Aquatic biofilms are subjected by multiple stressors and their responses to such perturbations are a growing concern for aquatic scientists. Here, we understand stress or perturbation as a measurable change in ecosystems that is caused by chemical, physical or biological anthropogenic pressures. In freshwater and brackish ecosystems, microbial biofilms are key players at the base of trophic networks and, due to their small size and fast generation time, they respond very quickly to environmental changes, performing as indicators of the ecosystem status. In turn, depending on the type and intensity of the stressor microbial biofilms could harbour or be conduit of mixtures of contaminants and/or microorganisms released in the receiving media, becoming barriers or drivers of environmental changes. The main goal of the session is to understand how aquatic microbial biofilms respond to stressors (or multiple stressors) and their potential to act as early warning indicators of ecosystem health. This session welcomes presentations that contribute to elucidating the effects of pollution (e.g., pharmaceutical residues, heavy metals, nutrient loadings, organic contaminants, microplastics, pesticides…) climate change (e.g., warming waters, increase in salinity, changes in precipitation patterns, land uses, droughts, extreme events) or biological stressors (e.g., invasive species) on microbial aquatic biofilms. This includes evidence from field, laboratory and theoretical or modelling based studies. Talks will encompass research conducted over broad spatial and temporal scales to create a comprehensive picture of the current knowledge base. It is worth mentioning that in an increasingly changing future, knowing how microbial communities – and their functions – respond to it will help us to predict the impacts of stressors in aquatic ecosystems.
Lead Organizer: Giulia Gionchetta, Eawag (giulia.gionchetta@eawag.ch)
Co-organizers:
Nuria Perujo, UFZ Helmholtz Center for Environmental Research (nuria.perujo-buxeda@ufz.de)
Anna Freixa, ICRA Catalan Institute for Water Research (afreixa@icra.cat)
Presentations
10:30 AM
Stream biofilms are a sink for microplastic: effects on biofilm properties. (6492)
Primary Presenter: Stephanie Merbt, CEAB.CSIC (stephanie.merbt@ceab.csic.es)
Stream biofilms are hotspots of nutrient cycling driving major ecosystem processes. Microplastic (MP) is an ubiquitious pollutant in the aquatic environment, with highly divers physical and chemical properties. Here we hypothesised that i) biofilms can act as sink for MP in streams ii) that MP induce changes of biofilm properties, and that iii) MP can act as pointsource of chemicals. Sampling in the river Ter (NE Spain) showed significant presence of MP in biofilms, confirming their role as major sink for MP. Combining a variety of novel techniques, we study the consequences of incorporation of MP in biofilm. Using microcoms experiments, we compared biofilms incorporating spherical polyethylene MP with either native/weathered surface structure (Surf-MP) or coated with Tricolsan (TCS-MP). All MP were incoroporated into the biofilm matrix with no effect on biomass accumulation, photosynthetic yield, and respriation. Yet, the exposures to MP induced a significant shift in microbials community composition. In contrast, while similar in exposures to MP, nutrient uptake rates were lower in biofilm exposed to TCS-MP. Mechanical properties measured in biofilm exposed to Surf-MP indicated higher stiffness upon MP expsure and biofilm spatial species organization measured in biofilm exposed to TCS-MP resulted to be significantly altered as a response to Triclosan on the MP surface. Our results confirm the fundamental role of biofilms as sink of MP and indicate that MP heavily impact biofilm structure, function and dislodgement behavior.
