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Phosphate dynamics in an acidic mountain stream: Interactions involving algal uptake, sorption by iron oxide, and photoreduction
Author(s) -
Tate Cathy M.,
Broshears Robert E.,
McKnight Diane M.
Publication year - 1995
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1995.40.5.0938
Subject(s) - phosphate , sorption , environmental chemistry , chemistry , dissolution , algae , iron oxide , nutrient , adsorption , ecology , biology , biochemistry , organic chemistry
Acid mine drainage streams in the Rocky Mountains typically have few algal species and abundant iron oxide deposits which can sorb phosphate. An instream injection of radiolabeled phosphate ( 32 PO 4 ) into St. Kevin Gulch, an acid mine drainage stream, was used to test the ability of a dominant algal species, Ulothrix sp., to rapidly assimilate phosphate. Approximately 90% of the injected phosphate was removed from the water column in the 175‐m stream reach. When shaded stream reaches were exposed to full sunlight after the injection ended, photoreductive dissolution of iron oxide released sorbed 32 P, which was then also removed downstream. The removal from the stream was modeled as a first‐order process by using a reactive solute transport transient storage model. Concentrations of 32 P mass −1 of algae were typically 10‐fold greater than concentrations in hydrous iron oxides. During the injection, concentrations of 32 P increased in the cellular P pool containing soluble, low‐molecular‐weight compounds and confirmed direct algal uptake of 32 PO 4 from water. Mass balance calculations indicated that algal uptake and sorption on iron oxides were significant in removing phosphate. We conclude that in stream ecosystems, PO 4 sorbed by iron oxides can act as a dynamic nutrient reservoir regulated by photoreduction.