Impact of the 2018 European Drought on Microbial Groundwater Quality in Private Domestic Wells: A case study from a temperate maritime climate

A significant volume of research over the past two decades has highlighted both direct and indirect links between climate change and groundwater quality. However, to date, few studies have sought to explore the relationship(s) between drought conditions and groundwater quality in i) private (unregulated) groundwater sources, or ii) temperate maritime climates not commonly prone to drought events. The Republic of Ireland (ROI) represents an appropriate case-study due to its’ high reliance on private groundwater supplies, and while the region is largely unaffected by climatological extremes, modelling studies indicate that drier summers and drought conditions will increase in frequency. Accordingly, the current study sought to quantify the effects of the Summer 2018 drought experienced throughout Europe on private groundwater quality in the southwest of Ireland via an opportunistic field study. A repeated measures sampling campaign comprised of “drought” (June/July) and “post-drought” (October/November) analyses of 74 wells was undertaken, with complementary mapping and statistical analyses. Both Total Coliforms (TCs) and Escherichia coli (E. coli) were present during both drought (TCs: 42/74; 56.8%, E. coli: 7/74; 9.5%) and post-drought (TCs: 42/74; 56.8%, E. coli: 18/74; 24.3%) sampling periods. E. coli contamination during drought conditions was unexpected due to an absence of recharge or infiltration for microbial transport. Bivariate analyses suggest a hydrodynamic change, with the significance of E. coli sources and pathways shown to switch between sampling periods i.e. a shift from a combination of regional and local (site specific) contamination mechanisms, to solely site-specific mechanisms. More specifically, during drought conditions, septic tank density (p = 0.001) and local subsoil type (p = 0.009) were both associated with the presence of E. coli, while neither variable was significant during post-drought conditions. The current study is the first to provide a quantitative comparison of private groundwater quality during and after a large-scale drought event in a temperate maritime climate and may be used to improve our understanding of the effects of extreme events, and thus necessary preventative and monitoring strategies, going forward

Paleolimnological investigations on a nutrient polluted freshwater lake, Lough Muckno, Northeast Ireland – Reconstructing anthropogenic impacts across timescales

This project is based on a paleolimnological investigation at Lough Muckno, a large lake system located in County Monaghan, Republic of Ireland. The investigation is centered on a sediment core retrieved from the lake and systematic analyses and interpretations of a range of physical and biological indicators in sediment sub-samples. The main indicators analyzed include fossil pollen and chironomidae (Insecta: Diptera) sub-fossils. Irish paleolimnology has greatly benefited from the glacial history of the island resulting in plentiful and readily accessible lake study sites, but also from the interest drawn by both local and foreign research clusters. Traditionally, Irish paleoecological investigations have mainly relied on pollen analysis (Mitchell et al, 2013), but paleolimnological applications involving of a range of physical, geochemical and biological indicators have become increasingly common (e.g., Anderson, 1997; Taylor et al, 2006; Dalton et al, 2014; McKeown and Potito, 2016). In the context of this investigation, apart from a brief and explorative geochemical study in L. Muckno (Douglas et al, 1978), the results presented represent the first robust paleolimnological investigation in the study site, and the second in Co. Monaghan (see Carson et al, 2014). This highlights the local and regional relevance of this project.2019-12-1

The role of the natural aquatic environment in the dissemination of extended spectrum beta-lactamase and carbapenemase encoding genes: A scoping review

The natural aquatic environment is a significant contributor to the development and circulation of clinically significant antibiotic resistance genes (ARGs). The potential for the aquatic environment to act as a reservoir for ARG accumulation in areas receiving anthropogenic contamination has been thoroughly researched. However, the emergence of novel ARGs in the absence of external influences, as well as the capacity of environmental bacteria to disseminate ARGs via mobile genetic elements remain relatively unchallenged. In order to address these knowledge gaps, this scoping literature review was established focusing on the detection of two important and readily mobile ARGs, namely, extended spectrum beta-lactamase (ESBL) and carbapenemase genes. This review included 41 studies from 19 different countries. A range of different water bodies including rivers (n = 26), seawaters (n = 6) and lakes (n = 3), amongst others, were analysed in the included studies. ESBL genes were reported in 29/41 (70.7%) studies, while carbapenemase genes were reported in 13/41 (31.7%), including joint reporting in 9 studies. The occurrence of mobile genetic elements was evaluated, which included the detection of integrons (n = 22), plasmids (n = 18), insertion sequences (n = 4) and transposons (n = 3). The ability of environmental bacteria to successfully transfer resistance genes via conjugation was also examined in 11 of the included studies. The findings of this scoping review expose the presence of clinically significant ARGs in the natural aquatic environment and highlights the potential ability of environmental isolates to disseminate these genes among different bacterial species. As such, the results presented demonstrate how anthropogenic point discharges may not act as the sole contributor to the development and spread of clinically significant antibiotic resistances. A number of critical knowledge gaps in current research were also identified. Key highlights include the limited number of studies focusing on antibiotic resistance in uncontaminated aquatic environments as well as the lack of standardisation among methodologies of reviewed investigations.This review was carried out as part of the AREST (Antimicrobial Resistance and the Environment – Sources, persistence, transmission and risk management) project which is jointly funded by the Irish Environmental Protection Agency and the Health Service Executive (Grant number 2017-HW-LS-1).peer-reviewe

