The Adriatic sea got its name from an ancient
port of the same name. The Adriatic spans from
the Balkan to the Apennine peninsula. The part
belonging to the Republic of Croatia is the east
coast which extends all the way from Prevlaka in
the south to cape Savudrija in the west,
including all islands, islets and cliffs along
the coast,and the archipelago of Palagruza (the
number of islands, islets and cliffs is more
than 1700).
This is a unique area in Europe for cruising
with motor boats, speedboats, or sailboats, but
also for enjoying the underwater world.
Hydro and Oceanographic Data
Depths
The shallowest part of our sea is in Istria,
where the depth does not exceed 50 metres. From
Pula, the seabed mildly drops, making a long,
narrow valley which extends from Zirje towards
Italy which is called Jabucka kotlina. The
biggest depth there is about 240 meter. From
Jabucka kotlina, the bottom rises to Palagruza
reef where the biggest depth is 130 meter.
Towards the south, the bottom drops steeply
towards the Juzno jadranska dolina, where the
biggest measured depth is about 1,300 meter.
Seabed
The appearance of the underwater relief is the
consequence of tectonic movements, abrasion or
erosion which were active several million years
ago, in times when certain parts of the seabed
were land or the coastal area. Uneven areas on
the bottom are constantly reduced by
sedimentation of detritus from the land. That
process is slow, but constant.
Tides
In the Adriatic, the high and low tides have
relatively small amplitudes. In the southern
part, the difference is rarely above some forty
centimeters, while in the northern part it is
somewhat bigger, so that it comes to 1 metre in
Istria and the Gulf of Trieste. In some narrow
channels and bays, the high tide can grow
considerably during a strong sirocco. That
phenomenon is characteristic for big and deep
bays of the southern Adriatic. The tides are of
a mixed type, which means that their rhythm is
semidiurnal during the new and full moon, and of
a daily type during the first and the last
quarter. Their amplitudes are very irregular.
Sea Currents
Sea currents occur under the influence of winds,
the difference in pressure, temperature, and the
differences in salinity. With respect to the
direction, they can be horizontal or vertical.
There are also bottom currents which appear as
the consequence of moving of water from warmer
areas to colder ones, during which the surface
layer gets cold and descends towards the seabed.
Currents are weakly observable in the Adriatic.
The speed of currents changes in particular
areas, but it also depends on time periods. The
average speed of currents is about 0.5 knots,
but they can also reach the speed of 4 knots.
Salinity of Sea
The total quantity of salt dissolved in one
kilogram of sea water is called salinity, which
is usually expressed in grams. The salinity of
the Adriatic Sea is 38.30 per mill averagely,
i.e. there is 38.30 g of salt dissolved in 1 kg
of water. In the northern part, the salinity is
somewhat lower than in the middle and southern
part because of the influence of the Po River.
Sea Temperature
The Adriatic Sea has a very marked annual change
of the surface temperature. The average annual
temperature is 11°C. During the winter, the sea
is the coldest and the surface temperature is
about 7°C; very seldom, it can drop below that
too. In the spring, the sea becomes warmer, and
the surface temperature rises to 18°C. In the
summer the surface of the sea reaches a very
high temperature, of up to 22 to 25°C, and in
the southern Adriatic and Istria up to 27°C. In
the Adriatic, thermo cline, i.e. parts of the
water column of the same temperature, are very
well distinguished. The thermo cline is most
evident during the summer, and, in the winter,
the isothermal process arises, i.e. equaling of
the temperature throughout the water column. In
the summer, we can notice the first thermo cline
at the depth of 3 to 5 meter, the next one is at
about 12 meter, and yet another one at 18 meter,
while below 30 meter the temperature is mostly
constant throughout the year.
Waves in the Adriatic
Waves occur primarily as the consequence of the
blowing of winds. The bigger the reach, i.e. the
surface across which the wind blows, the higher
the waves will be. Their strength depends on the
configuration and the exposure of the coast. In
that way, mixing of the surface layer with water
from the deep is enabled, and the interaction
between the atmosphere and the sea. We
distinguish the crest and the trough of a wave.
The length of the wave is the distance between
two troughs. Most often, heights of waves in the
Adriatic are between 0.5 and 1.5 meter, and they
very rarely exceed 5 meter.
