Seaweed Kills Horse In France

Killer seaweed? Yes. It’s not like a giant venus flytrap, but it is creating a killer gas that some scientists believe may have wiped out the dinosaurs.

After a horse was killed (and the horse rider lost consciousness) by hydrogen sulphide gas, vacationers are being advised to stay away from beaches in northern France. The gas is being formed and released from the great amounts of seaweed that is growing off the coast of France and washing up on the shores. When the seaweed dries up, “it forms an impermeable white crust under which hydrogen sulphide accumulates. When the crust is broken, the gas is released.


As the director of research at the French Institute for Sea Research and Exploitation, Alain Menesguen, says: “This is a very toxic gas, which smells like rotten eggs. It attacks the respiratory system and can kill a man or an animal in minutes.”

In the recent horse incident, the man whose horse was killed and who lost consciousness was a veterinarian and he identified that the gas was the cause of his horse’s death. This is nothing new to France. According to Jean-Francois Piquot from the environmental group Eau et Rivieres: “There are about five beaches that are unusable. The problem is getting worse.” Additionally, every summer, as much as 70,000 cubic meters of seaweed are cleared off about 70 beaches in Brittany (where the incident occurred).

What is the cause of this seaweed explosion? Piquot says: “There is no doubt that farming is to blame. Brittany has 5 per cent of French agricultural land but 60 per cent of the pigs, 45 per cent of the poultry and 30 per cent of the dairy farms. As our rivers are not long, the pollution does not have time to clear before the water reaches the sea. If it enters a closed bay and there is sunlight, that produces the seaweed.”

However, France is having problems with seaweed in other areas as well. Another beach was closed last week due to toxic seaweed as well, but this one is in Villefranche-sur-Mer on the Mediterranean coast. The cause of this seaweed explosion is said to be global warming.

For more on these stories, read “Killer seaweed clears French beaches

For more on a similar situation in the San Francisco Bay, read “San Francisco Bay Overrun by Alien Seaweed Forest

Image credit 1: innacoz via flickr under a Creative Commons license

Image credit 2: mikebaird via flickr under a Creative Commons license

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  • MD

    H2S – “sour gas” is comparable to hydrogen cyanide, it combines with the iron in blood and blocks oxygen from binding, its not something you want to mess with.

    On the other hand, maybe they could figure out a way to harvest it to get the hydrogen…

  • gosiek

    In Poland there are some plants in the rivers or maybe by the riversides – I’m not sure where exactly – which kill fish :( Those plants take oxygen from water and fish die….