Impact of earthquake on the communities of bacteria and archaea in groundwater ecosystems

Abstract We explored possible changes in microbial communities at the occurrence of an earthquake. For this, we examined effects of the 2016 Gyeongju Earthquake (ML 5.8) on the microbial communities in nearby aquifers, together with the associated hydrochemistry data. Fourteen water samples were collected from two types of wells (alluvial and fractured rock formation) for monitoring the hydrogeochemical parameters, groundwater level, radon concentration, strontium isotopes, and microbiological features. An earthquake could change the number of species or their abundance in groundwater ecosystems. The results obtained for microbial compositions and special bacteria were consistent with the hydrochemical results. We also observed distinctive microbial communities in groundwater samples taken adjacent to the earthquake epicenter. Flavobacterium and archaea showed center of movement of chemical data. The predominant bacteria were Pseudomonas and Flavobacterium in most samples. Radon concentrations, helium isotopes, and helium/neon ratio showed anomalies in one well (KW8) with microbial composition data. Strontium data indicate that the study site may have been affected by seawater intrusion, which is corroborated by the microbiological features of archaea. Therefore, microbial features might be a good additional indicator for analyzing effects of earthquake on the groundwater, together with major chemical parameters such as Rn, Sr, and He. This study highlights the microbiological features of an aquifer after an earthquake, in conjunction with chemical data. The microbiological features indicate that bacteria in the groundwater such as Pseudomonas and Flavobacterium are highly correlated with the Gyeongju Earthquake and the hydrochemical data.