The 7.5 m long SK13 sediment core, drilled at Lake Shkodra (Albania) bottom depth of 7 m in the central southern part of the lake, was selected for multidisciplinary analysis. Ostracods, Characeae, pollens, and stable isotopes were studied with the aim to reconstruct the past biodiversity and the palaeoenvironmental and palaeoclimatic changes occurred during the Middle-Late Holocene. The chronological framework of SK13 was already known and well constrained through radiometric datings. The sediment core age spans from 4560 cal year BP to present. Thirteen ostracod and five charophyte species were identified. Among them, the ostracods Candona montenigrina and Limnocythere scutariense are endemic of the lake; Candona meridionalis and Paralimnocythere georgevitschi have been collected for the first time in the Lake Shkodra while formerly were considered endemic respectively of Lake Dojran and Lake Prespa; Metacypris cordata, ?Carpathocandona sp., and Cyclocypris sp. were never recorded in the lake and were found only in the lower portion of the sediment core. Among the charopytes, Lychnothamnus barbatus and N. hyalina are recorded for the first time in the lake and occurs with high frequency throughout interval A of core. The faunal composition is quite homogeneous, with the percentages of the different species varying along the sediment core. The main change occurs between 1274 and 1197 cal yr BP, where charophytes disappear abruptly as well as 8 ostracod species out of 13, and the frequency of the remaining 5 species dramatically increases. Moreover at that moment, it occurs also the appearance of a peculiar not-tuberculate morphotypes of Ilyocypris monstrifica. The micropaleontological data suggest a decrease of the lake biodiversity since around 1200 cal years BP linked to the transition between an ancient marshland to a lacustrine environment. This drastic change seems to be independent from any global or local climate changes and could be related to the co-occurrence of two phenomena: 1) the Adriatic sea level rise during the Middle and Late Holocene, that that would have uplifted the base level of the River Bojana causing a decrease of its discharge and, consequently, reducing the drainage of the water from the Shkodra swamp; 2) the periodical change of the River Drin course over the last five centuries, which, when deviated into the Bojana river, blocked the River Bojana outflow.
|Titolo:||Historical evolution and Middle to Late Holocene environmental changes in Lake Shkodra (Albania): new evidences from ostracod analysis|
|Data di pubblicazione:||2015|
|Appare nelle tipologie:||1.1 Articolo in rivista|