Regime shifts of Cruces River wetland ecosystem: current conditions, future uncertainties

Abstract

During April-May 2004 the Cruces River wetland ecosystem, located in Valdivia (40ºS), southern Chile, was described as shifting from a clear water regime, dominated by the exotic macrophyte Egeria densa, to turbid waters and absence of submerged macrophytes. We analyzed the trophic status and ecological regime of the wetland from November 2011 through January 2013. The trophic status was determined comparing values of selected variables (nutrients, chlorophyll-a and transparency) with OECD criteria. The ecological regime was determined comparing the same variables with the criteria proposed by Ibelings et al. (2007). We further compared the concentration of nutrients and suspended solids with previous measurements. Current trophic status of the wetland is between eutrophic and hypereutrophic, as shown by results, and its ecological regime intermediate, between clear and turbid waters, with a considerable risk of returning to turbid waters. In this article we discuss the potential relationship between the watershed land use (agriculture, cattle feeding and forestry), the change in wetland’s trophic level and future conditions.