Canadian Expert Consensus on the Use of Halobetasol Propionate/Tazarotene Lotion for Plaque Psoriasis.

INTRODUCTION: An expert panel of Canadian dermatologists was assembled to develop consensus statements regarding the current landscape of topical therapies for plaque psoriasis and the place in therapy of the recently approved fixed-dose combination halobetasol propionate (HP)/tazarotene (TAZ) lotion (HP/TAZ) in the treatment algorithm for plaque psoriasis. METHOD: A modified nominal group technique, which combined both independent and group input from the expert panel, was used to develop the consensus statements. The expert panel completed surveys to elicit their independent views on the current landscape of topical therapies for plaque psoriasis in Canada. The first expert panel session was held to discuss the existing body of literature and develop draft consensus statements about topical therapies and the place in therapy of HP/TAZ. Independent feedback on the draft consensus statements was solicited from expert panel members prior to another expert panel session where the amended consensus statements were further discussed, edited and, finally, voted on. RESULTS: The expert panel reached consensus on 20 statements. CONCLUSION: Expert panel members agreed, based on the existing body of literature, that there is a place in therapy for HP/TAZ to address several current unmet treatment needs of patients with plaque psoriasis. Studies have shown that HP/TAZ is an effective and safe first-line treatment for moderate-to-severe plaque psoriasis. Due to its cosmetically pleasing vehicle and once-daily administration, HP/TAZ may improve patient acceptance and treatment adherence.

Selenium bioaccumulation in Daphnia pulex via aqueous and dietary exposure.

Pit lakes are currently being investigated as a way to store and reclaim waste materials in the Alberta Oil Sands (AOS) region, Canada. Lake Miwasin (LM) is a pilot-scale pit lake consisting of treated fine tailings overlayed with oil sands process-affected water (OSPW) blended with fresh surface water. In October 2021, the surface water contained a mean concentration of 1.33 ± 0.04 µg/L dissolved selenium (Se), slightly above the Canadian Council of Ministers of Environment water quality guideline for long-term protection of aquatic life (1 µg Se/L). This study assessed the bioaccumulation of Se by the cladoceran Daphnia pulex under laboratory conditions through both aqueous and dietary exposure routes for comparison to field-collected specimens. In 12-day semi-static tests, lab-cultured D.pulex were exposed to water, and algae grown in media spiked with selenate. Results showed that Se bioaccumulation by lab-cultured D. pulex increased in all exposure treatments from days 5 to 12, with maximum Se concentrations of 3.08-3.47 µg/g dry weight (dw) observed within the exposure range tested. Interestingly, lower Se bioaccumulation concentrations (1.26-1.58 µg/g dw) were observed in the highest dissolved Se and dietary Se treatments, suggesting potential internal regulatory mechanisms. In addition, native D. pulex (LM) collected from Lake Miwasin and cultured in-house were exposed in 8-day semi-static tests to Lake Miwasin surface water and algae cultured in Lake Miwasin surface water. Selenium bioaccumulation in native D. pulex (LM) ranged from 2.00 to 2.04 µg/g dw at day 8 and was not significantly different (p > 0.05) compared to Se concentrations in D. pulex collected from Lake Miwasin (2.15 ± 0.28 µg/g) in summer 2022.

Trophic dynamics of selenium in a boreal lake food web.

