title: Assessment of changes in potential nutrient limitation in an impounded river after application of lanthanum-modified bentonite.
abstract: With the advent of phosphorus (P)-adsorbent materials and techniques to address eutrophication in aquatic systems, there is a need to develop interpretive techniques to rapidly assess changes in potential nutrient limitation. In a trial application of the P-adsorbent, lanthanum-modified bentonite (LMB) to an impounded section of the Canning River, Western Australia, a combination of potential P, nitrogen (N) and silicon (Si) nutrient limitation diagrams based on dissolved molar nutrient ratios and actual dissolved nutrient concentrations have been used to interpret trial outcomes. Application of LMB resulted in rapid and effective removal of filterable reactive P (FRP) from the water column and also effectively intercepted FRP released from bottom sediments until the advent of a major unseasonal flood event. A shift from potential N-limitation to potential P-limitation also occurred in surface waters. In the absence of other factors, the reduction in FRP was likely to be sufficient to induce actual nutrient limitation of phytoplankton growth. The outcomes of this experiment underpins the concept that, where possible in the short-term, in managing eutrophication the focus should not be on the limiting nutrient under eutrophic conditions (here N), but the one that can be made limiting most rapidly and cost-effectively (P).
authors.affiliation: CSIRO Land and Water, Perth, WA, Australia. Electronic address: grant.douglas@csiro.au.
authors.forename: Grant B
authors.initials: GB
authors.lastname: Douglas
authors.affiliation: Department of Environmental Sciences, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: Miquel
authors.initials: M
authors.lastname: Lurling
authors.affiliation: Centre for Ecology and Hydrology, Penicuik, Midlothian, Scotland EH26 0QB, UK.
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Spears
mesh_terms: D001546:Bentonite; D005068:Eutrophication; D007811:Lanthanum; D009584:Nitrogen; D010758:Phosphorus; D045483:Rivers
chemical_list: D001546:Bentonite; D010758:Phosphorus; D007811:Lanthanum; D009584:Nitrogen
keywords: Lanthanum-modified bentonite; Nutrient limitation