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Enough Carbon Monoxide to Kill a Chicken ?

If you live on the West Coast, you may have heard someone say . . .   “There’s enough carbon monoxide (CO) in Bull Kelp to kill a chicken”.

Recently, while teaching a marine naturalist workshop, I was asked if this was true. And oh what a rabbit hole this took me on, leading not only to chickens, but elephants! Actually, just one elephant but it’s a whole menagerie of facts. You’ll see.

I knew that carbon monoxide is a byproduct of respiration in some brown algae like Bull Kelp (Nereocystis leutkeana). I also knew that carbon monoxide is one of the gases found in the float-like structure called the “pneumatocyst”, keeping the kelp buoyant so that the fronds can better photosynthesize, nearer to the sun. The stem-like structure, the stipe, is also hollow and directly connected to the pneumatocyst and, thereby, must contain some carbon monoxide too.

However, I had never checked if the amount of carbon monoxide could indeed be measured by the official scientific unit of “chicken killer”.

The fact-finding mission took me all the way back to 1917 and the research of Seth Langdon who discovered that there was carbon monoxide in Bull Kelp and then exposed the concentration to various animals. And yes, he killed chickens. So it’s true.

But it gets even more interesting.

Bull Kelp float (pneumatocyst) and fronds. ©Jackie Hildering.

Jump ahead to 2013 and the Masters thesis of Lauran Liggen. How thrilled I was to learn from her work that, not only is there enough carbon monoxide in Bull Kelp to kill a chicken – there’s enough to kill an adult man (don’t worry, she did not use Langdon’s lethal methods to prove this).

Specifically from her research: ” Earth’s atmosphere contains only a small amount of CO (~0.000025%) whereas pneumatocysts contain an average concentration of 1.6%  . . .  A study conducted by Landgon (1917) determined whether or not the concentration of CO was at a toxic level by exposing pneumatocyst gases to animals and measuring their physiological effects. Subsequently, the statement familiar to most phycologists [cool people who study algae], that the pneumatocysts of Nereocystis have enough CO “to kill a chicken” was a product of Langdon (1917). Without harming any animals, data collected during this study can further support this statement. 1.6% CO is a potentially toxic amount given that concentrations of CO greater than 100 ppm (0.01%) could kill or render a person unconscious (Suner et al. 2008). Given that an average adult male has a lung capacity of 5800 ml and the largest recorded pneumatocyst in this study (725 ml) had a CO concentration of 1.6%, if an average sized man inhaled the gas inside the largest sampled pneumatocyst, then in one breath he would ingest 1500 ppm of CO, 15-times greater than the maximum concentration a person could tolerate before passing out.”

Wow. Just wow. That’s a lot more than one chicken.

So where does the elephant come in? 

While trying to source the chicken and Bull Kelp story, I came across the following about Bull Kelp in the book “Pacific Seaweeds” by super phycologists, Louis Druehl and Bridgette Clarkston: “Ronald E. Foreman, in pursuit of his PhD (University of California, Berkley, 1970), discovered that the float, which may have a volume of up to 3 litres . . . has carbon monoxide, an infamous poison as one of its buoyancy gases. Some years ago LD [Louis Druehl] had the opportunity to test the herbivore’s ability to detect the kelp-packaged carbon monoxide. While teaching a seaweed course for the University of Alaska, [he] shared an apartment complex with Bo, a circus elephant [say WHAT?!] and once presented Bo with an entire fresh bull kelp. Bo’s response was to yank the plant from [his] hands (poor table manners) and eat the blades. Then, to Louis Druehl’s surprise, Bo stomped on the float, releasing the gas before he ate it. Does this behaviour suggest elephants once lived in association with kelp and learned to avoid the poisonous gas?”

Let me answer that. No! This is a sample size of ONE with a circus elephant who lived in an apartment complex in Alaska. This may not have been the wildest of elephants but possibly a pretty wild apartment complex. 🙂

Can’t make this stuff up and it’s great to be able to report that naturalists didn’t. Those who have been saying “Bull Kelp is kept afloat with enough carbon monoxide to kill a chicken” are right. In fact, they’ve been low-balling the amount. However, I would suggest that there is more valuable messaging around Bull Kelp and its great importance as habitat, fuel for the food web, oxygen production and carbon dioxide absorption.

And once again, with this blog, I feel like I have fulfilled part of my calling by providing essential, factual, life-enhancing information. In this case, involving kelp, chickens and an elephant named Bo.

You’re welcome.

Note: The genus for Bull Kelp, “Nereocystis”, is Greek  for “mermaid’s bladder”.

For more on Bull Kelp, please see my additional blogs:


All photos in this blog ©Jackie Hildering.

13 Responses to “Enough Carbon Monoxide to Kill a Chicken ?”

  1. Leah

    Awesome blog Jackie…informative and entertaining! Thank you! 😁

  2. Yvonne Maximchuk

    First thing I read today! Before coffee. Fascinating and edifying. And well written

  3. Melissa Anderson

    Superb post, Jackie! Great science and entertainment, a great combo for learning. I am trying to imagine the set up in that Alaskan apartment building.

  4. Suze

    So appreciate your sharings, which are more than educational. They inspire me to be more for my environment

  5. Ccgrowlette

    I know this blog is old, but elephants will stomp on larger pieces of food to break them down to manageable pieces they can eat! Nothing to do with the gas in it on that one. Google elephants eating giant pumpkin

    • The Marine Detective

      Thank you. Indeed! I hope it does comes across that I think that the elephant stomped the Bull Kelp re. carbon monoxide. Just quoting that source. 🙂

      • Ccgrowlette

        I was on a weird rabbit hole learning about bull kelp (last week it was bees, today it was the spider Gaius villosus… It’s a habit) and was really happy to find this post, lots of great info. The science teacher in me just had to find an answer to why the elephant stomped on it and I started searching to see if they did that with food items that are too big, and sure enough!

  6. Eric Cabot

    I don’t think that the elephant squashed the kelp bulb to free the gas.

    I am pretty sure that if you provide an elephant with something small, the first impulse will be to stomp it. My single point of data comes from the fate of a hidden camera-bearing fake tortoise in the PBS “Spy in the Wild” series.


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