Monitoring organic loading of Visovac and Brljan Lakes
22/10/2025
Monitoring organic loading of Visovac and Brljan Lakes
During 2024 and 2025, the Ruđer Bošković Institute conducted research on Visovac and Brljan Lakes
The research results indicate a significant increase in organic loading in Visovac Lake in comparison with Brljan Lake. Concentrations of dissolved organic carbon were 2.5 mg/L in Visovac Lake, and 1.6 mg/L in Brljan. Visovac Lake showed pronounced stratification, while Brljan Lake did not. During the summer months, the deeper layers of Visovac Lake recorded anoxic conditions, which significantly impacts the chemical and biological processes within the lake. Statistical analysis highlighted the nitrogen compounds, particularly nitrate, as important parameters that describe the trophic and ecological condition of Visovac Lake.
Cyanobacteria, an important component in primary production, was present in the water column of Visovac Lake, but not in Brljan Lake. The appearance of anoxia significantly impacted the composition of the microbial community in Visovac Lake. This was seen with the appearance of biofilm of Chloroflexota, an indicator of reductive conditions and anoxia in the deeper substrate layers in the lake.
Due to differences in the microbial community compositions, the primary metabolic pathways also differ: phototrophy is dominant in Visovac Lake, while aerobic chemoheterotrophy is dominant in Brljan Lake.
Research
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