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Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 7, issue 10
Biogeosciences, 7, 3083–3094, 2010
https://doi.org/10.5194/bg-7-3083-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Evolutionary and geological history of Balkan lakes Ohrid...

Biogeosciences, 7, 3083–3094, 2010
https://doi.org/10.5194/bg-7-3083-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  13 Oct 2010

13 Oct 2010

The last glacial-interglacial cycle in Lake Ohrid (Macedonia/Albania): testing diatom response to climate

J. M. Reed1, A. Cvetkoska2, Z. Levkov2, H. Vogel3, and B. Wagner3 J. M. Reed et al.
  • 1Department of Geography, University of Hull, Cottingham Rd., Hull HU6 7RX, UK
  • 2Institute of Biology, Faculty of Natural Sciences, Gazi Baba bb, 1000 Skopje, Republic of Macedonia
  • 3University of Cologne, Institute of Geology and Mineralogy, 50674 Cologne, Germany

Abstract. Lake Ohrid is a site of global importance for palaeoclimate research. This study presents results of diatom analysis of a ca. 136 ka sequence, Co1202, from the northeast of the lake basin. It offers the opportunity to test diatom response across two glacial-interglacial transitions and within the Last Glacial, while setting up taxonomic protocols for future research. The results are outstanding in demonstrating the sensitivity of diatoms to climate change, providing proxy evidence for temperature change marked by glacial-interglacial shifts between the dominant planktonic taxa, Cyclotella fottii and C. ocellata, and exact correlation with geochemical proxies to mark the start of the Last Interglacial at ca. 130 ka. Importantly, diatoms show much stronger evidence in this site for warming during MIS3 than recorded in other productivity-related proxies, peaking at ca. 39 ka, prior to the extreme conditions of the Last Glacial maximum. In the light of the observed patterns, and from the results of analysis of early Holocene sediments from a second core, Lz1120, the lack of a response to Late Glacial and early Holocene warming from ca. 14.7–6.9 ka suggests the Co1202 sequence may be compromised during this phase. After ca. 7.4 ka, there is evidence for enhanced nutrient enrichment compared to the Last Interglacial, followed by a post-Medieval loss of diversity which is consistent with cooling, but not definitive. Taxonomically, morphological variability in C. fottii shows no clear trends linked to climate, but an intriguing change in central area morphology occurs after ca. 48.7 ka, coincident with a tephra layer. In contrast, C. ocellata shows morphological variation in the number of ocelli between interglacials, suggesting climatically-forced variation or evolutionary selection pressure. The application of a simple dissolution index does not track preservation quality very effectively, underlining the importance of diatom accumulation data in future studies.

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