The San Diego red tide: FAQ from Scripps professor Dr. Peter Franks

Dr. Peter Franks

This is a guest post modified from two emails by professor of biological oceanography Peter Franks, reprinted here with his permission. Peter is a phytoplankton ecologist who studies how the physical processes in the ocean influence the growth and distribution patterns of phytoplankton, so he’s often the go-to guy on red tides. I have edited the emails slightly for clarity and context.

We’ve got a pretty spectacular red tide going in the waters off San Diego (and farther north and south). The organism is Lingulodinium polyedrum, my favorite dinoflagellate. Why favorite? Because it’s intensely bioluminescent. When jostled, each organism will give off a flash of blue light created by a chemical reaction within the cell. When billions and billions of cells are jostled – say, by a breaking wave – you get a seriously spectacular flash of light.

And the best part? The moon is in its “new” phase. That means that the bioluminescence will not be dimmed by moonlight for the next few days.

So please take the opportunity to go down to the beach tonight or tomorrow night to see one of nature’s most impressive light shows.

Or, if you’re like me (too lazy to get up after the sun goes down) get a clear drink bottle, get a friendly neighborhood surfer to fill it for you (knee-deep water is fine), and take it home. Put it in a cool, dark place – a closet or a bathroom without windows. Then, after the sun goes down go in there and let your eyes adjust to the darkness. Then give the bottle a shake – you’ll see blue sparks from the dinoflagellate’s bioluminescence. Then start experimenting: try your electric toothbrush. Or pour some on your arm, or on the countertop. Let some get sucked up into a towel. Or (this is the best) try adding vinegar. The acid makes the dinoflagellates release their bioluminescence chemicals all at once, giving a show similar to the finale of a 4th of July fireworks display. Unfortunately, like the 4th of July fireworks display, it’s terminal. That’ll be the end of the fun. Until you go and get some more red-tide water…

A 2005 red tide. Photo by Hayne Palmour IV, published by North County Times

I’ve received a number of inquiries about the red tide. Frequently Asked Question #1 is (in a nutshell): will it [this red tide] kill me?

The answer?


I know, I know. I’m as disappointed as you are. This species of dinoflagellate is not toxic. If it were, I’d have a lot more funding. It’s possible that it contains low levels of a toxin called “yessotoxin“, but this toxin is not one that’s tested for in the US (as far as I know), and there’s no records of it having any detrimental effects.

You’ve probably heard of various forms of toxic shellfish poisoning. Typically what happens is that shellfish such as mussels (which filter a “pant load” (technical term) of water each day) will concentrate the phytoplankton toxins in their tissues. When you eat the shellfish you get an extraordinarily magnified dose of the toxin, and bad things may ensue.

(Useful party fact: phytoplankton kill ten times more people globally than sharks each year.)

Frequently asked question number 2: Why do the dinoflagellates bioluminescence?

As far as we know (which is surprisingly not very far) the bioluminescence both deters grazers of the dinoflagellates (who likes eating food that flashes in your mouth?), and also attracts the predators of the grazers which are mostly visually oriented organisms such as fish (the so-called “burglar hypothesis”).

Frequently asked question number 3: When I surf in a red tide I get sick (ear aches, sinus infections, etc.). Why?

My usual answer is that you should bathe more. Or at least check to see whether you get sick when there isn’t a red tide.

However … a student of mine (Meg Rippy – please give her a postdoc) has some evidence that red tides can decrease the mortality of human pathogenic bacteria that get into the nearshore waters. These bacteria normally die pretty quickly; they may die slower during a red tide, perhaps due to the increased amounts of organic material in the water. So perhaps your ear infection is because of other bacteria that are present in higher concentrations in a red tide than they would normally be. (Please give us funding to pursue this.)

That covers most of the FAQ. If you have other questions, please keep them coming, and I’ll do my best to answer.

Miriam Goldstein (230 Posts)

101 Replies to “The San Diego red tide: FAQ from Scripps professor Dr. Peter Franks”

  1. What time of night is best for checking it out? Some people said that you can only view it around midnight.

    1. You can see it whenever it is dark enough. I was swimming yesterday around 9 PM and it was very glowy!

      1. Thanks! I hope it’s dark enough around seven thirty or so tonight. I would LOVE for my kids to see this! It’s a rare opportunity to show them something so cool!

