SEDIMENTARY RECORDS OF RECENT ENVIRONMENTAL-CHANGE IN LAKE BAIKAL, SIBERIA

Lake Baikal is the world's largest freshwater lake and is internationa lly famous for its rich and largely endemic biota. Concern about this unique ecosystem has grown since the late 1970s but whether recent bio logical changes result from natural fluctuations or pollution is uncle ar. One way of discriminating between these processes is to examine re cords of recent change in radiometrically dated deep-water sediment co res. Here we use high-resolution diatom analysis of one core to show t hat abundances have not changed significantly over recent decades. By contrast, we demonstrate that the lake is contaminated by atmospheric pollutants and has experienced a small qualitative change in soil deri ved magnetic minerals. Sedimentary lead concentrations show an increas ing trend in the c. 150-year core sequence and spheroidal carbonaceous particles (SCPs) contaminate post-1930 sediment. Although we provide no evidence that twentieth-century pollution has affected the endemic planktonic diatoms in the central western region of southern Lake Baik al, longer trends in species abundances could be related to naturally occurring climatic cycles or to global warming.