Abstract
Earthquakes are important natural events, yet their impacts on animal communities are poorly known. Understanding earthquake impacts on groundwater communities is essential to assess their resilience and hence to perform conservation actions. We investigated how a 6.3 Mw earthquake that occurred in 2009 altered the community structure (diversity, evenness, dominance, species abundance distributions and beta-diversity) of microcrustaceans (Crustacea Copepoda) inhabiting springs fed by the Gran Sasso Aquifer (Central Italy). Sampling was done in low-discharge (1997), high-discharge (2005), and post-seismic (2012) hydrological years. Stygobites (obligate groundwater species) and non-stygobites (non-obligate groundwater species) showed different patterns. A high-water discharge in 2005 altered abundance patterns of non-stygobites. The earthquake re-established former abundance patterns. Stygobites were less affected by high-water discharge in 2005, and showed strong increases in diversity and evenness after the earthquake. This effect was due to the fact that the earthquake induced a strong population decline of previously dominant stygobites (especially of Nitocrella pescei) in the aquifer, and subsequently at the main spring outlets, thus allowing a more equitable species-abundance distribution. These results highlight the importance of considering species ecology to understand the effects of a significant earthquake event on animal communities.
Highlights
Earth is a dynamic planet, whose surface is continuously re-shaped by extreme, sudden events, such as fires, floods, storms, volcanic eruptions, earthquakes, and tsunamis
The non-stygobiotic Pesceus schmeili (Mrázek, 1893), which accounted for 9.9% of the total copepod abundance in 1997, represented 24.4% of total copepod abundance in 2005; the non-stygobiotic Moraria poppei meridionalis Chappuis, 1929, which accounted for 0.6% of the total copepod abundance in 1997, was 16.8% in 2005; the non-stygobiotic Bryocamptus typhlops (Mrázek, 1893), which accounted for 4.8% of the total copepod abundance in 1997, represented 10.3% of the individuals in the 2005 community
The mainshock of L’Aquila earthquake on 6 April 2009 did not impact negatively on structural parameters of the copepod community, but re-established a more balanced species abundance distribution after the changes induced by the anomalous discharge occurred in 2005
Summary
Earth is a dynamic planet, whose surface is continuously re-shaped by extreme, sudden events, such as fires, floods, storms, volcanic eruptions, earthquakes, and tsunamis These phenomena are considered “natural disasters” from the human perspective, because they injure people and produce economic damages. In the last 20 years, for example, seven strong earthquakes have occurred in Italy, among which the 6.3 Mw that struck the city of L’Aquila on 6 April 2009 This earthquake had a profound impact on the hydrogeological setting of the Gran Sasso Aquifer (GSA) by inducing an increase in the bulk hydraulic conductivity of the recharge area, near the ruptured fault zone together with fracture clearing and/or microcrack formations, and led to an anomalous rising of the water table (up to one metre) and flow rate (≥30% of the previous 15 years) in discharge zones[34]. As in the previous papers[30,32], we used copepods (Crustacea Copepoda) because they comprise ~80% of the total abundance of meiofauna community at TS30,36,37, being the best suited model organisms for this type of study
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