Use of dinoflagellate cysts in paleolimnology as proxies: challenges and limits

The study of dinoflagellate cysts from sediments as biological proxies is strongly developed in marine environments, but it is still far behind in paleolimnology. Paleolimnological, taxonomical, ecological and physiological studies on dinoflagellates of the alkaline high mountain Lake Nero di Cornisello (NE Italian Alps) are being carried out in a PhD thesis at the University of Pisa (Italy) within the frame of the “Oloambient” project, a paleoclimatic and paleolimnological research financed by the Autonomous Province of Trento (Italy). A peridinioid dinoflagellate cyst occurred in the Holocene sediments of the lake. Comparison with data available in literature suggested morphological similarities with the marine genus Brigantedinium, but this mainly due to the paucity of information on the distribution and occurrence of fossil dinocysts in freshwater environments. Indeed, this dinocyst shows affinities with the dominant dinoflagellate taxon living at present in Lake Nero di Cornisello, on which studies on life cycle, ecology and taxonomy are in progress. Comparison between this taxon and the peridinioid dinocyst found in the sediments will be presented using classical (morphology) and modern (DNA sequences) approaches. Ecological significance of the species will be considered. The following questions will be discussed: are dinoflagellates potential biological proxies for paleolimnology? Is the realization of transfer functions for freshwater dinoflagellates in the middle period possible?