US EPA

4603819 

Book/Book Chapter 

Seasonal dynamics of phosphorus in Lake Erken surface sediments 

Rydin, E; Brunberg, AK 

1998 

Schweizerbart 

Stuttgart 

Lake Erken: 50 years of limnological research 

157-167 

English 

WOS:000078414300011 

Changes in total concentration and fractional composition of phosphorus in surface sediments (0 - 0.5 and 0.5 - 2 cm) from the mesotrophic Lake Erken were studied throughout one year. An accumulation of phosphorus was found during the ice covered period in the 0 - 0.5 cm layer. This may be explained by mobilisation of redox-sensitive phosphorus forms in deeper sediment layers, followed by a diffusion to the oxygenated sediment surface where it was trapped by iron and detected as BD-P in the fractionation analysis. During spring mixing, the total phosphorus content in the 0 - 0.5 cm layer decreased by one third, due to a decline in BD-P. The loss of phosphorus from the sediment, occuring under oxic conditions, was probably due to resuspension and aerobic dissolution of iron-bound phosphorus due to steeper diffusion gradients during spring mixing. Differences in phosphorus accumulation during the two winter periods investigated may be an effect of variations in climatic factors, e.g, length of the ice covered period and mixing patterns. The variation in NaOH-nrP (0 - 0.5 cm) concentration, partly corresponding to bacterial phosphorus, showed a delayed response to the spring diatom sedimentation, as decomposition probably was restricted by low temperature. The calculated release rate from the investigated sediment area from April through September was on average 6 mg P day(-1) m(-2), while the estimated external loading was 0.02 mg P day(-1) m(-2) during the summer period. Our results show that the concept of "Internal loading" is not restricted to highly eutrophic systems. It is relevant also in less nutrient rich systems, and may even play a major role when the external loading is restricted by a long water residence time. 

Forsberg, C; Pettersson, K 

Advances in Limnology, vol. 51 

9783510470532 

Seminar on Lake Erken - 50 Years of Limnological Research 

Uppsala, Sweden 

October 1996