Macrobenthic Community Changes of Intertidal Sandy Shores after a Mega-Disturbance

Abstract

Large-scale events of destruction and mortality trigger abrupt changes in the structure of natural communities. Testing the magnitude of such effects and the resilience of the impacted communities is difficult, however, because large-scale disturbances are generally unpredictable and thus available data are rare. Here, we studied the spatiotemporal variation of intertidal sandy-shore communities in relation to the Maule earthquake and tsunami that hit the south-eastern Pacific shore on the 27 February 2010. We analysed a dataset of four sampling times conducted over a period of 23 months, in which macrobenthic (>1 mm) species abundances were sampled before and consecutively three times after the Maule earthquake and tsunami took place. Our results indicated that the Maule earthquake and tsunami triggered abrupt and significant changes in species richness, total abundance, and community structure within the southern rupture area. Immediately after the earthquake and tsunami, sites within the southern rupture area of the earthquake showed significant changes in community structure, reaching up to 91 % dissimilarity with the pre-earthquake state. However, this high dissimilarity gradually decreased throughout time, indicating that the community subsequently tended to return toward its pre-event structure. Accordingly, a statistical model predicting a return toward the initial multivariate structure significantly fitted to our dataset. We suggest that the changes of intertidal sandy-shore communities are the result of the high abundance of species with high mobility and short generation times, producing populations that are highly dynamics. These traits may constitute therefore a negative feedback preventing the establishment of alternative community states after large-scale disturbances.