waters, such as pools in bogs. Marine species often produce large blooms in summer, particularly in coastal waters. Off the Japanese coast, the resulting red tides often cause disruption to fish farms, although raphidophytes are not usually responsible for toxic blooms.”


Would you call that a Plant, an Animal, an Alga, or something else altogether???

These tiny non-plant, non-animals also can significantly control marine bacteria populations.  – See:  Seong, Jeong, Kim, Kim, & Kang (2006)  Bacterivory by co-occurring red-tide algae, heterotrophic nanoflagellates, and ciliates:

“We investigated feeding of natural populations of red-tide algae, heterotrophic nanoflagellates (HNFs), and ciliates (<30 µm in cell length) on natural populations of marine bacteria (mostly heterotrophic bacteria) in diverse Korean waters … during red tides in 2004 to 2005. To explore the functional responses of the dominant red-tide algae to bacteria, we also measured the ingestion rates of the dinoflagellates Cochlodinium polykrikoides, Heterocapsa rotundata, H. triquetra, and Prorocentrum minimum as well as the raphidophytes Chattonella ovata and Heterosigma akashiwo as a function of bacterial concentration in the laboratory.

The results of the present study suggest that, potentially, red-tide algae can have a considerable grazing impact on populations of bacteria during red tides and are sometimes the most effective protistan predators of marine bacteria.” 

Bees and Wasps sting, but they also perform other critical ecological services!


More dead gobies on the shores of Lake Merritt on Sunday, August 28th.  Photo By Lorien Fono.


5. Good News! No fish kills have been observed in Lower South Bay (south of the Dumbarton Bridge) … yet.

  • I called Laine’s Bait Shop in Alviso on Sunday. They reported that people were fishing.  No one had reported dark brown water or dead fish.  Per Laine’s: at least one angler caught some Striped Bass and some sharks.
  • Eric Dunlavey, Compliance Manager at San Jose-Santa Clara Regional Wastewater Facility, had his crew collect water samples on Thursday, August 25th. BAD NEWS!  The San Jose team did see brown water downstream of the Railroad Bridge on Coyote Creek and the non-plant, non-animal known as Heterosigma akashiwo was detected! 

Red Alert! Red Tide threat in San Francisco Bay is extremely high!

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