In the Sistiana area there is a truly unique situation: Moving a few meters below water level, you can observe two completely different environments: you go from the intertidal reefs, to the muddy bottom, from the rocky cliff to the bio blocks built by the accumulation of empty shells.
These environments are not always in communication with each other but often seem as if they were islets separated by "insurmountable" ecological barriers. A condition that made, for example, that rocks not far from each other are colonized by completely different organisms generating a great and extraordinary biodiversity.
As you enter the water we find the rocky area, pebbles and boulders that descend to 6-7 m. It is an area affected by two factors: the solar brightness and, unfortunately, the high contribution of fresh water of Karst origin. Algae, sponges and worms (Protula and Serpula) are plentiful. The calcareous rocks are often pierced by seadates (you can see only the folds of the mantle because the mollusc is inside the rock), and encrusted with anemones in turn in commensalism with the small ghost shrimp (Periclimenes amethisteus).
The areas among the rocks and less exposed to light are instead dominated by the crustaceous (Galathee, Pisa, Pilumnus and all kinds of crabs but always including the spider crabs “Granseole” and some small lobsters). These areas are also abundant with bivalve shells (in particular: Lima and Clamys) and the gastropods (Murex and Haliotis). In this area it is easy to see nudibranches even if their abundance is often conditioned by the cycle of the seasons. However, the D. limbata and D. grandiflora, the small Thuridilla and the elegant Cratene are almost always present. The colorful F. villafranca are also very comon and if you are lucky you can find F. luteorosea, B. caerulescens and P. quadrilineata … but the list is really very long. Among the very abundant fish, you find the “small-peppers” (yellow and red) and the bavoses (cornuta, white, rust but also the rarest yellow cheeks and sphinx) that here they feel truly at home. Sea horses (Hippocampus guttulatus) sighting is also absolutely not uncommon , as well as salpe and bream shoals.
At a first glance the sandy area seems to be less interesting to explore., yet in these areas life is really abundant even if the organisms do everything to get unnoticed.
The sea floor is dominated with anemones (Cereus pedunculatus), cerianti with their colorful and magnificent tentacles (C. membranaceous and C. solitarius) and Spirographs (Sabella spallanzanii).
There are frequent encounters with large sea urchins (Sphaerechinus granularis) with unmistakable white-tipped purple thorns, trying to protect themselves from the sun’s rays by covering themselves with pieces of algae and shells … and they do not disdain of human made fragments like pieces of glass, plastic and even swimming goggles. Starfish and olothurias (Onchus plancii), black and white ascidians are everywhere and you’ll often find colonies of madrepores.
But from the muddy sand, also incredible skyscrapers stands out rising from the bottom: they are the large and noble shells (molluschi) (Pinna nobilis) which act as a support for hundreds of other organisms: from red seaweed to bryozoa, from spirographs to serpules, from shrimp to sponges … each shell is a real microcosm each one different.
Nubibranchs are not missing even during the less hot periods, you’ll find species such as R. rubra, R. rosi, D. limbata but it’s not rare to meet the majestic Tethys or the strange Bursathelle.
It is not uncommon to see cuttlefish and sepiole, meanwhile among the fish we find “ghiozzi”, schools of mullet, scarves and thrushes that in the reproduction season (April-May) build their nest with pieces of shells and plant remains. With good eyesight you can even easily see the small hairy soles that remain so still that you could almost touch them.
It’s the area where you can find seahorses, even if they often camouflage by having “mud baths”. Encounters with jellyfish are also quite frequent, especially with the Rhizostoma pulmo.
The area of the cliff (falesia) is located inside the protected marine park. It is a rocky wall that goes down to 8-9 m, almost completely covered by sponges and black ascidians where the colorful serpules sprout like flowers.
The whole wall is colonized by abundant anemones (Anemonia viridis) often surrounded by
clusters of misidiacs which seek shelter among the stinging tentacles. Nudibranches are frequently spotted here as well (F. villafranca, T. lineata, Paradois indecora etc).
At the base, where the rock meets the sand, the surf often creates a dug area creating a great shelter for lobsters, conger eels and large thrushes (tordi).
Finally the bioconstructed area. These are true islands that emerge from the mud and are formed by the cemented accumulation of dead bivalve shells. The dead shells act as a rigid substrate and allows the new molluscs to develop, grow and, once dead, will be colonized by other organisms.
In addition to the bivalves, in these blocks we will find abundant black ascidians and anemones. Always present are also sedentary worms such as spirographs and protules that in turn can accommodate small hermit crabs and nudibranches (eg. E. viridis). Often we find also the solitary madrepores (Balanophylla) that are very close relatives of the most spectacular tropical corals.
Also often you can spot cuttlefish eggs (small blackish oval spheres) and squid eggs (white ribbons that enclose the eggs), usually attached to the spirographs or ascidians. With little attention you can also observe large spider crabs while among the madrepores and cereus it will be easy to find some ghost shrimps. Also in this area it’s possible to meet seahorses and needlefish (Sygnatus sp.) and if you are lucky enough and move slowly you can discover the small and colorful suckling.
Now that you know what you could find in the “abysses” of Sistiana, aren’t you curious to come personally and discover all these fantastic creatures?
If the answer is yes, do not hesitate to contact us to know exactly where and when to find us!