Ecological Implications of Extreme Events: Footprints of the 2010 Earthquake along the Chilean Coast

Eduardo Jaramillo,Jenifer E Dugan,Roland Sanchez,Cesar Campos,Cristian Duarte,Mario Manzano,David M Hubbard,Daniel Melnick,Jack Anthony Gilbert

doi:10.1371/journal.pone.0035348

Eduardo Jaramillo, Jenifer E Dugan + Show 7 more

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https://doi.org/10.1371/journal.pone.0035348

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Abstract

Deciphering ecological effects of major catastrophic events such as earthquakes, tsunamis, volcanic eruptions, storms and fires, requires rapid interdisciplinary efforts often hampered by a lack of pre-event data. Using results of intertidal surveys conducted shortly before and immediately after Chile's 2010 M w 8.8 earthquake along the entire rupture zone (ca. 34–38°S), we provide the first quantification of earthquake and tsunami effects on sandy beach ecosystems. Our study incorporated anthropogenic coastal development as a key design factor. Ecological responses of beach ecosystems were strongly affected by the magnitude of land-level change. Subsidence along the northern rupture segment combined with tsunami-associated disturbance and drowned beaches. In contrast, along the co-seismically uplifted southern rupture, beaches widened and flattened increasing habitat availability. Post-event changes in abundance and distribution of mobile intertidal invertebrates were not uniform, varying with land-level change, tsunami height and coastal development. On beaches where subsidence occurred, intertidal zones and their associated species disappeared. On some beaches, uplift of rocky sub-tidal substrate eliminated low intertidal sand beach habitat for ecologically important species. On others, unexpected interactions of uplift with man-made coastal armouring included restoration of upper and mid-intertidal habitat seaward of armouring followed by rapid colonization of mobile crustaceans typical of these zones formerly excluded by constraints imposed by the armouring structures. Responses of coastal ecosystems to major earthquakes appear to vary strongly with land-level change, the mobility of the biota and shore type. Our results show that interactions of extreme events with human-altered shorelines can produce surprising ecological outcomes, and suggest these complex responses to landscape alteration can leave lasting footprints in coastal ecosystems.

Highlights

Chile overlies the convergent boundary between the Nazca plate and the South American continent (Fig. 1a), one of the most seismically active areas on Earth
To quantitatively sample invertebrate macrofauna we set up four replicated shorenormal transects 5 m apart from each other, extending from the upper intertidal to the low tide level of sites located in front of seawalls or rocky revetments and in unarmoured areas at each beach. Along these transects we sampled each of the three intertidal faunal zones typical of sandy beaches of south central Chile, which are dominated by crustaceans [39,40]: i) the upper zone occupied primarily by talitrid amphipods (Orchestoidea tuberculata), usually extending from the toe of the dunes or natural cliffs to the drift line or high tide level, ii) the mid zone occupied by cirolanid isopods (Excirolana braziliensis and Excirolana hirsuticauda), extending from the drift line to the effluent line, and iii) the lower zone occupied primarily by hippid crabs (Emerita analoga), extending from the effluent line to the lowest tide level or bore collapse line of incoming waves
Our novel results indicate that the extreme earthquake and tsunami of 27th February 2010, resulted in significant and lasting changes in physical and ecological attributes of sandy beaches on the affected coast

Summary

Introduction

Chile overlies the convergent boundary between the Nazca plate and the South American continent (Fig. 1a), one of the most seismically active areas on Earth. Along the Chilean margin, plate convergence at ,70 mm/yr [1] results in great earthquakes (Mw,8.0–8.5) on average every ,100–150 years, with occasional giant events (Mw.9.0) every ,300 years [2], like the 1960 earthquake that reached a moment magnitude (Mw) of 9.5 Such earthquakes result in substantial land-level changes of coastal and inland regions [3,4,5,6]. Plate-boundary slip associated with the Maule earthquake reached 20 m, localized mostly in two patches to the north and south of the epicentre [10,11,12] (Fig. 1b). The Maule event triggered a devastating tsunami that killed nearly 500 people [13], destroyed coastal infrastructure, and further reshaped coastal landscapes [4,5,6]

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