ORIGINAL PAPER Late Quaternary environmental changes in Helambu Himal, Central Nepal, recorded in the diatom flora assemblage composition and geochemistry of Lake Panch Pokhari Svetislav S. Krstic ´ • Wolfgang Zech • Igor Obreht • Zorica Svirc ˇev • Slobodan B. Markovic ´ Received: 16 July 2010 / Accepted: 7 October 2011 / Published online: 2 November 2011 Ó Springer Science+Business Media B.V. 2011 Abstract This study presents changes in diatom flora assemblage composition, TOC, TOC/N and biogenic opal in a 450 cm core of Lake Panch Pokhari, Central Nepal (4,050 m asl), indicating Late Quaternary environmental fluctuations. Four Diatom Zones (DZ) were detected, with two major changes. The first one was found in *430 cm depth (*14.8 cal. kyr BP), where the original flora characterized by Navicula digitulus Hustedt, Pinnularia rhombarea Krammer, P. aff. viridiformis var. minor Krammer, Encyonema silesiacum (Bleisch) D. G. Mann, Cymbopleura nav- iculiformis (Auerswald) Krammer and Nitzschia sp. was fully replaced by an assemblage consisting of Aulacoseira alpigena (Grunow) Krammer, Diatoma hyemalis (Roth) Heib., Tabellaria flocculosa (Ehrenberg) Ku ¨tzing, Brachysira brebissonii Ross and Pinnularia subgibba Krammer, creating a stable diatom assem- blage for *8 kyr (DZ3). The second change was found at *70 cm (*2.1 cal. kyr BP) when increased nutri- ent inputs lead to emergence of new taxa such as Fragilaria construens var. subsalina Hustedt, F. tenera (W. Smith) Lange-Bertalot, Eunotia cf. pseudopapilio Lange-Bertalot and M. No ¨rpel-Schempp and Gom- phonema subclavatum Grunow. In order to evaluate the past environmental conditions in the Lake Panch Pokhari, the detected diatom taxa were subjected to analyses of their autecological preferences and dom- inance within the specific assemblage. We also assumed that TOC/N ratios [ 10 indicate accelerated erosion due to the strengthening of the Summer Monsoon starting at *14.8 and between 13.7 and 12.8 cal. kyr BP. Monsoon intensity was most pro- nounced during the Early Holocene and at the begin- ning of the Late Holocene. The fluctuations of TOC and TOC/N in the Late Glacial sediments seem to correlate temporally and climatically with oscillations in the Northern Atlantic region. Keywords Diatoms Á Holocene Á Late glacial Á Indian summer monsoon Á Nepal Á Helambu Himal Á Lake Panch Pokhari S. S. Krstic ´(&) Institute of Biology, Faculty of Natural Sciences and Mathematics, ‘‘St. Cyril and Methodius’’ University, 1000 Skopje, Macedonia e-mail: skrstic@pmf.ukim.mk; svetakrstic@yahoo.com W. Zech Soil Science and Soil Geography, University of Bayreuth, 95440 Bayreuth, Germany e-mail: w.zech@uni-bayreuth.de I. Obreht Á S. B. Markovic ´ Department of Physical Geography, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovic ´a 3, 21000 Novi Sad, Serbia e-mail: slobodan.markovic@uni-bayreuth.de Z. Svirc ˇev LAPER, Department of Biology and Ecology, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovic ´a 2, 21000 Novi Sad, Serbia e-mail: izlecenje@yahoo.com 123 J Paleolimnol (2012) 47:113–124 DOI 10.1007/s10933-011-9563-4