SEASONAL AND LONG-TERM VARIABILITY OF NUTRIENTS IN LAKE MUGGELSEE

Seasonal and long-term variability of the nutrients phosphorus, nitrogen, and silicon were investigated in the eutrophic Lake Muggelsee and its inflow from 1979 to 1990. The lake concentrations were internally controlled during the summer season and by the inflowing river in winter, respectively. The lake acts as a sink of nutrients. 18 % of N and 3.5 % of P were retained in the 12-years-period. Phosphorus retention differed from year to year. The average retention rate of the investigated period was only 4 kgP/d, but in some years it was negative due to strong P-release from sediment. The P-retention rate was also influenced by bank filtration (withdrawal for a waterworks).