Preservation of the Adriatic
Aside from the rich cultural heritage, diverse
natural resources and attractions characterize
the Adriatic. Nature is specially protected
according to the Constitution of the Republic of
Croatia. The state body with the special task of
preserving nature is the Government Board for
the preservation of nature.
The coastal region holds a special place, and
therefore, there is a systematic policy of the
preservation of nature through urban planning
and managing of the sustainable development.
The institutes for research of the sea in Rovinj,
Split and Dubrovnik carry out continuous
biological, ecological and chemical research of
the Adriatic. The project for the development of
islands was recently introduced and should be an
incentive for the development of our for
islands. Except for the governmental bodies,
there is also a whole range of associations
which, through for for their programs and
activities, help to preserve natural resources.
Croatian biological and Croatian ecological
society carry out and support research projects
of the Adriatic and its underwater area. There
is also the project of the Good dolphin research
in cooperation with the Tethy Institute from
Milan and An Association Mediterranean Monk Seal
which examines research of the areas which used
to be inhabited by this sea mammal, Group of the
friends of nature 'Our Lovely' who also work on
the Blue flag project, Green flag and Eco School
with the primary task of educating younger
generations about ecological matters.
Life in the sea
Various animals and plants live in the Adriatic.
We can distinguish two types of habitats: the
plegic area or the area of the open sea where
two big groups of organisms live plankton, that
is to say, all organisms floating in the sea,
and nektons or real swimmers, all organisms
which can actively move around. The group of
benthos, or life at the bottom of the sea,
includes all organisms, which are constantly or
occasionally connected to the sea bottom. In the
water mass between the mentioned areas we can
distinguish different belts or steps with
different characteristics:
Supralythoral, which is the part, exposed to the
spraying of the sea, Mediolythoral which is the
area of the high and the low tide. Then comes
infralitoral or the area of photophilic algae
and, which in the Adriatic expands from the
border of the low tide to 30-50 meters, Abyssal
which reaches 50 to 200 meters, Hadal or the
deep sea area, which extends more than 200
meters in depth.
Abyssal exists only in the southern part of the
Adriatic, and in the area of the Jabuka basin,
and hadal does not exist in our sea Crabs
inhabit the supralythoral area of the Adriatic.
Endemic algae, the Adriatic bladder wrack and
sea anemone inhabit the mediolythoral area. In
the infralythoral area, which is the largest
one, many species of algae, corals, and
different sorts of fish like sheepshead bream,
the predatory yellow fish, ugly frog-fish,
gilthead, goby, bamboo fish and many others.
The Adriatic eco-destination
The quality of the water in the Adriatic is very
well preserved. The results reached through the
constant measuring of the quality of water on
more than 800 beaches are in accordance with the
strictest criteria. Except for the cleanliness
of the sea, another important quality of the
coastal area is its biological and geographical
particular quality, which can be seen in the
number of species of plants and animals, and in
the high number of endemic species (for example
human fish).
In order to protect and preserve such natural
wealth, a list of rare and endangered species,
the so called Red Book, has been made. Various
projects are carried out in Croatia by
government institutions or associations of
citizens with the goal of preserving natural and
cultural heritage, and its evaluation. One of
these projects is The Blue Flag Project, and
from the year 2001, the project Green Key also
starts with the goal of improving the quality of
surroundings in hotels, motels, camps and other
facilities. Another project is Eco habitat Green
Laguna in Porec, where the environment is
especially taken care of. Green Laguna has its
olive groves, orchards, horse stables etc. where
tourists can take active part in preserving the
environment.
Through the year several days are especially
marked in Croatia such as:
• International day for water preservation
• World meteorological day
• Day of the planet earth
• Day of the dolphins
• World day of preserving the environment
• Day of the Sun
Except for the natural, great significance lies
on the preservation of cultural heritage, as
well. National costumes and customs are
preserved. During the summer, in most coastal
towns special celebrations are organized in
order to show tourists our local traditions, for
example, traditional donkey race which is held
each year in Tribunje, Moreska - knights, dance
on Korcula.
Croatia is also, except for its ecological
cleanliness of air and water, an exceptionally
safe place where everybody feels pleasant and
welcome.
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