Microbial intrusion and seasonal dynamics in the groundwater microbiome of a porous basaltic rock aquifer used as municipal water reservoir

Abstract

Groundwater is a key resource for safe drinking water supply. Yet unconfined aquifers can be vulnerable to microbial contamination during extreme weather events that lead to surface runoff. The current study characterises the groundwater microbiome of a porous basaltic rock aquifer in South-West Iceland used for drinking water extraction and analyses the microbial community dynamics during surface runoff. The groundwater microbial community sampled from twelve wells across the extraction area contained over 745 prokaryotic genera and was phylogenetically similar between wells and most seasons, representing a diverse but homogenous ecosystem. The largest seasonal variation in the microbial community composition was detected during a period of concurrent snow melt and high precipitation leading to surface runoff. This period was characterised by an increased abundance of soil-associated taxa in the groundwater microbiome and specifically of taxa assigned to Aeromonas and Bacillus. A field experiment simulating high surface runoff around a groundwater well confirmed the increased abundance of surface soil microorganisms in the well water, indicating vulnerability of groundwater towards surface microbial intrusion during extreme weather events. As such events are likely to increase due to climate change, novel water management tools such as microbial community analysis could help ensure drinking water safety.

Effect of Snowmelt on Groundwater Bacterial Community Composition and Potential Role of Surface Environments as Microbial Seed Bank in Two Distinct Aquifers from the Region of Quebec, Canada

“…It is also worth noting that the majority of microorganisms in aquifers are not present as free-floating or planktonic communities but are rather present in microcolonies or biofilms attached to rock surface or sediment particles [3,40]. During recharge events or during period of important aquifer-river connections, increase in groundwater flow and level could cause these colonies to detach and enter the water column [12]. Therefore, sessile microorganisms from the subsurface could act as a microbial seedbank for planktonic communities during period of groundwater recharge [5].…”

“…Indeed, following period of recharge, important changes in the composition of the microbial communities was generally observed. While some attributed most of these differences to fluctuation of environmental conditions favoring or hindering certain taxa [4,6,11], the introduction of surface-derived taxa was also suggested as a factor responsible for the observed dissimilarity in microbial community composition [5,11,12]. However, it is likely that local hydrogeochemical characteristics of aquifers influence both the variation in abiotic conditions and migration of surface-derived taxa.…”

Effect of Snowmelt on Groundwater Bacterial Community Composition and Potential Role of Surface Environments as Microbial Seed Bank in Two Distinct Aquifers from the Region of Quebec, Canada

“…It is worth noting that the majority of microorganisms in aquifers are not present as free-floating or planktonic communities but are rather present in micro-colonies or biofilms attached to rock surface or sediment particles [ 3 , 42 ]. During recharge events or during periods of important aquifer–river connections, increases in groundwater flow and level could cause these colonies to detach and enter the water column [ 12 ]. This could explain the increased abundance of Aquicella .…”

“…Indeed, following a period of recharge, important changes in the composition of the microbial communities were generally observed. While some attributed most of these differences to the fluctuation of environmental conditions favoring or hindering certain taxa [ 4 , 6 , 11 ], the introduction of surface-derived taxa was also suggested as a factor responsible for the observed dissimilarity in microbial community composition [ 5 , 11 , 12 ]. However, it is likely that local hydrogeochemical characteristics of aquifers influence both the variation in abiotic conditions and migration of surface-derived taxa.…”

Methodology to Increase the Efficiency of the Mineral Water Extraction Process

“…The resort areas of the region, such as the ski resorts of Elbrus and Dombay, are the most attractive places for tourists not only due to their landscapes, but also due to their ecological cleanliness. A large number of medicinal plants and minerals can also be found in this region and are used for medicinal purposes [16][17][18][19].…”