Benthic Algae on Tufa Barriers

Benthic algae are widespread in all inland waters. As photoautotrophs, they are very important oxygen producers and food sources for organisms of higher trophic levels, as well as locus of intense calcification which makes them closely associated with tuff formation in carbonate-rich waters. Tuff formation is driven in part by the loss of CO2 from the water when the balance is in favour of CaCO3 sedimentation. Algae aid in this process chemically by utilising CO2 in the process of photosynthesis and physically by producing extracellular polymers as locus of intense calcification. All taxonomic groups of benthic algae are capable of both processes, but some taxa have more specific ecology and preferences for this highly specific habitat. Diatoms and cyanobacteria dominate on the tufa barriers of Plitvice Lakes, but red and green algae are also present in significant proportions. Diploneis plitvicensis, as an endemic diatom for Plitvice Lakes, was also found on tufa barriers. Of the non-diatoms, taxa such as Oocardium stratum, Phormidium incrustratum and Rivularia haematites are highly specific taxa for carbonate-rich waters and play an important role in tuff formation. Abundance and composition of benthic algae on the tufa barriers of Plitvice Lakes are mainly influenced by nutrient concentration, alkalinity and saturation.