Mediterranean coccolith ecobiostratigraphy since the penultimate Glacial (the last 145,000 years) and ecobioevent traceability

Abstract

The Mediterranean Sea is a miniature ocean ideal to test the response of marine ecosystems to amplified orbital and suborbital climate changes. Here we present coccolith data from a Sardinia Channel gravity core (Arcose C_33) analysed over the last 145,000 years, with a mean resolution of about 900 years. The study highlights that regional phytoplankton assemblages underwent significant modifications between the penultimate glacial and the last interglacial, as well as between the last glacial and the Holocene. The N ratio palaeoproductivity index suggests reduced productivity levels and the development of a deep nutricline during the last interglacial and the Holocene. Within the last glacial period, many taxa exhibit abundance fluctuations that parallel oscillations in delta O-18 values of Globigerina bulloides tests. Heinrich events and stadials seem to be associated with drops in primary productivity levels, as already observed in the Alboran Sea and the Sicily Channel. A total of 19 ecobioevents were identified in the Sardinia Channel sediments, including abundance fluctuations of Emiliania huxleyi >4 mu m, Florisphaera profunda and Gephyrocapsa oceanica. The comparison of events across the Mediterranean Sea suggests that traceability applies to the Sicily Channel, Balearic and Tyrrhenian Seas, supporting the adoption of a common ecobiostratigraphic scheme. Less certain is the correlation with the Alboran Sea, although peaks of Helicosphaera carteri and Syracosphaera histrica during Heinrich events and stadials suggest similar nutrient dynamics in response to suborbital climatic variations in the Sicily Channel, southern Tyrrhenian and Alboran Seas. The traceability of events within eastern Mediterranean cores is strongly limited, possibly due to different physico-chemical properties and nutrient dynamics. (C) 2014 Elsevier B.V. All rights reserved.