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The place where the dragon awakens

Rogoznica Lake, a natural phenomenon that is also known as Dragon’s Eye has a unique water system on the Adriatic coast which is the last 20 years the subject of research of many Croatian and foreign scientists.

If you feel desire to visit the beautiful environmental scenes you do not need to go on a journey around the world, our homeland has it all. Lake in Rogoznica, a natural phenomenon that is also known as Dragon’s Eye has a unique water system on the Adriatic coast which is the last 20 years the subject of research of many Croatian and foreign scientists. Dragon’s Eye is a unique karst closed ecological system with distinct characteristics similar to those in the Black Sea. Dragon’s Eye is located on the peninsula Gradina, near Rogoznica, about thirty kilometers southeast of Sibenik.

rogoznica

In the lake is sea water which is in constant contact with the surrounding sea through cracks in the limestone cliffs that surround it. It is irregular in shape, area of ​​approximately 10,000 m². It’s surrounded with almost vertical cliffs high 4-24 meters above sea level. The bottom of the lake is sediment with a maximum depth of 15 meters near the middle of the lake.

Scientists believe that the geological occurrence of the lake is linked to the collapse of the ceiling of large cave formed by water in limestone rocks. This created hollow filled with sea after the last ice age and rising sea levels. In the lake there is almost always present stratification of water column based on temperature, salinity, density, concentration of oxygen and the presence of hydrogen sulfide. The occurrence of hydrogen sulfide is the result of sedimentation and disintegration of a large amounts of organic matter from the upper layers.

Color of the sea in the Dragon’s eye is greenish – blue in the surface layer, then relatively suddenly transition in yellow – green color, until the layer where the conditions with oxygen exceed in the conditions without oxygen (at 9-11 m depth). On that line there are large amounts of sulfur bacteria for which this water layer is pink to purple color. Deeper in the anoxic layer (layer without oxygen) until the bottom the sea is gray – olive to dark brown. Occasionally, there is a mixing of the aqueous layers with changing the color of the lake. This phenomenon locals also call the “awakening the dragon“.

The phenomenon that intrigues the scientists the most is the emergence of overturning the water column, where in fact there is a release of elemental sulfur and creating anoxic conditions throughout the water column in the lake. Such conditions were recorded in 1997, when died 20 thousand tons of living organisms in the lake. The last time this phenomenon has been recorded was in October 2011. However, what is, according to Dr. Irene Ciglenečki – Jušić from the Institute Ruđer Bošković, which studies this lake since 1994, positive is the fact that the organisms that live in the lake completely customize the extreme conditions of life in this ecosystem and therefore life in the lake will rebuild on it’s own.

Suzana Kišiček

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