Puyehue Cordón –Caulle: post-eruption analysis of changes in stream benthic fauna of Patagonia

Mailén Elizabeth Llallement,Patricio J Macchi,Santiago M Juárez,Pablo H Vigliano

doi:10.25260/ea.14.24.1.0.38

Mailén Elizabeth Llallement, Patricio J Macchi + Show 2 more

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https://doi.org/10.25260/ea.14.24.1.0.38

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Journal: Ecología Austral	Publication Date: Apr 1, 2014
Citations: 22	License type: cc-by

Affiliation: University of Buenos Aires

Abstract

Ecologia Austral, 24:64-74 (2014) Volcanic eruptions are natural phenomena with the most diverse and varied consequences, and have important effects on both terrestrial and aquatic environments. On June 4 th , 2011 the volcanic Puyehue Cordon-Caulle complex (2.236 MASL, 40o 32´ S-72o 2´ W, Chile) erupted explosively ejecting on the first day, 950 million metric tons of ashes into the atmosphere. Due to predominant westerly winds, 24 million hectares of Argentinian Patagonia were covered by the ashfall. We studied three streams in northwestern Patagonia in order to explore the ash fall impact and possible recovery processes in water quality and macroinvertebrate communities. We selected three streams representing maximum, intermediate and minimum ash deposition levels. For each stream, we selected two sampling sites to measure pH, conductivity, total dissolved solids (TDS), turbidity (NTU) and to take three macroinvertebrate samples during summer 2012 and 2013. After the eruption of the Puyehue-Cordon Caulle complex, substantial environmental changes were observed in association with the large amount of ash ejected by the volcano and deposited on the nearest areas. Low benthic fauna densities, as well as low values of Ephemeroptera, Plecoptera and Trichoptera (EPT) and Biotic Monitoring Patagonian Streams (BMPS) indexes, reflected changes in water quality due to ash fall, mainly in the two streams closer to the volcano. After eighteen months, the streams had not reached the density, taxa composition and structure of trophic webs comparable to other streams previously studied in the region. The exploratory analysis suggests that the main impact was a consequence of ash fall in terms of the amount and particle size proportions.

Highlights

Volcanic eruptions are natural phenomena, creating diverse and varied consequences which give place to a mosaic of environmental conditions
We studied three streams in northwestern Patagonia in order to explore the ash fall impact and possible recovery processes in water quality and macroinvertebrate communities
Terrestrial insect populations were highly reduced due to the abrasive effects of volcanic ash (Edwards et al 1986), surviving colonies could not prosper due to the scarcity of resources left

Summary

Introduction

Volcanic eruptions are natural phenomena, creating diverse and varied consequences which give place to a mosaic of environmental conditions (both in terrestrial and aquatic environments). A variety of factors influences species survival after the ash fall such as life stories, recolonization mechanisms and dispersal strategies (Dale et al 2005; Marske et al 2007; Miserendino et al 2012; Masciocchi et al 2013), as well as the availability of safe sites and the characteristics of each affected environment (Death et al 2003). Terrestrial insect populations were highly reduced due to the abrasive effects of volcanic ash (Edwards et al 1986), surviving colonies could not prosper due to the scarcity of resources left (del Moral 1981). In aquatic environments, suspended solid increased after the deposit of ejected materials, and it was observed even during several months after Mount St. Helens eruption (Antos & Zobel 2005). There was a decrease in some taxa of macroinvertebrates, in relation to the instability of the substrate, which affected recolonization processes (Anderson 1992)

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