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Stream drying drives microbial ammonia oxidation and first‐flush nitrate export
Author(s) -
Merbt Stephanie N.,
Proia Lorenzo,
Prosser James I.,
Martí Eugènia,
Casamayor Emilio O.,
Schiller Daniel
Publication year - 2016
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1002/ecy.1486
Subject(s) - streams , nitrate , sediment , environmental science , cycling , fluvial , nitrogen cycle , ammonia , nutrient , environmental chemistry , ecology , hydrology (agriculture) , nitrogen , flow conditions , nitrification , chemistry , flow (mathematics) , biology , geology , history , computer network , paleontology , geometry , geotechnical engineering , mathematics , archaeology , organic chemistry , structural basin , computer science
Stream microbial communities and associated processes are influenced by environmental fluctuations that may ultimately dictate nutrient export. Discharge fluctuations caused by intermittent stream flow are increasing worldwide in response to global change. We examined the impact of flow cessation and drying on in‐stream nitrogen cycling. We determined archaeal ( AOA ) and bacterial ammonia oxidizer ( AOB ) abundance and ammonia oxidation activity in surface and deep sediments from different sites along the Fuirosos stream (Spain) subjected to contrasting hydrological conditions (i.e., running water, isolated pools, and dry streambeds). AOA were more abundant than AOB , with no major changes across hydrological conditions or sediment layers. However, ammonia oxidation activity and sediment nitrate content increased with the degree of stream drying, especially in surface sediments. Upscaling of our results shows that ammonia oxidation in dry streambeds can contribute considerably (~50%) to the high nitrate export typically observed in intermittent streams during first‐flush events following flow reconnection. Our study illustrates how the dry channels of intermittent streams can be potential hotspots of ammonia oxidation. Consequently, shifts in the duration, spatial extent and severity of intermittent flow can play a decisive role in shaping nitrogen cycling and export along fluvial networks in response to global change.