        1. We went down to Sand Diego last night (Oct 1). Spectacular! Many people were just parked by the highway and looked out to the sea. We went in and touched the water. The little “glowy” things were stuck to our hands and they glowed right in our hands-like fireflies! We actually went into the water and experienced the “glow” first hand, as it were.

          One of my kids got excited and dipped his face in the water and shouted, “my face is glowing”. Guess what, he now has one swollen eye. The doc says it’s an allergic reaction and not contagious. Kids!

          What a wonderful experience it was for us. Definitely take the kids and tell your neighbors to take their kids as well.

          Happy times!

  2. I was just down at Scripps this weekend, checking out the magical glowing waves and swimming with the neon fish. I survived. And loved every minute of it :) Thanks for the article! It was an awesome experience.

    1. You want to have a carefully temperature and pH balanced saltwater swimming pool…then fill it with dinoflagellates?!

      1. But one would never need pool lights again! I also have a potent drink named Red Tide in my undersea D&D game, a welcome alternative to inkwine.

  3. How long will this red tide spectacular be going on for? Where
    are the best beach spots in San Diego you have heard it is being viewed?

    1. Hi Wena,

      There is no way of really saying how long the red tide will go on – if conditions change (for example, a windy day) it could disappear very quickly. I am also not sure of the extent of the red tide, but we had an excellent view from the Scripps pier in La Jolla. Happy viewing!

  4. I live in Orange County and the red tide is has been very spectacular up here as well. I have gone to Bolsa Chica State Beach in Huntington Beach the last few nights, and it has been the best viewing I have seen in many years. Very bright. Everyone should see this!

  5. This is a Question, not a Reply. Are there particular beaches near downtown that have a more concentrated grouping of these incredible dinoflagellates? Coronado, Silver Strand or OB? Also, are they in the bay and visible in e.g., the wake of a boat? I want to check it out after the Padres game :) Thank you.

    1. Hello Sarah,

      I emailed your question to Peter Franks and this is what he said: “Unfortunately, I don’t know. Perhaps some of the other readers could answer this one. Certainly the wake of a boat will glow brightly as it passes through a patch of dinoflagellates. But I don’t know where the patches are most likely to occur. From what I’ve heard, La Jolla Cove is always a good spot for bioluminescence.”

  6. What do you think caused this particular red tide? Usually they seem to be associated with offshore winds, sunshine and upwelling. Do you think the huge influx of “nutrients” from the latest sewage spills during the power outage might have triggered it?

    1. Hello Michelle,

      I emailed your question to Peter Franks and this is what he said: “I don’t know. The conditions you list are certainly correlated with red tides, but we don’t always get red tides when we have those conditions. I doubt that the sewage spill caused it – the bloom is geographically pretty extensive. But it’s possible that it contributed. The organisms that form these red tides are very complex – they can photosynthesize, but they can also take up organic molecules from the water, and even eat other organisms. Kind of like a photosynthetic cow. So it’s hard to discover what factors cause a red tide – you need to sample all kinds of very difficult-to-measure things for a long time before, during and after a red tide. And we just don’t/can’t do that.”

  7. The claims in this article are not entirely true. The red tide causes irritation to my eyes, nose, sinus passage each time I surf in it. Even if I bathe right after contact, same effect . . .

    1. Hello Andrew,

      I am not sure what claims you are referring to. The last paragraph of the article deals with human pathogens (e.g, ear infections) – there is some evidence that human bacteria can persist longer in the ocean during a red tide event. But the red tide organisms themselves cannot infect you.

      However, irritation is not an infection. It seems possible that these dinoflagellates might irritate (but not infect) your mucous membranes.

    2. We went down to Sand Diego last night (from Dana Point). Spectacular! Many people were just parked by the highway and just looked out to the sea. We went in and touched the water. The little “glowy” things were stuck to our hands and they glowed right in our hands-like fireflies! We actually went into the water and experienced the “glow” first hand, as it were.

      One of my kids got excited and dipped his face in the water and shouted, “my face is glowing”. Guess what, he now has one swollen eye. The doc says it’s an allergic reaction and not contagious. Kids!

      What a wonderful experience it was for us.

  8. A friend and I went to Moonlight Beach tonight around 8:30 – it was amazing, absolutely facinating and exciting. How often does this happen? My friend has lived in CA her entire life and has never seen the blue flash from the red tide.

