Ecological Transformations of a Tropical River During the SARS‐CoV‐2 Pandemic: Evidence From the Sierra Nevada de Santa Marta, Colombia, South America

ABSTRACT

Tourism is one of the main anthropogenic stressors affecting tropical freshwater ecosystems, frequently causing deterioration in water quality and ecological integrity. The SARS‐CoV‐2 pandemic and the lockdown measures implemented in 2020 created a unique opportunity to evaluate ecosystem responses to reduced human activity. This study assessed changes in the ecological quality of the Gaira River, located in the Sierra Nevada de Santa Marta, before (2019), during (2020) and after (2021) the COVID‐19 Lockdown period using the phytoplankton‐based Ecological Quality Index (EQI _RG‐PHY ). Eleven monitoring campaigns were conducted across four sampling stations. During Lockdown, dissolved oxygen increased from 5.4 ± 0.6 mg L ⁻¹ to 7.1 ± 1.6 mg L ⁻¹ , whereas conductivity and nutrient concentrations decreased. EQI _RG‐PHY values improved from critical conditions in the Pre‐lockdown period (4.54–5.16) to moderate–good ecological quality during lockdown (5.76–6.05), followed by a decline back to critical conditions in the Post‐lockdown period (4.50–4.62). Highly significant differences among periods were observed (ANOVA), using the four sampling stations as replicates for each period. Phytoplankton diversity showed greater stability during lockdown and slight reductions afterward, particularly in dominant taxa. Results demonstrate that tourism‐related pressures strongly influence the ecological quality of tropical rivers and that short‐term reductions in anthropogenic activity can promote rapid ecosystem recovery. The study also highlights the remarkable resilience of aquatic ecosystems and emphasizes the urgent need to strengthen environmental awareness, sustainable tourism practices and conservation strategies to reduce long‐term human impacts on freshwater ecosystems.