Implications of flow intermittency on sediment nitrogen availability and processing rates in a Mediterranean headwater stream |
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| Authors: | María Isabel Arce María del Mar Sánchez-Montoya María Rosario Vidal-Abarca María Luisa Suárez Rosa Gómez |
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| Institution: | 1. Department of Ecology and Hydrology, Faculty of Biology, Regional Campus of International Excellence “Campus Mare Nostrum”, University of Murcia, Campus of Espinardo, 30100, Murcia, Spain
2. Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 301, 12587, Berlin, Germany
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| Abstract: | Most streams draining to the Mediterranean basin are temporary. As a result of their hydrological regime, temporary streams are affected by drying and rewetting periods. Drying can alter in-stream nitrogen (N) availability and reduce N processing rates and subsequent retention after re-wetting. We sought to determine if hydrologic drying modifies reach-scale sediment chemical properties and constrains the response of N processing to rewetting. We compared different abiotic characteristics of sediments and nitrification and denitrification rates between a perennial and intermittent reach in the same stream over a wet period, when surface water flowed in both reaches, and a dry period, when the intermittent reach dried up. We analyzed N processing rates by incubating sediments with stream water, thereby simulating a rewetting when sediments from the intermittent reach were dry. We found that drying increased the sediment nitrate (NO3 ?) content. Conversely, drying did not reduce the recovery of N processing rates to pre-dry levels after simulated flooding conditions. Our results suggest that dry reaches may act as a potential NO3 ? source by releasing downstream NO3 ? pulses after stream flow recovery. Given the European Water Framework Directive requirements to assess stream ecological status, these N pulses following rewetting should be considered when designing management plans in temporary streams. Our study highlights the rapid response of in-stream N processing to rewetting period following a drought. This high resilience to process N should be seen as a vital ecosystem service provided by temporary streams despite annual dry periods. |
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