Nitrogen Elimination in Two Deep Eutrophic Lakes

Nitrogen elimination was investigated in two eutrophic Swiss lakes with different hypolimnetic oxygen conditions. Nitrogen burial was estimated from sediment-trap and sediment-core studies. Denitrification and NO3 --ammonification rates were quantified with15NO 3 -and acetylene incubation experiments and whole-lake mass balances. The study confirmed earlier reports that the acetylene-block technique yields denitrification rates that are systematically too low. Denitrification rates obtained from isotope tracer experiments were compatible with nitrogen consumption rates observed in flux chamber experiments and whole-lake mass balances. The NO3 --ammonification contributed