Holocene palaeolimnological and palaeohydrological changes in the Baćina Lakes

We investigated the lake evolution under the light of sedimentary, geochemical and mineralogical processes ; endogenic lacustrine carbonate production/formation ; and the association between the limnological evolution, climatic changes and human impact. Analysis of the sedimentary record from Lake Crnisevo, the deepest lake, provides a representative palaeoenvironment of the Bacina Lakes from the end of Late Glacial to the Holocene (Fig. 17 ; Ilijanic et al., 2015 ; Miko et al., 2015). Sediment records from the Bacina Lakes suggest that lake water levels were low during the early Holocene period when the outflow from the lake was possible only through the karstic underground (ponors) due to the lower sea level. The Holocene sea level rise caused the lake high stand in the Bacina Lakes, which is determined to be up to +9 m asl, by the sediment characteristics in the lake catchment. The Lake level didn’t change until the present and recent human interventions, especially the outflow tunnel constructed in 1913, which drained the water from Lake Sladinac to the sea and caused the lowering of the lake level in the Bacina Lakes by up to approximately 40%, representing the biggest human intervention in the lake ecosystem that significantly changed the palaeolimnological conditions (Miko et al., 2015). The water outflow changed from ponors in Lakes Crnisevo and south of Lake Vrbnik (connected at that time) to surface outflow from Lake Sladinac to the sea. Lowering the lake level separated Lake Vrbnik from the rest of the lakes, and isolated Lake Crnisevo. Generated anoxia in Lake Crnisevo initiated formation of recent varved lake sediments as a result of increased lake productivity and eutrophication.