Tufa of the Plitvice Lakes National Park

Tufa

of the Plitvice Lakes National Park

What are the other names for tufa (sedra) in Croatia?

Bigar, travertin, lehnjak, sedraš, sedravac, vodeni meki kamen (soft water stone), vapneni mačak (lime cat), pršinac

Waters of the Plitvice Lakes National Park cover less than 1% of the Park’s total surface area, but nevertheless they are still its most attractive and most visited part. The watercourse from the spring of the Bijela and Crna River over 16 cascading lakes to the Korana River transverses numerous barriers and cascades, creating a landscape of remarkable beauty.

The waters hold the secret to outstanding universal value of the Plitvice Lakes — the tufa-formation process in which tufa barriers form and grow. This highly complex process that has created the cascade lake system has not been fully explained to this day, but it is known that it includes a number of physico-chemical and biological factors.

One of the first researchers who pointed out the value of the biological component of tufa formation was Academic Ivo Pevalek.

Thanks to his research and insight, the Plitvice Lakes area was declared a National Park in 1949.

A c a d e m i c i v o p e va l e k

Tufa barriers are the Natura 2000 habitat type under designation 32A0 Tufa cascades of karstic rivers of the Dinaric Alps.

A GROWING ROCK Tufa is a porous rock formed and growing due to the deposition of dissolved calcium carbonate (CaCO3) in the water with the help of mosses, algae and microorganisms.

g r a p h i c r e p r e s e n tat i o n o f t h e t u fa f o r m at i o n p r o c e s s

LIFE ON TUFA BARRIERS The most common mosses on tufa barriers are Palustriella commutata and Ptychostomum pseudotriquetrum, but there are also mosses from the Eucladium genus.

Insect larvae participate in the tufa formation process either by integrating calcite in their cases (like caddisflies) or by calcium carbonate crystals being deposited on the fine nets used by insects for catching food. d e ta i l o f a t u fa– e n c r u s t e d m o s s

What is invisible to us but, crucial for this specific biodynamic system, are the blue-green algae (Cyanobacteria), the diatomaceous algae (Diatoms), various bacteria, protozoans (single-celled organisms) and multicellular microscopic organisms (e.g. rotifers, ciliates) that represent the periphyton of the tufa barriers.

Life on the barriers also includes caddisfly, mayfly and stonefly larvae, as well as other invertebrates such as gammarids, gastropods and some bivalves. However, the largest group on the tufa barriers are fly larvae.

c a d d i s f ly l a r va e

Periphyton is a living community of organisms that develop on rocks, plants and objects immersed in water.

AGE OF TUFA BARRIERS The process of tufa formation in Plitvice Lakes dates way back into the geological past of the Quaternary period.

The age of the active tufa barriers has been estimated at between 6,000 and 7,000 years, while the analysis of older barriers has shown that they are between 250,000 and 300,000 years old. The barriers of that age are found outside the present day watercourses, which shows that this system was continuously changing throughout its history.

Warm and humid climate conditions favour the process of

d e ta i l o f a d r y t u fa b a r r i e r b y L a k e G ava n o va c

C l u s t e r o f d i at o m a c e o u s a l g a e

tufa formation. Tufa is deposited faster in the summer than in the winter, in particular in the places intensely splattered with water. Calcite deposition is significantly slower in the lakes (around 1 mm) than on the barriers (10–30 mm).

ENDANGERMENT OF TUFA BARRIERS

Breaking off of tufa barriers

The complex process of tufa formation and tufa barrier growth can be endangered by: increased inflow of organic matter, eutrophication, changes of the watercourse, breaking off of tufa barriers – due to sudden melting of ice and snow, trees falling off the barriers, visitors walking on the barriers although it is forbidden, climate change.

A b r o k e n o f f p i e c e o f t h e t u fa b a r r i e r o n L a k e M i l i n o

d r y t u fa b a r r i e r s a n d l a k e

Conditions such as frequent and sudden melting of snow, freezing and unfreezing of water, and increased flow can cause smaller or larger pieces of tufa barriers to break off.

That can completely change the hydrological conditions on the barriers or parts of the lake system.

About 400 years ago, Kozjak Lake was divided into two lakes, separated by a waterfall.

However, the tufa barrier at the outflow of Kozjak Lake grew much faster than the barrier that separated these two lakes. This made the water level in the lake rise and gradually cover the waterfall. When the barrier became submerged, the two lakes merged into one, as we see it today.

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Znanstveno-stručni centar ‘Dr. Ivo Pevalek’ 53231 Plitvička Jezera — hr tel +385 (0)53 751 015, +385 (0)53 751 014 e-mail info@np-plitvicka-jezera.hr web www.np-plitvicka-jezera.hr

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Plitvice Lakes National Park is part of Lika Destination – destination of protected areas and a gastro-destination which offers an unique combination of inland and the sea, where you have the opportunity to experience no less than three climates in an only 30-minute drive, like in few other places, and truly experience this one-of-a-kind phenomenon of contrasts.

impressum — publisher Public Institution Plitivice Lakes National Park photos Public Institution Plitivice Lakes National Park Archives, Antun Alegro, Igor Stanković cover: Tufa barriers of the Upper lakes with Palustriella commutata mosses (photo: A. Alegro) text National Park Conservation Service