| 个人简介 | |
|---|---|
 Prof. Jerzy Nitychoruk Warsaw University, Poland |
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| 标题： CLIMATIC CHANGE IN NORTHERN POLAND, INFERRED FROM DIATOMS RECORDS OFMŁYNEK LAKE SEDIMENTS | |
| 摘要： A sediment core, 350 cm long recovered from Młynek Lake, northern of Poland was analyzed with respect to their content of diatoms and chrysophyte cysts. The aim was to reconstruct the environmental and climatic changes during the past 2500 years. The recognized diatom assemblages displayed marked floristic changes along the sediment core samples. The main change in diatom composition consists of a shift from an assemblage dominated by benthic Fragilariasensulato species through marked intervals to a planktonic one in distinct zones.A high proportion of benthic to plankton has been reported as indicative for cold climate and long ice cover, and a shift from benthic to planktonic diatom taxa, reflect the longest growing season and reduced ice cover on the lake during warm climate.Multivariate statistical analysis included hierarchical ascending clustering distinguished four diatom ecological groups. Each ecological group is containing dominant and distinctive diatom taxa that reflect marked environmental changes during the time of sediment deposition. The analyzed core section was divided into eleven diatom zones according to the distribution of ecological groups and the variations in abundance of dominant species supported by 14C data. The results displayed a developmental history of Młynek Lake that can be divided into six main phases of alternating warm wet and cold dry shifts. A distinct dominance of planktonic eutrophic indicators diatoms accompanying with low abundance of chrysophyte cysts indicates an increase in the lake trophicity and a general trend for increasing anthropogenic impacts. | |