Selenium (Se) is both an essential micronutrient and a contaminant of concern that is of particular interest in mining-influenced waterbodies in Canada. The objective of this research was to characterize the trophic dynamics of selenium along a gradient of exposure concentrations in a Canadian boreal lake ecosystem. From June 20 to August 22, 2018, six limnocorrals (littoral, ∼3000 L enclosures) were spiked with mean measured concentrations of 0.4, 0.8, 1.6, 3.4, 5.6 and 7.9 µg Se/L as selenite, and three limnocorrals served as untreated controls (background aqueous Se = 0.08-0.09 µg/L). Total Se (TSe) concentrations in water, periphyton, phytoplankton, sediment, benthic macroinvertebrates, zooplankton and female finescale dace (Phoxinus neogaeus; added on day 21 of the experiment) were measured throughout and at the end of the experiment. Total Se bioaccumulation by organisms was generally non-linear. Greater uptake by phytoplankton than periphyton was observed. Taxonomic differences in accumulation of TSe by invertebrates (Heptageniidae = Chironomidae > zooplankton) were observed as well. Fish muscle and ovary tissue TSe bioaccumulation was more variable than that at lower trophic levels and uptake patterns indicated that fish did not reach steady state concentrations. This research provides field-derived models for the uptake of Se by algae and invertebrates, and contributes to a better understanding of the dynamics of TSe bioaccumulation over a gradient of exposure concentrations in cold-water lentic systems.

Differences in long-term quality of life between hemithyroidectomy and total thyroidectomy in patients treated for low-risk differentiated thyroid carcinoma.

BACKGROUND: The long-term health-related quality-of-life implications of treating low-risk differentiated thyroid cancer with total thyroidectomy or hemithyroidectomy is important to patients but remains poorly understood. METHODS: Using a cross-sectional mailed survey, we compared long-term health-related quality-of-life in low-risk differentiated thyroid cancer survivors treated with hemithyroidectomy to those treated with total thyroidectomy between 2005 and 2016 at a university hospital. European Organisation for Research and Treatment of Cancer Quality of Life core Questionnaire version 3.0, the supplementary Thyroid Cancer specific questionnaire module version 2.0, and the Assessment of Survivor Concerns (ASC) questionnaires were used. Our primary outcome was the global scale of quality of life. Exploratory outcomes included differences among other health-related quality-of-life items corrected for potential confounders in multivariable regression analyses. RESULTS: The response rate was 51.0% (270 of 529), of which 59 patients (21.9%) were treated with hemithyroidectomy. Main outcome score global quality of life did not differ between groups (76.9 hemithyroidectomy vs 77.7 total thyroidectomy, P = .450). Exploratory analyses showed hemithyroidectomy to be associated with more worry about recurrence on the Assessment of Survivor Concerns questionnaire (2.4 hemithyroidectomy vs 2.1 total thyroidectomy, P = .021). CONCLUSION: Long-term quality of life was not significantly different between low-risk differentiated thyroid cancer patients treated with total thyroidectomy compared with hemithyroidectomy. In secondary analyses, worry about recurrence appeared to be higher in individuals treated with hemithyroidectomy. These data highlight previously unreported impact of surgical regimen to the health-related quality-of-life for low-risk differentiated thyroid cancer patients.

Preoperative Computed Tomography Changes Surgical Management for Clinically Low-Risk Well-Differentiated Thyroid Cancer.

BACKGROUND: In the current guidelines for differentiated thyroid cancer (DTC), computed tomography (CT) of the neck has a limited role. The authors hypothesized that adding CT to the workup of clinically low-risk DTC size 4 cm or smaller changes the surgical management for a portion of patients due to detection of clinically significant lymph node metastases not located by ultrasound of the neck. METHODS: A prospective cohort of DTC patients at an academic referral center between 2012 and 2016 was reviewed. All the patients with fine-needle aspiration cytopathology results suspicious for malignancy or malignant tumor (Bethesda category 5 or 6, respectively) underwent CT before surgery. Clinically low-risk DTC patients were selected if they had a tumor diameter of 4 cm or less and no evidence for local invasion or suspicious lymph nodes seen on ultrasound. Outcomes focused on alteration of the surgical plan based on CT and correlation with pathology. RESULTS: The CT findings for 25 (22.5%) of 111 patients with clinically low-risk DTC led to a change in surgical management. Of these 25 patients, 16 (14.4% of the entire cohort) benefited due to the removal of clinically significant lymph node disease not seen on ultrasound. Categorization of the group that had a change in management showed that 6 (85.7%) of 7 lateral neck dissections and 10 (55.6%) of 18 central neck dissections (CND) harbored metastatic nodes larger than 2 mm. CONCLUSIONS: In the group with clinically low-risk DTC, CT changed surgical management for a substantial number of the patients with clinically significant nodal disease not detected by ultrasound. This highlights the fact that in certain practice settings, adding CT to the preoperative staging may be favorable for the detection of nodal metastasis.

