Coralligene – a diversity of species, structures and colours

Prospekt Depths, Interesting facts, News


Photo 1. The colourful coralligenous community is made up of calcareous
algae, moss animals (bryozoans) and sponges. (Photo by Sara Kaleb)

CORALLIGENE – A DIVERSITY OF SPECIES, STRUCTURES AND COLOURS

In the Mediterranean Sea, at depths from 30 to 100 metres
and in conditions of semi-darkness, strong sea currents and steep-sloping
rocky bottoms, a community of marine organisms evolved, whose diversity
of species, structures and colours makes it one of the most appreciated
and attractive marine habitats. The community received its name from calcareous
red algae of the family Corallinaceae, which are the core of the community.
Similar to other sedentary groups (for example, encrusting bryozoans and
corals), these algae absorb calcium carbonate to create sturdy calcareous
structures. In addition to biological building, the coralligenous community
is also characterised by biological deconstruction. For example, molluscan
borers and rock-boring sponges bore into the calcareous foundation, dissolving
it. A large number of threatened species, such as groupers, moray eels,
scorpion fish and crayfish , hide in these holes and cracks. Overfishing
and changes in sea water quality, together with mechanical damage caused
by anchoring and excessive diving, have an adverse impact on the delicate
equilibrium of coralligene. Because of their vulnerability and value,
coralligenous communities are protected at the European level by the Directive
on the Conservation of natural habitats and of wild flora and fauna (NATURA
2000 habitats).

Anyone who takes even the briefest look at the Kvarner
undersea world is amazed by the multitude of different colours and shapes
of calcareous algae, corals, gorgonians, sponges, moss animals and numerous
other colourful coralligenous organisms. Divers enjoy exploring the sea
bottom because of the unique natural beauty it contains. However, as often
as not, some divers like to take a “souvenir” from the seabed. But what
looks magnificent under water turns into a lifeless copy when plucked
from the seafloor and brought to the surface. The MedMPAnet project involved
the research of coralligenous habitats around the islands of Krk, Cres,
Prvić, Grgur, Goli and Plavnik and the seabeds of Brseč and Mošćenička
Draga. The aim of research was to develop and put in place a system for
monitoring coralligenous communities as part of the European Ecological
Network NATURA 2000.

Keywords: coralligene, calcareous red algae (Corallinaceae),
NATURA 2000

Patrik Krstinić/Marko Randić