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| Titel |
The diatom flora of Lake Kinneret (Israel) - Paleolimnological evidence for Holocene climate change and human impact in the southeastern Mediterranean |
| VerfasserIn |
Hannah Vossel, Jane M. Reed, Thomas Litt |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103861
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| Publikation (Nr.) |
 EGU/EGU2015-3280.pdf |
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| Zusammenfassung |
| The Mediterranean basin is a region of highly complex topography and climatic variability,
such that our understanding of the past environmental variability is still limited. Diatoms
(single-celled siliceous algae, Bacillariophyceae) are abundant, diverse and sensitive to a
wide range of environmental parameters. They are often well preserved in lake sediment
records, and have well-recognised potential to generate high-quality paleolimnological data.
Diatoms remain one of the least-exploited proxies in Mediterranean palaeoclimate research.
Here, we present results of diatom analysis of an 18 m sediment core from Lake
Kinneret (Israel) as part of a multi-proxy study of Holocene climate change and
human impact in the Levant (http://www.sfb806.uni-koeln.de). Results are compared
with other proxy data including pollen, and with output data from regional climate
modelling, to strengthen interpretation of environmental change in the southeastern
Mediterranean.
The results show remarkable shifts in the diatom flora over the last ca. 8,000 years.
Preliminary investigations show that 98% of the diatom taxa can be classified as
oligohalobous-indifferent and as alkaliphilous, as is typical of freshwater, alkaline lakes of
open hydrology in limestone, karst-dominated catchments.
Changes in the diatom data over time can be interpreted mainly in terms of productivity
shifts, with a clear trend from oligotrophic at the base to hypereutrophic in the modern lake.
The eutrophication trend accelerates after ca. 3,000 cal. yrs. BP, indicating the influence of
increased human activity in the catchment, identified previously by analysis of the
vegetational history (Schiebel, 2013).
The analysis of the composition of the diatom flora also provides some evidence for
lake-level fluctuations, as a proxy for shifts in moisture availability. Low lake-level stands are
characterized by low diatom concentration and increased relative abundance of littoral taxa.
High lake-level stands are marked by the clear dominance of planktonic species, such as
Cyclotella ocellata PANTOCSEK and Cyclotella paleo-ocellata VOSSEL & VAN DE VIJVER
(a newly described centric diatom which may be endemic (Vossel et al., 2015), in phases of
high diatom concentration. Such inferred lake-level oscillations correlate well with the output
from the climatic models from the Levant region, representing changes in moisture
availability (Litt et al., 2012), although the signal is obscured in the last 3,000 years by the
effects of anthropogenic eutrophication.
References
Litt, T.; Ohlwein, C.; Neumann, F. H.; Hense, A. & Stein, M. (2012): Holocene climate
variability in the Levant from the Dead Sea pollen record. – Quat. Sci. Rev., 49:
95-105.
Schiebel, V. (2013): Vegetation and climate history of the southern Levant during
the last 30,000 years based on palynological investigation. – Unpublished PhD
thesis.
Vossel, H.; Reed, J. M.; Houk, V.; Cvetkoska, A. & Van de Vijver, B. (2015): Cyclotella
paleo-ocellata, a new centric diatom (Bacillariophyta) from Lake Kinneret (Israel). Fottea, 15
(1), in press. |
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