C/N ratio and fossil pigments in sediments ofsome Estonian lakes: an evidence of human impact andHolocene environmental change

The content of carbon (C), nitrogen(N), fossil carotenoids (TC) and chlorophyllderivatives (CD) in the sediments of five Estonianlakes was analysed. Historical records of man-inducedchanges on catchments were used for the interpretationof the obtained data. On the basis of the C/N ratiosit was estimated that the planktonic matter formed ca.25% (C/N ratio 24) to 90% (C/N ratio 8) of theorganic pool matter of lake sediments. In eutrophicLake Ruusmäe the fraction of the phytoplanktonproduced in lakes was highest, amounting toapproximately 80–95% of the deposited organic matter.Remarkable C/N changes were noted in the sedimentsfrom lakes Matsimäe and Viitna, where the contentof planktonic matter has increased during lastdecades, reflecting an increase in recreationalactivity around these lakes. The variations in pigmentconcentrations in the sediments of lakes Matsimäeand Ruusmäe could be explained by changes in theland-use that have altered the intensity of primaryproduction and conditions of TC and CD degradationbefore the final burial.