10:45 AM
FRESHWATER TO MARINE, A PINCH OF SALT ON PATHOGEN DISSEMINATION ON PLASTICS (4754)
Primary Presenter: Joseph Christie-Oleza, University of the Balearic Islands (joseph.christie@uib.eu)
The widespread plastic pollution has raised social concern regarding these materials acting as vectors for pathogenic bacteria and antimicrobial resistance (AMR). To investigate the presence of potential pathogens within the plastisphere we performed in situ incubations of plastics i) in a river downstream from a wastewater treatment plant (WWTP), and ii) in a WWTP with posterior transition into the sea. The biofilms developed on plastics and control materials were analysed by metagenomics. Plastic materials –especially pre-weathered plastics– were enriched in AMR genes that confer resistance to various antibiotic classes, when compared to other materials and surrounding waters. In the river, typical genera associated with human pathogenicity (e.g., Escherichia, Salmonella, and Streptococcus) were relatively more abundant in the surrounding water samples than in biofilms, and metagenome assembled genomes (MAGs) belonging to these taxonomic families were among those containing AMR genes and virulence-related genes. Similar results were observed in the WWTP incubations though, most interestingly, the transition to marine conditions showed a drastic variation of the microbial community colonising the plastics, mainly due to the rapid flocculation and loss of the biofilms due to the high ionic strength of seawater. Overall, while plastics develop a distinct microbial community containing high relative abundance of AMR, in the long run, the microbial community in the plastisphere is strongly conditioned by its surrounding environment. Also, there is a need to distinguish between ‘real’ clinically relevant pathogenic and non-pathogenic taxa, as well as their survival over environmental transitions, before drawing conclusions that plastics are vectors for pathogens.
11:00 AM
MICROPLASTIC AND NATURAL ORGANIC PARTICLES SELECTS FOR SPECIFIC BACTERIAL BIOFILMS ALLOWING SURVIVAL OF ALLOCHTHONOUS BACTERIA IN COASTAL TYRRHENIAN SEA WATERS (5912)
Primary Presenter: Gianluca Corno, CNR-IRSA (gianluca.corno@cnr.it)
Microplastic particles (MPs) in the Mediterranean Sea are released mainly from coastal discharges and are colonized by a several of bacteria, including pathogens and antibiotic resistant bacteria (ARB), absent in seawaters. MPs are suggested to be novel substrates (spatial or ecological niches), allowing these bacteria to survive, or even to proliferate, in seawaters. We compared the bacterial communities in biofilms from MPs and natural organic particles with the planktonic community in samples collected in 3 sites in the Tyrrhenian Sea: V Terre (marine reserve, low coastal impact) and Forte Dei Marmi (city beach, diffuse anthropogenic impact) at 500 mt from the shore, and open sea, about 15 km east of Palmaria Island. We defined bacterial communities, antibiotic and heavy metal resistomes. We found large differences in the planktonic communities in comparison to the particles biofilm, and identify a number of human and animal pathogens finding a refuge on the particles, with a surprising prevalence of the latest on natural particles. The same was detected for antibiotic resistances, while heavy metal resistances were equally distributed between particles and water. We did not find a specific impact from the shores, independently from the level of anthropogenic pressure. The natural movement of water masses seems to rapidly reduce the impact of anthropogenic pollution. Our study highlights the plasticity of allochthonous bacteria (including potential pathogens and ARB) that can use as a refuge, or as source of nutrients, not only MPs, but also other organic substrates in waters.
11:15 AM
EXPOSURE TO ENVIRONMENTAL STRESSORS DECREASES RESILIENCE OF RIVER MICROBIOMES TOWARDS INVASION BY FOREIGN RESISTANT BACTERIA (6594)
Primary Presenter: Uli Klümper, TU Dresden (uli.kluemper@tu-dresden.de)
The release of wastewater effluents into rivers exposes river microbiomes to high loads of antibiotic resistant bacteria (ARB) along with complex mixtures of abiotic pollutants acting as stressors. To understand the proliferation of antimicrobial resistance (AMR) it is crucial to determine the factors that govern invasion of ARB into the river microbiome. Consequently, we here aim at elucidating how the resilience of resident microbiome against invasion by foreign ARB is determined by stress exposure. To achieve this, we grew natural microbial biofilms on glass slides in rivers for 1 month. Biofilms were then transferred to laboratory, recirculating flume systems and exposed to a single pulse of resistant invader bacteria (E. coli) either in presence or absence of stress induced by Cu2+. The invasion dynamics of E. coli into the biofilms were then monitored over time. Despite an initially successful introduction of E. coli into the biofilms, independent of the imposed stress, over time the invader perished in absence of stress. However, under stress the invading strain successfully established and proliferated in the biofilms. Noteworthy, the increased establishment success of the invader coincided with a loss in microbial community diversity under stress conditions, likely due to additional niche space becoming available for the invader. In conclusion, the intrinsic resilience of the river microbiome towards invasion by ARB is strongly linked with maintaining environmental diversity and that co-exposure to stressors that disrupt diversity increases long-term invasion success.
