Hypertrophic Wadi Feeds Bizerte Lagoon While Glyphosate Persists

Guenniche Wadi, the principal tributary of the ecologically and economically significant Bizerte Lagoon, is in a state of severe and persistent eutrophication, according to a study published in Plant Biosystems.

The trophic evaluation rested on four indicators measured throughout the monitoring period: nitrate concentrations, soluble reactive phosphorus, chlorophyll a, and Carlson’s Trophic State Index. Together, these consistently indicated a persistent hypertrophic condition. The hypertrophic state was accompanied by reduced dissolved oxygen concentrations, a combination the authors describe as confirming severe eutrophication and ecological degradation in the Wadi.

Glyphosate and its primary metabolite, AMPA, were detected persistently across the entire study period. The researchers report that these herbicide residues were associated with tolerant filamentous Cyanobacteria.

The biological component of the assessment focused on suspended microalgal communities, which included both true planktonic taxa and benthic taxa that had been resuspended into the water column. Monthly sampling of these communities revealed low diversity. The assemblage was dominated by pollution- and nutrient-tolerant taxa, a composition the authors say supports the hypertrophic status indicated by the chemical indices.

Nutrient limitation analysis identified phosphorus as the principal limiting nutrient in the system. Phosphorus exhibited significant correlations with total microalgal abundance and with most taxonomic groups, underscoring its pivotal role in driving the eutrophication process.

The integration of trophic indicators, suspended microalgal communities and herbicide monitoring provided a comprehensive assessment of the ecological status of Guenniche Wadi. The authors state that this integrated assessment highlights the need for management strategies that reduce both nutrient and herbicide inputs to protect the Wadi and the downstream Bizerte Lagoon simultaneously.

Subject of Research: Eutrophication status and herbicide contamination in Guenniche Wadi, a tributary of Bizerte Lagoon, assessed with trophic indices and suspended microalgae

Article Title: Integrated assessment of eutrophication and herbicide stress in Guenniche Wadi using trophic indices and suspended microalgae

Article References: Azizi, S., Sahraoui Khalifa, I., Melliti Ben Garali, S., Mejri Kousri, K., Béjaoui, M., Saber, A. A., Pezzolesi, L., Cantonati, M., & Sakka Hlaili, A. (2026). Integrated assessment of eutrophication and herbicide stress in Guenniche Wadi using trophic indices and suspended microalgae. Plant Biosystems, 160(6), Article 302. https://doi.org/10.1007/s44473-026-00288-1

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00288-1

Keywords: eutrophication, Guenniche Wadi, Bizerte Lagoon, hypertrophic, glyphosate, AMPA, microalgae, phosphorus limitation, Cyanobacteria, trophic state index, Mediterranean, water quality