Environmental changes and macroinvertebrate responses in Patagonian streams (Argentina) to ashfall from the Chaitén Volcano (May 2008)

MARÍA LAURA MISERENDINO, MIGUEL ARCHANGELSKY, CECILIA BRAND, LUIS BELTRÁN EPELE

SCIENCE OF THE TOTAL ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2012 vol. 424 p. 202 - 212

0048-9697

On May 2nd of 2008 the Chaitén Volcano (Chile, 42°50′S and 72°39′W) erupted explosively producing astrong emission of volcanic ash. As a result of this eruption wide areas on the Argentinean side became coveredby ashes. In order to investigate the effects of ashfall on environmental features, water quality andmacroinvertebrate communities we conducted a study on 10 rivers affected by ash deposition in their hydrographicbasins. Sites were visited seasonally (June 2008–March 2010) and results were compared with dataobtained from previous research projects. Measures of pH, conductivity, oxygen content, main nutrients, andtotal suspended solids (TSS) were taken. Macroinvertebrate samples were obtained from riffles and pools.Community attributes were measured and metrics were calculated. A strong and significant increase in TSSvalues at most sites was recorded and although the peak diminished rapidly during the following months,resuspension and remobilization of ash continue even 20 months after. No significant changes in pH, conductivityand nutrients, comparing with data previous to the ashfall, were detected. Most rivers showed a strongdiminution on macroinvertebrate density and richness, being small riversmore severely affected than the bigones. Correspondence analysis based on abundance data allows distinguishing preeruption from posteruptiondates at five rivers. Density data and species richness showed low values in March of 2010, indicatingthat the community was not completely recovered at some sites. At least 25 taxa resulted significantly andnegatively affected. Increased mortality could be related to several factors such as habitat deterioration,food quality diminution, interference with breathing mechanisms and with other physiological and morphologicalcharacteristics. Specific-taxa responses on the recolonization process were related to dispersal mechanismsand specific strategies.