    1. It happens every couple years – the last one that I know of off La Jolla was Spring 2010, and I believe there was one in 2005 as well.

    1. There is no way of really saying how long the red tide will go on – if conditions change (for example, a windy day or an influx of grazers) it could disappear very quickly. The swell coming in today might break it up a bit too.

  9. Hey Doc,

    Where are the “Blooms” most concentrated??? More specifically, what beach would be best (Closest proximity to Sunset Cliffs) to take my twelve year-old daughter, to see the amazing bioluminescent light show?

    1. Unfortunately we don’t have information on the extent of the bloom, especially south of La Jolla. I can personally attest to a nice glow around the Scripps pier and on La Jolla Shores/Blacks Beach. Check out the comments above for other places that people have seen it!

  10. When I was a kid the red tide was day glow green and now in the past 10 years or so it is blue do we know why the color has changed?

    1. That’s a great question! I have emailed your question to Peter Franks. In the meantime, I would say that there are different species of plankton that can form a red tide, and perhaps the ones that you remember were made of different species than this current one.

  11. I want to take my son to see the red tide tonight but he has asthma. Are all red tides toxic to asthmatics. Is there any distance he can be to see it or what can we do to protect him so he can view the spectacular phenomenon.

    1. I have emailed your question to Peter Franks. However, you are thinking of the very nasty Karenia brevis red tides that occur in Florida. This red tide in San Diego is a different species of plankton that is not very toxic, and should not be a problem for asthmatics. The water is also safe to swim in. However, I am not a doctor or a phytoplankton specialist, and you should consult your doctor if you are concerned about this.

  12. You must go out and see it tonight last night I went and it was beautiful at Wind n Sea !!!!! Try the Cove definitely closer to Scripps and up to Encinitas are spectacular sights Enjoy !!!!!

  13. is there a way to look at aerial photos of the region to see where the most concentrated growth is?

    1. I don’t know of any photos that have been made publicly available. However we have just published some aerial photos taken over La Jolla Shores. Also, it’s looking pretty concentrated off Scripps pier today!

    1. It’s still going strong around the Scripps pier in La Jolla! I don’t know about other parts of San Diego County.

  14. This is a question for everyone; how far North have you seen this particular bloom? We’re in Northern California and are driving south today to see the bloom but of course if we can see it in Malibu instead of La Jolla that’d be awesome! Anyone seen it north of Encinitas? Thanks!

  15. Has it ever lasted more than a week? Boyfriend just left town, I guess I should go see it without him, huh?

    1. It has already lasted more that a week, but there’s no guarantees. You can always go again when your boyfriend comes back!

  16. In fireflys bioluminescence is part of mating. Do scientists have any ideas on what role the bioluminescence plays in dinoflagellates?

  17. Forgive me if this was asked before but I am partially blind and can’t read all the questions. Does this red tide occur in any other location besides the pacific Coast?

    1. “Red tide” is a term for any phytoplankton (microscopic ocean plant) bloom that turns the water a brown or red color. Red tides in general are found all over the world, whenever there is an intense bloom of phytoplankton. You can find more information about red tides here, though I want to emphasize that the current red tide in San Diego is safe to view & swim in. The organism making up this red tide, Lingulodinium polyedrum is found worldwide in many temperate and subtropical areas, and has also formed red tides in the Adriatic Sea by Italy and Yugoslavia.

  18. We were cruising Alamitos Bay in Long Beach tonight and there is still plenty of red tide in our area. We will be checking out Seal Beach tomorrow night.

    1. Thanks for the info! I know a lot of folks want to know about the northern extent of the red tide, and I’m sure your post is much appreciated.

  19. Could rain have an effect on the red tide? Seal/Huntington Beaches are expecting rain in the coming days and I was hoping to gather my friends to watch it afterwards.

    1. It is possible, especially if the rain is associated with wind that will cause ocean mixing. I wouldn’t wait to see the bioluminescence – you can always go again with your friends!

      1. Point taken and duly noted. I’ll take however many friends are available to see the red tide tonight. After the rain, I’ll scout the beaches and if luck persists, I’ll take the rest out on Thursday or so.

