| Abstrakt: |
Macrophytes are an excellent indicator of the lake's local conditions and state changes. However, their pollen are rarely used in paleoreconstructions due to low occurrence and poor preservation in lake sediments. In the course of paleolimnological research in recent years, we have studied five lakes located on the Valaam Island in the northern part of Lake Ladoga, Russia. All lakes, placed at different absolute altitudes above the sea level, were part of Lake Ladoga and became isolated during its last regression. In this study, we present the dynamics of macrophyte pollen in the Late Holocene on the example of two of them. The research material is the lake sediments for pollen analysis. We have obtained data on changes in the macrophyte diversity, abundance, and distribution. We have reconstructed the stages of lake development due to the transgressive–regressive phases of Lake Ladoga. The first stage was associated with the transgression when the Ladoga waters covered the study area and the macrophyte distribution was low. In the second stage, at the end of the Sub-boreal period, Ladoga regression occurred and caused the beginning of the lakes' isolation. The temporary disappearance of macrophyte pollen indicates this period. As the lakes gradually lost their connection with Lake Ladoga, various macrophytes began to repopulate them. Since the isolation, the distribution and changes of aquatic vegetation were determined by natural succession and human influence. Now these are shallow overgrown lakes. The results allowed us to refine the island lakes isolation stages from Lake Ladoga and confirm the significance of macrophyte pollen in paleolimnological studies by revealing the correlation between their dynamics and the stages of lake development. [ABSTRACT FROM AUTHOR] |
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