| Abstract | Chemical and biological sedimentary records of the high alpine lake Bubreka, Rila Mountains, Bulgaria, were used to reconstruct palaeoecological conditions and to determine the phases in the ontogeny of the lake. Sediment cores taken in 2000 were dated by 210Pb and 137Cs and analysed for percentage of dry weight (%DW), loss-on-ignition (LOI), pigments, diatoms, chrysophyte stomatocysts, cladocerans, chironomids and spheroidal carbonaceous particles (SCPs). The studies on Lake Bubreka show that high mountain lakes are good sites for the study of the evolution and effects of the long range transport of atmospheric pollutants from the industrial lowlands to mountain regions. Four distinct successional phases can be described in the lake history during the last ~ 250 years, revealing complex interactions between anthropogenic impact and climate. Phase 1 (c. AD 1762-1834) is characterised by stable oligotrophical conditions. During Phase 2 (c. AD 1834 -1928) there is a change from oligotrophic to mesotrophic conditions. Phase 3 (c. AD 1928 - 1994 ± 2) shows an increase in LOI due to the high proportion of organic material. The shorter ice cover period in the lake may have created conditions more suitable for the growth of phyto- and zooplankton and changed the overall primary production from benthos to plankton. In Phase 4 (c. AD 1994 ± 2 - 2000) there is increased LOI, increasing percentages of periphytic diatoms, less favorable conditions for cladocerans, and rheophilic chironomid assemblages which indicate rapid input of nutrients causing mesotrophication. The SCP record and comparisons with other European mountain lakes suggest there is a moderate impact from atmospheric deposition compared with similar lakes elsewhere in Europe. |
| Text | 71929 2009 Rila Mountains alpine lake sediments spheroidal carbonaceous particles pigments diatoms Environmental changes in the Rila Mountains, Southwestern Bulgaria, as recorded by the sediments of a remote lake Ognjanova Rumenova N. 1 ; Botev I. 2 ; Velle G. 3 ; Rose N.L. 4 ; Appleby P. 5 ; Brancelj A. 6 ; Lami A.; Musazzi S. 1 Institute of Geology, Department of Palaeontology and Stratigraphy, Bulgarian Academy of Sciences 2 Institute of Zoology, Department of Hydrobiology, Bulgarian Academy of Sciences 3 Bergen University Museum, University of Bergen, Norway 4 ECRC, University College London, London, UK 5 Dept. Mathematical Sciences, University of Liverpool, UK 6 National Institute of Biology, Ljubljana, Slovenia Chemical and biological sedimentary records of the high alpine lake Bubreka, Rila Mountains, Bulgaria, were used to reconstruct palaeoecological conditions and to determine the phases in the ontogeny of the lake. Sediment cores taken in 2000 were dated by 210Pb and 137Cs and analysed for percentage of dry weight %DW , loss on ignition LOI , pigments, diatoms, chrysophyte stomatocysts, cladocerans, chironomids and spheroidal carbonaceous particles SCPs . The studies on Lake Bubreka show that high mountain lakes are good sites for the study of the evolution and effects of the long range transport of atmospheric pollutants from the industrial lowlands to mountain regions. Four distinct successional phases can be described in the lake history during the last 250 years, revealing complex interactions between anthropogenic impact and climate. Phase 1 c. AD 1762 1834 is characterised by stable oligotrophical conditions. During Phase 2 c. AD 1834 1928 there is a change from oligotrophic to mesotrophic conditions. Phase 3 c. AD 1928 1994 ± 2 shows an increase in LOI due to the high proportion of organic material. The shorter ice cover period in the lake may have created conditions more suitable for the growth of phyto and zooplankton and changed the overall primary production from benthos to plankton. In Phase 4 c. AD 1994 ± 2 2000 there is increased LOI, increasing percentages of periphytic diatoms, less favorable conditions for cladocerans, and rheophilic chironomid assemblages which indicate rapid input of nutrients causing mesotrophication. The SCP record and comparisons with other European mountain lakes suggest there is a moderate impact from atmospheric deposition compared with similar lakes elsewhere in Europe. 62 Key words Rila Mountains, alpine lake sediments, spheroidal carbonaceous particles, pigments, diatoms, chironomids, cladocerans, chrysophyte stomatocysts Environmental changes in the Rila Mountains, Southwestern Bulgaria, as recorded by the sediments of a remote lake OGNJANOVA_RUMENOVA_etal_Bulgarian_lakes_AdvLimnol_2009.pdf Articolo in rivista Schweizerbart 1612 166X Advances in limnology 1995 Advances in limnology 1995 Adv. limnol. 1995 Advances in limnology. 1995 Ergebnisse der Limnologie 1995 1995 Archiv fur Hydrobiologie. Special issues Ergebnisse der Limnologie 1995 simona.musazzi MUSAZZI SIMONA andrea.lami LAMI ANDREA TA.P02.005.002 Uso della paleolimnologia come strumento per lo studio del paleoclima e dell evoluzione climatica |
