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The postglacial sediments of Kortowskie Lake contain well preserved chrysophycean cysts. Forty-six morphotypes were identified by scanning electron microscopy (SEM) and light microscopy (LM). Ten new morphotypes of fossil chrysophycean cysts are described. Some of the most abundant taxa show clear trends associated with the increase in lake trophic status. The cyst flora is divided into four groups: eutrophic forms (Cysta globata, C. cortoviensis, C vermicularis); oligotrophic forms (Cysta curvicollis); cool-water forms (Cysta carinifera, C. crassicollis, C. microspinosa, C. modica and Cysta stellata), and indifferent forms (all other morphotypes which did not show a clear tendency). The percentage abundance of chrysophycean cysts wa related to climate changes, showing a considerable increase during the Subboreal period. mo factors, lake fertility and water level changes affected the abundance of the fossil cyst flora in the sediments of Kortowskie Lake.

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Fossil chrysophycean cysts were identified and counted from the laminated sediment core from Crawford Lake. Thirty-two morphotypes have been described, most of them for the first time. The detailed description of the cysts is presented, including scanning electron photomicrographs. The abundance of certain morphotypes appears to be related to lake paleoproductivity. On this basis, fossil cyst flora have been divided into three characteristic groups: eutrophic–, mesotrophic–, and oligotrophic–meromictic forms. Our data demonstrate that chrysophycean cyst distribution can reflect lake conditions and, therefore, are potentially useful in paleoecological studies.