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  26.05.2020, 07:00h

How it all began: ecological factors

Preserving the good ecological condition of water at the barriers is a top priority task of ecological protection, as the development and survival of the living communities on the barriers depends on it.

Global climate change and changes in water quality are the primary causes of change in sensitive ecosystems. Long-term monitoring of the ecological factors that most influence the development and survival of the living community in the Krka River enables a timely reaction to any observed changes.

The Krka River is a typical karst watercourse, which in the hydrological sense, is marked by pronounced seasonal fluctuations. Due to the reduced abundance of the source, in the dry summer period, the water levels drop. This significantly changes the hydrological conditions at the barriers, as the living world of the travertine builders begin to die off at the dried up barriers. Once these habitats are again under water, they begin to regenerate.

It has long been known that reduced flow rates negatively impact the travertine building process. Rising air temperatures and the stagnation trend in precipitation levels have resulted in a reduction of the mean annual flows of the Krka River, and with that a reduction in mean annual water levels. It can be expected that these trends will also result in an increase in the mean annual water temperature. The quantity of dissolved oxygen in the water, essential for all organisms living within, is directly associated with both temperature and flow rates, as cold water is better able to retain dissolved oxygen and therefore is more oxygen rich. As water temperatures rise, the dissolved oxygen levels drop, and the direct consequence is a decline in the number of living organisms in the water. The quantity of dissolved oxygen also depends on the rate of water flow: faster water is richer in oxygen and tends to warm more slowly than “calm” waters.

The travertine building communities are very sensitive to pollution and reduced water flow rates. Since the building of new travertine barriers depend on the specific communities of organisms involved in their construction and that inhabit them, these communities must be preserved in their original form, to ensure that the travertine building process continues on these barriers. All these changes to the quality of water at the travertine barriers leads to changes in the composition of the living world. The appearance of unfavourable conditions for the development of mosses, the building communities at the barriers, would jeopardise the entire process of travertine deposition and barrier growth. For that reason, preserving the quality of the water in the Krka River and the travertine deposition process is a long-term goal in the management of Krka National Park.