A Comprehensive Study of Phytoplankton and Heterotrophic Protists in the Context of Urbanization: A Comparative Analysis Between Mburucuyá National Park (Corrientes, Argentina) and Urbanized Areas.

Urbanization is a major driver of biodiversity loss in freshwater ecosystems, yet comparative assessments integrating multiple planktonic communities remain scarce in subtropical wetlands of northeastern Argentina. We assessed the influence of urbanization on the composition and diversity of phytoplankton, ciliates, and testate amoebae in wetlands from Mburucuyá National Park (Corrientes, Argentina) and adjacent urban areas. Two natural sites (Laguna Pedersen and Arroyo Portillo) were compared with two urbanized sites (Laguna Aguirre and Laguna Limpia) using plankton samples collected in October 2025. Physicochemical parameters were recorded in situ, and nutrient concentrations were determined in the laboratory. Live and fixed plankton samples were examined using optical microscopy for identification and quantification. Community structure was evaluated through richness, abundance, multiple-site beta diversity (βSOR), partitioned into species turnover (βSIM) and nestedness (βSNE), and Local Contribution to Beta Diversity (LCBD) to identify compositionally unique sites. Natural sites exhibited higher conductivity (54 µS/cm), total dissolved solids (27.2 ppm), and nitrates (0.057 mg/L) than anthropized sites (24.6 µS/cm, 12.3 ppm, and 0.035 mg/L, respectively). Phytoplankton richness and abundance remained comparable between environments (16 vs. 17), whereas ciliates showed no clear environmental pattern. Testate amoebae showed a consistent reduction in richness (5 vs. 3) and abundance (4166 vs. 1333 ind/L) at urbanized sites. Compositional differences across environments (βSØR= 74%) were primarily driven by species turnover (βSIM 71%). Laguna Limpia harbored the most compositionally unique amoebae and phytoplankton communities regionally (LCBD = 0.32), while Laguna Pedersen presented the most dissimilar ciliates (LCBD = 0.39).

These preliminary findings suggest that planktonic communities respond differentially to urbanization and highlight the value of jointly evaluating multiple communities to better understand their ecological status. Further sampling and complementary analyses are underway to validate these patterns.