Exploring the recovery of a large wetland using black‐necked swan blood parameters and body condition 16 years after a pollution‐induced disturbance.

This article focuses on assessing the long-term recovery of the Río Cruces Wetland in southern Chile following a pollution-induced disturbance caused by pulp-mill wastewater discharge that precipitated iron (Fe) in the water. Using physiological parameters of the black-necked swan (Cygnus melancoryphus), a key aquatic bird species dependent on the wetland, the study compares data from before (2003), immediately after (2004), and 16 years post-disturbance (2019). Despite increased swan abundance and body mass index in 2019, several hematological and biochemical indicators—including lower hemoglobin, elevated uric acid, and altered enzyme levels—suggest incomplete recovery and ongoing oxidative stress likely linked to Fe exposure and environmental factors such as megadrought and altered food quality. The findings highlight limitations of using bird abundance alone as an indicator of wetland recovery and advocate for integrating physiological measures over broad temporal and spatial scales to more accurately evaluate ecosystem resilience after pollution events.