Fear over Arcachon Bay

A threatening seaweed

Maria and Jean-Michel Douet are standing on hot coals. In their cabin of the Cap-Ferret, the two young oyster famers are waiting for a fateful text message. « Tests performed in Arguin and in the Bassin came out positive for oyster and mussels. Everything is shut down. Courage and see you soon. » In oyster farming language this means disaster. Especially since the same scenario has been happening over and over again for the past five years and threatens 380 farms working on the 780 hectares of oyster beds yielding between 8,000 and 10,000 tons of oysters a year.

Jean-Michel and Maria Douet, young oyster farmers, are under pressure of the sanitary authorities © Philippe Henry / OCEAN71 Magazine

Dinophysis, a natural but toxic micro-alga seems to be the culprit. It releases a toxin which causes diarrhea in oyster eaters who ingest it. Oysters are water filters. They absorb and reject liters of sea water on a daily basis. They are thus the first to be contaminated. Even if this unwelcomed alga has never caused a single fatality, the European Union imposes the famous mouse biological test (see in chapter 2) in the name of the holly precaution principle, making oyster farmers hostages of the death, or survival of the little white mice…

The micro-seaweed dinophysis. If ingested the result in most cases is diarrhea. But this is enough for the French health authorities to forbid the sell of oysters © Philippe Henry / OCEAN71 Magazine

After years of research, the teams of the Institut français de recherche pour l’exploitation de la mer (Ifremer – French Institute for Exploitation of the Sea) have established a list of elements coinciding with the apparition of the dinophysis. « Spring unfortunately combines a number of events which seem to perfectly suit the alga, explains Roger Kantin, head of the Arcachon Ifremer station. Increasing daylight period, rise in water temperature (from 17°C) combined with fresh water influx carrying nitrates and phosphates from rivers which flow into the Bassin d’Arcachon. » As for the last two elements, they seem to be clearly resulting from human activity.

Other files

  • a recreated ancient wreck near Marseille © Francis Le Guen

    Underwater archeology: a dive amid cops and robbers

    Culture4 chapters

    According to UNESCO, there are around 3 million shipwrecks that sleep peacefully at the bottom of our seas and oceans. With the second largest marine area in the world, France has decided to go to war against the plunder of the remaining wrecks. But is it even possible? For almost a year, OCEAN71 Magazine led a lengthy investigation that took us at the heart of the French authorities and the ocean looters.

  • Gallery The ruins of Jazira Al Hamra © Philippe Henry / OCEAN71 Magazine

    Red Island’s mysterious village

    Culture, Economy1 chapter

    The United Arab Emirates is well known for its passion for extravagant skyscrapers and constructions, its exuberance and its financial power thanks to oil and gas. The emirs even try to conceal their relatively poor nomadic tribes’ history. Along the coast, we managed to find one of the last old villages of fishermen, abandoned. It is said to be haunted…

  • Video

    Secrets in the black eagles’ land

    Culture4 chapters

    Exploring Albania’s coast, the OCEAN71 team has discovered the existence of a forgotten antique city. The take-over of this port by Julius Ceasar during the Civil War has been one of the key events that led him to absolute power. Swiss archaeologists are currently the first to study the site. Discover this exclusive documentary through the 4 episodes of the first season.