MAERL

Maerl is a very special marine habitat.

It is formed by calcareous red algae that live freely on the seabed. They are not attached to rocks.

As they grow, they form small branches that pile up.

Many little spaces appear between these branches, where animals can hide.

Maerl is therefore both alive and able to create a habitat for other living things.

When sand becomes maerl
This colourful carpet is not simply made of little pebbles. Part of it consists of living calcareous red algae accumulating on the seabed. © dive.explo360.fr — All rights reserved. Reproduction prohibited without permission.
Underwater, maerl can form a surprising pink, red, purple or whitish carpet.

At first glance, you might think it is made of small pebbles.

Yet some of these pieces are calcareous red algae.

They live freely on the seabed and are not attached to a rock.

As they grow and accumulate, they can cover large areas.

Maerl algae can be as hard as little pieces of stone.

They produce and deposit a chalky material called calcium carbonate in their tissues.

They can then form small branches or rounder shapes.

These rounded shapes are called rhodoliths.

Some have many branches and others are more compact.

Under the sea, what looks like a little pebble can sometimes be an alga!

An alga that looks like a stone
Maerl algae can look like small branches or rounder little pieces called rhodoliths. They sometimes resemble pebbles. © dive.explo360.fr — All rights reserved. Reproduction prohibited without permission.

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