Contrasting ontogeny among ephemeral hardwater lakes as revealed by sediment P-fractionation
Brunberg, Anna-Kristina; Blomqvist, Peter; Rydin, Emil
published: Feb 27, 2002
ArtNo. ESP141015303008, Price: 29.00 €
Lakes are continuously formed along the Baltic coast, due to the shoreline displacement, which is still substantial after the last glaciation period. In order to track remnants of a past ephemeral oligotrophic hardwater stage, deep sediment cores were analysed for total concentrations and fractional composition of phosphorus in two lakes of an area north of Stockholm, where post-glacial sediments are rich in calcium carbonate. Indications of such conditions were found only in one of the lakes, despite similar characteristics of their drainage areas. The contrasting lake ontogeny is explained by differences in water depth, i.e. light availability at the sediment surface. Shallow hardwater lakes in this area develop a "microbial mat" of photosynthesising organisms, which cause high pH and oxygenated conditions at the sediment surface. This photosynthesis may promote precipitation of calcium carbonate and thereby coprecipitation of phosphorus. Phosphorus thus is trapped within the sediment in a form which is unusually stable and constitutes a historical record of the lake evolution.