Evaluating chemical precipitation as a strategy for lake restoration: effects on aquatic flora and fauna at Lake Busa (Ecuador)

García-Avila F.; García-Pizarro E.; Malla-Aguilar G.; Criollo-Illescas F.; Jiménez-Ordoñez M.; Valdiviezo-Gonzales L. · Frontiers in Water (2026) · DOI: 10.3389/frwa.2026.1736315

Resumen

Excess phosphorus in aquatic ecosystems promotes eutrophication, leading to ecological alterations that modify the abundance of phytoplankton and aquatic macrophytes. This study evaluated chemical precipitation with aluminum sulfate as a management strategy for Lake Busa by assessing phosphorus removal and its effects on the aquatic macrophyte Schoenoplectus californicus (C.A.Mey.) Soják and the fish Cyprinus carpio Linnaeus, 1758. Jar tests were performed to determine the optimal aluminum sulfate dose for phosphorus removal. The effects of treated water were subsequently evaluated biologically in a 35-day microcosm experiment using 54 S. californicus individuals distributed among 12 experimental containers. Acute toxicity was assessed in newly hatched C. carpio fry through 96-h laboratory exposure tests using untreated water, treated water, and potable-water controls. Because the experimental design did not include replicated containers for each treatment, the biological responses are presented as observed patterns under the tested conditions rather than statistically validated treatment effects. Under the experimental conditions evaluated, aluminum sulfate doses of 34−40 mg/L removed 88.9−90.9% of phosphorus (from 0.09−0.11 mg/L to 0.01 mg/L), while residual aluminum concentrations remained between 0.061 and 0.071 mg/L. Under the experimental conditions evaluated, S. californicus grown in treated water showed a mean height increase of 5.28 cm and a mean stem diameter increase of 0.12 cm, whereas plants maintained in untreated lake water showed mean increases of 12.5 cm and 0.27 cm, respectively. A mortality rate of 93.33% was observed in newly hatched C. carpio fry after 96 h of exposure to treated water containing residual aluminum. These findings indicate that although aluminum sulfate effectively reduces phosphorus and limits macrophyte growth, the associated residual aluminum may adversely affect aquatic biodiversity. Consequently, chemical precipitation should be evaluated using both water-quality and biological indicators before large-scale application in eutrophic lakes. Copyright

Instituciones: Universidad Tecnológica del Perú