Resilience and recovery: the effect of triclosan exposure timing during development, on the structure and function of river biofilm communities

Triclosan toxicity in a model cyanobacterium (Anabaena flos-aquae): Growth, photosynthesis and transcriptomic response

Exposure to triclosan (TCS) has been reported to reduce photosynthetic pigments, suppress photosynthesis, and inhibit growth in both prokaryotic and eukaryotic algae including Anabaena flos-aquae (a model cyanobacterium). In particular, cyanobacteria are more sensitive to TCS toxicity compared to eukaryotic algae possibly due to the structural similarity to bacteria (target organisms); however, whether TCS exerts its toxicity to cyanobacteria by targeting signaling pathways of fatty acid biosynthesis as in bacteria remains virtually unknown, particularly at environmental exposure levels. With the complete genome sequence of A. flos-aquae presented in this study, the transcriptomic alterations and potential toxic mechanisms in A. flos-aquae under TCS stress were revealed. The growth, pigments and photosynthetic activity of A. flos-aquae were markedly suppressed following a 7-day TCS exposure at 0.5 µg/L but not 0.1 µg/L (both concentrations applied are environmentally relevant). The transcriptomic sequencing analysis showed that signaling pathways, such as biofilm formation - Pseudomonas aeruginosa, two-component system, starch and sucrose metabolism, and photosynthesis were closely related to the TCS-induced growth inhibition in the 0.5 µg/L TCS treatment. Photosynthesis systems and potentially two-component system were identified to be sensitive targets of TCS toxicity in A. flos-aquae. The present study provides novel insights on TCS toxicity at the transcriptomic level in A. flos-aquae.

Research trends and hotspots of aquatic biofilms in freshwater environment during the last three decades: a critical review and bibliometric analysis

Freshwater periphytic biofilms (FPBs), existing widely in various aquatic environments, have attracted extensive attention for many years. In the present study, a bibliometric analysis based on Web of Science Core Collection (WoSCC) was used to understand the research progress, trends, and hot topics of FPBs qualitatively and quantitatively. The results indicated that publications on FPBs have increased from 1991 to 2020 rapidly, and researchers have focused more on the areas of environmental sciences, microbiology, and marine freshwater biology. The most influential countries were mainly the USA, Spain, France, and Germany. Cooperation network analysis reflected that the USA and its affiliated institutions played crucial roles in the research of FPB cooperation, but the collaboration between core author groups still fell short. Based on the analysis of top 20 high-cited FPB documents over the last 30 years, research hotspots mainly included micro-observation and assembly mechanisms of FPBs; interactions of FPBs and pollutants including heavy metals, antibiotic resistance genes, pathogens, organic pollutants, and nanoparticles; and the role of FPBs for biogeochemical cycling, especially nitrogen cycling. Additionally, future research directions were proposed. Overall, this study provides a comprehensive and systematic overview of FPBs, which is useful for research development and researchers who are interested in this area.

Community-level and function response of photoautotrophic periphyton exposed to oxytetracycline hydrochloride

Periphyton is considered important for removal of organic pollutants from water bodies, but knowledge of the impacts of antibiotics on the community structure and ecological function of waterbodies remains limited. In this study, the effects of oxytetracycline hydrochloride (OTC) on the communities of photoautotrophic epilithon and epipelon and its effect on nitrogen and phosphorus concentrations in the water column were studied in a 12-day mesocosm experiment. The dynamics of nitrogen and phosphorus concentrations in the epipelon and epilithon experiment showed similar patterns. The concentrations of total nitrogen, dissolved total nitrogen, ammonium nitrogen, total phosphorus and dissolved total phosphorus in the water column increased rapidly during the initial days of exposure, after which a downward trend occurred. In the epilithon experiment, we found that the photosynthesis (Fv/Fm) and biomass of epilithon were significantly (P < 0.05) stimulated in the low concentration group. Contrarily, growth and photosynthesis (Fv/Fm) were significantly (P < 0.05) reduced in the medium and high concentration group. We further found that the photosynthetic efficiency of photoautotrophic epilithon was negatively correlated with the concentrations of nitrogen and phosphorus in the water column (P < 0.05). Principal coordinate analysis (PCoA) showed that the communities of epilithic algae in the control group and in the low concentration group were significantly (P < 0.05) different from that of the high concentration group during the initial 4 days. After 8 days' exposure, all groups tended to be similar, indicating that epilithon showed rapid adaptability and/or resilience. Similar results were found for the relative abundance of some epilithic algae. Our findings indicate that the biofilm system has strong tolerance and adaptability to OTC as it recovered fast after an initial suppression, thus showing the important role of periphyton in maintaining the dynamic balance of nutrients with other processes in aquatic ecosystems.

