Researching the potential and intensity of tufa-building at target areas on the Krka River

Researching the potential and intensity of tufa-building at target areas on the Krka River
In 2023, the Croatian Biological Society conducted research to determine the potential and intensity of tufa-building on the seven tufa waterfalls of the Krka River

As part of the research, they installed experimental plots, measured environmental factors, and collected samples for analysis. The obtained results indicate the complementary activity of various tufa-building communities specific to each of the seven tufa falls on the Krka River, and that each waterfall has a unique sample of the presence and abundance of those organisms. Researching tufa deposition on the natural and artificial surfaces shows that the Krka River has a very high tufa-building potential on all its waterfalls, and that the intensity of this process depends on the specific environmental conditions and biological components, varying from low to very high, but is never negative.

Living and viable tufa-building communities, tufa-building mosses and conglomerates of cyanobacteria responsible for encrusting tufa were recorded at all the waterfalls, in addition to a wealth of macrozoobenthos fauna that contributes to the process of calcite mineral deposition.

An additional experimental plot was installed at Skradinski buk downstream of the waterfalls, at the locality where the swimming area was previously located. It shows the recent formation of tufa on living moss communities, and on old blocks in the main river channel and alongside it.

Also at this locality, in addition to the moss and cyanobacteria tufa, large colonies of green algae have developed on blocks of old tufa along the main river. Of special note are the communities of the terrestrial green alga Trentepohlia aurea, a species first recorded in the Krka River area in 1890, making this the oldest record of a terrestrial algal species in Croatia (Hansgrig 1890). In later research, this species was not recorded up until now, 30 years later, again in the same area. This species of terrestrial algae from the group of green algae (Chlorophyta), has an intensive orange colouration due to direct exposure to sunlight, and indicates the return and revitalisation of the community after the cessation of human activities at this site.