Limnol. Rev. (2019) 19, 2: 77–91 DOI 10.2478/limre-2019-0007 The late Holocene decline of Trapa natans L. in Northern Poland in the light of new palaeobotanical and geochemical data Agnieszka Lewandowska1*, Przemysław Niedzielski2, Mariusz Gałka3 1Department of Biogeography and Palaeoecology, Adam Mickiewicz University in Poznan, Krygowskiego 10, 61-680 Poznań, Poland, e-mail:
[email protected] (* corresponding author) 2Department of Analytical Chemistry, Adam Mickiewicz University in Poznan, Umultowska 89, 61-614 Poznań, Poland, e-mail:
[email protected] 3Department of Geobotany and Plant Ecology, University of Lodz, Banacha 12/16, 90-237 Łódź, Poland, e-mail:
[email protected] Abstract: Trapa natans (water chestnut) is an aquatic, thermophilic plant whose decline has been observed in many localities in central Europe during the last decades. In this paper, we present a description of two new T. natans subfossil sites located outside its present northern distribution in Poland. High-resolution analysis of plant macrofossils supported by geochemical analysis were undertaken to reconstruct the palaeoecological habitat and examine the cause of the late Holocene decline of T. natans that took place ca. 4000 calibrated years before AD 1950 (cal. yr BP) in a paleolake, presently the Bagno Kusowo bog. Its disappearance was a consequence of terrestrialisation and the development of peatland. In paleolake sediments covered by the peat layer in the Mechacz Wielki bog, T. natans macrofossils were found from before ca. 3300 cal. yr BP. The decline ofT. natans could have resulted from the changes and development of other plant communities where the dominant role was played by Stratiotes aloides and Nymphaea sp.