engleski

Paleolimnology of Holocene karst lakes along the eastern Adriatic coast

Lake sediments provide opportunities to reconstruct aquatic ecosystems through the past. Evaluating the stored environmental information in the sediments depends on the knowledge about the ecosystem and the understanding of the present-day lake response to environmental variability. Lake sediments are the result of the input material from the catchment and the lake productivity itself. Terrestrial input to the lake is carried through erosional processes and anthropogenic paths. Knowing the processes driving the terrestrial input is essential to understand for instance carbon deposition and nutrient input, which are linked to climate through weathering and transport processes. On the other hand, understanding the anthropogenic impact is key to assess the environmental status of a lake today and in recent history. Karstic lakes, wetlands, paleolakes as present karstic poljes in the central Mediterranean, Eastern Adriatic, are studied to determine depositional environmental changes. In carbonate bedrock, karstic processes such as dissolution and collapse are very effective in creating drainage patterns and depressions for lake development, which leads to the formation of dolines filled with water. Development of lakes on limestone substrate favors carbonate-rich waters. Therefore, endogenic carbonates are the main components of the Eastern Adriatic lake sediments in Croatia. The lakes are relatively small and relatively shallow (3 to 55 m). The depositional environment in such lakes is dynamic, with abrupt changes in geochemical and sedimentological parameters. Hydrology is dominated by groundwater inflow, with none with a direct connection to the fluvial drainage. Direct connection to aquifers makes the system very sensitive to regional hydrological balances, evident in lake level fluctuations. The key compositional properties for the karstic area are carbonate versus siliciclastic and organic material, to reconstruct environmental changes. Karstic freshwater lakes are subject to endogenic carbonate production during the dry summer periods, triggered by aquatic productivity. The main aspects considered in the present work are lake evolution under the light of sedimentary, geochemical and mineralogical processes ; endogenic lake carbonate production/formation ; and the association between limnological evolution and climatic changes. The endogenic carbonate production in karstic lakes is tested to the registration of the climatic signals throughout the Holocene and the influence of the seawater on the lake ecosystem. In studied lakes, the main sedimentological and geochemical characteristics in mainly profundal environments were described and paleoenvironmental changes during the Late Pleistocene/Holocene were interpreted. There will be mentioned karstic barrier lake on the Eastern Adriatic coast, Lake Prokljan as marine lake and Lake Visovac in River Krka, alongside submerged paleolake systems in the karstic isolated basins, like present marine lake Veliko jezero on the Island of Mljet, as well as paleolakes in Pirovac and Lošinj Bay.

lake sediments, eastern Adriatic Sea, Holocene

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