MAERL
Their calcareous branches form an uneven carpet on the sediment surface and create many small spaces where organisms can live or find shelter.
Maerl thus provides a structure and complexity absent from a bare sandy seabed.
This environment shows that a landscape which seems mineral can actually be built by living organisms.
The seabed takes on pink, reddish, purple or whitish hues and seems to consist of countless small calcareous fragments.
Yet it is not simply gravel. Some of these pieces are calcareous red algae living freely on the seabed, without being attached to rock.
As they grow, branch and accumulate, they can form extensive areas called maerl beds.
The algae that form it deposit calcium carbonate in their tissues. They thus become rigid and can take the shape of small branches, nodules or concretions.
The nodular forms produced by these algae are generally called rhodoliths.
Their shape depends in particular on the species and environmental conditions. Some are highly branched, while others are more compact.
In the Mediterranean, these formations can occur on the soft seabeds of the continental shelf, often several tens of metres deep.
What looks like a field of small pebbles can therefore partly consist of living organisms.
AMIGANSEAU CONTENT
The rest of this article is for subscribers
Log in with your AMIGANSEAU licence to continue reading.
All active AMIGANSEAU licences give access to the full article.Explore the same world
