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

Abstract

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. Keywords: regime shift, macrophytes, nutrients, eutrophication, wetland, ecosystem, southern Chile. Cambios de régimen en el ecosistema del humedal del río Cruces:condiciones actuales, incertezas futuras RESUMEN. Durante abril-mayo 2004 el ecosistema del humedal del río Cruces, localizado en Valdivia (40ºS), en el sur de Chile, fue descrito como cambiando de un régimen de aguas claras, dominado por la macrófita introducida Egeria densa, a aguas turbias con ausencia de macrófitas. En este artículo se analiza el estado trófico y el régimen ecológico del humedal entre noviembre 2011 y enero 2013. El estado trófico se determinó comparando los valores de variables seleccionadas (nutrientes, clorofila-a y transparencia) con los criterios de la OECD. El régimen ecológico se determinó comparando las mismas variables con los criterios propuestos por Ibelings et al. (2007). Asimismo, se comparó la concentración de nutrientes y de sólidos en suspensión con mediciones previas. Los resultados muestran que el estado trófico actual del humedal es entre eutrófico e hipereutrófico, y su régimen ecológico intermedio, entre aguas claras y turbias, con un considerable riesgo de retornar a aguas turbias. Además se discute la posible relación entre el uso del suelo de la cuenca (agricultura, alimentación de ganado y silvicultura), el cambio en el nivel trófico del humedal y su condición futura. Palabras clave: cambio de régimen, macrófitas, nutrientes, eutrofización, humedal, ecosistema, sur de Chile.

Taxonomic and Functional Responses of Species-Poor Riverine Fish Assemblages to the Interplay of Human-Induced Stressors

“…The sensitivity of species-poor riverine biota that inhabits these rivers to pollution could have been clearly evidenced in 2004 in the Cruces River (tributary of the Valdivia River) which has undergone ecosystem collapse due to nutrient pollution and water quality decreasing as consequence of inefficient operation of a pulp-mill plant [44]. During the collapse, various taxonomic groups of organisms died massively due to bottom-up effect [37,77]. Currently, an increase in depuration technology standards has allowed for the improvement of the rivers' ecological status, reflected in the composition and functional structure of fish assemblages in the Cruces River (which does not seem to be highly affected by pollution according to our results).…”

“…The Valdivia River basin is free of major hydropower dams. It accommodates one pulp mill plant located in the Cruces River tributary and it has fewer urban centers (three) compared to the Biobío River basin [36][37][38].…”

A multi-period risk sharing supply chain contract under consideration of price and demand uncertainties

“…At the same time I appreciate the generous support given to me by my husband Serdar Tari, my mother Ulku Basmaci and my father Murat Basmaci. (Marin et al 2014) . .…”