Thanks to this condition, sea creatures typically living on sandy bottoms coexist with others which are endemic of rocky marine habitats, thus enabling visitors to witness a wide range of fauna in a single and easily accessible site.
The set of organisms that live on, in, or near the seabed is called benthos. Larvae, fish at juvenile stages and adult fish which are populating the benthic community feed on organisms coming from the water column, called zooplankton. The term “zooplankton” is generally used to describe groups of small herbivorous crustaceans called copepods, which in turn feed on phytoplankton, produced by algae and plants belonging to the marine ecosystem.
This series of interconnections forms the reef’s food web: while vertebrates tend to be at the top of the food pyramid, algae and plants are the organisms populating its bottom levels. As a matter of fact, algae and plants have the ability to produce their own food using solar energy, while representing an important food source for many different types of other organisms.
Algae and aquatic vegetation are important components of marine ecosystems. They represent the first link in the food chain. Through the energy they receive from light, they can make their own food by photosynthesis; moreover, they also are food for a wide range of creatures up the food chain. However, although they share this fundamental feature, algae and plants are two profoundly distinct groups.
From a biological point of view, they generally are considered as belonging to two different kingdoms.
Although bearing a remarkable resemblance to plants, the vegetative body of algae, called thallus, does not have the specializations of the latter. As a matter of fact, nutrient uptake and gas exchange take place along the entire surface of the algae.
The role of algae in marine ecosystems is crucial. They are very important as primary producers: thanks to photosynthesis, they produce energy and, at the same time, they provide oxygen and nourishment for a wide variety of aquatic life. However, algal blooms, which are often linked to human pollution, can cause serious imbalances in underwater ecosystems.
Hidden among the grains of the sandy seabed extending right in front of Mount San Bartolo, Lumbrineris luti is a marine polychaetes worm that lives sunken in the sand and that can be detected through the presence of small holes in the ground. Of the same family but belonging to another genus, Sabellaria worms inhabit this area, too, but they live in rigid tubes that they build using sand and shell fragments.
These tubular structures play a significant role in the conservation of the coastal environment as they stabilize sediments and reduce coastal erosion.
The sandy shoreline is also populated by numerous bivalve mollusks, such as the Adriatic clam (Chameleagaliina), and sea snails (Nassarius nitidus). For the crustacean group, some of the species living in thisecosystem are the small hermit crab (Diogenes pugilator), the grey swimming crab (Liocarcinus vernalis) andthe Squilla mantis shrimp (Squilla mantis). Some species of fish live in or right above the surface of the sand to disguise their presence, such as the greater weever (Trachinus draco) and the common sole (Solea solea),while shoals of striped seabreams (Lithognathus mormyrus) and cow breams (Sarpa salpa) swim in the water column. Red mullets (belonging to several Mullus species) live on the edge of rocky areas, still preferring sandy bottoms as they usually search for food in this type of seabed. In late spring, European common cuttlefish (Sepia officinalis) also use this area for reproduction and can thus be seen in large
Cetaceans, such as groups of common bottlenose dolphins (Tursiops truncatus), and loggerhead sea turtles (Caretta caretta) can also be spotted crossing sandy sea waters.
Rocky areas in the aquatic section of the Natural Park of San Bartolo are of great significance from the point of view of biodiversity. Many organisms use the hard substrates as an anchoring point or exploit nooks and crannies in the rocks as a hiding place, thus attracting predators which in turn increase diversity.
Purple-tipped snakelocks anemone (Anemonia viridis) is a cnidarian animal with slightly stinging tentacles and it is very common in this area. Some species of crustaceans find refuge among its tentacles, such as the shrimps of the genus Palaemon, which are immune to the toxin produced by the anemones. Numerous bivalve mollusks live on the reefs, too, such as the Mediterranean mussel (Mytilus galloprovincialis) and the European flat oyster (Ostrea edulis). Some polyplacophores are present mainly at intertidal level, such as the green chiton (Chiton olivaceous). Among the crustaceans, it is also common to spot the marbled rock crab (Pachigraspus marmoratus) and the European spider crab (Maja, several species). Concerning fishes, the wildlife of the area include a large and varied population of gobies (Gobius niger, Gobius paganellus) and combtooth blennies (Salaria pavo, Parablennius incognitus, Parablennius rouxi). Other species populating the site are seabreams (Diplodus, several species), wrasses (Sympodus, several species), saddled seabreams (Oblada melanura), grey mullets (Mullus, several species).
With a bit of luck, in the nooks and crannies visitors might spot a European conger (Conger conger) or a long-snouted seahorse (Hippocampus guttulatus).