Research Article

Mid-Holocene changes in the geochemical and biotic conditions of an aquatic ecosystem, in Eastern Mediterranean

¹ Geoservice ltd, Eirinis 15 street, 55236, Panorama, Thessaloniki, Greece
² Hellenic Centre for Marine Research. Athens-Sounio Avenue (46.7 km), P.O. Box 712, P.C. 19013 Anavyssos, Attiki, Greece

^* Corresponding author: elias@hcmr.gr

Received: 3 October 2017
Accepted: 30 March 2018

Abstract

Mediterranean Temporary Ponds (MTPs) are unique and sensitive aquatic ecosystems that due to their hydrological characteristics constitute an ideal setting for the study of past environmental dynamics. A 176 cm core was retrieved from the littoral zone of Omalos MTP in Lefka Ori massif, to provide a general view of the processes that drove its Lateglacial and Holocene evolution. The sedimentary sequence is partitioned in two major units: (i) Unit II (∼17–4.7 ka BP), characterized by the catchment-derived transport, allogenic deposition of fine, Al₂O₃-rich, sediments and endogenic deposition of clays, under overall anoxic and dry climatic conditions, and (ii) Unit I (∼4.7 ka to present), characterized by increasing wetness, establishment of watershed, aquatic and herbaceous vegetation and by SiO₂ dominated sedimentation under overall oxic conditions. The enrichment of SiO₂ in the littoral sediments since the mid-Holocene, can be of clastic, aeolian and biogenic origin, but the undertaken analyses did not permit such distinction. The overall dryness of Unit II was interrupted between ∼14.7 and 13 ka BP by wet conditions, evidenced by the establishment of littoral vegetation. The transition to the mid-Holocene system reorganization, was expressed by peak values of Al₂O₃, Fe₂O₃, K₂O, MgO and Cr₂O₃ and by the deposition of calcite under warm and dry conditions. The mid-Holocene (∼4.7 ka BP) period of Omalos MTP ecosystem disturbance, likely corresponds to the “4.2 ka mega drought event” widespread in the eastern Mediterranean region. The potential of MTP's sedimentary sequences in reconstructing past environmental conditions is emphasized.