Effects of Long-Term Triclosan Exposure on Microbiota in Zebrafish

Background: Triclosan (TCS) is a widely used antibacterial agent in personal care products and is ubiquitous in the environment. We aimed to examine whether TCS exposure affects microbiota in the gastrointestinal tract of zebrafish.

Methods: After exposure to TCS 0 (Dimethyl Sulphoxide, DMSO control), 0.03, 0.3, 3, 30, 100, and 300ng/ml, respectively, from day 0 to 120days post fertilization (dpf), or for 7days in adult 4-month zebrafish, the long- and short-term impact of TCS exposure on the microbiome in the gastrointestinal tract was evaluated by analyzing 16S rRNA gene V3-V4 region sequencing.

Results: The top two most dominant microbiota phyla were Proteobacteria and Fusobacteria phylum in all zebrafish groups. In TCS exposure 0–120 dpf, compared with DMSO control, the mean number of microbial operational taxonomic units (OTUs) was 54.46 lower (p<0.0001), Chao indice 41.40 lower (p=0.0004), and Ace indice 34.10 lower (p=0.0044) in TCS 300ng/ml group, but no change was observed in most of the other TCS concentrations. PCoA diagram showed that the microbial community in the long-term TCS 300ng/ml exposure group clustered differently from those in the DMSO control and other TCS exposure groups. A shorter body length of the zebrafish was observed in the long-term TCS exposure at 0.03, 100, and 300ng/ml. For 7-day short-term exposure in adult zebrafish, no difference was observed in alpha or beta diversity of microbiota nor the relative abundance of Proteobacteria or Fusobacteria phylum among DMSO control and any TCS levels, but a minor difference in microbial composition was observed for TCS exposure.

Conclusions: Long-term exposure to high TCS concentration in a window from early embryonic life to early adulthood may reduce diversity and alter the composition of microbiota in the gastrointestinal tract. The effect of short-term TCS exposure was not observed on the diversity of microbiota but there was a minor change of microbial composition in adult zebrafish with TCS exposure.

Environmental Concentrations of Sulfonamides Can Alter Bacterial Structure and Induce Diatom Deformities in Freshwater Biofilm Communities

Since the early 1920s, the intensive use of antibiotics has led to the contamination of the aquatic environment through diffuse sources and wastewater effluents. The antibiotics commonly found in surface waters include sulfamethoxazole (SMX) and sulfamethazine (SMZ), which belong to the class of sulfonamides, the oldest antibiotic class still in use. These antibiotics have been detected in all European surface waters with median concentrations of around 50 ng L^–1 and peak concentrations of up to 4–6 μg L^–1. Sulfonamides are known to inhibit bacterial growth by altering microbial production of folic acid, but sub-lethal doses may trigger antimicrobial resistance, with unknown consequences for exposed microbial communities. We investigated the effects of two environmentally relevant concentrations (500 and 5,000 ng L^–1) of SMZ and SMX on microbial activity and structure of periphytic biofilms in stream mesocosms for 28 days. Measurement of sulfonamides in the mesocosms revealed contamination levels of about half the nominal concentrations. Exposure to sulfonamides led to slight, transitory effects on heterotrophic functions, but persistent effects were observed on the bacterial structure. After 4 weeks of exposure, sulfonamides also altered the autotrophs in periphyton and particularly the diversity, viability and cell integrity of the diatom community. The higher concentration of SMX tested decreased both diversity (Shannon index) and evenness of the diatom community. Exposure to SMZ reduced diatom species richness and diversity. The mortality of diatoms in biofilms exposed to sulfonamides was twice that in non-exposed biofilms. SMZ also induced an increase in diatom teratologies from 1.1% in non-exposed biofilms up to 3% in biofilms exposed to SMZ. To our knowledge, this is the first report on the teratological effects of sulfonamides on diatoms within periphyton. The increase of both diatom growth rate and mortality suggests a high renewal of diatoms under sulfonamide exposure. In conclusion, our study shows that sulfonamides can alter microbial community structures and diversity at concentrations currently present in the environment, with unknown consequences for the ecosystem. The experimental set-up presented here emphasizes the interest of using natural communities to increase the ecological realism of ecotoxicological studies and to detect potential toxic effects on non-target species.

