Diatom-inferred lateglacial and Holocene climatic variability in the South Carpathian Mountains (Romania) Krisztina Buczkó a, * , Enik } o Katalin Magyari b , Mihály Braun c , Miklós Bálint d, e a Hungarian Natural History Museum, Department of Botany, Könyves Kálmán krt. 40,1476 Budapest, P.O. Box 222, Hungary b Hungarian Academy of Sciences e Hungarian Natural History Museum, Research Group for Paleontology,1476 Budapest, P.O. Box 222, Hungary c University of Debrecen, Department of Inorganic and Analytical Chemistry, 4010 Debrecen, P.O. Box 21, Hungary d Biodiversity and Climate Research Centre (BiK-F), Senckenberg Gesellschaft für Naturforschung Senckenberganlage 25, 60325 Frankfurt am Main, Germany e Molecular Biology Center, Babes-Bolyai University, Treboniu Laurian 42, 400271 Cluj, Romania article info Article history: Available online xxx abstract Climatic and environmental changes were studied using siliceous algae (diatoms and chrysophycean cysts) analyses in a mountain lake in the South Carpathian Mountains for the lateglacial and Holocene. Lake Brazi (1740 a.s.l.) is a small, shallow lake in the Retezat Mountains. According to the basal radio- carbon dating of the core, the lake was formed around 15,750 cal BP and sediment accumulation has been continuous ever since. High resolution diatom analyses were carried out together with loss-on- ignition and biogenic silica measurements. Total epilimnetic phosphorus (TP) concentrations and pH were reconstructed quantitatively. Ten statistically significant zones were distinguished, six of which appeared in the lateglacial and Early Holocene suggesting the instability of diatom assemblages after deglaciation. The uppermost zone covered six thousand years, which suggests that diatom assemblages remained quite stable during the second half of the Holocene. High lake level occurred between 9500 and 9000 cal BP. After 6300 cal BP the lake level gradually increased again until 5800 cal BP. A further increase was detected at 3000 cal BP, while after 1500 cal BP water level decreased. Although there is limited knowledge regarding the environmental constraints of several diatom taxa present in the sequence (e.g. Aulacoseira laevissima), which makes the precise environmental interpretation of the diatom record more difficult, the available data provide an important new insight into the environmental history of Lake Brazi and the Carpathian Mountains. The most remarkable changes in the aquatic ecosystem were observed at 6000 cal BP in the Holocene and 12,800 cal BP, at the onset of the Younger Dryas. Marked changes were also detected at 10,500e10,300; 9800; 9500e9000; 8900e8800; 8300; 6300e5800 and 3100e3000 cal BP. Ó 2012 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction With the ongoing climate change there is a growing demand for revealing and understanding the forcing mechanisms and impacts of past rapid climatic changes on the environment, especially in areas where these relationships have not been subject to thorough investigation (e.g. Shakun and Carlson, 2010). One way to look back in time is the studying of biological proxies in lake sediments (Smol et al., 2001; Lotter et al., 2010). Although a large number of studies have initiated syntheses of the lateglacial and Holocene climatic variability (e.g. Mayewski et al., 2004; Wanner et al., 2008; Shakun and Carlson, 2010; Shuman and Plank, 2011), the available database is usually insufficient or heterogenic, especially in East-Central Europe. This unevenness is salient in the well-organized project ‘European Mountain Lake Ecosystems: Regionalisation Diagnostics and Socio-Economic Evaluation’ (EMERGE, http://www.mountain- lakes.org) that aimed to assess the ecological status of remote high-altitude and high-latitude mountain lakes across Europe. More than two hundred lakes were sampled in the frame of EMERGE, and only four were located in Retezat Mts. (Clarke et al., 2005; Catalan et al., 2009.) As a result of intensive multi-proxy palaeoecological investiga- tions since 2007, Lake Brazi has become a reference sequence for mountain lakes in the South Carpathians (Magyari et al., 2009a). The sediment cores obtained from Lake Brazi revealed continuous limnic sedimentation throughout the past 15,700 cal BP, and allowed detailed documentation of the regional climatic and environmental history. The first results of a multi-proxy analyses, * Corresponding author. E-mail address: krisztina@buczko.eu (K. Buczkó). Contents lists available at SciVerse ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint 1040-6182/$ e see front matter Ó 2012 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2012.04.042 Quaternary International xxx (2012) 1e13 Please cite this article in press as: Buczkó, K., et al., Diatom-inferred lateglacial and Holocene climatic variability in the South Carpathian Mountains (Romania), Quaternary International (2012), doi:10.1016/j.quaint.2012.04.042