Human- and climate-induced changes of mollusc assemblages of millpond deposits in the valley of Jarosławianka Stream (Poland)

Abstract

Deposits from a millpond in the Jarosławianka Stream valley (Sławno Plain, NW. Poland) were subject to malacological analysis in order to reconstruct the history of environmental transformations of the pond from its establishment in 1351 to the end of its functioning in 1960. Thirty five mollusc taxa occurred in the pond during its functioning: 21 taxa of water snails, 11 bivalves, and 3 terrestrial snails. Six phases of development of the pond were distinguished, based on the mollusc assemblages: phase I (1351–1450 CE) – very favourable habitat conditions, high species richness and diversity; phase II (1450– 1490 CE) – deterioration of habitat conditions – decrease in the number of species and individuals; phase III (1490–1590 CE) – improving conditions and reappearance of species which had occurred in the pond in phase I; phase IV (1590–1750 CE) – the least favourable conditions and poor malacofauna in terms of species number and abundance; phase V (1750–1790 CE) – renewed development of the malacofauna; phase VI (after 1790 CE) – end of functioning of the pond. The phases of pond development were associated with hydrological transformations, resulting from climatic factors and human economic activity. key Words: mollusc assemblages; millpond deposits; last millennium; Jarosławianka Stream; Pomerania; Poland