Effects of rocky shore coseismic uplift and the 2010 Chilean mega-earthquake on intertidal biomarker species

Abstract

The devastating earthquake (moment magnitude: 8.8 MW) that struck Chile on 27 February 2010 and the following tsunami waves produced widespread damage, coastal coseismic uplifts, and large-scale mortality of rocky intertidal and shallow subtidal organisms. The effects were particularly remarkable around the Gulf of Arauco, Santa María Island and the Bay of Concepción (~36 to 38°S). Measurements of rocky intertidal and shallow subtidal belt-forming (biomarker) species conducted a few weeks after the earthquake indicated coastal uplifts ranging from ~0.2 to 3.1 m, which are similar to uplifts estimated by FitzRoy (1839; Voyages of the Adventure and Beagle, Vol. II) and Darwin (1839; Voyages of the Adventure and Beagle, Vol. III) after the 1835 Chilean earthquake. In major uplifted sites, there was massive mortality of the main intertidal and shallow subtidal beltforming species, such as lithothamnioid melobesioid coralline algae, brown kelps and mussels, and dramatic changes in the marine rocky intertidal ecosystem. We suggest that in the southeastern Pacific, drastic and rapid coastal deformations seriously impinge on rocky shore populations, communities and ecosystems and may have significance for management and conservation practices, as for example in connection with alterations of parental stocks and recruitment rates. 418: 17-23, 2010 mic trench and is ~12 km above where the Nazca tectonic plate is being subducted beneath the South American plate. In fact, the island is the result of earthquake uplifts and deformations that have occurred since the late Pleistocene (Melnick et al. 2006). Major coseismic uplifts on Santa María Island and adjacent mainland sites have previously been reported, although not quantified (e.g. uplifts caused by an earthquake in 1751 (~8.5 MW; Lomnitz 1970, Comte et al. 1986). Santa María Island was also in the rupture zone of the ~8.2 MW mega-earthquake (Melnick et al. 2006) that occurred on 20 March 1835. HMS 'Beagle' visited the region in March, and FitzRoy and Darwin made observations based on the visible evidence of dead shellfish, water marks, surroundings and the verbal testimony of inhabitants. Darwin (1846) summarized FitzRoy's uplift reports: 2.4 m for the southern end, 2.7 m for the central part and 3 m for the northern end of the island. On the mainland, at Tubul (Fig. 1), there was an uplift of 1.8 m. Uplifts of 2.4 m for the Quiriquina Island (36°37' S, 73°03' W) and 1.5 to 2.4 m for Talcahuano harbor (36°43' S, 73°07' W) were also The ~2 m coseismic uplift contour derived from these data has been interpreted as being parallel to the northeast-striking reverse fault system (Melnick et al. 2006). The rocky shore-level changes reported by FitzRoy (1839) and Darwin (1839Darwin ( , 1846 were determined using mostly the emerged upper limit of the dead belt of Mytilus as a pre-earthquake biomarker of the lower limit of the intertidal zone. KEY WORDS: Drastic events · Coastal deformation · Intertidal biomarkers · Massive mortality Resale or republication not perm...

Levantamiento cosismico e impacto del tsunami a lo largo de la costa de Chile central asociado al terremoto del Maule Mw8,8 de 2010.

“…These algae can be found attached to the rocks between the subtidal and the lower intertidal zones. The taxonomy of these algae is complex and precludes a rapid determination of genus or species in the field (Meneses, 1993;Castilla et al, 2010). The most obvious lithothamnioids algae recognizable in the field are of reddish/pinkish color (Guiler, 1959) and turn white when suddenly exposed to solar radiation with no permanent humidification, possibly because of calcareous secretions (e.g., Ortlieb et al, 1996).…”

“…4a), from the observation of bleached and desiccated fringes of algae and other organisms typical of the intertidal zone. From the observation of rocky shore communities, Castilla et al (2010) assessed the massive mortality of belt-forming intertidal and subtidal species, such as lithothamnioids coralline algae, brown kelp and mussels, produced by the coastal uplift and tsunami that followed the Maule earthquake, estimating uplift values of 2.1-3.1 m at Santa María Island, 1.6 m at Punta Lavapié and 0.2-0.3 m at Caleta Tumbes and Mocha Island, which are similar to our estimates (Table 2). Evidences for coseismic land subsidence were observed in places located some kilometers inland from the coastline (Figs.…”

Tectonic and morphosedimentary features of the 2010 Chile earthquake and tsunami in the Arauco Gulf and Mataquito River (Central Chile)

“…Coseismic coastal land-level changes have been estimated by intertidal organisms in different tectonic settings (subduction zones, strike-slip fault systems, and continental thrust belts) by means of barnacles, corals, coralline algae, serpulids and molluscs (i.e. Plafker and Ward, 1992;Ortlieb et al, 1996;Ramírez-Herrera and Orozco, 2002;Ferranti et al, 2007;Shishikura et al, 2009;Castilla et al, 2010;Farías et al, 2010;Vargas et al, 2011;Melnick et al, 2012) but as has been pointed by Melnick et al (2012): "few studies have focused on the distribution of such markers along an uplifted coastline, discussing the influence of local site effects on the accuracy of uplift measurements and the specific methodological aspects that may improve the reliability".…”

Interacción entre defensas costeras artificiales en playas arenosas y perturbaciones naturales de gran escala: el terremoto del 27F de 2010 en la costa del centro-sur de Chile

“…Plafker, 1965;Plafker & Savage, 1970;Ortlieb et al, 1996aOrtlieb et al, , 1996bCastilla, 1988;Boggs & Shephard, 1999;Castilla et al, 2010;Farías et al, 2010;Vargas et al, 2011;Jaramillo et al, 2012). Charles Darwin (1851) fue uno de los primeros en describir tales cambios; para ello se basó en las mediciones realizadas por él mismo en la costa de la península de Arauco, y por Robert Fitz Roy en la costa rocosa de la isla Santa María (circa 37ºS), quien midió alzamientos de hasta 2,4-3,0 m, basado en las distribuciones verticales de restos muertos de moluscos bivalvos de la familia Mytilidae.…”

“…Vargas et al, 2011;Jaramillo et al, 2012), lo que resultó en mortandades masivas de la fl ora y fauna bentónica del litoral rocoso afectado (e.g. Castilla et al, 2010). En este estudio se evalúa el efecto de ese levantamiento sobre el paisaje físico y las abundancias poblacionales de la macrofauna intermareal de playas arenosas ubicadas frente a defensas costeras artifi ciales que con anterioridad al 27F, tenían diferentes grados de interacción con olas y mareas durante marea alta.…”