Effects of selenium on benthic macroinvertebrates and fathead minnow (Pimephales promelas) in a boreal lake ecosystem.

Selenium (Se) is a contaminant of concern in many aquatic ecosystems due to its narrow range between essentiality and toxicity in oviparous (yolk-bearing) vertebrates. The objective of the present study was to determine the effects of Se, experimentally added to in situ limnocorrals as selenite, on invertebrate communities and fathead minnow (Pimephales promelas) at environmentally realistic Se concentrations. Nine limnocorrals were deployed in a mesotrophic lake at the International Institute for Sustainable Development - Experimental Lakes Area in Ontario, Canada in May 2017. From June 1 to August 17, 2017, selenite was added to six enclosures to attain mean measured aqueous Se concentrations of 1.0 ±â€¯0.10 or 8.9 ±â€¯2.7 µg/L Se (in triplicate) and three limnocorrals were untreated controls (background mean aqueous Se = 0.12 ±â€¯0.03 µg/L). Benthic macroinvertebrates were collected throughout and at the end of the exposure period using artificial substrates to determine density, dry biomass, diversity, and taxa richness at the family level. Reproductively mature female fathead minnows (added on d 33 of the study) were collected throughout and at the end of the exposure period. After 77 d, Chironomidae and Gammaridae densities and biomass were significantly lower in the 8.9 µg/L Se treatment relative to the 1.0 µg/L Se treatment and the control. Invertebrate diversity (measured as Shannon's and Simpson's indices) significantly declined in the 1.0 µg/L and 8.9 µg/L Se treatments relative to the control (0.12 µg/L Se group). Fulton's condition factor for fathead minnow was significantly less in the 8.9 µg/L treatment compared to 0.12 and 1.0 µg/L Se experimental groups. The results of this study indicated that exposure to relatively low aqueous selenite concentrations can negatively affect invertebrate density and biomass, as well as fish condition. More research is necessary to characterize the risk of selenite exposure to aquatic invertebrates under realistic field conditions, and future risk assessments may need to consider reduced food availability as a factor that may impair the health of higher trophic level organisms in areas with elevated selenite.

Vanadium and thallium exhibit biodilution in a northern river food web.

Trophic transfer of contaminants dictates concentrations and potential toxic effects in top predators, yet biomagnification behaviour of many trace elements is poorly understood. We examined concentrations of vanadium and thallium, two globally-distributed and anthropogenically-enriched elements, in a food web of the Slave River, Northwest Territories, Canada. We found that tissue concentrations of both elements declined with increasing trophic position as measured by δ15N. Slopes of log [element] versus δ15N regressions were both negative, with a steeper slope for V (-0.369) compared with Tl (-0.099). These slopes correspond to declines of 94% with each step in the food chain for V and 54% with each step in the food chain for Tl. This biodilution behaviour for both elements meant that concentrations in fish were well below values considered to be of concern for the health of fish-eating consumers. Further study of these elements in food webs is needed to allow a fuller understanding of biomagnification patterns across a range of species and systems.

Papillary Thyroid Cancers with Focal Tall Cell Change are as Aggressive as Tall Cell Variants and Should Not be Considered as Low-Risk Disease.

