Abstract
Determining the effects of unpredictable disturbances on dynamic ecological systems is challenged by the paucity of appropriate temporal and spatial coverage of data. On 27 February 2010, an 8.8 Mw mega-earthquake and tsunami struck central Chile and caused coastal land-level changes, massive damage to coastal infrastructure, and widespread mortality of coastal organisms. Wave-exposed sandy beaches showed significant changes of species abundances from before to after the earthquake, but the highly dynamic biotic and abiotic conditions of these habitats make difficult to draw clear-cut conclusions from these patterns. Here, we analysed a beyond-BACI (Before-After Control-Impact) sampling design to test whether the effects of the Maule earthquake on sandy-shore species diversity, abundance, and structure were heterogeneous along the shore. Invertebrate species abundances were quantified before (i.e. February 2010) and after (i.e. March 2010, September 2010, and March 2011) the earthquake at three sandy shores randomly located within the earthquake rupture area and three sites within a “control” area located >400 km southward from epicentre. Immediately after the earthquake took place, the three sites located in the rupture area showed anomalous beach-profile uplifts that did not comply with the erosion (i.e. “negative” uplifts) that regularly occurs during late summer in the region. Species richness, abundance, and community structure significantly varied from before to after the strike, but these patterns of change varied among sites within both areas. Only the site with the strongest and persistent beach-profile uplift within the rupture area showed significant concomitant changes in species richness and community structure; after 13 months, this community showed a similar multivariate structure to the before-disturbance state. This site, in particular, was located in the section of the rupture area that received most of the impact of the after-earthquake tsunami. Therefore, our results suggest that the effects of the Maule mega-earthquake on the ecological communities were spatially heterogeneous and highly localised. We suggest that high mobility and other species’ adaptations to the dynamic environmental conditions of sandy beaches might explain the comparatively high resilience of these assemblages. With this work we hope to motivate further experimental research on the role of individual- and population-level properties in the response of sandy-beach communities to interacting sources of disturbances.
Highlights
Understanding the patterns of species diversity, abundance, and community structure after natural and anthropogenic disturbances is central to provide accurate predictive models of community recovery and resilience
Our results showed concurrent patterns of change in beach profiles and sandy-beach assemblages from before to after the Chile 8.8 mega-earthquake
In agreement with recent geomorphological studies [7,19], we observed that the deformation of beach profiles following the doi:10.1371/journal.pone.0157910.g005
Summary
Understanding the patterns of species diversity, abundance, and community structure after natural and anthropogenic disturbances is central to provide accurate predictive models of community recovery and resilience. The Mw 8.8 megaearthquake and tsunami that struck central Chile on 27 February 2010 generated coastal landlevel changes, sand deposition, and mortality of coastal organisms at a number of locations along the shores [5,6]. The epicentre of this earthquake, the fifth largest ever instrumentally recorded in the world, was located ca. Post-stroke changes in intertidal sandy-shore species abundance were heterogeneous along the rupture area, and depended on particular features of sites such as land-level change, height wave, and local coastal infrastructure [6]
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