Aquatic microorganisms are considered important components of wetland ecosystems, and variations in physical and hydrological environmental conditions can affect their density and dynamics. This study was conducted to investigate the relationship between the density of biological factors (nematodes and protozoa) and changes in turbidity, rainfall, and seasonal variations in the Chah‑Nimeh III Wetland, Sistan and Baluchestan Province, Iran, during the period from April 2025 to May 2026. In this study, surface water samples were collected periodically from the wetland, and the density of biological groups including protozoa and nematodes was measured along with physicochemical parameters including temperature, pH, electrical conductivity (EC), and turbidity. Rainfall data were also collected throughout the study period.

To evaluate the relationships among variables, statistical analyses including Pearson correlation, Spearman correlation, analysis of variance (ANOVA), and regression analysis were performed. The results indicated a significant positive relationship between protozoa density and water turbidity, such that protozoa density increased with increasing turbidity. The highest protozoa density was observed in October 2025, simultaneously with the highest turbidity level. A positive relationship was also observed between nematode density and turbidity, which was statistically significant according to the Spearman correlation test. In contrast, the relationship between rainfall and the density of nematodes and protozoa was generally weak and negative, while Pearson correlation analysis showed no statistically significant association, suggesting possible nonlinear relationships or high variability in the data.

Overall, the results demonstrated that turbidity is a more suitable indicator than rainfall for predicting changes in microorganism populations in this wetland. Furthermore, seasonal variations play an important role in fluctuations in the density of microscopic organisms. These findings may contribute to a better understanding of the biological dynamics of aquatic ecosystems and support regional water resource management.