BACKGROUND: The tall cell variant of papillary thyroid carcinoma (PTC) is as an aggressive histological variant. The proportion of tall cells needed to influence prognosis is debated. METHODS: Patients with PTC and tall cells, defined as having a height-to-width ratio of ≥ 3:1, seen at a high-volume center between 2001 and 2015, were reviewed. Specimens were classified as (1) focal tall cell change, containing < 30% of tall cells; (2) tall cell variant, ≥ 30% of tall cells; and (3) control cases selected from infiltrative classical PTCs without adverse cytologic features. Univariate, sensitivity, and multivariate analyses were performed with persistent/recurrent disease as the primary outcome. RESULTS: We identified 96 PTCs with focal tall cell change, 35 with the tall cell variant and 104 control cases. Factors associated with poor clinical prognosis were significantly greater in those with focal tall cell change and tall cell variants. Regarding primary outcome, hazard ratios were 2.3 (95% confidence interval [CI] 1.0-5.7) for focal tall cell change, and 3.4 (95% CI 1.2-8.7) for tall cell variants compared with controls. Five-year disease-free survival was higher for the control group (92.7%, CI 87.4-98.0) compared with focal tall cell change (76.3%, CI 66.1-86.5) and the tall cell variant (62.2%, CI 43.2-81.2). When stratified in groups consisting of tall cell proportions (< 10%, 10-19%, 20-29% and ≥ 30%), identification of ≥ 10% tall cell change was associated with worse outcome (p = 0.002). CONCLUSIONS: PTCs with ≥ 10% tall cell change have worse prognosis than those without tall cells. Our data indicate that thyroid cancer management guidelines should consider PTCs with focal tall cell change outside of the low-risk classification.

Distribution of Experimentally Added Selenium in a Boreal Lake Ecosystem.

Human activities have increased the release of selenium (Se) to aquatic environments, but information about the trophic transfer dynamics of Se in Canadian boreal lake systems is limited. In the present study, Se was added as selenite to limnocorrals (2-m-diameter, 3000-L in situ enclosures) in a boreal lake in northwestern Ontario to reach nominal concentrations of 1 and 10 µg Se/L in triplicate each for 77 d, and 3 additional limnocorrals were controls with no Se added. Total Se concentrations were determined in water, sediment, periphyton, benthic macroinvertebrates, zooplankton, and reproductively mature female fathead minnows (Pimephales promelas; added on day 33) collected throughout (and at the end of) the exposure period. Mean measured water Se concentrations in the control, 1-, and 10-µg/L treatments were 0.12, 1.0, and 8.9 µg/L. At the end of exposure (day 77), enrichment functions ranged from 7772 L/kg dry mass in the 8.9-µg/L treatment to 23 495 L/kg dry mass in the 0.12-µg/L treatment, and trophic transfer factors for benthic macroinvertebrates ranged from 0.49 for Gammaridae to 2.3 for Chironomidae. Selenium accumulated in fathead minnow ovaries to concentrations near or above the current US Environmental Protection Agency criterion (15.1 µg/g dry mass for fish ovary/egg) in the 1.0- and 8.9-µg/L treatments, suggesting that, depending on aqueous Se speciation, such exposures have the potential to cause Se accumulation in fish to levels of concern in cold-water, boreal lake systems. Environ Toxicol Chem 2019;38:1954-1966. © 2019 SETAC.

Selenium oxyanion bioconcentration in natural freshwater periphyton.

