Retention of Spike Additions of Soluble Phosphorus in a Northern Eutrophic Stream

• Published in: Journal of the North American Benthological Society 1999-06, Vol.18 (2), p.185-198
• Main Authors: Meals, Donald W., Levine, Suzanne N., Wang, Deane, Hoffmann, James P., Cassell, E. Alan, Drake, John C., Pelton, Deborah K., Galarneau, Heather M., Brown, Adam B.
• Format: Article
• Language: English
• Subjects: Dyes; Macrophytes; Phosphorus; Phosphorus cycle; Plumes; Sediments; Solutes; Sorption; Streams; Watersheds
• ISSN: 0887-3593; 1937-237X
• DOI: 10.2307/1468460

We evaluated P transport through a 3rd-order eutrophic stream in 2 seasons, December 1994 and September 1997, by adding spikes of dissolved P (orthophosphate) and dye tracer (Rhodamine WT) to a 3-km reach. The December experiment occurred under ice cover when biological growth was minimal; during the September experiment plant growth was abundant. Both the dye and P plumes were dispersed in space and time as a result of mixing and transient storage; only P was retained in the stream reach. Initial reversible short-term P retention in the stream reach was demonstrated in both seasons. In December, 36% (318 g) of added P was retained for about 2.5 h, then released over the next 12 h. In September, 39% (116 g) of added P was retained over 12 h, with negligible subsequent release. All the P added in December was exported from the reach within 24 h; 38% of added P (4 mg P/m2) was still retained in the stream reach at the end of the 48-h September experiment. Phosphorus retention was apparently influenced by flow, temperature, concentration gradient, and biological activity. Short-term retention probably resulted from sorption by inorganic sediments and organic biofilms; long-term retention may have been a result of biological uptake. Instream P retention processes may not be capable of reducing P transport significantly during high flows and cold temperatures, but may temporally attenuate inputs delivered during small stormflows in the growing season.