Subfossil diatoms from Hann Park pond, Dakar, Senegal: floristic inventory and palaeoenvironmental reconstruction

Abstract

Diatoms in a 100 cm-long core from a pond in Hann Forest Park, western Senegal, were studied with the aim of reconstituting this interdune depression’s history, particularly the human influence, during the last century. Sixty-three species and varieties of diatoms belonging to 32 genera were identified, of which twelve are reported for the first time in Senegambia. The genera most represented were Nitzschia (10 species), Eunotia (9 species) and Pinnularia (6 species). The microflora was characterised by a dominance of epipelic, epiphytic and aerophilic species. Diatom assemblage analyses, combined with lithological core data, showed that the pond has remained very shallow throughout its evolution. The disappearance of acidophilic species and the development of mesosaprobes and mesoeutrophic alkaliphilic species in the upper part of the core can be attributed to organic pollution caused by human activities, which resulted in eutrophication of the pond waters since the beginning of the 20th century.

Keywords:

• eutrophication
• human influences
• organic pollution
• pH
• salinity