A 40000-Year Record of Environmental Change from Ancient Lake Ohrid
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J Paleolimnol (2009) 41:407–430 DOI 10.1007/s10933-008-9234-2 ORIGINAL PAPER A 40,000-year record of environmental change from ancient Lake Ohrid (Albania and Macedonia) Bernd Wagner Æ Andre´ F. Lotter Æ Norbert Nowaczyk Æ Jane M. Reed Æ Antje Schwalb Æ Roberto Sulpizio Æ Verushka Valsecchi Æ Martin Wessels Æ Giovanni Zanchetta Received: 19 December 2007 / Accepted: 24 June 2008 / Published online: 11 July 2008 Ó Springer Science+Business Media B.V. 2008 Abstract Lake Ohrid is considered to be of Pliocene vegetation had changed to forest dominated by pine origin and is the oldest extant lake in Europe. A 1,075- and summer-green oak. Several of the proxies suggest cm-long sediment core was recovered from the south- the impact of abrupt climate oscillations such as the eastern part of the lake, from a water depth of 105 m. 8.2 or 4.0 ka event. The observed changes, however, The core was investigated using geophysical, granu- cannot be related clearly to a change in temperature or lometric, biogeochemical, diatom, ostracod, and humidity. Human impact started about 5,000 cal. year pollen analyses. Tephrochronology and AMS radio- BP and increased significantly during the past carbon dating of plant macrofossils reveals that the 2,400 years. Water column mixing conditions, inflow sediment sequence spans the past ca. 39,500 years and from subaquatic springs, and human impact are the features a hiatus between ca. 14,600 and 9,400 cal. most important parameters influencing internal lake year BP. The Pleistocene sequence indicates relatively processes, notably affecting the composition and stable and cold conditions, with steppe vegetation in characteristics of the sediments. the catchment, at least partial winter ice-cover of the lake, and oxygenated bottom waters at the coring site. Keywords Lake Ohrid Á Mediterranean Á The Holocene sequence indicates that the catchment Pleistocene Á Holocene Á Palaeolimnology B. Wagner (&) A. Schwalb Institut fu¨r Geologie und Mineralogie, Zu¨lpicher Str. 49a, Institut fu¨r Umweltgeologie, TU Braunschweig, 50674 Ko¨ln, Germany Pockelsstrasse 3, 38106 Braunschweig, Germany e-mail: wagnerb@uni-koeln.de R. Sulpizio A. F. Lotter Á V. Valsecchi CIRISIVU, c/o Dipartimento Geomineralogico, Laboratory of Palaeobotany and Palynology, Institute of via Orabona 4, 70125 Bari, Italy Environmental Biology, Universiteit Utrecht, Budapestlaan 4, 3584 CD Utrecht, The Netherlands M. Wessels Institut fu¨r Seenforschung, LUBW, Argenweg 50/1, N. Nowaczyk 88045 Langenargen, Germany Geoforschungszentrum Potsdam, Telegrafenberg, 14473 Potsdam, Germany G. Zanchetta Dipartimento di Scienze della Terra, University of Pisa, J. M. Reed via S. Maria 53, 56126 Pisa, Italy Department of Geography, University of Hull, Cottingham Road, Hull HU6 7RX, UK 123 408 J Paleolimnol (2009) 41:407–430 Introduction as proposed by Collier et al. (2000) may explain some of these discrepancies, but more research is In the Northern Hemisphere, most present-day lakes needed to elucidate spatial variability in climate and are of glacial origin and were formed during the late environmental history over time. Pleistocene or early Holocene. Lakes of tectonic Despite the age of Lake Ohrid and the extensive origin, however, can be much older, sometimes dating biological, biogeographical, and, more recently, lim- back to the Tertiary. Lake Ohrid, a transboundary lake nological studies, there has been very little between the Republics of Albania and Macedonia, is palaeolimnological research to date. A study on short located in a deep tectonic graben (e.g. Aliaj et al. gravity cores gives evidence for eutrophication during 2001) and is considered to be the oldest lake in Europe. the past decades (Matzinger et al. 2006a, 2007), and High levels of endemism with more than 200 endemic highlights significant heterogeneity in sediment accu- species described, mainly comprising invertebrates mulation rates across the basin, with relatively low and algae, but also some fish (e.g. Jerkovic 1972; Kenk sedimentation rates in the central part and increasing 1978; Decraemer and Coomans 1994; Michel 1994; sedimentation rates towards the littoral zone (Wagner Levkov et al. 2007) are an indication of its age. Based et al. 2008). The only longer-term study published to on biogeographical principles, Stankovic (1960) esti- date is a low-resolution analysis of an 8.85-m-long mated that the origin of Lake Ohrid dates back to the sediment core recovered in 1973 (Roelofs and Kilham Pliocene, some 3–5 million years ago. 1983). This core is estimated to span the past ca. Because of its geographic position and its age, 30,000 years. Proxies such as water content, organic Lake Ohrid represents an important link between matter, CaCO3, and diatom assemblages show evi- climatic and environmental records from the Medi- dence for an increase in