Palaeoecology of the Holsteinian lake in vicinity of Wilczyn (eastern Poland) based on molluscan studies

Malacological studies of two profiles of the Holsteinian (Mazovian) Interglacial from eastern Poland – Roskosz and Wilczyn 1/12 – are presented. They are connected with the northern part of the Wilczyn palaeolake and seems to document palaeoecological changes in the part of the climatic optimum and the post-optimal period. Mollusc communities are typical of lake environs. The latter is supported by biometry of Pisidium moitessierianum. Higher energy conditions are evidenced by rheophile species P. henslowanum and P. nitidum in the lowermost part of the Roskosz section. Mollusc assemblages with Lithoglyphus jahni, with Valvata piscinalis and Bithynia tentaculata as well as with Valvata piscinalis are distinguished at Roskosz. They record changes in aquatic vegetation and depth conditions. Malacofauna from Wilczyn 1/12 is dominated by V. piscinalis, V. piscinalis f. antiqua and B. tentaculata. Limited contribution of temperate gastropods Viviparus diluvianus and L. jahni as well as the occurrence of some cold-loving forms indicate a deterioration of thermal conditions. Shallow-water habitats and expansion of reed zones are inferred from proportions of Bithynia shells and opercula.