Selenium (Se) enrichment has been demonstrated to vary by several orders of magnitude among species of planktonic algae. This is a substantial source of uncertainty when modelling Se biodynamics in aquatic systems. In addition, Se bioconcentration data are largely lacking for periphytic species of algae, and for multi-species periphyton biofilms, adding to the challenge of modelling Se transfer in periphyton-based food webs. To better predict Se dynamics in periphyton dominated, freshwater ecosystems, the goal of this study was to assess the relative influence of periphyton community composition on the uptake of waterborne Se oxyanions. Naturally grown freshwater periphyton communities, sampled from five different water bodies, were exposed to environmentally relevant concentrations of selenite [Se(IV)] or selenate [Se(VI)] (nominal concentrations of 5 and 25 µg Se L-1) under similar, controlled laboratory conditions for a period of 8 days. Unique periphyton assemblages were derived from the five different field sites, as confirmed by light microscopy and targeted DNA sequencing of the plastid 23S rRNA gene in algae. Selenium accumulation demonstrated a maximum of 23.6-fold difference for Se(IV) enrichment and 2.1-fold difference for Se(VI) enrichment across the periphyton/biofilm assemblages tested. The assemblage from one field site demonstrated both high accumulation of Se(IV) and iron, and was subjected to additional experimentation to elucidate the mechanism(s) of Se accumulation. Selenite accumulation (at nominal concentrations of 5 and 25 µg Se L-1 and mean pH of 7.5 across all treatment replicates) was assessed in both unaltered and heat-killed periphyton, and in periphyton from the same site grown without light to exclude phototrophic organisms. Following an exposure length of 8 days, all periphyton treatments showed similar levels of Se accumulation, indicating that much of the apparent uptake of Se(IV) was due to non-biological processes (i.e., surface adsorption). The results of this study will help reduce uncertainty in the prediction of Se dynamics and food-chain transfer in freshwater environments. Further exploration of the ecological consequences of extracellular adsorption of Se(IV) to periphyton, rather than intracellular absorption, is recommended to further refine predictions related to Se biodynamics in freshwater food webs.

Dynamic arterial elastance measured by uncalibrated pulse contour analysis predicts arterial-pressure response to a decrease in norepinephrine.

BACKGROUND: Dynamic arterial elastance (Eadyn) has been proposed as an indicator of vascular tone that predicts the decrease in arterial pressure in response to changes in norepinephrine (NE). The purpose of this study was to determine whether Eadyn measured by uncalibrated pulse contour analysis (UPCA) can predict a decrease in arterial pressure when the NE dosage is decreased. METHODS: We conducted a prospective study in a university hospital intensive care unit. Patients with vasoplegic syndrome for whom the intensive care physician planned to decrease the NE dosage were included. Haemodynamic and UPCA (VolumeView and FloTrac; Edwards Lifesciences, Irvine, CA, USA) values were obtained before and after decreasing the NE dosage. Responders were defined by a >10% decrease in mean arterial pressure (MAP). RESULTS: Of 35 patients included, 11 (31%) were pressure responders with a median decrease of 13%. Eadyn was correlated to systolic arterial pressure (SAP) (r=0.255; P=0.033), diastolic arterial pressure (r=0.271; P=0.024), MAP (r=0.310; P=0.009), heart rate (r=0.543; P=0.0001), and transthoracic echography cardiac output (r=0.264; P=0.024). Baseline Eadyn was correlated with MAP changes (r=0.394; P=0.019) and SAP changes (r=0.431; P=0.009). Eadyn predicted the decrease in arterial pressure with an area under the receiver-operating-characteristic curve of 0.84 (95% confidence interval: 0.70-0.97). The best cut-off was 0.90. CONCLUSIONS: The present study confirms the ability of Eadyn measured by UPCA to predict an arterial pressure response to a decrease in NE. Eadyn may constitute an easy-to-use functional approach to arterial tone assessment regardless of the monitor used to measure its determinant. CLINICAL TRIAL REGISTRATION: DRCIT95.

Combining High-Throughput Sequencing of sedaDNA and Traditional Paleolimnological Techniques To Infer Historical Trends in Cyanobacterial Communities.

Freshwaters worldwide are under increasing pressure from anthropogenic activities and changing climate. Unfortunately, many inland waters lack sufficient long-term monitoring to assess environmental trends. Analysis of sedimentary ancient DNA ( sedaDNA) is emerging as a means to reconstruct the past occurrence of microbial communities of inland waters. The purpose of this study was to assess a combination of high-throughput sequencing (16S rRNA) of sedaDNA and traditional paleolimnological analyses to explore multidecadal relationships among cyanobacterial community composition, the potential for cyanotoxin production, and paleoenvironmental proxies. DNA was extracted from two sediment cores collected from a northern Canadian Great Plains reservoir. Diversity indices illustrated significant community-level changes since reservoir formation. Furthermore, higher relative abundances in more recent years were observed for potentially toxic cyanobacterial genera including Dolichospermum. Correlation-based network analysis revealed this trend significantly and positively correlated to abundances of the microcystin synthetase gene ( mcyA) and other paleoproxies (nutrients, pigments, stanols, sterols, and certain diatom species), demonstrating synchrony between molecular and more standard proxies. These findings demonstrate a novel approach to infer long-term dynamics of cyanobacterial diversity in inland waters and highlight the power of high-throughput sequencing to reconstruct trends in environmental quality and inform lake and reservoir management and monitoring program design.

