Nitrification rates in the hypolimnion of Lake Constance, Germany

The aim of this work was to study freshwater Nitrososphaeria and their impact on the nitrogen cycling in lakes. We performed stable isotope experiments with addition of 15N-ammonium in 2019 to analyze potential nitrification rates in the hypolimnion of Lake Constance. Water was taken with a Niskin bottle. The indicated time represents the sampling time.
We incubated 4.5 L lake water of 85 m in June, July, August and November 2019 with (15NH4)2SO4-2 (10 µM final concentration) for 48 h (67 h in June) at in-situ temperature of 4°C in the dark. 15N-Nitrite and 15N-Nitrate production was then determined and converted into ammonia oxidation rates. For more details see Klotz et al. (2021).