2022 Early Hearing Detection & Intervention Virtual Conference

March 13 - 15, 2022

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5/26/2021 | 8:30 AM - 10:30 AM | Who rules, hot or cold spots? Implications of small-scale heterogeneity for reach-scale N uptake in streams | Virtual Platform

Who rules, hot or cold spots? Implications of small-scale heterogeneity for reach-scale N uptake in streams

Hot spots of Nitrogen (N) processing in streams are proposed to be linked to areas of high flow as it increases the mass transfer of nutrients into the biofilms. By definition, hot spots are small areas that influence biogeochemical processes at larger scales (i.e. reach scale). We proposed that N uptake at the reach scale will increase with increasing the area of high flow. In six indoor 4-m flumes with comparable mean flow we varied the frequency distribution of high flow areas (from 0 to 100%) using ripple-like bedforms. After four weeks of biofilm colonization, we made an addition of 15N-NO3 for 9 hours in re-circulating mode. Our results show that as the frequency distribution of high flow areas increased, flume N uptake decreased. In fact, the extent of the cold spots created by the bed elements at their lee side was larger than that of the hot spots, reducing N uptake. Since in this context hot and cold spots are strongly linked, our results suggest that instead of spotting hot spots, cold spots could provide stronger predictions of N uptake at the reach scale.

Nutrient cycling
Flow
Stream

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Presenters/Authors

Clara Mendoza-Lera (), iES, University of Koblenz-Landau (Germany), clara.mendozalera@gmail.com;