Effects of thorium on bacterial, microalgal and micromeiofaunal community structures in a periphytic biofilm

Few ecotoxicity studies are available on thorium (Th) which hinders the ability to evaluate its ecotoxicological risk. Its release in the environment is often associated with the extraction of rare earth elements and uranium, as well as the field applications of phosphate fertilizers. This study investigates the effects of Th on microbial communities of periphytic biofilms. Ceramic plates were left to colonize for one month in the laboratory with a biofilm sampled from Cap Rouge river (QC, Canada). Plates were randomly placed in channels containing culture media representing three different conditions: a control condition (C0; background Th concentrations of 0.004 ± 0.002 nM), a low Th concentration condition (C1; 0.18 ± 0.09 nM Th) and a moderately high Th condition (C10; 8.7 ± 3.4 nM) for up to 4 weeks. The presence of Th modified the diatom community by changing its taxonomic structure, reducing diversity and increasing cell density. The taxonomic structure of the bacterial community, followed by 16S metabarcoding analysis, was affected with a significant decrease in Pseudanabaena and Shingopyxis genera in the two Th exposed conditions. No direct toxic effect of Th was observed on counted micromeiofauna but the changes in diatom and bacterial communities could explain the higher number of individual diatoms and micromeiofauna observed in Th-exposed conditions. This work shows that low concentrations of Th can modify biofilm structure, which, in turn, could disturb its ecologically key functions.

Triclosan changes community composition and selects for specific bacterial taxa in marine periphyton biofilms in low nanomolar concentrations

The antibacterial agent Triclosan (TCS) is a ubiquitous environmental contaminant due to its widespread use. Sensitivity to TCS varies substantially among eu- and pro-karyotic species and its risk for the marine environment remains to be better elucidated. In particular, the effects that TCS causes on marine microbial communities are largely unknown. In this study we therefore used 16S amplicon rDNA sequencing to investigate TCS effects on the bacterial composition in marine periphyton communities that developed under long-term exposure to different TCS concentrations. Exposure to TCS resulted in clear changes in bacterial composition already at concentrations of 1 to 3.16 nM. We conclude that TCS affects the structure of the bacterial part of periphyton communities at concentrations that actually occur in the marine environment. Sensitive taxa, whose abundance decreased significantly with increasing TCS concentrations, include the Rhodobiaceae and Rhodobacteraceae families of Alphaproteobacteria, and unidentified members of the Candidate division Parcubacteria. Tolerant taxa, whose abundance increased significantly with higher TCS concentrations, include the families Erythrobacteraceae (Alphaproteobacteria), Flavobacteriaceae (Bacteroidetes), Bdellovibrionaceae (Deltaproteobacteria), several families of Gammaproteobacteria, and members of the Candidate phylum Gracilibacteria. Our results demonstrate the variability of TCS sensitivity among bacteria, and that TCS can change marine bacterial composition at concentrations that have been detected in the marine environment.

Triclosan has a robust, yet reversible impact on human gut microbial composition in vitro

The recent ban of the antimicrobial compound triclosan from use in consumer soaps followed research that showcased the risk it poses to the environment and to human health. Triclosan has been found in human plasma, urine and milk, demonstrating that it is present in human tissues. Previous work has also demonstrated that consumption of triclosan disrupts the gut microbial community of mice and zebrafish. Due to the widespread use of triclosan and ubiquity in the environment, it is imperative to understand the impact this chemical has on the human body and its symbiotic resident microbes. To that end, this study is the first to explore how triclosan impacts the human gut microbial community in vitro both during and after treatment. Through our in vitro system simulating three regions of the human gut; the ascending colon, transverse colon, and descending colon regions, we found that treatment with triclosan significantly impacted the community structure in terms of reduced population, diversity, and metabolite production, most notably in the ascending colon region. Given a 2 week recovery period, most of the population levels, community structure, and diversity levels were recovered for all colon regions. Our results demonstrate that the human gut microbial community diversity and population size is significantly impacted by triclosan at a high dose in vitro, and that the community is recoverable within this system.