        That’s three times for myself alone, lucky me! It’s times like these where I love being a marine ecology geek (:

  20. You could see the murkiness of the red tide yesterday in Newport and Laguna Beach waters. I did some scuba diving and it didn’t seem to effect me or the dive. I wanted to dive tonight for lobster, but you mentioned that it may have an ill-effect on the underwater wildlife. How long should I wait to catch lobster for consumption?

    Thank you.

  21. We have had the red tide here about 10 miles south of Rosarito Beach for about a week, I notice no fish activity or Pelicans diving in it. The whole month before this started we had huge fish boils in close and massive amounts of pelicans going for them. Now zip. We also have what appears to be a sick Pelican roaming our property. My question, is this tide poisoning them? fish and birds? Thank You

    1. While the algae forming the red tide, Lingulodinium polyedrum, is known to be produce a toxin, this red tide has been going on for over a week without any fisheries closures or mass mortality events. This probably means it is not very toxic. But is impossible to say if this is why this particular pelican is sick without testing its tissue for the specific toxin produced by Lingulodinium.

    2. Hi, I was thinking about going to Puerto Nuevo in Baja on Thursday as I have a place to stay there – do you know if it’s going on down there now? Thanks very much.

  22. Hi, I got some red tide water in a closed container last night and had a lot of fun with the blue glow. However, this morning my dinoflagellate friends decided to shut down the light show. What are optimal conditions for them to stay glowing the longest? Do they need oxygen? What do they feed on? Thanks!

    1. Dinoflagellates can photosynthesize, so they don’t need oxygen. They do need light, but the most likely cause of your little friends’ demise is overheating – did you happen to leave them out at room temperature? They’ll last longer if you put them in the fridge. If you make them glow a lot they may use up all their enzyme and need some time to make more. But don’t get too upset if they don’t last a long time – it’s hard to keep them alive in a jar. Enjoy!

  23. Is the Red Tide still occurring in San Diego County? I live way up north, closer to San Clemente. Please advise!

    1. All I can tell you is that it’s not looking very strong off La Jolla Shores/Scripps pier today. It is pretty faint, and what color there is is offshore. Anyone else have additional information?

  24. When is this over? I really want to check it out but I’m afraid it my be too late. I live in Escondido which is the best beach to check out

  25. My family and I went along the coast from mission beach to La Jolla cove on wednesday night and could only see slight blue flashes in the far distance. will the red tide resume after the storm passes? It was trully the most amazing thing my kids have ever seen and would like to see again.

  26. I want to go up to Del Mar or Carlsbad to get pictures. Did the storm from the other day have any impact on the intensity?

  27. Today off La Jolla Shores it looks like the red tide is pretty much gone. I haven’t been out at night. Anyone else have more info?

  28. We were just at Ponto Beach in South Carlsbad, and we saw the bioluminescence – it was really cool. The brightness of the moon made it more difficult to see, but it was definitely there :)

  29. Today it looked pretty red around Scripps Pier, so tonight might be a good one for bioluminescence!

  30. Iam confused. My daughter and I went to see the blue waves on Friday night and didnt see as little as a twinkle all the way from del mar to mission beach. We also went on Wednesday and seen very little flashes far off. so do some nights have nothing and then it comes back on others. just wanted to know because we seen it very well last sunday and monday and I really wanted to show my son. so if anyone can tell me if anyone seen any last night or see red today please let me know where.

  31. Went to Scripps Pier last night and saw some. A few of the waves had great light but they were few and far between.

  32. We went to Oceanside and Carlsbad on Saturday and missed the red tide. When will the next one occur and where will it be?

  33. does anyone know if there is any bioluminescence still happening tonight or if it has moved on for good?

  34. Defiantly still going on in La Jolla. I went around 10pm last night, AMAZING!!! I even decided to go for a swim, it was electric!!

      1. Scripps pier, so northern la jolla shores. Its much darker up there so the luminescence was really bright and some big waves, we had a great time. We even saw some at the the Ocean Beach pier but there are way too many lights for a good show.

  35. we picked up some pismo clams from silver strand yesterday and no red tide was present how long will the red tide effect the mollusk population and will filtering in clean water with corn meal flush out any toxins?

    1. The California Department of Public Health says: “…another bloom is occuring on the San Diego coast that is related to the dinoflagellate Lingulodium polyedrum, which is known to produce yessotoxin (YTX). CDPH notes the lack of evidence for human health effects associated with ingesting YTX, but nevertheless advises against consuming seafood collected from areas affected by this bloom.”

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