An expanded ostracod-based conductivity transfer function for climate reconstruction in the Levant

Steffen Mischke, Ahuva Almogi-Labin, Bety Al-Saqarat, Arik Rosenfeld, Hadar Elyashiv, Ian Boomer, Mordechai Stein, Lilach Lev, Emi Ito

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24 Scopus citations

Abstract

We present the first modern calibration dataset linking ostracod assemblage composition to water chemistry, and other site-specific variables, in the hydrologically and geopolitically sensitive southern Levant region. A total of 42 ostracod taxa were recorded from the 178 sampled sites in Israel and Jordan. Ilyocypris spp., Heterocypris salina and Cypridopsis vidua are the most abundant taxa. Species strictly confined to freshwater conditions are Prionocypris zenkeri, Gomphocythere ortali and Prionocypris olivaceus. In contrast, H.salina, Bradleytriebella lineata and Cyprideis torosa show high frequencies in brackish waters (waters with higher conductivity). Humphcypris subterranea, G.ortali, P. olivaceus and Cypridopsis elongata apparently prefer flowing waters. Specific conductivity optima and tolerance ranges were calculated for the recorded ostracod species and may be used for the palaeoenvironmental assessment of fossil ostracod assemblages. In addition, a transfer-function for quantitative specific conductivity estimation based on 141 samples was established with weighted averaging partial least squares regression (WA-PLS). The resulting coefficient of determination r2 between observed and predicted conductivity values (0.72) and the root-mean-square error of prediction (RMSEP) in % gradient length (13.1) indicate that conductivity may be reliably estimated from ostracod assemblage data. The transfer function was first applied to last glacial ostracod assemblage data from an archaeological trench in the Sea of Galilee (northern Israel). Relatively large conductivity fluctuations between ca1 and 7mScm-1 were inferred for the period 24-20cal ka BP. In addition, four episodes of freshwater influx near the site of the trench were identified from the presence of shells of freshwater and stream-dwelling species intermingled with very abundant shells of Cyprideis torosa. The results of our study allow a better use of Quaternary ostracods from the Levant as palaeoenvironmental indicators of water-body types and past conductivity levels and will contribute to a better understanding of Quaternary environmental and climate change in the Levant.

Original languageEnglish (US)
Pages (from-to)91-105
Number of pages15
JournalQuaternary Science Reviews
Volume93
DOIs
StatePublished - Jun 1 2014

Bibliographical note

Funding Information:
We are grateful to Elke Heyde for hydrochemical analysis and to two anonymous reviewers for constructive comments. This research was supported by the Deutsche Forschungsgemeinschaft (grant Mi 730/13-1 to SM ) and the USA–Israel Bi-National Science Foundation (BSF grant 2010347 to AAL and EI).

Keywords

  • Conductivity
  • Near East
  • Ohalo Site
  • Ostracoda
  • Salinity
  • Sea of Galilee
  • Transfer function

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