Carbon and oxygen isotope composition of organic matter and carbonates in recent lacustrine sediments

The distribution of stable isotopes (O-18 and C-13) and radiocarbon in organic materials, carbonates and water samples collected from the environment of lacustrine sediments in Gosciaz Lake (Central Poland) and Wigry Lake (NE Poland) were investigated. The oxygen and carbon isotopic analysis of terrestrial semi submerged and submerged plants, shells and water samples were compared with the results of the uppermost sediments from lakes. It was found that the concentration of isotopes in different components of organic and carbonate materials in lakes and their environments are reflected in isotope composition averaging of lakes sediments, whereas the isotope composition of plants and carbonate depends on biogeochemical factors. The research carried out revealed significant variations in the distribution of the stable isotopes and C-14 in different elements of lacustrine ecosystem. We have analyzed mean values and variations of C-14 concentration, delta O-18, delta C-13 of plants, carbonates and the relationship between the total content of carbon and delta C-13. In the case of plants, the isotope composition depends also on the physiognomy and the photosynthesis pathway. We noticed variations in delta C-13 and delta O-18 within plant tissues, variations in delta C-13 among whole tissue material and alpha-cellulose, carbon isotopic composition of photosynthetically fixed carbon and syntaxonomic dependences and then we compared the results of isotope composition of plants and carbonates in Wigry Lake and Gosciaz Lake.