Biology subjects

Brack, W.

Publications and source records attributed to Brack, W..

6 recordsLinked to original sources

bioRxiv2026

Urban chemical stress disrupts cross-domain microbial networks in river sediments

Freshwater sediments face increasing anthropogenic stress, yet their effects on cross-domain microbial interactions remain understudied. We analysed co-occurrence networks encompassing bacteria, protists, and fungi in sediments from two urban river systems in central Chile (Aconcagua and Maipo), using high throughput metabarcoding. Sites under multidimensional pollution stress exhibited fragmented networks, reduced cross-domain connectivity, and a predominance of positive correlations, consistent with stress-induced facilitation. Keystone taxa shifted, with Firmicutes, Ciliophora and Rozellomycota gaining prominence under stress. Conversely, reference sites displayed cohesive networks and balanced interaction types, driven by Proteobacteria, Ascomycota and Basidiomycota. Negative co-occurrences between protists and bacteria in contaminated zones suggest intensified competition or top-down trophic control. Our findings highlight the vulnerability of cross-domain microbial assemblages to urban pollution and identify specific metrics as candidate bioindicators for ecosystem integrity.

microbiology↗

bioRxiv2026

Metabarcoding reveals that bacterial and fungal microbiomes are perturbed by micropollutants in a fjord system (Hakefjorden and Askerofjorden) at the Swedish west coast

Fjord systems are susceptible to anthropogenic pressures, including discharges from wastewater treatment plants (WWTPs), which introduce micropollutants into coastal waters. We investigated the impact of micropollutants on bacteria and fungi within a fjord system adjacent to a significant petrochemical industry hub on the Swedish west coast. We characterised microbial assemblages along a land-to-sea transect, encompassing freshwater streams receiving agricultural and urban runoff, as well as the direct effluent from a WWTP. Our findings revealed elevated concentrations and a diverse array of micropollutants in the WWTP effluent and the stream running through the urban/industrial zone, highlighting these areas as major sources of pollution to the fjord. Bacterial and fungal communities inhabiting the WWTP effluent and the receiving marine waters near the marine outflow exhibited distinct structural compositions, indicating a selective pressure exerted in part by the micropollutant load. While freshwater sites generally displayed higher overall microbial diversity compared to marine sites, the WWTP effluent showed reduced diversity in both bacterial and fungal communities, likely due to the impact of micropollutants. Interestingly, marine sites far from the WWTP discharges exhibited a recovery in bacterial diversity, suggesting a potential response or adaptation. In contrast, fungal diversity remained comparable to that observed in other marine locations. Multivariate analyses identified physicochemical parameters and nutrients, alongside with summed fungicides and antibiotic stress as key factors driving the community dissimilarities across the fjord. Significant disruptions in potential bacterial metabolism and fungal ecological functions were evident at the WWTP discharge point, underscoring the ecological consequences of wastewater pollution. HighlightsO_LIWWTP discharge is the primary source of complex micropollutants in the fjord. C_LIO_LIAntibiotics and fungicides significantly shape bacterial and fungal communities. C_LIO_LIWastewater impacts reduce microbial diversity and disrupt functional potential. C_LIO_LIMarine sites show microbial recovery and enrichment away from discharge points. C_LIO_LIeDNA and toxic unit modeling link chemical stress to microbiome restructuring. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC="FIGDIR/small/711609v1_ufig1.gif" ALT="Figure 1"> View larger version (64K): org.highwire.dtl.DTLVardef@1751e5forg.highwire.dtl.DTLVardef@1d0d78org.highwire.dtl.DTLVardef@15f446aorg.highwire.dtl.DTLVardef@184bb0a_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2024

AI-aided chronic mixture risk assessment along a small European river reveals multiple sites at risk and pharmaceuticals being the main risk drivers

