Abstract
Paleolimnological assessment of Ladik Lake (N Turkey) using diatoms was carried out along a 62 cm-long sediment core recovered from the southeastern part of the lake. The chronology of the sediments was established by 137Cs - 210Pb dating. Accordingly, three major chronostratigraphical diatom assemblage zones (DAZ) were defined by the CONISS (constrained cluster analysis) program. The oldest assemblage, DAZ C (AD 1925-1958), was dominated by Ulnaria ulna (Nitzsch) Compere, Cocconeis placentula Ehrenb. and Cocconeis pediculus Ehrenb. taxon. In DAZ B (AD 1958-1986), in addition to Ulnaria ulna species that dominated through the whole core, Epithemia spp. occasionally dominated the assemblage in this zone. Ulnaria ulna and Pantocsekiella ocellata (Pant.) K.T. Kiss & acs predominated since the beginning of DAZ A (AD 1986-2006). After the first regime of the lake with dystrophic character, the diatom community underwent a significant shift, with decreased abundance of periphytic diatom samples. The improvement of the regulator in 1986 resulted in a larger water level increase that affected the lake ecology, causing a shift from a diverse periphytic diatom to planktonic diatom assemblage. Based on our monitoring it can be inferred that the limnological regime shifts in Ladik Lake during the 20th century are of anthropogenic origin, rather than being due to climatic changes.