Perinatal Triclosan exposure in the rat induces long-term disturbances in metabolism and gut microbiota in adulthood and old age

Triclosan (TCS), as a widely used antimicrobial compound, is commonly detected in pregnant women and newborns indicating exposure risk during early development. However, whether perinatal TCS exposure has long-term effects on the host microbiome which further contributes to metabolic disorder is still unclear. The long-term effects of perinatal TCS exposure on gut microbiota and liver metabolism in adulthood and old age were investigated. Rats were given 0, 10 or 50 mg TCS/kg body weight per day, administered daily by gavage from gestation day 0 until lactation day 21. RNA-sequencing and 16 S rDNA amplicon sequencing analysis were performed to explore the potential mechanisms. Increased blood glucose and serum HDL-C were observed at 10 mg/kg/day in old rats and at 50 mg/kg/day in both adult and old rats. Serum leptin were increased at two doses in old rats. Serum TG and LDL-C were increased at two doses in both adult and old rats. Hepatic glycogen were decreased at 50 mg/kg/day in adult rats and at two doses in old rats. Increased hepatic TG were observed at two doses in old rats. Hepatic RNA-sequencing revealed that more differentially expressed genes were found at 50 mg/kg/day in both adult and old rats. More up-regulated genes in pathways of carbohydrate and lipid metabolism were observed in old rats at 50 mg/kg/day. Diversity reduction and compositional alteration were found in gut microbiota at 50 mg/kg/day in adult rats and at two doses in old rats. These effects lasted for a long time even without TCS exposure and accumulated over time inducing metabolic disorder in old rat offspring. TCS exposure during early life causes disturbances in metabolism and gut microbiota which last a lifetime and accumulated over time at 50 mg/kg/day. Further research is needed to investigate the effects of early life TCS exposure on metabolism and gut microbiota in humans.

N,N-Diethyl-m-Toluamide Exposure at an Environmentally Relevant Concentration Influences River Microbial Community Development

Studies of the South Saskatchewan River confirmed that N,N-diethyl-m-toluamide (DEET) is ubiquitous at 10 to 20 ng/L, whereas in effluent-dominated Wascana Creek, levels of 100 to 450 ng/L were observed. Effects of DEET exposure were assessed in microbial communities using a wide variety of measures. Communities developed in rotating annular reactors with either 100 or 500 ng/L DEET, verified using gas chromatography-mass spectrometry analyses. Microscale analyses indicated that both DEET concentrations resulted in significant (p < 0.05) declines in photosynthetic biomass, whereas bacterial biomass was unaffected. There was no detectable effect of DEET on the levels of chlorophyll a. However, pigment analyses indicated substantial shifts in algal-cyanobacterial community structure, with reductions of green algae and some cyanobacterial groups at 500 ng/L DEET. Protozoan/micrometazoan grazers increased in communities exposed to 500 ng/L, but not 100 ng/L, DEET. Based on thymidine incorporation or utilization of carbon sources, DEET had no significant effects on metabolic activities. Fluorescent lectin-binding analyses showed significant (p < 0.05) changes in glycoconjugate composition at both DEET concentrations, consistent with altered community structure. Principal component cluster analyses of denaturing gradient gel electrophoresis indicated that DEET exposure at either concentration significantly changed the bacterial community (p < 0.05). Analyses based on 16S ribosomal RNA of community composition confirmed changes with DEET exposure, increasing detectable beta-proteobacteria, whereas actinobacteria and acidimicrobia became undetectable. Further, cyanobacteria in the subclass Oscillatoriophycideae were similarly not detected. Thus, DEET can alter microbial community structure and function, supporting the need for further evaluation of its effects in aquatic habitats. Environ Toxicol Chem 2019;38:2414-2425. © 2019 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Fate and effects of triclosan in subtropical river biofilms

Triclosan (TCS, 5-chloro-2-(2,4-dichlorophenoxy) phenol) is a broad-spectrum antimicrobial compound. Owing to its wide use, TCS has been frequently detected in river systems, especially in the (sub-)tropics. However, little information on its interaction with river biofilm in the (sub)tropics is currently available. In the present study, subtropical river biofilms were chronically exposed to TCS for 14 d at concentrations of 0.1-100 μg/L in artificial river water, which was followed by a 7 d recovery period. The results show that 100 μg/L TCS inhibited the growth of river biofilms and the no-observed-effect concentration (NOEC) of TCS on river biofilms was 10 μg/L. The affected biofilms did not completely recover within the 7 d of recovery period due to the adsorbed TCS which was not removed together with dissolved TCS. Exposure to TCS caused significant changes in prokaryotic species composition of river biofilms but no significant effects on eukaryotic species composition. In particular, the relative abundance of several TCS-tolerant bacterial species (e.g., Pseudoxanthomonas mexicana, Sphingopyxis alaskensis and Sphingomonas wittichii) in river biofilms increased following exposure to 10 and 100 μg/L TCS. River biofilm efficiently removed TCS from the liquid phase and the pH values of the aquatic system significantly affected the removal efficiency of TCS (from 36% at pH 6.5 to 60% at pH 8.5). No degradation products were detected in the liquid phase after 5 days of exposure, possibly due to strong adsorption of the hydrophobic degradation products to river biofilms and through biodegradation by bacteria utilizing TCS and its degradation products as source of carbon and energy for growth, such as Methyloversalitis universalis and Methylobacterium aquaticum.

