The salt marsh is the upper part of the sea mud flats which can be grazed. This flat natural expanse with low vegetation is flooded by salt water only during high tides.

The toponymy indicates that sheep farming must have been widely practiced at the Mer Blanche (Kermaout = Sheep Farm / Kerboc'h = Goat Farm / Kerouanquen = White Lamb Farm).

The surface seems perfectly horizontal, but it is not. The channel which meanders by forming real meanders is an extension of the slikke in the schorre.

All its ramifications are brought up by the sea at each tide and the depth of the channel is sometimes significant. Very shallow water holes are scattered throughout the salt meadow. Sometimes dry, they then show the classic desiccation polygons of the mud.

Every fortnight at least, the high tides renew the water there.

A whole life (fish, crabs, shrimps, plankton) finds in these ponds exceptional conditions in spring and autumn because the water is warmer there than at sea, as in the channel elsewhere.

On the other hand, the excessive heat makes the conditions very difficult for animal life in the summer, especially since evaporation increases the salinity rate of the water every day.