Evolution of the Eemian lake-mire ecosystem at the Wola Starogrodzka site (Central Poland)

The assessment of detailed palaeoecological data obtained from the analysis of pollen, plant macrofossils, Cladocera, geochemistry, and stable isotopes of sediments has provided valuable information on the evolution of lakes. The target was the Eemian lake-mire ecosystem located in Central Poland, within palaeolakeland on the Garwolin Plain. Pollen analysis of biogenic sediments from the PWS2-19 profile collected at the Wola Starogrodzka site revealed that the studied lake existed from the beginning (E1 R PAZ) to the final phase (E7 R PAZ) of the Eemian Interglacial. In total, five stages of lake-mire ecosystem development were recognized. Stages I-III spanned a shallow open-water ecosystem with rising trophic state indicated by vegetation and Cladocera communities. However, it remained in opposition to the low content of organic matter in sediments accumulated at the time. Both dense forest cover and possible flow through the water body could be key for the low organic matter content. High mineralization may also have been an important factor. The first signs of lake overgrowth were noted during stage IV, and then the lake was transformed into mire (stage V), which was recorded in all proxies. Mire development was probably associated with two sedimentation hiatuses: in the middle part of E5 R PAZ and at the beginning of E6 R PAZ. Such hiatuses, as the results of lower groundwater level, were also known at these phases from other profiles, and not only from Poland.