engleski

Carbon Based Proxies of Palaeoenvironmental Records in the Sediments of Two Lakes, the Plitvice Lakes, Croatia

Six sediment cores, top 30-40 cm, from two lakes of different sizes, Lake Prošće and Lake Kaluđerovac, situated in the karst region of the Plitvice Lakes system, Croatia, were studied by mineralogical and structural, C/N and total organic carbon (TOC) and isotopic analyses (a14C and δ13C of carbonate and organic fractions). Morphological and structural properties of the calcite particles at micron and submicron-sized level indicate that calcite mineral phase is formed by active authigenic precipitation in investigated lake systems. In the small Lake Kaluđerovac measured distributions of carbonate and OM fractions, C/N, TOC, and a14C and δ13C values of both fractions along the sediment depth showed similar values for all three cores with small variations in each core indicated very homogenous precipitation of autochthonous calcite inside the lake without allochthonous fraction. In the bigger Lake Prošće, the large difference in sediment composition of the three cores indicated different conditions of sediment precipitation inside the lake: in the coastal area the sediment was found to be a mixture of allochthonous and autochthonous fractions, while the deep-water sediment in the same lake indicated in-situ calcite precipitation and aquatic OM produced in the lake. The response of the lake sediment to the environmental conditions does not depend particularly on the size of the lake, but the surrounding environmental conditions could have great influence on the sediment composition. Extreme hydrological events in 1981 and 2010 were identified by disturbances in carbon isotopes distributions. Local anthropogenic influence was not evident, but the response to the global contaminations was observed by the occurrence of the a14C peak in both, carbonate and organic fractions. Increased bioproductivity in the last decades was observed in the Lake Prošće what can be correlated with slight increase of the lake water temperature in last three decades. The detailed work has been described in article accepted for publishing: N. Horvatinčić, A. Sironić, J. Barešić, I. Sondi, I. Krajcar Bronić, D. Borković, Quarternary International, 2017. doi: 10.1016/j.quaint.2017.01.022

lake sediments ; carbon isotope analyses ; C/N analyses ; mineral composition ; Plitvice Lakes ; Croatia

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