productivity at the terranean Sea and the adjacent continent. In the Pleistocene–Holocene boundary. However, the inter- eastern Mediterranean Sea, most records focus on the pretation was hampered by chronological uncertainty, Late Pleistocene and Holocene history (e.g. Geraga probably due to sediment slumping resulting from et al. 2005) and only a few cover several glacial– tectonically-induced mass movement, a common interglacial cycles (e.g. Schmiedl et al. 1998; Howell phenomenon in this region (e.g. Aliaj et al. 2004). et al. 1998). Similarly, most terrestrial records from In order to generate rigorous palaeoclimatic and the northern Mediterranean region are restricted to palaeoenvironmental data for the northern Mediterra- the Late Pleistocene and Holocene (e.g. Dene`fle et al. nean region, and to assess the potential of Lake Ohrid 2000; Ramrath et al. 2000; Schmidt et al. 2000; for longer-term palaeoenvironmental reconstruction, a Sadori and Narcisi 2001); longer continuous records sediment sequence from the lake is investigated in this covering more than the last glacial/interglacial cycle study using a multidisciplinary approach, which are relatively sparse (e.g. Wijmstra 1969; Ryves et al. includes chronological, geophysical, sedimentologi- 1996; Tzedakis et al. 1997; Brauer et al. 2000). In cal, biogeochemical, and biological proxies. addition, the Pleistocene and Holocene records from the northern Mediterranean region suggest significant spatial climate variability (cf. Tzedakis 2007). For Setting example, while some authors propose relatively cold and dry climatic conditions with a typical steppe Lake Ohrid (40°540–41°100 N, 20°380–20°480 E) is biome during the Last Glacial Maximum and low located at an altitude of 693 m a.s.l. It is about 30 km lake levels in some regions (e.g. Rossignol-Strick and long, 15 km wide, and covers an area of 360 km2 Planchais 1989; Wijmstra et al. 1990; Watts et al. (Fig. 1). Bathymetric measurements revealed that the 1996; Allen et al. 2000; Digerfeldt et al. 2000), lake has a simple, tub-shaped basin morphology with others suggest moister conditions for the same period, a maximum water depth of 286 m (e.g. Stankovic as for example indicated by significantly higher lake 1960). A complete overturn of the entire water levels or faunal remnants (e.g. Alessio et al. 1986; column occurs approximately once every 7 years, Giraudi 1989; Narcisi et al. 1992; Belis et al. 1999). whereas the upper up to 200 m of the water column is Enhanced seasonality during the glacial period, with mixed every winter (Stankovic and Hadzisce 1953; cool, dry summers and wet winters in the region, such Hadzisce 1966; Matzinger et al. 2007). The episodic 123 J Paleolimnol (2009) 41:407–430 409 15° 20°E (A) Crni Drim Sateska R. Koselska R. Lake Ohrid L a k e P r e s p a Neapolitan volcanoes 40° Mount Etna volcano Mediterranean 0 100 200km 35° Sea N Fig. 1 Map of the northern Mediterranean region showing the location of Lakes Ohrid and Prespa at the Macedonian/ Albanian border. Coring location Lz1120 is indicated by the white dot in the southeastern part of Lake Ohrid 50 m Lz1120 isolation of the bottom waters causes oxygen deple- 100 m 150 m tion and increases the total dissolved hypolimnetic 200 m phosphorus concentration. This dissolved phosphorus N Cerava R. 250 m T can be transferred to the epilimnion during complete 004 km overturn, where it enhances productivity. Today, (B) 100 m Lake Ohrid is oligotrophic (TP = 4.6 lgl-1; Matz- Lz1120 inger et al. 2007), which is reflected by a Secchi disc transparency of more than 9 m (Stankovic 1960; Ocevski and Allen 1977; Naumoski 2000; Matzinger et al. 2006a; Naumoski et al. 2007). Macrozooben- 120 m thos is common at the sediment surface, even in the deepest part of the lake (Stankovic 1960). 200 m The high water transparency also results from a high proportion ([50%) of inflow from karst aquifers SW NE and minor contributions from rivers and direct Fig. 2 (A) Lake Ohrid with bathymetry in 50 m contour precipitation (Matzinger et al. 2006a). River runoff intervals. The main inlets and outlets are indicated by the 3 -1 contributes ca. 20% to the total inflow of 37.9 m s arrows. St. Naum (N) and Tushemisht (T) spring areas to the and was even lower prior to 1962, when the River southeast of the lake are indicated by asterisks. (B) Seismic Sateska was diverted into the northern part of Lake profile (SW–NE) across the coring location Lz1120 Ohrid (Fig. 2). About 50% of aquifer input is thought to enter the lake as sublacustrine flow, and 50% as surface inflow, which is concentrated at the southeast- 2006a; Fig. 1). The outflow of Lake Ohrid is the river ern and northwestern edge of the lake. The karst Crni Drim in the northern part of the lake, which aquifers are charged by precipitation and by the 150 m accounts for 63% of the water loss, with the remaining higher Lake Prespa, located 20 km to the east and 37% accounted for by evaporation (Watzin et al.