“Grotta della Ghigliottina” (Guillotine Cave)
The walls of the Cave that emerge from the water still preserve the holes dug by millions of bivalve stone-eaters, when the water level was higher than now.
All the underwater cliffs are characterised by the presence of stone-eater animals and building algae.
Sponges (Cliona) and bivalves (Lithophaga) settle themselves in the limestone, weakening the wall’s structure, exposed to the incessant erosive action of the waves.
On the contrary, in the darker areas, red limestone algae create jutting formations rich in gorges, environments fit for many others living organisms. A particular species creates concretions shaped like sidewalks, that stretch out from the cliff, just under the sea level, in correspondence of splits exposed to strong hydrodynamism. Its name is Lithophyllum lichenoides, and it indicates good environmental health, because it is especially sensitive to polluting agents, above all hydrocarbons.
The southern side depths.
These depths are rich in cliffs, which drop down to 22 m under the sea.
At the foot of the wall, big rock landslides, nibbled by sea-urchins, alternate with areas colonised by Posidonia Oceanica.
Small Karst-formations open up in several points, creating typical cave environments where slipper lobsters (Scyllarides latus) reproduce.
This side is surrounded by a small landslide area, not very deep, that ends on a detrital plain where praires of Posidonia are set.
In correspondence of “Punta del Papa” (Tip of the Pope), approx. a quarter of a mile from the seashore, the highest pinnacle of the “Secca del Papa” (Sand bank of the Pope) raises itself from 42 meters underwater up to 15 m above the sea level.
It is surrounded by many damselfish, ready to disperse and soon come together again, for fear of the arrival of voracious amberjacks.
Descending towards north-west, below the top of the sand bank, Paramuricee open up like big fans, between swarms of red damselfish (photo on the right).
The light from the electric torches shows the red colour of the colonies; there are many yellow variants, and the sight is even more beautiful.
Continuing along other two lower rock spires, covered with gorgonias, you come to a wide coral-area.
Sometimes you can see groupers and shoals of dentex.
Molara and Molarotto
The seascape is remarkablly different around these two islands and other smaller ones.
Granites reproduce underwater the same background you can see on land. Big, rocky “panettoni” with slits and holes and rich in “tafoni” (hollows produced by erosion) cover the depths between Molara and Tavolara.
The Fico reef, just a few metres away from Molara, is the prototype of this sequence of rocky banks. Under the water granite is covered with a thin algae felt, on which colonies of Hydrozoans (Medusae) frequently stand out, populated by coloured asteropoda molluscs without a shell.
In the shaded parts the red, yellow and orange sponges appear.
In the splits and gorges there usually are “corvine” and groupers.
Seabreams are common, while it is not easy to see the greater sargos.
From Molara up to Molarotto, a rugged seascpe replaces the round shapes, and alternates with wide detrital and Posidonia areas where big “gnacchere” (Pinna nobilis) often stand out.
Deeper down, some tangled coral formations give shelter to groupers, sargos, and lobsters (photo above).
The depths between Tavolara and Molara
This may be the most interesting underwater environment, if you
consider the variety and abundance of the populations; there are small
rocky juts in the channel between Tavolara and Molara (photo on the right), more than 36 m under the water level.
It is a typical coral habitat, with gorgonias (Paramuricea clavata and Eunicella verrucosa), big sponges (Axinella polipoides, Spongia agaricina) and black coral (Gerardia savaglia), a hexacoral common in deep depths.
Coral (Corallium rubrum) is not present in these environments, while it’s very common, also at low depths, in similar areas along the western coasts of Sardinia.
With this only exception, the sea environment that surrounds Tavolara, Molara and Molarotto offers such a variety of sceneries and populations that it represents a synthesis of all that you can find in the Mediterranean Sea, especially within the first 25 metres.
The results of the increase in coastal tourism and navigation around the islands are visible, mainly along the coast facing Sardinia.
The moderate increase of sedimentation and the slow regression of the Posidonia prairies are signs of a potential deterioration, not of a turnabout in the quality of the environment.