EXPLORING THE RECOVERY OF A LARGE WETLAND 16 YEARS AFTER A POLLUTION-INDUCED DISTURBANCE USING BLACK-NECKED SWAN BLOOD PARAMETERS AND BODY CONDITION.

Resilience theory has gained a center stage to tackle challenges in wetland recovery on a fast-changing planet. Because their high dependence on wetlands, waterbird numbers had long been used as surrogates of wetland recovery through time. However, immigration of individuals can mask actual recoveries at a given wetland. One alternative to expand the understanding of wetland recovery is the use of physiological parameters from aquatic organism populations. We explored the variation in black-necked swan physiological parameters before, during and after a 16-years period of a pollution-induced disturbance originated from a pulp mill wastewater discharge. This pollution-induced disturbance triggered the precipitation of iron (Fe) in the water column of Río Cruces wetland in southern Chile, one of the main sites for black-necked swan Cygnus melancoryphus global population. We compared our recent (2019) original data (body mass index, hematocrit, hemoglobin, mean corpuscular volume, blood enzymes and metabolites) with available datasets from the site obtained before pollution-induced disturbance (2003) and immediately after pollution-induced disturbance (2004). Results indicate that after 16 years of the pollution-induced disturbance some important parameters of animal physiology did not return to their initial state. For instance, body mass index, triglycerides and glucose were significantly higher in 2019 than right after the pollution-induced disturbance in 2004. By contrast, hemoglobin concentration was significantly lower in 2019 compared to 2003 and 2004, and uric acid was 42% higher during 2019 than in 2004. Our results show that, despite higher, black-necked swan numbers with larger body weights present in 2019, Río Cruces wetland has only partially recovered. We suggest that the impact of megadrought and wetland disappearance far from the site results in high rate of swan's immigration, casting uncertainty about the use of swan's numbers alone as honest indicators of wetland recovery after a pollution disturbance. This article is protected by copyright. All rights reserved. Integr Environ Assess Manag 2023;00:0-0. © 2023 SETAC.