Holocene environmental changes reflected by pollen, diatoms, and geochemistry of annually laminated sediments of Lake Suminko in the Kashubian Lake District (N Poland) Anna Pędziszewska a , Wojciech Tylmann b , Małgorzata Witak c , Natalia Piotrowska d , Emilia Maciejewska a , Małgorzata Latałowa a, ⁎ a Lab. of Palaeoecology and Archaeobotany, Dept. of Plant Ecology, University of Gdańsk, ul. Wita Stwosza 59, 80-308 Gdańsk, Poland b Dept. of Quaternary Geology and Geomorphology, Institute of Geography, University of Gdańsk, ul. Bażyńskiego 4, 80-952 Gdańsk, Poland c Dept. of Marine Geology, Institute of Oceanography, University of Gdańsk, al. Piłsudskiego 46, 81-378 Gdynia, Poland d GADAM Centre, Institute of Physics, Silesian University of Technology, ul. Krzywoustego 2, 44-100 Gliwice, Poland abstract article info Article history: Received 25 July 2013 Received in revised form 22 January 2015 Accepted 31 January 2015 Available online 10 February 2015 Keywords: Postglacial vegetation history Holocene cool climatic event Laminated lake sediment Paleolimnology Southern Baltic region Pollen, non-pollen palynomorphs (NPPs), diatoms, and geochemistry of lake sediments with partially preserved annual lamination were used to reconstruct post-glacial environmental changes of northern Poland in the Baltic region. The main stages in the lake's evolution indicate the following: (1) eutrophic conditions in the final stage of the Lateglacial, (2) very low trophy and strongly changeable water levels in the early Holocene, (3) slowly rising trophy through the mid- and late Holocene enabling persistence of the oligotrophic state of the lake up to c. AD 1450, (4) strong cultural eutrophication of the lake in the recent period (c. 150 years), and (5) maximum Ca con- tent in the early Holocene followed by a gradual decline to minimum values in recent time. Distinct, concurrent shifts in limnological proxies and tree pollen accumulation rates (PARs) enabled the identification of several potential Holocene cool climatic events of different magnitudes and durations. Strong reduction in Tetraëdron minimum and declines in tree PARs illustrate limitation of physiological processes in plants, which could result from shorter growing seasons and lower summer temperatures and insolation. Higher precipitation of Fe and Mn indicates more intensive weathering in the catchment, while peaks in Fe/Mn ratio and concurrent drops in Ca content suggest at least seasonal anoxia, which could result from a longer duration of ice cover and shorter periods of mixing. The data seem to display striking conformity of the main cooling events with the “Bond cycles” (Bond et al., 1997, 2001), but also indicate a more variable pattern that may reflect traces of a more complex cy- clicity of climatic shifts. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Although the number of lakes with annually laminated sediments being subject to paleoecological studies is increasing, additional such sites are very important as they provide almost ideal archives of infor- mation on past environmental changes (Hughen and Zolitschka, 2006; Francus et al., 2010). Among the most important features is their high potential for enabling very precise chronological control of paleoecological events as reconstructed through various methods (Ralska-Jasiewiczowa et al., 1998; Zolitschka, 2007). The increasing interest in paleolimnological studies in the past two decades is not only due to the need for perfect archives of information on the past, but also to contribute to an increased understanding of long-term environmental changes which is a necessary basis for predictions of Earth ecosystem responses to future conditions. Paleolimnology, like all other paleosciences, provides data which extend the information obtained from long-term surveys and monitoring pro- grams up to centennial and millennial scales. This information is neces- sary for understanding complex behavior and interactions between particular environmental constituents (Dearing, 2013). Recently, the paleoscientific community has focused on how this knowledge should be implemented in the forecasting, management, conservation, and res- toration of natural resources under various scenarios of future climate change and increasing human pressure (Jackson and Hobbs, 2009; Willis et al., 2010; Sayer et al., 2012). Climate dynamics is the most important factor that directly or indi- rectly drives changes in other environmental elements. Thus, a better understanding of the climate system and the spatial and temporal pat- terns of climate changes are most important scientific challenges (Bradley et al., 2003; Snyder, 2010; PAGES 2k Consortium, 2013). There- fore, despite the rapid increase in paleoclimatic data, there is a further need for a refined network of paleoecological sites that contribute to the knowledge on regional expression of global climate events. These Review of Palaeobotany and Palynology 216 (2015) 55–75 ⁎ Corresponding author. Tel.: +48 58 5236113. E-mail address: m.latalowa@ug.edu.pl (M. Latałowa). http://dx.doi.org/10.1016/j.revpalbo.2015.01.008 0034-6667/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Review of Palaeobotany and Palynology journal homepage: www.elsevier.com/locate/revpalbo