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. I’ve been a surfer in San Diego since I was a kid and am now 41. I just surfed last Thursday in the red tide and have the worst ear infection I’ve ever had. It’s completely swollen shut, I can’t hear and it hurts really bad. Got the drops yesterday for it.

    Over the years I’ve gotten very sick from surfing when there is a red tide. I DO NOT experience severe ear infections like the one I have currently when there is no red tide. Red Tide is very nasty and I don’t care what these scientists and biologists are claiming, it can and does make me very ill and causes all sorts of issues.

    My advice is to stay out of the water during red tides.

    1. I also get very sick from Red Tide when I surf. Very bad sinus problems that last several days. It only happens when I surf in Red Tide and sometimes starts happening before I even get out of the water. I start sneezing, that’s how I know it is red tide even if the water does not have brown or red color to it.

      I have many long time surfing friends this happens to as well. It is miserable. This sickness is real and seems to be getting worse. The MANY others that experience this say the same thing. I think it may be an allergy.

    2. I’m from Chile and I’ve been surfing most of my life in different parts of the world including northern CA, OR and WA. I’ve never ever gotten so sick after surfing as I’ve had here in San Diego when there is red tide present in the water. I surfed all summer long day after day and nothing, but as soon as there was red tide present I got sick; the first time I didn’t know what it was so I blamed it on a “cold”. I’m shocked that it does affect me almost immediately because I start sneezing too like the other person posted, and I have to stay out of the water (which sucks!). I ended up with antibiotics one time because the sinus infection was too bad. I agree that most scientist don’t have a clue when they say that it does not affect humans. My wife (who is a surfer too) also gets sick immediately with red tide present. Sometimes the reaction is like an allergy, but other times it is like a infection or cold/flu symptons. I can’t find a reliable red tide map online that shows concentration in the water for every single day by area, that would really help.

  2. I have an urgent question. I am supposed to take my 10 month old infant to the beach in the Gulf of Mexico which is also having a red tide but from a different species. (South Padre Island). I am not planning on taking the baby in the water, however there are bad aerosols right now. I’m concerned for his respiratory health and all I can find is that this species is a neurotoxin, which sounds even more dangerous. Can you help me determine the risk to having my baby stay by the beach and breathe the air? I would normally cancel the trip but it’s a long planned family reunion with guests traveling from all over the country. :( Thanks for any input or opinion you have. (I know there’s no research because I can’t find info anywhere on the developmental risks for a 10 month old).

    Thanks in advance!

    1. I wish I could help – that is so scary and disappointing. However, I am neither a red tide specialist or a doctor, and am utterly unqualified to give medical advice. Here is the Facebook page of a red tide group in Florida that deals with the same species (Karenia brevis) – perhaps they have more information?

  3. Does anyone know if it still going on? I live over a hour and a half away. I have been to la jolla four times since october 1st to see the red tide. The first time was amazing. The second and third time I seen nothing at all from mission beach all the way to Del mar. The fourth time my wife and I were able to see little bit of blue at scripps pier. That was on October 10th. My disabled son decided he really wants to fight through the obstacles to see the red tide. hopefully someone can tell me if it is still happening and if it is can tell me A) where they seen it last B) when they seen it last C) what time it is best to see it. Thank you for any info you can provide. I just want to be able to have my son experience this. If anyone knows of a different website or any other resources to use to be able to check the status of the red tide.

  4. Thank you for all the info you have contributed during the red tide. I have family that live near monterey and their neighbors told them that it usually occurs at least once a year around Monterey bay. We just moved here last summer and from what I have read the last good red tide was back in 2005. Do you know if it occurs more often that that? I really want to show my son and I know the last few red tides I read about only lasted a few days at the longest. Do you know if there is a website or blog that I could follow so I would be informed of a red tide blooming again before it would be to late? Again thank you very much for all the details about the red tide, I really enjoyed learning how and what causes a red tide!

    1. I’m glad you’ve enjoyed our red tide coverage! The best website to follow is the Southern California Ocean Observing System (SCOOS). They usually have water quality info that includes red tides. The last really big red tide was 2005, but there was also a pretty good red tide in spring 2010. There’s no way of knowing when the next one will occur – though there are places in the world with more reliable bioluminescence than here in San Diego, such as this bay in Puerto Rico.

  5. Chris,
    We saw the red tide last weekend ( oct.15-17). A little north of bodega bay, ca.

  6. How many Red Tides does San Diego usually get a year? Also, do they cause/trigger asthma attacks in asthma sufferers (on land near the water). I read that Florida Red Tides cause respiratory problems for people living near the beach (who already are asthma prone) but the microscopic organisms in Florida Red Tides are also different (if I am reading correctly) than in San Diego waters. Do SD Red Tides also trigger asthma?

    Also, could probiotics (much like probiotics used to keep the digestive system balanced) be used to control Red Tides, or could probiotics also be used to help control San Diego’s frequently high marine water sewage bacterial levels?

    To the San Diego government: Please give this lady funding and get her working to help answer these questions.

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