Distribution of chironomid subfossil assemblages in sediments of an Irish lake: controls and potential for paleoenvironmental applications

A survey of chironomid subfossil remains was carried out in Lough Muckno, a lake system located in northeast Ireland. The dataset provides new insights into chironomid ecology and subfossil taphonomy in the Irish Ecoregion. A significant degree of homogeneity in subfossil assemblages and presence of efficient offshore redeposition mechanisms was evident. The potential role of the thermocline and river discharge in determining subfossil assemblage composition was also explored. Redundancy analysis indicated that sample (spatial) location and water depth are governing and intertwined controls on chironomid assemblage composition. Profundal habitats at a sensible distance from the littoral best integrated basin-wide remains representing suitable locations for paleoecological reconstructions based on a single-core approach. However, assemblages in deep mid-lake habitats characterized by advanced diagenesis and low head capsule counts were deemed unsuitable for paleoecological applications. The results highlight the importance of accounting for both lake depth and distance metrics in the design of paleolimnological investigations in systems with a complex basin morphology.</p

Microbial impact assessment of the 2018 European drought on groundwater quality in the Republic of Ireland: An opportunistic field study

&amp;lt;p&amp;gt;Global climate change models predict an increase in both the frequency and severity of extreme weather events, including prolonged drought conditions, thus posing a unique set of challenges for regions traditionally unaccustomed to severe climate phenomena. This is particularly significant for the occurrence of severe drought events in areas characterised by temperate maritime climates, such as the Republic of Ireland (ROI). While numerous studies have explored the impacts of drought on groundwater levels and chemical contamination, few studies have sought to investigate the impacts of sporadic drought events on the microbial quality of groundwater for human consumption. Accordingly, the 2018 (June-August) European drought event represented a unique opportunity to investigate the effects of prolonged low rainfall and elevated temperature (relative to seasonal means) on the incidence of faecal indicator organisms (FIOs) among unregulated domestic groundwater supplies in the ROI.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;A dual-sampling fieldwork regime (during and post-event) of private wells (n=74) and subsequent risk factor (logistic regression) and bivariate analyses were used to evaluate the potential role of meteorological and site specific (hydrogeology, contaminant sources etc.) conditions on the incidence of microbial contamination. During absolute drought conditions (&amp;amp;#8805;15 days characterised by no measureable precipitation, June 2018), the sampled cohort exhibited a significantly decreased risk of microbial contamination (OR: 0.356, p = 0.024) with 12.2% (n = 9/74) of supplies contaminated with Escherichia coli (E. coli), increasing to 28.4% (n = 21/74) upon abatement of drought conditions (October 2018). No analysed risk factors were associated with E. coli presence at the 95% confidence level, although, the presence of onsite domestic wastewater treatment systems (U = 1.03 p = 0.057) approached statistical significance during the drought. Findings suggest that the 2018 European drought served to decrease background levels of FIO within private wells in the ROI, likely due to reduced hydraulic loading from the surface, soil moisture deficits and consequently, significantly decreased bacterial survival. Results would seem to reiterate the significance of onsite domestic wastewater treatment systems as a source of subsurface contaminants in Ireland. The presented opportunistic field study provides a critical characterization of the impacts of unprecedented drought events on microbiological water quality in domestic groundwater supplies in temperate regions, and may be used by sanitary/environmental engineers, hydrologists, hydrogeologists, policy-makers, planners and healthcare practitioners to safeguard against the future human health effects of climate change and extreme weather events. &amp;amp;#160;&amp;amp;#160;&amp;lt;/p&amp;gt; </jats:p

Mapping and Analysing Potential Sources and Transmission Routes of Antimicrobial Resistant Organisms in the Environment using Geographic Information Systems—An Exploratory Study

Antimicrobial resistance (AMR) is one of the leading threats to human health worldwide. The identification of potential sources of antimicrobial resistant organisms (AROs) and their transmission routes in the environment is important for improving our understanding of AMR and to inform and improve policy and monitoring systems, as well as the identification of suitable sampling locations and potential intervention points. This exploratory study uses geographic information systems (GIS) to analyse the spatial distribution of likely ARO sources and transmission routes in four local authority areas (LAAs) in Ireland. A review of relevant spatial data in each LAA, grouped into themes, and categorised into sources and transmission routes, was undertaken. A range of GIS techniques was used to extract, organise, and collate the spatial data into final products in the form of thematic maps for visual and spatial analysis. The results highlight the location of &#8216;clusters&#8217; at increased risk of harbouring AMR in each LAA. They also demonstrate the relevance of aquatic transmission routes for ARO mobility and risk of human exposure. The integration of a GIS approach with expert knowledge of AMR is shown to be a useful tool to gain insights into the spatial dimension of AMR and to guide sampling campaigns and intervention points