Response of sediment bacterial community to triclosan in subtropical freshwater benthic microcosms

The response of sediment bacterial communities in subtropical freshwater benthic microcosms to sediment-associated triclosan (TCS; 28 d exposure) was analysed using Illumina high-throughput sequencing. This study highlights the interactive effects of TCS and the presence of benthic macroinvertebrates (Limnodrilus hoffmeisteri and Viviparidae bellamya) on sediment bacterial communities. Our results show that TCS alone significantly altered the taxonomic composition and decreased alpha diversity of sediment bacterial communities at concentrations ≥80 μg TCS/g dry weight (dw) sediment (sed). Regarding dominant phyla, TCS significantly reduced the relative abundance of Bacteroidetes and Firmicutes at these concentrations, whereas the relative abundance of Chloroflexi and Cyanobacteria increased. In the presence of benthic macroinvertebrates, the sediment bacterial community was affected by 8 μg TCS/g dw sed as well. However, the presence of benthic macroinvertebrates did not cause measurable changes to bacterial community in unspiked (i.e., control) sediment. These results indicate that TCS alone would not alter the sediment bacterial community at environmentally relevant concentrations (up till 8 μg/g dw sed), but may have an effect in combination with the presence of benthic macroinvertebrates. Therefore, we recommend to include benthic macroinvertebrates when assessing the response of sediment bacterial communities during exposure to environmental stress such as organic contaminants.

Insights into Long-Term Toxicity of Triclosan to Freshwater Green Algae in Lake Erie

This study explored the long-term impacts of a pulse disturbance of triclosan on five nontarget green algae in Lake Erie. Comprehensive analyses were performed using multiple physiological end points at community and subcellular scales. The toxic mechanism of triclosan in a wide range of concentrations was analyzed. The diverse sensitivity of algae species and complex interrelationships among multiple end points were revealed. The results showed the taxonomic groups of algae were the key issue for sensitivity difference. High doses of triclosan caused irreversible damage on algae, and environmentally relevant doses initiated either inhibition or stimulation. Smaller cells had higher sensitivity to triclosan, while larger cells had a wider size variation after exposure. Colonial cells were less sensitive than unicells. For chlorophyll, there were better dose-response relationships in Chlorococcum sp., Chlamydomonas reinhardtii CPCC 12 and 243 than Asterococcus superbus and Eremosphaera viridis. For chlorophyll fluorescence, F_v/ F_m was the most sensitive parameter, and q_N was more sensitive than q_P. Triclosan showed long-term effects on biochemical components, such as lipids, proteins, and nucleic acids. The findings will be helpful for a systematic and complete assessment of triclosan toxicity in natural waters and the development of appropriate strategies for its risk management.

Triclosan exposure, transformation, and human health effects

Triclosan (TCS) is an antimicrobial used so ubiquitously that 75% of the US population is likely exposed to this compound via consumer goods and personal care products. In September 2016, TCS was banned from soap products following the risk assessment by the US Food and Drug Administration (FDA). However, TCS still remains, at high concentrations, in other personal care products such as toothpaste, mouthwash, hand sanitizer, and surgical soaps. TCS is readily absorbed into human skin and oral mucosa and found in various human tissues and fluids. The aim of this review was to describe TCS exposure routes and levels as well as metabolism and transformation processes. The burgeoning literature on human health effects associated with TCS exposure, such as reproductive problems, was also summarized.

