Photographer's Note

Another shot from Greece...
This is the water of Dafnoudi beach, near Fiskardo.
It's a little lovely beach, really enchanting expecially in the first afternoon (but too often really crowded also, with many people crying - my compatriot unfortunately are the best in this game) .
The water is crystal-clear and the pinewood smells of summer.
I was attracted by this "S" in the blue water, made by Posidonia alga, remaining only here because of the many boats anchoring nearby and destroying the Posidonieto. I find the cyan of the water fascinating, anyway I would prefer the dark blue showing that Posidonia and her inhabitants (fishes and sea horses) are still alive and healthy.

""The Posidonia ((L.) Delile, 1813) is an aquatic plant, endemic in the Mediterranean Sea, belonging to the family of Posidoniacee (Angiospermae Monocotiledoni).
It has characteristics similar to terrestrial plants, roots, stem and leaves rizomatoso long nastriformi up to a meter and united in tufts 6-7. It flowers in autumn and spring produces fruit floating vulgarly called "ear-sea".
Form of underwater meadows that have a major ecological importance, and is the climax communities of the Mediterranean Sea and exerting considerable action in protecting the coastline from erosion. Inside living organisms many animals and plants that are on the Prairie nourishment and protection.
The posidonieto is considered a good biometer of the quality of coastal marine waters.
A prairie of posidonia is the "climax community" of the Mediterranean, that represents the highest level of development and complexity that an ecosystem can achieve. The posidonieto is, therefore, the most important ecosystem of the Mediterranean Sea and was listed as "priority habitat" in Annex I of the Habitats Directive (Dir. No 92/43), a law that brings together all sites Community Importance (SCI) that need to be protected [21].

In the ecosystem the coastal posidonia plays a key role for several reasons:

* Thanks to its development into the leaf free up to 20 litres of oxygen per day per m2 of prairie [5]
* Biomass produces and exports both in neighbouring ecosystems both in depth;
* Provides shelter and breeding area for many fish, cephalopods, bivalves, gastropods, echinoderms and tunicates;
* Consolidates the seabed near the coast helping to counteract an excessive transport of fine sediment from coastal currents;
* Acts as a barrier soffolta [22] dead that the strength of currents and waves preventing coastal erosion;
* Damping wave operated by the layer of dead leaves on beaches protects them from erosion, especially during the winter storm surges.

Throughout the Mediterranean the grasslands of posidonia are regression [23], a phenomenon that has been increasing over the years with increasing human pressure on the coastline.

The disappearance of grasslands of posidonia has negative effects not only on posidonieto but also on other ecosystems, just think that the loss of a single linear meters of grassland can lead to the disappearance of several meters from the beach front, because of erosive phenomena [2 ]. In addition, the regression of grasslands involves a loss of biodiversity and a deterioration of water quality.
The Caulerpa taxifolia is an alga from other seas that in some areas of the Mediterranean is supplanting the P. ocean.
The Caulerpa taxifolia is an alga from other seas that in some areas of the Mediterranean is supplanting the P. ocean.

The causes regression can be found at:

* Pollution: the posidonia is very sensitive to pollutants;
* Trawling [24];
* Yachting (scraping from anchors on the seabed, oil spills, detergents, paints, solid waste etc. ...)[ 25]
* Construction of coastal works and hence the release of sewage at sea and increasing the turbidity of water hampering photosynthesis [26];
* Construction of dams, dikes and barriers that modify the rate of sedimentation in the sea [27];
* Eutrophication of coastal waters that causes abnormal epiphytic growth of algae, thus hampering photosynthesis [28].

Recently, the grasslands are also threatened by competition with two tropical algae accidentally released into the Mediterranean, Caulerpa taxifolia [29] and Caulerpa racemosa [30]. The two algae have rapid growth and are gradually supplanting the posido
The posidonieto is considered a good biometer the quality of coastal marine waters.""

chiaretta, bema ha contrassegnato questa nota come utile

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Additional Photos by Laura Torsellini (niphredil76) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 202 W: 50 N: 167] (850)
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