Nitrogen retention, removal, and saturation in lotic ecosystems

• Published in: Ecosystems (New York) 2005-06, Vol.8 (4), p.442-453
• Main Authors: Bernot, M.J, Dodds, W.K
• Format: Article
• Language: English
• Subjects: adsorption; Animal and plant ecology; Animal, plant and microbial ecology; biogeochemical cycles; Biological and medical sciences; Denitrification; denitrifying microorganisms; Downstream; Ecological function; Ecosystems; Fresh water ecosystems; Fundamental and applied biological sciences. Psychology; General aspects; limnology; Load; Load distribution; Nitrification; Nitrogen; nutrient uptake; pollution load; rivers; Saturation; streams; Synecology; water pollution
• ISSN: 1432-9840; 1435-0629
• DOI: 10.1007/s10021-003-0143-y

Increased nitrogen (N) loading to lotic ecosystems may cause fundamental changes in the ability of streams and rivers to retain or remove N due to the potential for N saturation. Lotic ecosystems will saturate with sustained increases in the N load, but it is unclear at what point saturation will occur. Rates of N transformation in lotic ecosystems will vary depending on the total N load and whether it is an acute or chronic N load. Nitrogen saturation may not occur with only pulsed or short-term increases in N. Overall, saturation of microbial uptake will occur prior to saturation of denitrification of N and denitrification will become saturated prior to nitrification, exacerbating increases in nitrate concentrations and in N export downstream. The rate of N export to downstream ecosystems will increase proportionally to the N load once saturation occurs. Long term data sets showed that smaller lotic ecosystems have a greater capacity to remove in-stream N loads, relative to larger systems. Thus, denitrification is likely to become less important as a N loss mechanism as the stream size increases. There is a great need for long-term studies of N additions in lotic ecosystems and clear distinctions need to be made between ecosystem responses to short-term or periodic increases in N loading and alterations in ecosystem functions due to chronic N loading.[PUBLICATION ABSTRACT]