Last glacial- Interglacial Cycle Palaeoclimatology and Palaeoecology Reconstruction: Ostracod Stable Isotope Records From Ohrid Lake and Palaeolake "Les Echets"

delta18O and delta13C signals are inferred from lacustrine ostracod shells to document the terrestrial climate changes from the penultimate glacial maximum (Rissian) to the last interglacial (Eemian). These proxies are recorded in two sediment cores taken in Ohrid Lake (Southern Balkans) and palaeolake Les Echets (SE France), sites chosen to reflect the climate dynamics under north Atlantic and Mediterranean influences. The d18O signal shows high fluctuations probably linked to the water balance effects (evaporative enrichment) associated with the very complex hydrological settings of both lakes. The d13C seems to respond more accurately to climate changes as evidenced by others proxies (Pollen, magnetic susceptibility). The ostracod d13C is directly linked to the d13C of the Dissolved Inorganic Carbon (DIC), which in our case is controlled first by the isotopic composition of DIC in the incoming water and, secondly, by a number of lake-internal processes (production, carbon deposition, and CO2 exchange with the atmosphere). At the beginning of the Eemian, the negative excursions of d13C are likely due to an increase of the biogenic CO2 production in the soils (mainly related to the plant respiration and microbial activity). Conversely, the high values observed at the Rissian late glacial are a consequence of the sparse vegetation and weak soil activities. The agreement between the d13C variations in both lakes with other well constrained proxy shows the high potential of our records in monitoring climate- induced vegetation changes. Overall our results are consistent with the main climate trends documented in other records (ice and marine sequences) but reveal complex leads and lags. One of the most striking features of both records is the interruption of the warming trend (a Dansgaard-Oeshger like event) during transition from IS6 to IS5 already mentioned by others studies conducted in the northern Atlantic Ocean. Such rapid climate shifts are very well known in Greenland ice cores but only from early IS4 and younger. To our knowledge, so far no continental data show this rapid event before and during transition from IS6 to IS5 in the northern hemisphere; therefore comparing continental and marine data as far as penultimate glacial stage 6 will help to better constrain the forcing mechanisms responsible for such rapid climate changes.