Marine flora and fauna

For Asinara, the marine environment constitutes an element of particular value and scientific interest and is substantially characterized by a high integrity and diversity of floro-faunal communities, a remarkable landscape value, and excellent water quality in terms of ecology and chemical contamination.

The movements of the sea

Along the western side of the island, the surface circulation exhibits a marked seasonality: during winter the currents have a northeast to southwest direction and carry water masses from the west coast of Corsica, while in summer their motion is reversed. Within the Gulf of Asinara, the currents tend to move according to an hourly circulation that appears most pronounced in westerly winds, and to arrange themselves parallel to the coastline, particularly in the marine belt close to the shore. In the presence of southwesterly winds, the currents near the coast have a significant component in a direction perpendicular to it toward the open sea, resulting in vertical water movement of the deeper waters of the gulf.
The data collected by the Air Force over the course of 32 years from the station located near Punta Scorno, although referring to a period that is not recent, allow us to define a general picture of the state of the sea on the island of Asinara.
According to these data, the sea at Asinara is nearly calm on 20 percent of days and slightly rough one day out of two. However, for 25 percent of the days the sea à very rough. During the period between May and September, sea conditions appear more favorable for navigation (particularly in the summer months), while the winter months are characterized by more severe sea states.
By virtue of the considerable exposure to westerly and northwesterly winds, the seas on the western side and northern cape of the island occur more frequently in states that are not favorable for navigation. The eastern side of the island, facing the Gulf of Asinara, is more protected and accessible, here are located the landing points among which the Reale pier is the least exposed to easterly winds. At present, the marinas of Cala d’Oliva and Fornelli, although sheltered from westerly winds, suffer most from exposure to easterly and sirocco winds.
Within the gulf, based on maximum wave height data recorded by the oceanographic buoy located in the Gulf of Asinara at Porto Torres during June 2000 to April 2001, waves rarely exceed one meter.

Water quality

The waters surrounding the island of Asinara are generally of high quality, as indicated by the remarkable transparency and low concentrations of anthropogenic impact indicator compounds or elements, to which corresponds a remarkable integrity of biological communities.
In the summer period, the water column appears vertically stratified, with maximum temperature differences of about 6 °C and surface temperature reaching as high as 26 °C in August. In winter the opposite process takes place, with a water temperature of 17°C in December.
Similarly, salinity, which, however, has a more limited time range, increases its values in summer.
In summer, the value of dissolved oxygen in the water also increases: this enrichment is probably related to the metabolism of the posidonia prairie that can provide the system with a large supply in terms of oxygen, which due to summer thermal stratification remains more localized on the bottom.
The trophic state of the water, measured by the combination of some parameters (chlorophyll, dissolved oxygen, total phosphorus and dissolved inorganic nitrogen), indicates high water quality and absence of significant alterations.

The morphology of the seabed

The seabed on the two sides of the island has profoundly different characteristics.
The open sea side is characterized by slopes with considerable steepness that continue in the submerged part and rapidly sink more than 50 m even a short distance from the coast. Strong currents and considerable mistral wave action prevent the formation of significant sandy deposits and shape the coastline with ravines, gullies and rifts. A cave of significant size is located at Cala di Peppe, set at sea level at a depth of about 8 m and a height at the entrance of about 10 m.
The eastern side is generally characterized by low, mostly rocky and sometimes entirely sandy coastlines. The seabed toward the gulf, taking up the morphology of the emerged part, tends to slope gently to the typical average depth of the Gulf of Asinara, which is about 50 meters.
The area between Punta Scorno and Punta Sabina has intermediate characteristics between those typical of the two slopes. The sea floor appears uneven as a result of frequent outcropping of the rocky substrate.
In the area between Cala d’Oliva and Punta Trabuccato, and particularly in the Rada della Reale, the seabed is predominantly sandy and hosts extensive and intact Posidonia oceanica meadows. Further offshore, around the 50 m bathymetric, the substrate consists of sediment and organogenic detritus.