Assessment of Phoslock® application in a tropical eutrophic reservoir: An integrated evaluation from laboratory to field experiments

• In microcosms Phoslock®  application caused RSP reduction of 82% in the water column.
• In mesocosms Phoslock®  application caused RSP reduction of 81% in the water column.
• Negative toxic impacts of Phoslock®  addition to the water column were temporary.
• Changes in prevalent algae taxa were observed in the water column of mesocosms.

The main objective of this study was to develop laboratory and in situ experiments to control reactive soluble phosphorus (RSP) concentration and to evaluate the possible changes and toxic effects caused by Phoslock®  application in the Ibirité reservoir (SE Brazil). Microcosm trials indicated that Phoslock®  is a promising treatment because it shows fast response and effective RSP immobilization (reductions of 82% in the water column and 69% in the sediment interstitial water). Acute toxicity test results suggested that the negative impacts of Phoslock®  addition to the water column were temporary. In situ mesocosm trials did not suggest significant physicochemical alterations after Phoslock®  application. Only turbidity was drastically altered by this treatment. Mean reductions in RSP concentration of 81% and 90% in the water column and sediment interstitial water, respectively, were observed 600 h after treatment. The mortality of Ceriodaphnia silvestrii and changes in prevalent algae taxa were observed in the water column. In the sediment, no acute toxic effect was observed, although the richness of benthic groups decreased due to the treatment. Overall, the results indicate that Phoslock®  is a good option for the control of eutrophication in the studied reservoir.

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