Antimicrobial resistance (AMR) represents a major global health threat, as well as a major hazard to sustainable economic development and national security. It remains, therefore, vital that current research aligns to policy development and implementation to alleviate a potential crisis. One must consider, for example, whether drivers of antibiotic resistance can be controlled in the future, or have they already accumulated in the past, whether from antibiotics and/or other pollutants? Unfortunately, industrial heritage and its pollution impact on the prevalence of environmental AMR have largely been ignored. Focussing on industrialised estuaries, we demonstrate that anthropogenic pollution inputs in addition to the natural diurnal environmental conditions can sufficiently create stressful conditions to the microbiome and thus promote selective pressures to shift the resistome (i.e., collection of resistance traits in the microbiological community). Unfortunately, the bacteria’s survival mechanisms, via co-selective pressures, can affect their susceptibility to antibiotics. This review highlights the complexity of estuarine environments, using two key contaminant groups (metals/toxic elements and polyaromatic hydrocarbons), through which a variety of possible chemical and biological pollutant stressors can promote the emergence and dissemination of antimicrobial resistance. We find compelling divers to call on more focused research on historically disrupted ecosystems, in propagating AMR in the real world.

As waste management regulations become more stringent, yet demand for resources continues to increase, there is a pressing need for innovative management techniques and more sophisticated supporting analysis techniques. Sequential extraction (SE) analysis, a technique previously applied to soils and sediments, offers the potential to gain a better understanding of the composition of solid wastes. SE attempts to classify potentially toxic elements (PTEs) by their associations with phases or fractions in waste, with the aim of improving resource use and reducing negative environmental impacts. In this review we explain how SE can be applied to steel wastes. These present challenges due to differences in sample characteristics compared with materials to which SE has been traditionally applied, specifically chemical composition, particle size and pH buffering capacity, which are critical when identifying a suitable SE method. We highlight the importance of delineating iron-rich phases, and find that the commonly applied BCR (The community Bureau of reference) extraction method is problematic due to difficulties with zinc speciation (a critical steel waste constituent), hence a substantially modified SEP is necessary to deal with particular characteristics of steel wastes. Successful development of SE for steel wastes could have wider implications, e.g., for the sustainable management of fly ash and mining wastes.

The direct impacts of anthropogenic pollution are widely known public and environmental health concerns, and details on the indirect impact of these are starting to emerge, for example affecting the environmental microbiome. Anthropogenic activities throughout history with associated pollution burdens are notable contributors. Focusing on the historically heavily industrialised River Clyde, Scotland, we investigate spatial and temporal contributions to stressful/hostile environments using a geochemical framework, e.g. pH, EC, total organic carbon and potentially toxic elements: As, Co, Cr, Cu, Ni, Pb and Zn and enrichment indicators. With regular breaches of the sediment quality standards in the estuarine system we focused on PTE correlations instead. Multivariate statistical analysis (principle component analysis) identifies two dominant components, PC1: As, Cr, Cu, Pb and Zn, as well as PC2: Ni, Co and total organic carbon. Our assessment confirms hot spots in the Clyde Estuary indicative of localised inputs. In addition, there are sites with high variability indicative of excessive mixing. We demonstrate that industrialised areas are dynamic environmental sites dependant on historical anthropogenic activity with short-scale variation. This work supports the development of ‘contamination’ mapping to enable an assessment of the impact of historical anthropogenic pollution, identifying specific ‘stressors’ that can impact the microbiome, neglecting in estuarine recovery dynamics and potentially supporting the emergence of antimicrobial resistance in the environment.