The vast amount of registered chemicals leads to a high diversity of substances occurring in the environment and the creation of new substances outpaces chemical risk assessment as well as monitoring strategies. Hence, risk assessment strategies need to be modified ensuring that they remain aligned with the rapid development and marketing of new substances. Here we performed a longitudinal chronic mixture risk assessment considering a real-world case study scenario with diverse anthropogenic impact types characterised by different land uses along a river in Central Germany. We sampled river water using large-volume solid phase extraction at six selected sampling sites. Following chemical analysis using liquid chromatography-high resolution mass spectrometry, we quantified 192 substances. For 34% of them, we obtained empirical chronic effect data for freshwater organisms. Furthermore, we used the open-source artificial intelligence (AI) model TRIDENT to predict chronic toxicity for all substances. A multi-scenario mixture risk assessment was conducted for three taxonomic groups, using the concentration-addition concept and considering various hazard and exposure scenarios. The results showed that the chronic risk estimates for all taxonomic groups were considerably higher when the empirical data was amended with data from in silico modelling. We identified hot spots of chemical pollution and our analysis indicated that fish were the most vulnerable taxonomic group, with pharmaceuticals being the most relevant risk drivers. Our study exemplifies the application of an AI model to predict chronic risk for aquatic organisms in combination with the consideration of multiple risk scenarios, that may complement future risk assessment strategies. HighlightsO_LI192 organic chemicals were quantified in six surface water samples along a river. C_LIO_LIMultiple hazard and exposure scenarios were considered in mixture risk assessment. C_LIO_LIArtificial intelligence was used to fill data gaps and predict chronic ecotoxicity. C_LIO_LIFish were identified as the most vulnerable taxonomic group for chronic toxicity. C_LIO_LIPharmaceuticals were the most prevalent mixture risk drivers. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC="FIGDIR/small/623722v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1836b85org.highwire.dtl.DTLVardef@107eeaaorg.highwire.dtl.DTLVardef@1c60caaorg.highwire.dtl.DTLVardef@16995d0_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

bioRxiv2024

Dataset of emerging contaminants in surface water, bottom water, porewater, and sediment: Urban and aquaculture impacts in the central and southern coast of Chile

Synthetic organic chemicals, including pesticides, pharmaceuticals, and industrial compounds, pose a growing threat to marine ecosystems as they enter through a variety of pathways, including direct discharges of wastewater (untreated or treated) from industrial, agricultural, and urban sources. Additionally, runoff from residential and agricultural land, as well as inland waterways, transport these chemicals to coastal zones. Despite their potential impact, data on the co-occurrence of these contaminants in the marine environment remains limited. Such information is critical for assessing coastal chemical status, establishing environmental quality benchmarks, and conducting comprehensive environmental risk assessments. In this study, we describe a multifaceted monitoring campaign targeting pesticides, pharmaceuticals, and industrial chemicals along the central-south coast and in northern Patagonia, Chile. Surface water, bottom water, porewater, and adjacent sediment samples were collected for analysis. Our results show the detection of up to 83 chemicals in surface water, 71 in bottom water, 101 in porewater, and 244 in sediments. To enhance data utility, we provide valuable information on the mode of action and molecular targets of the identified chemicals. This comprehensive dataset contributes to defining pollution fingerprints in coastal areas of the Global South, including remote regions in Patagonia. It serves as a critical resource for future research, policymaking, and the advancement of environmental protection in these regions.

pharmacology and toxicology↗

bioRxiv2024

Multi-compartment impact of micropollutants and particularly antibiotics on bacterial communities using environmental DNA at river basin-level

