Even though the Gulf of Trieste is in the Mediterranean it is difficult to find here the typical elements of this sea. The depth never exceeds 25 meters compared to 2500 meters of the Tyrrhenian Sea or 250 meters in the middle of the Adriatic Sea.
The depth create the conditions for considerable water movements and therefore for the big exchange of water which, because of the closeness of the city, is important for the Gulf. The Bora, for example, screened by the highland, doesn’t affect very much the North-western slope but blows almost parallel to the Barcola seashore towards the Castle and creates rather impetuous currents. Another very important current is the one connected to the Isonzo floods. Enormous water masses wedge in the sea a few kilometres from the Reserve. This provokes local movements sometimes so strong as if they were rivers near the shore and often in the direction opposite to the incoming current.
The Mediterranean Sea is transparent while those that arrive in Trieste almost always encounter cloudy water due to the sequence of rivers that flow into the small gulf such as Isonzo and Timavo on the first place. The situation changes already over the eastern border. In Dalmatia scarce inflow of water and greater depth “bring back” the Mediterranean features.
Another element that distinguishes the Gulf of Trieste from other seas is the range of the tide. In the Mediterranean tides practically do not exist whereas here, enlarged because of the particular, closed shape of the Adriatic Sea, they are very evident, especially along the sandy coasts near Grado and Marano lagoons where the sea can ebb for more than 100 meters. If one observes the Italian Adriatic coast another exceptional element can be noticed. In Duino the sequence of sandy beaches is interrupted and the karst highlands descend directly to the sea. Miramare is the first rocky promontory encountered after the multitudes of small bays, islands and small islands of Istria and Dalmatia
Water temperature can range from 7°C in February to 26°C in August while in the Mediterranean Sea the temperature is rarely bellow 13°C or above 24°C. It can be distinguished different seasons at sea, slightly late compared to the ‘on-air’ seasons but still well characterised. There is summer period (June-November) and winter period (December-May). Intermediate seasons cannot be identified since the change from one condition to the other is almost always very abrupt. For example a violent spring Scirocco is enough to change winter condition to summer one or an impetuous Bora to bring the condition back to the previous season.
In this peculiar sea there are, therefore, organisms used to living in extremely variable conditions. There are typical organisms of the intertidal zone such as brown algae, Fucus virsoides with particular adaptation to submersion, organisms resistant to the sudden changes of salinity due to the presence of rivers (sometimes even the trouts were seen and fished) and organisms able to resist high or low temperatures. The whole Gulf environment depends very much on the temperature. The first defence of the organisms is to move away. Almost all fish do so while the invertebrates simply reduce their activity.
One year in the Reserve
Normally the year begins with a long period characterised by stable hydrodynamic conditions, transparent water and a good illumination due to the clear sky even if the day is short. In such an environment, limited by a low sea temperature (7°C), a big increase of algae coverage bloom, favoured by the light, was noticed. The brown algae, used to a rigorous climate, are easily seen, followed by the red algae Chylocladia verticillata with typical blue-violet colour that will disappear as soon as the temperature reaches 14-15°C.
On the surface, as far as one metre and a half deep, Scytosiphon lomentaria, a brown, filamentuous algae shows that the temperature must be much bellow 10°C. It is obvious that near the surface the environment is affected more by the temperature. The Bora that blows in February lowers the temperature creating evident differences between the data taken in the open sea and near the shore. In this period the transparent water and favourable conditions for diving are in contrast with the underwater landscape - fish are missing. Some of them stay in the cracks in a kind of hibernation while others move a bit farther away, where the water, even if cold anyway, doesn’t reach such cold temperatures as in the Reserve. With the rise of the temperature and the first sea-storms in March and April, the algae coverage detaches from the seabed, the snow in the mountains starts melting and the rivers carry the silt. Cold and clear water slowly becomes cloudy and warm. It is the period of nudibranch’s reproduction and the egg spirals of Chromodoris luteorosa and Cratena peregrina are easily seen on the rocks.
