Cyanobacterial resilience and productivity decoupling from declining phosphorus during a four-year whole-lake aeration.

Authors

Virginia Fleitas, Guillermo Goyenola

Published in

Journal of environmental management. Volume 413. Pages 130432. Jul 05, 2026. Epub Jul 05, 2026.

Abstract

Urban eutrophic lakes in subtropical regions represent a persistent management challenge due to their strong internal feedbacks that resist rehabilitation. We report a four-year whole-lake intervention evaluating the effectiveness of artificial aeration in a 10 m-deep, eutrophic urban lake in Uruguay, using a Before-After Control-Impact (BACI) design with a comparable reference lake. Despite continuous operation, aeration did not alter the seasonal warm-monomictic regime nor eliminate summer deep-layer anoxia. However, it partially weakened thermal stratification and drove a sustained, statistically significant decline in surface total phosphorus (∼18 μg P L^-1 yr^-1), shifting the TP-based trophic state index from hypereutrophic to eutrophic. In contrast, chlorophyll-a remained hypereutrophic throughout, revealing a marked decoupling between nutrient availability and phytoplankton productivity. Persistent cyanobacterial dominance, rising phosphorus-use efficiency, and cycles of intense bloom growth, collapse, and rapid recovery indicate physiological adjustment to declining phosphorus rather than a proportional loss of biomass. The reference lake showed no equivalent directional changes, supporting the attribution of these trends to aeration. The intervention altered specific processes-thermal stability and internal phosphorus release-without shifting the dominant feedbacks sustaining eutrophy, consistent with "pathological resilience", wherein internal mechanisms perpetuate a degraded state despite external perturbation. Aeration alone proved insufficient to trigger structural reorganization within four years, underscoring the need for integrated, adaptive rehabilitation strategies in urban lakes with strong self-sustaining eutrophic feedbacks.

PMID:
42402233
Bibliographic data and abstract were imported from PubMed on 06 Jul 2026.

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