When Exception Becomes the Rule : Ecological Dynamics and Management Challenges of a Spirulina-Dominated Continental Aquatic Ecosystem

This innovative research investigates the composition and behavior of the phytoplankton community in the Kheneiga pond, a 6-hectare freshwater habitat situated in the dry region of Laghouat, Algeria. The ecological analysis, derived from monthly samples collected in 2022, indicates a severe community imbalance marked by the near-complete dominance of the cyanobacterium Spirulina (>99.9% of total abundance). The computed diversity indices (Shannon H' = 0.0086; Equitability E = 0.0016) demonstrate exceedingly low diversity and a markedly uneven distribution of taxa.Statistical analysis reveals that pH and mineralization parameters (conductivity, TDS) predominantly influence the structure of the phytoplankton community, accounting for over 58% of the observed variance in algal density. The temporal dynamics indicate a gradual shift from a diverse community to a near-total predominance of Spirulina, coinciding with an elevation in pH (from 7.46 to 8.65) and conductivity (from 2230 to 11480 μS/cm).This biological succession indicates a eutrophication phenomenon likely associated with wastewater discharges that partially nourish this wetland. The positive relationships between Spirulina density and organic load markers (COD, BOD) substantiate this hypothesis. The significant reduction of the phytoplankton community raises apprehensions regarding the ecosystem's resilience and its capacity to deliver diverse ecosystem services.This work underscores the susceptibility of continental aquatic ecosystems in dry regions to human-induced disturbances and stresses the necessity of adopting tailored management measures to safeguard the biodiversity of Saharan wetlands.