Impacts of coseismic uplift caused by the 2010 8.8 Mw earthquake on the macrobenthic community of the Tubul-Raqui Saltmarsh (Chile)

Coseismic uplift, as caused by high-magnitude earthquakes, can modify shoreline morphologies and the functioning of coastal wetlands. This phenomenon occurred with the 8.8-Richter scale earthquake that affected central-south Chile in 2010. The recorded coseismic uplift was 1.6 m.a.s.l. significantly changed the Tubul-Raqui Saltmarsh. The most important impact of this event was decreased marine intrusion, which, in turn, led to desiccation within the saltmarsh and, consequently, the death of aquatic organisms. This study recorded the effects that physical/chemical changes in water quality and the sedimentary environment had on the macrobenthic community (> 500 mu m) 2, 6, and 10 months after the uplift event, with data compared against historical records. Non-metric multidimensional scaling evaluated changes in the biological community, while principal components analysis was used to assess environmental changes. Both matrices were adjusted through correlation. Significant pre-versus post-earthquake modifications were found at sites closest to the estuary inlet. The most significantly affected macroinvertebrate was Paracorophium hartmannorum. The most tolerant taxa to environmental perturbations (i.e., Diptera, Annelid, and Polychaeta) surpassed pre-earthquake abundance records after just ten months, whereas the most sensitive taxa were not found after the earthquake. Most (81.8%) variables of water quality (Le., total suspended/inorganic/organic solids and chlorophyll-a), as well as the sedimentary environment (i.e., sediment redox potential, fine fraction, and area of emerged bed), were significantly correlated with the macrobenthic community. The results of this study show the resilience capacity of important components of a saltmarsh after a major natural disturbance.

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