The Biodiversity of Arcachon Bay

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Arcachon Bay

Arcachon Bay is like a small landlocked sea. It is located about 50km southern to Bordeaux and it is linked to the Atlantic Ocean by a bottleneck. This basin is also supplied with fresh water by Eyre. Its shores with fine sand represent 80km of beaches.

Arcachon Bay is famous for its oyster farming and there are a lot of oyster beds here.

The diving in Arcachon Bay is pure pleasure. It is a sheltered place, very rich in fauna. Also, it is a sea slugs and flatworms paradise here.

In July 2004 I moved to Bordeaux and since then I have never stopped diving in Arcachon Bay and listing its fauna.

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Arcachon Bay

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Dune du Pilat

Arcachon Bay is a blend of the sea, sand and pine forest.
In the South of basin there is the famous Dune du Pilat. It is about 8 000 years old.

It is the highest dune of Europe and its size is imposing : 2.7km in length, 500m in large and 106m high. From the top, the view is beautiful.

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Ile aux Oiseaux
Eastwards you could see Banc d'Arguin, Cap Ferret, the basin and the ocean. Westwards the pine forest stretches away endlessly into the distance.
In the centre of the Bay there is Ile aux Oiseaux (Birds Island) with its famous tchanque cabins. Originally, these cabins sheltered the watchmen in charge of oyster beds surveillance.

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Ile aux Oiseaux

The biological balance of Arcachon Bay is delicate because we need to reconcile tourism with oyster-farming and with environment protection.
And for now, the beaches are dredged to the detriment of seagrass beds. Channels and oyster-farming harbours are regularly dredged and the mud is tipped out elsewhere in the Bay, and it smothers the fixed fauna. And seemingly nobody realizes the damage caused to this beautiful environment.


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Saint-Yves

Biodiversity study of Arcachon Bay

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Arcachon Bay

I'm diving steadily and I 'm aiming to list exhaustively opisthobranchs (sea slugs) and polyclads (flatworms) species of Arcachon Bay. This work started in 2003 and it is carrying on now.
I'm working in twos with Michel Barrabes, a big enthusiast of Arcachon generally and of the sea slugs particularly.

I hope to remind the need to protect Arcachon Bay by making known the exceptional biodiversity of this beautiful place.

Below you could see the list of species I photographed in Arcachon Bay. I will need more time to put all of them online.
Nudibranchs species list (59)

Suborder Doridina


Suborder Dendronotina

  • Dendronotus sp
  • Doto coronata
  • Doto maculata

  • Doto millbayana


Suborder Arminina

  • Janolus cristatus
  • Janolus hyalinus



Suborder Aeolidina

Opisthobranchs (other than nudibranchs) species list (16)

Order Anaspidea
  • Aplysia parvula
  • Aplysia punctata


Order Notaspidea



Order Cephalaspidea

  • Haminoea spp (x3)



Order Sacoglossa

  • Calliopaea bellula

  • Elysia viridis
  • Ercolania viridis
  • Limapontia depressa


Polyclads species list (12)

Suborder Cotylea
  • Pseudoceros maximus
  • Thysanozoon brocchii


Suborder Acotylea

  • Acotyleans spp (x7)
  • Leptoplanid sp.



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