Acanthamoeba is an opportunistic free-living heterotrophic protist that is the most predominant amoeba in diverse ecological habitats. Acanthamoeba causes amoebic keratitis (AK), a painful and potentially blinding corneal infection. Major risk factors for AK have been linked to non-optimal contact lens hygiene practices and Acanthamoeba contamination of domestic and recreational water. This study investigated the incidence and seasonal variation of Acanthamoeba spp. within coastal lagoons located on the eastern coast of Australia and then examined the association between Acanthamoeba and water abiotic factors and bacterial species within the water. Water samples were collected from four intermittently closed and open lagoons (ICOLLs) (Wamberal, Terrigal, Avoca and Cockrone) every month between August 2019 to July 2020 except March and April. qPCR was used to target the Acanthamoeba 18S rRNA gene, validated by Sanger sequencing. Water abiotic factors were measured in situ using a multiprobe metre and 16S rRNA sequencing (V3-V4) was performed to characterise bacterial community composition. Network analysis was used to gauge putative associations between Acanthamoeba incidence and bacterial amplicon sequence variants (ASVs). Among 206 water samples analysed, 79 (38.3%) were Acanthamoeba positive and Acanthamoeba level was significantly higher in summer compared with winter, spring, or autumn (p = 0.008). More than 50% (23/45) water samples of Terrigal were positive for Acanthamoeba which is a highly urbanised area with extensive recreational activities while about 32% (16/49) samples were positive from Cockrone that is the least impacted lagoon by urban development. All sequenced strains belonged to the pathogenic genotype T4 clade except two which were of genotype clades T2 and T5. Water turbidity, temperature, intl1 gene concentration, and dissolved O₂ were significantly associated with Acanthamoeba incidence (p < 0.05). The ASVs level of cyanobacteria, Pseudomonas spp., Candidatus spp., and marine bacteria of the Actinobacteria phylum and Acanthamoeba 18S rRNA genes were positively correlated (Pearson's r ≥ 0.14). The presence of Acanthamoeba spp. in all lagoons, except Wamberal, was associated with significant differences in the composition of bacterial communities (beta diversity). The results of this study suggest that coastal lagoons, particularly those in urbanised regions with extensive water recreational activities, may pose an elevated risk to human health due to the relatively high incidence of pathogenic Acanthamoeba in the summer. These findings underscore the importance of educating the public about the rare yet devastating impact of AK on vision and quality of life, highlighting the need for collaborative efforts between public health officials and educators to promote awareness and preventive measures, especially focusing lagoons residents and travellers.

The rapid growth in the human population has led to an increased requirement for readily available food sources. The aquaculture industry is a fundamental source for maintaining food supplies; however, it is subjected to mounting pressures to meet supply demands. Thus, limiting factors that negatively impact the cultivation of farmed aquatic organisms is essential. Gill disease is an increasing area of concern, resulting in substantial losses in farmed fish. Several microbial pathogens are known to cause gill disease and, in many instances, multiple pathogens or factors can be involved in the disease, resulting in complex gill disease (CGD). The role of mixed infections in gill disease is largely unknown, as such this review aims to examine data on previous infections and highlight the variety of microbes that might be involved in gill disease. The influence of climate change in the context of CGD is also discussed given the strong links between physicochemical extremes and numerous microbial gill pathogens. Understanding these factors will allow for improved diagnostic and therapeutic strategies to be implemented.

Estuaries are critical components in the environmental risk assessment of anthropogenic contamination. They funnel the emissions from upstream terrestrial catchments and are often within historically established population and industrial centers. They are sensitive and biodiverse and increasingly acknowledged be subject to increasing risks and hazards from urban development and climate change. To understand these effects, regular monitoring is essential but needs to be appropriate to allow impact assessment and direct long-term mitigation strategies, building resilience under the advancing impacts of climate change. A One Health approach to environmental assessment is needed to counter the emergence of global public health threats, such as antimicrobial resistance (AMR) supporting the interaction between estuarine ecology, humans and the environment. We focus on Thane Creek, Mumbai, India as a critical case being recently designated a RAMSAR site and India’s only urban RAMSAR wetland. The necessity of a robust environmental monitoring system for regulatory policy development reflects impacts from historic and emerging pollution sources. It is a particularly sensitive environment, and one of the largest creeks in Asia, with ecosystem function identified to be highly vulnerable to the impacts of climate change. Rapid urbanization, causing alterations to creek geometry over relatively short timescales, has impinged on wetland habitats. Data from governmental monitoring and previous studies of environmental quality in Thane Creek are compared to data for other Indian estuaries. Overall, there is evidence of contamination from sources including domestic sewage and nearby industries, which may have chronic impacts on the ecosystem. Dissolved oxygen was lower, biochemical oxygen demand higher, and coliform counts similar in Thane Creek compared to other estuaries. The influence of tidal dynamics and sediment movement is likely to develop seasonal variation in AMR within water and sediments with potential impact on a rich and diverse ecology, especially for migratory birds. Subsets of organic contaminants and potentially toxic elements are currently monitored infrequently in water but have been found enriched in the creek’s sediments. These key geochemical parameters are likely to have significant impacts on environmental health and highlight the need for wider assessment of environmental stressors and the development of more robust estuarine health indicators. Given both the ecological and geographical sensitivity of the region focusing on one health is a more appropriate monitoring strategy to address the emerging ecosystem challenges.