Clinical Safety of Renaming Encapsulated Follicular Variant of Papillary Thyroid Carcinoma: Is NIFTP Truly Benign?

BACKGROUND: Renaming encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) to noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) was recently suggested to prevent the overtreatment, cost and stigma associated with this low-risk entity. The purpose of this study is to document the incidence and further assess the clinical outcomes of reclassifying EFVPTC to NIFTP. METHODS: We searched synoptic pathologic reports from a high-volume academic endocrine surgery hospital from 2004 to 2013. The standard of surgical pathology practice was based on complete submission of malignant thyroid nodules along with the nontumorous thyroid parenchyma. Rigid morphological criteria were used for the diagnosis of noninvasive EFVPTC, currently known as NIFTP. A retrospective chart review was conducted looking for evidence of malignant behavior. RESULTS: One hundred and two patients met the strict inclusion criteria of NIFTP. The incidence of NIFTP in our cohort was 2.1% of papillary thyroid cancer cases during the studied time period. Mean follow-up was 5.7 years (range 0-11). Five patients were identified with nodal metastasis and one patient with distant metastasis. Overall, six patients showed evidence of malignant behavior representing 6% of patients with NIFTP. CONCLUSION: Our study demonstrates that the incidence of NIFTP is significantly lower than previously thought. Furthermore, evidence of malignant behavior was seen in a significant number of NIFTP patients. Although the authors fully support the de-escalation of aggressive treatment for low-risk thyroid cancers, NIFTP behaves as a low-risk thyroid cancer rather than a benign entity and ongoing surveillance is warranted.

Assessment of changes in lactate concentration with intravascular microdialysis during high-risk cardiac surgery using the trend interchangeability method.

Background: Blood lactate is a strong predictor of mortality, and repeated blood lactate assays are recommended during surgery in high-risk patients. We hypothesized that the use of intravascular microdialysis incorporated in a central venous catheter would be interchangeable with the reference blood gas technique to monitor changes in blood lactate. Methods: Microdialysis and central venous blood lactate measurements were recorded simultaneously in high-risk cardiac surgical patients. The correlation between absolute values was determined by linear regression, and the Bland-Altman test for repeated measurements was used to compare bias, precision, and limits of agreement. Changes in lactate measurements were evaluated with a four-quadrant plot and trend interchangeability method (TIM). Results: In the 23 patients analysed, the central venous catheter was used as part of standard care, with no complications. The correlation coefficient for absolute values ( n =104) was 0.96 ( P <0.0001). The bias, precision, and limits of agreement were -0.19, 0.51, and -1.20 to 0.82 mmol litre -1 , respectively. The concordance rate for changes in blood lactate measurements ( n =80) was 94% with the four-quadrant plot. In contrast, the TIM showed that 23 (29) changes in lactate measurements were not interpretable, and among the remaining 57 (71) interpretable changes, 18 (32) were interchangeable, 8 (14) were in the grey zone, and 31 (54) were not interchangeable. Conclusions: Microdialysis with a central venous catheter appears to provide reliable absolute blood lactate values. Although changes in blood lactate measurements showed an excellent concordance rate, changes between the two methods were poorly interchangeable with the TIM. Clinical trial registration: NCT02296593.

Open-water and under-ice seasonal variations in trace element content and physicochemical associations in fluvial bed sediment.