11:30 AM
TRANSLATING FLUVIAL BIOFILMS INTO ECOSYSTEM SERVICE PROVIDERS (5850)
Primary Presenter: Nuria Rubio Morales, Centro de Estudios Avanzados de Blanes (nurisarubio@yahoo.com)
Rivers are dangerously impacted by human activities, with chemical pollution being one of the most pressing concerns. In this context, fluvial biofilms act both as a mirror and as a driver of water quality and are particularly linked to the capacity of the river to provide environmental services. Biofilms have been proposed as early-warning signs of chemical contamination, but exactly what aspect of biofilms is symptomatic of ecosystem service deficiencies? We defined 3 main ecosystem services (i.e. nutrient cycling, carbon uptake, toxicant removal) and 14 associated variables (8 structural, 6 functional) and organic matter decomposition as a proxy for ecosystem functioning, to evaluate epilithic and sediment biofilms as ecosystem service providers (ESPs) in response to pollution. We tested this framework in two different settings: laboratory experiments using simplified fluvial systems, and a snapshot field sampling of 30 rivers along Catalonia (NE Spain, fall 2022) covering a wide array of contamination profiles. Preliminary results from four of the study variables indicate that chemical pollution primarily affected biofilm structure whilst functional endpoints show no obvious pattern yet. With further analyses, we expect to identify keystone aspects of biofilms associated with carbon and nutrient cycling that can be linked to ecosystem service loss and serve as predictors of environmental damage.
11:45 AM
COMPARATIVE METAGENOMICS REVEALS SUBSTRATE SPECIFICITY OF BIOFILMS PROXIMATE TO HISTORIC SHIPWRECKS (5979)
Primary Presenter: Rachel Mugge, United States Naval Research Laboratory (rachel.mugge.ctr@nrlssc.navy.mil)
The continuous addition of built structures to the seabed, such as shipwrecks, energy platforms, and pipelines, is contributing to ocean sprawl in coastal and offshore regions. These structures, typically composed of steel or wood, are substrates for microbial attachment and biofilm formation. Success of biofilm growth depends on substrate characteristics and local environmental conditions, though it is unclear which feature is dominant in shaping biofilm microbiomes. The goal of this study was to understand substrate- and site-specific impacts of built structures on short-term biofilm composition and functional potential. Seafloor experiments containing steel and wood surfaces were deployed for four months at distances extending up to 115 m away from three historic (>50 years old) shipwrecks in the Gulf of Mexico. DNA from biofilms on steel and wood was extracted and metagenomes were sequenced on an Illumina NextSeq. Bioinformatics analysis revealed taxonomic composition was significantly different between substrates and sites, with substrate being the primary determining factor. Regardless of site, steel biofilms had a higher abundance of genes related to biofilm formation, and sulfur, iron, and nitrogen cycling, while wood biofilms showed a higher abundance of manganese cycling and methanol oxidation genes. This study demonstrates how substrate composition shapes biofilm microbiomes and suggests marine biofilms may contribute to nutrient cycling at depth. Analyzing the marine biofilm microbiome is a first step to understanding the ecological consequences of ocean sprawl.
SS074B Aquatic Biofilms Under Stress: Barriers or Drivers of Environmental Changes
Description
Time: 10:30 AM
Date: 8/6/2023
Room: Sala Menorca A