New determination of Pediastrum orientale in polar lake sediments and its palaeoecological implications – Reindeer Lake, Bellsund, Spitsbergen

Abstract

The main component of microfossils in the bottom sediments of Reindeer Lake from Spitsbergen, documenting the almost 8,000-year history of this water body, are algae representing colonies of a very rare species Pediastrum orientale (Skuja) Jankovská et Komárek 1995 with only a very small (lower than 1%) admixture of other green algae species. It has also been recorded in other lake sediments in Spitsbergen. The specimens belong to the morphotype “b” of the species, known previously from the Scandinavian lakes. Due to its unique nature and scarce information on ecological conditions, this study analysed the palaeoenvironmental factors favouring the occurrence of Pediastrum orientale together with an assessment of its bioindication value. The affinity of the species to oligotrophic lakes, where blooms of this alga are observed, was confirmed. The presence of numerous colonies of Pediastrum orientale in fossil lake sediments can provide a rationale for inferring palaeoecological conditions, including the trophic state of water bodies, thus expanding knowledge of their evolutionary directions and documenting key events in the geological history of the catchment. Further studies of lake gyttjas in Spitsbergen should pay more attention to the taxonomic composition of Pediastrum and other green algae, as well as to the determinants of sediment deposition in different lake catchment environments.