Microbial communities, in particular bacterial assemblies, play pivotal roles in sustaining biogeochemical processes within ecosystems. They are also responsible for the degradation of toxic chemicals, while the development of resistance against antimicrobial drugs jeopardises human health. Bacterial communities respond to environmental conditions with diverse structural and functional changes depending on their compartment (water, biofilm or sediment), type of environmental stress, and type of pollution to which they are exposed. In this study, we combined amplicon sequencing of bacterial 16S rRNA genes from water, biofilm, and sediment samples collected in the anthropogenically impacted River Aconcagua basin (Central Chile, South America), in order to evaluate whether micropollutants alter bacterial community structure and functioning based on the type and degree of chemical pollution. Furthermore, we evaluated the potential of bacterial communities from differently polluted sites to degrade contaminants. Our results show a lower diversity at sites impacted by agriculture and urban areas, featuring high loads of micropollution with pesticides, pharmaceuticals and personal care products as well as industrial chemicals. Nutrients, antibiotic stress, and micropollutant loads explain most of the variability in the sediment and biofilm bacterial community, showing a significant increase of bacterial groups known for their capabilities to degrade various organic pollutants, such as Nistrospira and also selecting for taxa known for antibiotic resistance such as Exiguobacterium and Planomicrobium. Moreover, potential ecological functions linked to the biodegradation of toxic chemicals at the basing level revealed significant reductions in ecosystem-related services in sites affected by agriculture and wastewater treatment plant (WWTP) discharges across all investigated environmental compartments. Finally, we suggest transitioning from simple concentration-based assessments of environmental pollution to more meaningful toxic pressure values in order to comprehensively evaluate the role of micropollutants at the ecological (biodiversity) level. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/587215v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@4dfdc9org.highwire.dtl.DTLVardef@50c884org.highwire.dtl.DTLVardef@19c62aforg.highwire.dtl.DTLVardef@12db45_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIMicropollutant mixtures altered bacterial community structure and functioning C_LIO_LIAntibiotic stress correlated significantly with changes in community structure C_LIO_LIReduction of ecological functions related to the degradation of contaminants C_LIO_LIWater, biofilm, and sediments relevant for microbial ecotoxicology C_LI

microbiology↗

bioRxiv2023

A multi-scenario risk assessment strategy applied to mixtures of chemicals of emerging concern in the River Aconcagua basin in Central Chile

Streams and rivers are characterised by the presence of various chemicals of emerging concern (CECs), including pesticides, pharmaceuticals, personal care products, and industrial chemicals. While these chemicals are found usually only in low (ng/L) concentrations, they might still harm aquatic life and disrupt the ecological balance of aquatic ecosystems due to their high ecotoxicological potency. Environmental risk assessments that account for the complexity of exposures are needed in order to evaluate the toxic pressure of these chemicals, which also provide suggestions for risk mitigation and management, if necessary. Currently, most studies on the co-occurrence and environmental impacts of CECs are conducted in countries of the Global North, leaving massive knowledge gaps in countries of the Global South. In this study, we implement a multi-scenario risk assessment strategy to improve the assessment of both the exposure and hazard components in the chemical risk assessment process. Our strategy incorporates a systematic consideration and weighting of CECs that were not detected, as well as an evaluation of the uncertainties associated with Quantitative Structure-Activity Relationships (QSARs) predictions for chronic ecotoxicity. Furthermore, we present a novel approach to identifying mixture risk drivers. To expand our knowledge beyond well-studied aquatic ecosystems, we applied this multi-scenario strategy to the River Aconcagua basin of Central Chile. The analysis revealed that the concentrations of CECs exceeded acceptable risk thresholds for selected organism groups and the most vulnerable taxonomic groups. Streams flowing through agricultural areas and sites near the river mouth exhibited the highest risks. Notably, the eight risk drivers among the 153 co-occurring chemicals accounted for 66-92% of the observed risks in the river basin. Six of them are pesticides and pharmaceuticals, chemical classes known for their high biological activity in specific target organisms. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/554257v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@179dc1dorg.highwire.dtl.DTLVardef@162082aorg.highwire.dtl.DTLVardef@10616baorg.highwire.dtl.DTLVardef@be1b32_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LI153 chemicals of emerging concern detected in complex multi-component mixtures. C_LIO_LI108 possible mixture risk assessment scenarios were investigated. C_LIO_LINon-detects, QSARs, and experimental ecotoxicological data were integrated for risk assessment. C_LIO_LI8 chemicals of emerging concern were responsible for driving chronic environmental risks. C_LI

pharmacology and toxicology↗