Effects of erythromycin, trimethoprim and clindamycin on attached microbial communities from an effluent dominated prairie stream

In this study, differing metrics were utilized to measure effects of erythromycin (ER), trimethoprim (TR) and clindamycin (CL) on the structure and function of attached Wascana Creek, SK microbial communities. All three test antibiotics, especially ER, affected community structure and function of biofilms grown in rotating annular reactors. Biofilm thickness, bacterial biomass, and lectin binding biovolume (exopolymeric substances) were consistently less in ER treated biofilms when compared to the control. As well negative effects on protozoan numbers, and carbon utilization were detected. Finally, PCA analyses of DGGE results indicated that bacterial community diversity in ER exposed biofilms was always different from the control. ER exhibited toxic effects even at lower concentrations. Observations on TR and CL exposed biofilms indicated that bacterial biomass, lectin binding biovolume and carbon utilization were negatively affected as well. In terms of bacterial community diversity, however, CL exposed biofilms tended to group with the control while TR grouped with nutrient additions suggesting both nutritive and toxic effects. This study results represent an important step in understanding antibiotic effects, especially ER, on aquatic microbial communities. And because ER is so ubiquitous in receiving water bodies worldwide, the Wascana study results suggest the possibility of ecosystem disturbance elsewhere.

CAPSULE ABSTRACT

Erythromycin (ER) is ubiquitous in waterbodies receiving sewage effluent. Structure and function of microbial communities from an effluent dominated stream were negatively affected by ER, at realistic concentrations.

Triclosan: A review on systematic risk assessment and control from the perspective of substance flow analysis

Triclosan (TCS) is a broad spectrum antibacterial agent mainly used in Pharmaceutical and Personal Care Products. Its increasing use over recent decades have raised its concentration in the environment, with commonly detectable levels found along the food web-from aquatic organisms to humans in the ecosystem. To date, there is shortage of information on how to investigate TCS's systematic risk on exposed organisms including humans, due to the paucity of systematic information on TCS flows in the anthroposphere. Therefore, a more holistic approach to mass flow balancing is required, such that the systematic risk of TCS in all environmental matrices are evaluated. From the perspective of Substance Flow Analysis (SFA), this review critically summarizes the current state of knowledge on TCS production, consumption, discharge, occurrence in built and natural environments, its exposure and metabolism in humans, and also the negative effects of TCS on biota and humans. Recent risk concerns have mainly focused on TCS removal efficiencies and metabolism, but less attention is given to the effect of mass flows from source to fate during risk exposure. However, available data for TCS SFA is limited but SFA can derive logical systematic information from limited data currently available for systematic risk assessment and reduction, based on mass flow analysis. In other words, SFA tool can be used to develop a comprehensive flow chart and indicator system for the risk assessment and reduction of TCS flows in the anthroposphere, thereby bridging knowledge gaps to streamline uncertainties related to policy-making on exposure pathways within TCS flow-lines. In the final analysis, specifics on systematic TCS risk assessment via SFA, and areas of improvement on human adaptation to risks posed by emerging contaminants are identified and directions for future research are suggested.

Microbial interactions with naturally occurring hydrophobic sediments: Influence on sediment and associated contaminant mobility

The erosion, transport and fate of sediments and associated contaminants are known to be influenced by both particle characteristics and the flow dynamics imparted onto the sediment. The influential role of bitumen containing hydrophobic sediments and the microbial community on sediment dynamics are however less understood. This study links an experimental evaluation of sediment erosion with measured sediment-associated contaminant concentrations and microbial community analysis to provide an estimate of the potential for sediment to control the erosion, transport and fate of contaminants. Specifically the paper addresses the unique behaviour of hydrophobic sediments and the role that the microbial community associated with hydrophobic sediment may play in the transport of contaminated sediment. Results demonstrate that the hydrophobic cohesive sediment demonstrates unique transport and particle characteristics (poor settling and small floc size). Biofilms were observed to increase with consolidation/biostabilization times and generated a unique microbial consortium relative to the eroded flocs. Natural oil associated with the flocs appeared to be preferentially associated with microbial derived extracellular polymeric substances. While PAHs and naphthenic acid increased with increasing shear (indicative of increasing loads), they tended to decrease with consolidation/biostabilization (CB) time at similar shears suggesting a chemical and/or biological degradation. PAH and napthenic acid degrading microbes decreased with time as well, which may suggest that there was a reduced pool of PAHs and naphthenic acids available resulting in their die off. This study emphasizes the importance that any management strategies and operational assessments for the protection of human and aquatic health incorporate the sediment (suspended and bed sediment) and biological (biofilm) compartments and the energy dynamics within the system in order to better predict contaminant transport.