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We demonstrate the utility and reproducibility of the saltmarsh foraminifera-based 'geological tide gauge' (GTG) approach by developing two independent records of relative sea-level (RSL) change for Dublin, Ireland. Our records, recovered from two different saltmarshes, indicate that RSL rose at a century-scale rate of 1.5 ± 0.9 mm yr-1 over the last 200 years. This compares favourably with the shorter, but more precise, mean sea level (MSL) record from the Dublin Port tide gauge, which indicates long-term (1953-2016 CE) rise at a rate of 1.1 ± 0.5 mm yr-1. When corrected for the influence of glacio-isostatic adjustment our saltmarsh-based reconstruction suggests sea levels in Dublin rose at a rate of 1.6 ± 0.9 mm yr-1 since the start of the 19th century, which is in excellent agreement with the regional value of MSL rise over the same period (1.5 ± 0.2 mm yr-1) calculated from a compilation of tide gauge records around Britain. Whilst our record has decadal-scale temporal resolution (1 sample every 8 years), we are currently unable to resolve multidecadal-scale variations in the rate of sea-level rise which are masked by the size of the vertical uncertainties (± 20 cm) associated with our reconstruction of palaeomarsh-surface elevation. We discuss the challenges of applying the GTG approach in the typically minerogenic saltmarshes of the NE Atlantic margin and outline potential solutions that would facilitate the production of Common Era RSL reconstructions in the region. [ABSTRACT FROM AUTHOR]

• National evaluation of antibiotic resistance in sewage sources and water bodies. • Detection of carbapenemase producers in waters designated of good/excellent quality. • Natural resistome is highlighted by the detection of ESBLs in 'cold spot' locations. • Highly similar Klebsiella isolates from sewage and water suggest a single sub-lineage. • Results highlight need for regular monitoring of waters for antibiotic resistance. Water bodies worldwide have proven to be vast reservoirs of clinically significant antibiotic resistant organisms. Contamination of waters by anthropogenic discharges is a significant contributor to the widespread dissemination of antibiotic resistance. The aim of this research was to investigate multiple different anthropogenic sources on a national scale for the role they play in the environmental propagation of antibiotic resistance. A total of 39 water and 25 sewage samples were collected across four local authority areas in the West, East and South of Ireland. In total, 211 Enterobacterales were isolated (139 water, 72 sewage) and characterised. A subset of isolates (n=60) were chosen for whole genome sequencing. Direct comparisons of the water versus sewage isolate collections revealed a higher percentage of sewage isolates displayed resistance to cefoxitin (46%) and ertapenem (32%), while a higher percentage of water isolates displayed resistance to tetracycline (55%) and ciprofloxacin (71%). Half of all isolates displayed extended spectrum beta-lactamase (ESBL) production phenotypically (n = 105/211; 50%), with bla CTX-M detected in 99/105 isolates by PCR. Carbapenemase genes were identified in 11 isolates (6 sewage, 5 water). The most common variant was bla OXA-48 (n=6), followed by bla NDM-5 (n=2) and bla KPC-2 (n=2). Whole genome sequencing analysis revealed numerous different sequence types in circulation in both waters and sewage including E. coli ST131 (n=15), ST38 (n=8), ST10 (n=4) along with Klebsiella ST405 (n=3) and ST11 (n=2). Core genome MLST (cgMLST) comparisons uncovered three highly similar Klebsiella isolates originating from hospital sewage and two nearby waters. The Klebsiella isolates from an estuary and seawater displayed 99.1% and 98.8% cgMLST identity to the hospital sewage isolate respectively. In addition, three pairs of E. coli isolates from different waters also revealed cgMLST similarities, indicating widespread dissemination and persistence of certain strains in the aquatic environment. These findings highlight the need for routine monitoring of water bodies used for recreational and drinking purposes for the presence of multi-drug resistant organisms. [ABSTRACT FROM AUTHOR]

Over recent years, Ireland has reported the highest crude incidence rates of Shiga toxin-producing Escherichia coli (STEC) enteritis in Europe. Unregulated private groundwater sources have emerged as an important potential transmission route for STEC, with up to 750,000 Irish residents reliant on these sources for domestic waters. This study aimed to investigate the prevalence and serogroup profile of STEC contamination from domestic private wells in western Ireland. Fifty-two groundwater sources were analysed during two sampling campaigns in the autumn (September/October) of 2019 (n = 21) and 2021 (n = 31). Untreated groundwater samples (30 L) were collected and analysed using the "CapE" (capture, amplify, extract) method. Extracted DNA was tested using multiplex real-time PCR for Shiga toxin stx1 and/or stx2 and eae genes. STEC positive DNA samples were tested for clinically relevant serogroups by real-time PCR. Data relating to 27 potential groundwater contamination risk factors were geospatially linked to each well and assessed for association with E. coli, stx1 and/or stx2 and eae presence/absence. Overall, 20/52 wells (38.4 %) were positive for E. coli (median concentration 8.5 MPN/100 mL as assessed by Colilert-18 method). Stx1 and/or stx2 was detected in 10/52 (19.2 %) wells overall and 8/20 E. coli positive wells, equating to a STEC to "generic" E. coli detection ratio of 40 %. Six of these wells (30 %) were also positive for eae. One or more serogroup-specific gene targets were identified in all but one stx1 and/or stx2 positive sample, with O145 (n = 6), O157 (n = 5) and O103 (n = 4) most prevalent. STEC presence was significantly associated with decreasing well depth (U = -2.243; p = 0.024) and increasing 30-day mean antecedent rainfall (U = 2.126; p = 0.034). Serogroup O104 was associated with increased sheep density (U = 2.089; p = 0.044) and detection of stx1 and/or stx2 + eae with increased septic tank density (U = 2.246 p = 0.023). Findings indicate high detection rates of clinically relevant STEC in E. coli contaminated groundwater sources in Ireland., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)