Phosphorus Fractionation in Sediment Cores Collected In 2005 Before and After Onset of an Aphanizomenon flos-aquae Bloom in Upper Klamath Lake, OR, USA

Simon, Nancy S.; Lynch, Dennis; Gallaher, Thomas N.

Phosphorus Fractionation in Sediment Cores Collected In 2005 Before and After Onset of an Aphanizomenon flos-aquae Bloom in Upper Klamath Lake, OR, USA

2009

Simon, Nancy S. | Lynch, Dennis | Gallaher, Thomas N.

We tested the hypothesis that there would be measurable losses of phosphorus (P) from surficial sediments of Upper Klamath Lake (UKL), Oregon, if sediments were a source of P during an algal bloom. We compared concentrations of total and forms of P at various depths in cores collected before and after the onset of a large Aphanizomenon flos-aquae bloom. Concentrations of inorganic P were determined in extraction solutions of MgCl₂ (1 M, pH 8), citrate-dithionite-bicarbonate, and 1 M HCl. Sediments below 2 cm were dominated by residual P which is defined as total P minus inorganic P. During the study period, data from the top 2-cm of sediment indicated (a) significant decrease in total P concentration, primarily associated with iron oxyhydroxides at one site, and (b) significant increase in total P concentration associated with residual P at a second site. Data from two other sites indicated no net changes in concentrations of total P.

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