Ανοιξε το γραφείο του ΝΟΑ στο Πατητήρι για τα μέλη του και πληροφορίες για το κοινό. | Sea Flora |
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| Written by Jimmy |
| Saturday, 10 January 2009 14:06 |
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The peacefulness of nature in the Northern Sporades is unique. Sit on a rock by the sea and eavesdrop on the sounds of nature: the gentle passage of the breeze through the cistus and lentisk plants, the passing buzz of an insect, the rustling of a lizard, sounds mingled with the monotonous splashing of the waves on the rocks and shingle. As on dry land, where, except in the many transient places, the various biotopes can be discerned, so this transitional area between land and sea is divided into zones. The narrowest part of the shore, known as the white zone, is sea-beaten by storms and high winds. Especially in Autumn and Winter when rain is frequent, the water licks and ‘eats’ the surface of the shore. The sea comes up onto the rocks and the salt that remains gives them their white colour. Above that is the so-called grey zone, often soaked by the sea and so covered in a thin layer of weed. This gives way to the black zone. Here the rocks, affected by the blue weeds that break down limestone, are lacerated with grooves and spikes. Rocky Shores and Sea-Caves. The rocky shores are home to a rich underwater population. Along the length of the precipitous shores of the Northern Sporades, the bottom is mostly rocky, Either by origin or from the deposition of limestone formed from such things as bruozoa, solen, and coral. The life-forms are almost the same in both types of seabed, while their distribution depends on light penetration and the undersea currents. The first things to establish themselves entirely on the seabed are seaweed and other sea plants. A plethora of other organisms follows, such as bruozoa, knidozoa, solen, limpets and various types of shellfish. The sea-urchin (Arbacia lixula) lives on the rocks and eats plant life with its five teeth, which work like the head of a drill. A large concentration of sea urchins in one place is often an indication of pollution, because sea urchins adapt well to dirty water. Starfish move slowly on the rocks in their characteristic way and live on molluscs met on their way. A World of Sponges and Corals. Unique inhabitants of the depths are the sponges, among the lowest forms of life. In the seas of the Northern Sporades live, for example, Chondrosia reniformis, Achinoe tenacior, Crambe crambe and Axinella verrucosa. Many sponges are gathered for household use. Here in the Northern Sporades sponge-fishing has not been much developed, as happened chiefly in Kalymnos. The sponge fishers of Kalymnos have however exhausted the depths of sponges in many parts of the Aegean, and are now obliged to go in their caïques as far as the North coast of Africa to get a worthwhile supply. Around 600 kinds of sponge live in the Mediterranean. Sponges have existed on the planet for an impressive 600 million years. Among the sponges live various crabs and worms. The pollution of the sea is driving the sponges towards a quick extinction. Of the roughly 6,000 kinds of coral that exist in the world, only 86 live in the Mediterranean. The various Gorgonacea and Madreporaria are met with only rarely. Red Coral (Corralium rubrum) is found at great depths in the seas of the Northern Sporades. This rare and beautiful coral is unfortunately often made into ornaments in bad taste, sold as souvenirs. In some parts of the Mediterranean there are still professional divers who descend to 50 or 100 metres to gather them. The exploitation of coral in the Mediterranean is not confined to traditional methods. Special tools have been devised, terminating in steel pipes, six to eight metres in length, fitted with chains and nets which, as might be expected, destroy the sensitive environment of the depths. Of the coral gathered by this method only about 20% is usable, the remainder being thrown, destroyed, back in the sea. This practice is entirely illogical and should be forbidden at once. It is high time the European Union took an interest in these insupportable methods, set strict limits and ensured these were observed. Fortunately in Greece this method is little used. Throughout the Mediterranean the stocks of coral have been much depleted. If this exploitation continues Coral will remain only in protected areas, and there only on the assumption of correct use. Another significant type of coral growing in the Northern Sporades is Eunicella cavolinii, a thread-like coral with many wrinkles on its surface. It grows in caves, like Red Coral. Sea caves, formed by the action of waves on the steep coasts, are home to plants and animals that need little or no light, and their usual environment is the greater depths. Such inhabitants are the shrimps Pleisionika narval and Stenopus spinosus and other types of crustacean, also fish and sponges which are typically found only at great depth.Where these caves terminate in small beaches not covered by the sea, they can be used in certain circumstances by Mediterranean seals as resting places or places to feed their young. Let us say again how important it is to keep away from these caves so as to leave, at least here, nature untroubled. Also, when we dive with masks, we should approach this magic but oh-so sensitive underwater world with caution and respect. Forests of Poseidonia and Sandy Depths. The dense fields of Poseidonia are the ‘forests’ of the Mediterranean seabed. Their place in the Northern Sporades is the shallow waters of the southern shores. They grow according to the direction of the light, on sandy or muddy bottoms in the shallow coastal areas, at a depth of between 30 and 40 metres. The Oceanic Poseidonia (Posidonia oceanica), found only in the Mediterranean, is the dominant type of this underwater plant-carpet. Poseidonia is not a seaweed but a higher type of plant (with exposed reproductive parts), for all that the areas in which it grows are known as ‘Seaweed fields’. Other less common sea-plants are Zostera marina, Zostera hana, and Cyntodosea nodosa. These are to be found only on sandy or muddy bottoms at up to ten metres depth. Of course the young fishes find a safe refuge among these seaweed fields. The Poseidonia forests produce a lot of oxygen and are therefore of vital significance for the Mediterranean ecosystem. For this reason they have correctly been called ‘The lungs of the Mediterranean.’ In one square metre of such a forest can be found up to 7,000 plants, producing up to 14 litres of oxygen a day. Many kinds of creatures find food and refuge in these dense forests of the deep. The Pina (Pinna nobilis) the common sea-urchin (Paracentrosus lividus) and the shrimp (Hippolyte spec) are representative inhabitants. Typical shellfish of the forests are Bouchona (Tonna galea) and various kinds of the genus Cassididae. Both these live on sea-urchins and produce acid the better to dissolve the spiky weapons of their prey. At greater depths or in open seas exposed to the waves, the forests diminish and the sandy depths are bare. At a first glance the depths resemble a desert, but many creatures make their homes here too. Sole, skate, and dragon-fish do very well in this environment. Here also will be found starfish and olothouria (the common sea-cucumber). Squid of the family Sepia find their food in the sand, where many sand-worms and various kinds of shellfish are hidden. As we get further from the shore the bottom becomes muddy, with clay. In shallow waters one never sees actinozoa, acalephia or starfish. At greater depths live lobsters and crayfish, also many crabs and bivalves, such as the mooncomb (Pecten jacobaens) and Acanthocardia aculeata. The Open Sea Plankton are the most microscopic inhabitants of the open sea, but not the least significant. All the swaying organisms of the sea are described as plankton if they don’t move independently but are carried by currents. They are either plant-life (Phytoplankton) or animal life (Zooplankton.) Plankton are an important link in the sea’s food chain and are indeed the actual fount of all sea life. Many jellyfish also live in the open sea. When they are small they are carried by the sea currents and can be considered plankton. However when they grow up they are not so innocent: for instance Carybdea marsupialis gives a nasty sting on the skin to the unsuspecting swimmer. Representative fish of this biotope are tuna, shark, and swordfish. In the depths also swim the mammals of the Mediterranean; the dolphins and whales. Bibliography: Northern Sporades – National Marine Park (Gerald Hau / Claus Peter Hunter.) Translated from the Greek by Simon Darragh. |
| Last Updated on Tuesday, 03 February 2009 00:24 |
