Abstract

Although explosive volcanic eruptions are natural disturbances that cause significant environ-mental repercussions and impose multiple changes on ecosystems, post-eruption studies of rivers andstreams are not common. The most recent eruption of the Puyehue-Cordon Caulle volcanic complex(PCCVC) began on 4 June 2011 with a large explosion and the emission of a column of gas and volcanicash (particle size <0.001–2 mm) followed by the release of silica magma, and lasted approximately untilJune 2012. The wind-dispersed volcanic ash affected the area surrounding the PCCVC in southern Chileand, subsequently, most of South America, but local effects on streams and rivers in the vicinity were moredrastic. We collected water, ash, and benthic macroinvertebrate samples four months after the eruptionfrom four rivers: Two were visibly impacted (Gol-Gol and Nilahue) in areas where volcanic ash thicknessranged between 1 and 5 cm, in the vicinity of the PCCVCfissure (8–15 km), and two adjacent rivers (Cal-currupe and Chanleufu) were located 20–40 km from the PCCVCfissure where ash thickness was <1 cmand did not present visible impacts. Results were then compared with data obtained from previousresearch projects. This study reports that this natural disaster induced an increase in concentrations of totalsuspended solids and of phosphorous in the rivers Gol-Gol and Nilahue, as well as habitat destruction,deterioration of environmental quality, and the consequent devastation of macroinvertebrate assemblagesinhabiting these rivers directly following the eruption. We conclude that volcanic eruptions can generatelocal extinctions of benthic macroinvertebrates in the short term, compared with rivers that were notaffected by volcanic ash.