engleski

Holocene lake sedimentary record and impact of sea-level rise in coastal wetland Velo blato on Pag Island

Coastal wetlands represent a critically vulnerable environment as transitional between continental and marine settings: i.e. between freshwater and seawater environments. The impact of anthropogenic activities on these environments has become a matter of concern. This study assessed the geochemical composition of lake sediments of several karstic wetlands within the Island Pag: Kolansko, Malo and Velo blato. Sediment core in Velo blato (568 cm) allows paleoenvironmental reconstruction using multiproxy approach, including sedimentological, mineralogical and geochemical analyses, measurement of 137Cs activity, radiocarbon dating and ostracod assemblage. Kolansko and Malo blato are small brackish wetlands connected to the sea, with an average water depth of less than 1 m. The maximum thickness of recovered sediment core in Malo blato is 35 cm, which shows the transition from terrestrial freshwater to the brackish environment. Kolansko blato archives the sediment record of the last 1800 years in 107 cm long sediment core. Sediments are characterized by homogenous dark gray to black sediments, sandy silts, macrofossil remains (marine shells), brackish ostracods and the consistent mixture of carbonates, quartz and organic carbon. In the sediment core from Velo blato, authigenic carbonate sedimentation prevails on weathered flysch bedrock at the bottom of the core. The time span of the sediment record is 8300 cal yr BP which gives the timing of the Velo blato formation as a freshwater lake. Brackish ostracods occur at 5000 cal yr BP caused by the Holocene sea-level rise. During the freshwater phase, 250 cm of the lake marl sediments were deposited, followed by 280 cm of brackish lake carbonates. Surficial samples (upper 20 cm) of the Velo blato are enriched in total organic carbon indicating high productivity and eutrophication processes in recent times. The influence of anthropogenic activities on the metal levels tends to be low in the sediments.

coastal lake and wetlands ; lake sediments ; karst ; eastern Adriatic coast ; geochemistry ; heavy metals ; total organic carbon ; ostracods

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