Biological traits and community patterns of Trichoptera at two Patagonian headwater streams affected by volcanic ash deposition

Cecilia Brand,María Laura Miserendino

doi:10.1186/s40555-014-0072-9

Abstract

BackgroundSediment deposition constitutes a major disturbance having negative effects on aquatic ecosystems. The Chaitén Volcano eruption occurred on May 2008. As a consequence, broad areas along the Argentine Andes (40° S to 46° S) were covered with ash. This event provided an excellent opportunity to investigate how a natural and exceptional sedimentation episode affects Trichoptera communities.ResultsWe assessed changes in caddisfly community attributes (composition, density and diversity) and 11 biological traits, by comparing pre-eruption (May 2007 to April 2008) and post-eruption (July 2008 to March 2010) data at two headwater streams. As a consequence of the event, total suspended solids increased and Trichoptera richness and density significantly diminished. By March 2010, two common species of Hydroptilidae (Metrichia patagonica and Metrichia neotropicalis) were no longer recorded at one site; while species richness and density values were still low indicating that the community had not recovered. Scrapers, shredders, and predators were among the most affected functional feeding groups and changes in their relative abundance were tracked in subsequent years after the ashfall event.ConclusionsIn this study, species tolerance to sedimentation was related to certain traits such as poorly synchronized life history, filter-feeding habits, rounded body shape, tegument respiration mode, and poorly sclerotized life forms.

Highlights

Sediment deposition constitutes a major disturbance having negative effects on aquatic ecosystems
Physicochemical variables Substrate size composition at Nant y Fall site was dominated by gravel (30%), cobbles (25%), and boulders (20%), and the remaining 25% was distributed among smaller fractions; Chiquito Stream dominant fractions were cobbles (30%), pebbles (25%), and boulders (15%), with the remaining 30% distributed among smaller fractions
Substrate occurring within a riffle were 50% covered in ash, while at deposition areas, up to 70% was covered with ash

Summary

Introduction

Sediment deposition constitutes a major disturbance having negative effects on aquatic ecosystems. Broad areas along the Argentine Andes (40° S to 46° S) were covered with ash. This event provided an excellent opportunity to investigate how a natural and exceptional sedimentation episode affects Trichoptera communities. Fine volcanic ash deposition is often responsible for the more widespread impact of a volcanic eruption, affecting hundreds of square kilometers (km2) by covering the soil with dense layers of volcanic material, leading to significant changes in both terrestrial and aquatic environments (McDowall 1996; Del Moral and Grishin 1999; Martin et al 2009). Strong wind storms may result in ash resuspension, causing similar effects to those of the original eruption (Inbar et al 1995; Ruggieri et al 2011)

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