Across the circumpolar world, intensive anthropogenic activities in the southern reaches of many large, northward-flowing rivers can cause sediment contamination in the downstream depositional environment. The influence of ice cover on concentrations of inorganic contaminants in bed sediment (i.e., sediment quality) is unknown in these rivers, where winter is the dominant season. A geomorphic response unit approach was used to select hydraulically diverse sampling sites across a northern test-case system, the Slave River and delta (Northwest Territories, Canada). Surface sediment samples (top 1 cm) were collected from 6 predefined geomorphic response units (12 sites) to assess the relationships between bed sediment physicochemistry (particle size distribution and total organic carbon content) and trace element content (mercury and 18 other trace elements) during open-water conditions. A subset of sites was resampled under-ice to assess the influence of season on these relationships and on total trace element content. Concentrations of the majority of trace elements were strongly correlated with percent fines and proxies for grain size (aluminum and iron), with similar trace element grain size/grain size proxy relationships between seasons. However, finer materials were deposited under ice with associated increases in sediment total organic carbon content and the concentrations of most trace elements investigated. The geomorphic response unit approach was effective at identifying diverse hydrological environments for sampling prior to field operations. Our data demonstrate the need for under-ice sampling to confirm year-round consistency in trace element-geochemical relationships in fluvial systems and to define the upper extremes of these relationships. Whether contaminated or not, under-ice bed sediment can represent a "worst-case" scenario in terms of trace element concentrations and exposure for sediment-associated organisms in northern fluvial systems. Environ Toxicol Chem 2017;36:2916-2924. © 2017 SETAC.

Genetic Characterization of Periphyton Communities Associated with Selenium Bioconcentration and Trophic Transfer in a Simple Food Chain.

A major source of uncertainty in predicting selenium (Se) distribution in aquatic food webs lies in the enrichment factor (EF), the ratio of Se bioconcentration in primary producers and microorganisms relative to the concentration of Se in the surrounding water. It has been well demonstrated that EFs can vary dramatically among individual algal taxa, but data are lacking regarding the influence of periphyton community composition on EFs for a given geochemical form of Se. Therefore, the goals of this study were first to assess whether different periphyton communities could be established in aquaria with the same starting inoculum using different light and nutrient regimes, and second, to determine if the periphyton assemblage composition influences the uptake of waterborne Se (as selenite) and subsequent Se transfer to a model macroinvertebrate primary consumer. Periphyton biofilms were grown in aquaria containing filtered pond water (from Saskatoon, SK) spiked with approximately 20 µg Se/L (mean measured concentration 21.0 ± 1.2 µg Se/L), added as selenite. Five different light and nutrient regimes were applied to the aquaria (three replicates per treatment) to influence biofilm community development. After 6 weeks of biofilm maturation, 40 to 80 immature cultured snails (Stagnicola elodes) were added to each aquarium. The bacterial and algal members of the periphyton community were characterized by targeted metagenomic analyses before and after addition of snails to ensure the snails themselves did not significantly alter the biofilm community. Samples were collected for Se analysis of water, periphyton, and whole-body snail. The nutrient and light treatments resulted in substantially different compositions of the periphytic biofilms, with each being relatively consistent across replicates and throughout the study. Although the aqueous concentration of dissolved Se administered to treatments was constant, uptake by the different periphytic biofilms differed significantly. Both the low-light (61.8 ± 12.1 µg Se/g d.w.) and high-light (30.5 ± 4.7 µg Se/g d.w.) biofilms, which were found to have high proportions of cyanobacteria, contained statistically higher concentrations of Se relative to the other treatments. Furthermore, the concentration of Se in bulk periphyton was predictive of Se bioaccumulation in grazing snails but as an inverse relationship, opposite to expectations. The trophic transfer factor was inversely correlated with periphyton enrichment factor (r = -0.841). A number of different bacterial and algal taxa were correlated (either positively or negatively) with Se accumulation in periphyton biofilm and snails. Recent advancements in genetic methods make it possible to conduct detailed characterization of periphyton assemblages and begin to understand the influence that periphyton composition has on Se biodynamics in aquatic systems.