Max L. Bothwell Steven R. Chipps John Carreiro Daniel A. James 2015 <p><span>Blooms of the benthic alga, </span><i>Didymosphenia geminata</i><span> [Lyngbye (Schmidt)], were first documented in Rapid Creek, South Dakota, in 2002 and have since been associated with changes to aquatic resources. Low concentration of P has been associated with </span><i>D. geminata</i><span> stalk development (i.e., blooms), so we considered elevating P as a possible method to reduce </span><i>D. geminata</i><span> blooms. We conducted 2 whole-stream P-enrichment experiments in Rapid Creek during 2007 and 2008. Enrichment with a slow-release fertilizer (Osmocote</span>^®<span>: 14-14-14) in 2007 significantly reduced </span><i>D. geminata</i><span> blooms (indexed by </span><i>D. geminata</i><span> biomass) compared to upstream control sites. The reduction in biomass was less pronounced as distance from the enrichment source increased, a result indicating that P augmentation effectively decreased </span><i>D. geminata</i><span> biomass. In 2008, we implemented a before-after–control-impact (BACI) study to assess effects of a quick-release fertilizer (MAP: 11-52-0) on </span><i>D. geminata</i><span> biomass. The addition of 6 μg/L P to Rapid Creek resulted in a significant decrease in </span><i>D. geminata</i><span> biomass within 0.6 km downstream of the nutrient-addition point. Effects on </span><i>D. geminata</i><span> biomass were not evident further downstream. This study provides evidence to support the hypothesis that low P concentration regulates </span><i>D. geminata</i><span> blooms.</span></p> application/pdf 10.1086/683038 en The University of Chicago Press Use of phosphorus to reduce blooms of the benthic diatom <i>Didymosphenia geminata</i> in an oligotrophic stream article