Spatio-temporal dynamics of physico-chemical parameters in a forest stream: The Hana river, Taï national park, Côte d’Ivoire

This study aimed to assess the spatial and seasonal variation of physicochemical parameters in the Hana River within Taï National Park in order to strengthen monitoring of its aquatic environment and support biodiversity conservation. Monthly measurements were conducted from May 2016 to April 2017 at three stations—upstream, midstream, and downstream—during three daily intervals. Using a LOVIBOND SENSO DIRECT 150 multiparameter meter, the annual mean values recorded were: temperature (26.89 ± 2.17 °C), pH (7.14 ± 0.51), dissolved oxygen (5.70 ± 1.67 mg/L), conductivity (52.28 ± 17.33 µS/cm), total dissolved solids (37.07 ± 12.46 mg/L), and redox potential (75.08 ± 41.33 mV). Nutrient concentrations measured with HANA mini-photometers included nitrites (0.011 ± 0.008 mg/L), nitrates (3.18 ± 2.27 mg/L), phosphates (0.273 ± 0.24 mg/L), total phosphorus (0.890 ± 1.39 mg/L), ammonium (2.927 ± 1.82 mg/L), total chlorine (0.088 ± 0.04 mg/L), and free chlorine (0.111 ± 0.11 mg/L). Hydromorphological parameters—velocity (0.361 ± 0.20 m/s), transparency (45.3 ± 17.62 cm), depth (2.179 ± 1.43 m), and width (19.29 ± 8.79 m)—were also recorded. Seasonal patterns showed that most parameters peaked during the dry season across all stations. Principal Component Analysis suggested that observed variations and local impairments were largely linked to agricultural and rural activities, with natural watershed processes contributing to a lesser extent. Overall, the Hana River exhibited lower physicochemical levels than typically reported in similar ecosystems, and nutrient concentrations remained within acceptable limits. However, areas influenced by rural activities displayed higher pollution indicators. These findings highlight the need to establish a standardized chemical monitoring framework to ensure long-term protection of the Hana River.