May, in spite of its instability, is the period of the year when the beginning of fish activity can be noticed. The water temperature reaches and exceeds 15°C often very quickly. First sea basses, thin because of the winter, can be seen as they start catching the smelts around the rocks bellow the Castle.
Already in April, though, Blennies and Gobids and even sea-horses Hippocampus guttulatus can be seen near the coast. The peacock wrasse, Crenilabrus tinca, and the brown wrasse, Labrus merula, seem to be the only species seen also during the winter. The first ones to appear, at first sporadically and then in bigger number, are wrasses such as Crenilabrus ocellatus, Crenilabrus cinereus and Crenilabrus mediterraneus, some of which already start making the nests.
Juveniles of the genus Diplodus are found off-shore followed by other species among which (after 14°C) the brown meagre, Sciaena umbra, maybe the most characteristic species of the Reserve since it is present in very big shoals. During the summer there is a gradual diminishing of algae coverage especially near the surface where water reaches and exceeds 28°C. This phenomenon besides extreme environmental conditions is almost certainly due to the water temperature and the presence of herbivores such as the saupe, Boops salpa, a gregarious species that feeds in very numerous shoals during the months of August and September. During the summer, sea breams Diplodus sargus, Diplodus annularis and Carax puntazzo appear in groups near the shore. For the whole summer they stay there together with saddled bream, Oblada melanura. As far as other species are concerned, their presence is highest in this period. Mating of Mediterranean damselfish, Chromis chromis, continue in this period and starting from September the blue skin of the juveniles can be seen. Our autumn corresponds to the lowering of the sea temperature, gradual disappearance of fish species and gradual reappearance of the algae since they are no more subject to grazing.
As the temperature lowers to 14°C and then to 10°C, almost the same sequence of species is noticed as during the winter. In this period rapid changes in the fish population are also noticed. With the lowering of the temperature the first departures of the species occur starting from the rapid disappearance of the brown meagre, Sciaena umbra, towards the end of October. With the first blows of Bora the Reserve assumes its winter appearance waiting for the warm season.
An international Marine Park ?
Gulf of Trieste is the most northern point of the Mediterranean and thanks to the numerous and interesting biological and landscape characteristics it can be rightly considered a big “marine park”.
There are already various marine and coastal protected areas in the gulf and other could be created in the future. In fact, apart from the already existing Miramare Marine Reserve in Italy, Strugnano and Piran in Slovenia and the natural park on the Island of Cona, the following can be considered as possible areas to be protected: the mouths of Timavo, the wetlands of river Cavana in Monfalcone and very important lagoon environment.
All these areas that form a complete biogeographical unity, not divided by geopolitical borders, could form “The International Marine Park of the Gulf of Trieste” which, so far, is only an idea.
But even if the international park is still only an idea it is not the case of the continuous interchange of collaboration between Miramare Marine Reserve and Slovene Marine Reserve in Strugnano, a protected sea area of 60 hectares under the municipality of Piran established in 1989. It is situated on the extreme east of the Gulf of Trieste together with the small reserve of Punta Madonna.
This collaboration was rendered official in December, 1990, when an agreement was signed with the Institute for the Protection of Natural and Cultural Resources of Republic of Slovenia that runs the reserve. The interchange of information and experience, the joint work on publications, the study and the use of methods of education and spreading of knowledge of the sea were agreed upon.
Together with the efforts to strengthen the collaboration with the institutes of Republic of Slovenia in order to protect globally the Gulf of Trieste another thing to be mentioned is the remarkable work done within the MEDPAN (Mediterranean Protected Areas Network). It is a union of marine parks and marine protected areas of the Mediterranean whose representative in Italy is Miramare Marine Reserve. The MEDPAN’s main office is in Port Cros, France which is the first marine park created in the Mediterranean. It was created by EPM (Environmental Program for the Mediterranean) supported by World Bank and European Investment Bank in order to respond to the needs of Mediterranean countries as far as environmental policies and financial and institutional needs are considered.
The main purpose of MEDPAN is to increase the co-operation and the interchange between the protected areas located along the Mediterranean coast.
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