A competitive, bead-based assay combined with microfluidics for multiplexed toxin detection.

The requirement for rapid, in-field detection of cyanotoxins in water resources necessitates the developing of an easy-to-use and miniaturized system for their detection. We present a novel bead-based, competitive fluorescence assay for multiplexed detection of two types of toxins: microcystin-LR (MC-LR) and okadaic acid (OA). To automate the detection process, a reusable microfluidic device, termed toxin-chip, was designed and validated. The toxin-chip consists of a micromixer where the target toxins were efficiently mixed with a reagent solution, and a detection chamber for magnetic retainment of beads for downstream analysis. Quantum dots (QDs) were used as the reporter molecules to enhance the sensitivity of the assay and the emitted fluorescence signal from QDs was reversely proportional to the amount of toxins in the solution. An image analysis program was also developed to further automate the detection and analysis steps. Two toxins were simultaneously analyzed on a single microfluidic chip, and the device exhibited a low detection limit of 10-4 µg ml-1 for MC-LR and 4 × 10-5 µg ml-1 for OA detection. The bead-based, competitive assay also showed remarkable chemical specificity against potential interfering toxins. We also validated the device performance using natural lake water samples from Sunfish Lake of Waterloo. The toxin-chip holds promise as a versatile and simple quantification tool for cyanotoxin detection, with the potential of detecting more toxins.

Ecosystem responses of shallow thermokarst lakes to climate-driven hydrological change: Insights from long-term monitoring of periphytic diatom community composition at Old Crow Flats (Yukon, Canada).

Shallow waterbodies are abundant in Arctic and subarctic landscapes where they provide productive wildlife habitat and hold cultural and socioeconomic importance for Indigenous communities. Their vulnerability to climate-driven hydrological and limnological changes enhances a need for long-term monitoring data capable of tracking aquatic ecosystem responses. Here, we evaluate biological and inferred physicochemical responses associated with a rise in rainfall-generated runoff and increasingly positive lake water balances in Old Crow Flats (OCF), a 5600 km2 thermokarst landscape in northern Yukon. This is achieved by analyzing periphytic diatom community composition in biofilms accrued on artificial-substrate samplers at 14 lakes collected mostly annually during 2008-2019 CE. Results reveal that diatom communities at 10 of the 14 lakes converged toward a composition typical of lakes with rainfall-dominated input waters. These include six of nine lakes that were not initially dominated by rainfall input. The shifts in diatom community composition infer rise of lake-water pH and ionic content, and they reveal that northern shallow lake ecosystems are responsive to climate-driven increases in rainfall. Based on data generated during the 12 -year-long monitoring period, we conclude that lakes located centrally within OCF are most vulnerable to rapid climate-driven hydroecological change due to flat terrain, larger lake surface area, and sparse terrestrial vegetation, which provide less resistance to lake expansion, shoreline erosion, and sudden drainage. This information assists the local Indigenous community and natural resource stewardship agencies to anticipate changes to traditional food sources and inform adaptation options.

Episodic loadings of phosphorus influence growth and composition of benthic algae communities in artificial stream mesocosms.

Phosphorus (P) is an essential macronutrient for algal communities, but in excess can exacerbate stream eutrophication. However, P loadings to streams vary temporally from continuous to episodic as a result of inputs from point and non-point sources, respectively. P loading pattern can thus alter the temporal availability of P and may influence effects of P enrichment on algal communities. We assessed how P loading pattern influences algal biomass and composition by conducting a 29-day P enrichment experiment in nine artificial streams exposed to either: (1) continuous P enrichment; (2) episodic P enrichment, or; (3) no P enrichment. P enrichment increased algal biomass accrual, but peak biomass did not differ between continuously and episodically enriched treatments. Maximum absolute growth rates were also comparable between P enriched treatments. However, episodic P additions sustained elevated rates of biomass accrual, whereas absolute growth rates in the continuously enriched communities declined towards the end of the experiment. P enrichment resulted in comparable increases in relative abundance of chlorophytes and decreased proportions of bacillariophytes and charophytes in algal communities for continuously and episodically enriched treatments. However, composition of bacillariophyte (diatom) assemblages differed significantly among all P enrichment treatments in accordance with species autecological attributes for P. Our results demonstrate that episodic and continuous P enrichment may augment algal biomass similarly. Yet, P loading pattern regulated the composition of algal communities. Thus, remedial management strategies for the control of nuisance algae production may require focus on the predominant source of P to streams. Finally, species specific responses of diatom assemblages to P enrichment and associated loading patterns suggests this taxonomic group may have potential as diagnostic indicators for identifying the presence of key nutrient sources associated with eutrophication of stream ecosystems.

Development and application of benthic algal reference condition models to assess stream condition in the South Nahanni Watershed.

Monitoring biologists continually strive to improve the effectiveness of protocols to quantify environmental and ecological effects of anthropogenic activities. We developed and applied a reference condition approach (RCA) model to assess the ability of 3 descriptors of algal community structure (algal taxonomy, diatom taxonomy, and algal pigments) to identify impairment in 2 northern rivers in the South Nahanni River Watershed, Northwest Territories, Canada. We established reference conditions by sampling 62 regional reference (i.e., minimally disturbed) sites in 2008 (n = 44) and 2009 (n = 18) and assessed the condition of 38 test sites downstream of 2 mines in 2008 (N = 20 sites) and 2009 (N = 18 sites). Patterns of impairment downstream of the 2 mines were assessed and zones of influence were identified for each algal descriptor. Results showed that the 3 RCA models using the 3 descriptors of algal community structure identified reasonably consistent assessments downstream of Prairie Creek mine with changes in algal pigments being more sensitive than the other 2 descriptors. In Flat River, however, assessment of test sites varied considerably depending on the descriptor of algal community structure. Our results suggest that benthic algal RCA models show promise as biological monitoring tools, but additional investigations are required to better understand variance in site assessments among the 3 algal community descriptors. Integr Environ Assess Manag 2017;13:728-745. © 2016 SETAC.

Relations between water physico-chemistry and benthic algal communities in a northern Canadian watershed: defining reference conditions using multiple descriptors of community structure.

Defining reference conditions is central to identifying environmental effects of anthropogenic activities. Using a watershed approach, we quantified reference conditions for benthic algal communities and their relations to physico-chemical conditions in rivers in the South Nahanni River watershed, NWT, Canada, in 2008 and 2009. We also compared the ability of three descriptors that vary in terms of analytical costs to define algal community structure based on relative abundances of (i) all algal taxa, (ii) only diatom taxa, and (iii) photosynthetic pigments. Ordination analyses showed that variance in algal community structure was strongly related to gradients in environmental variables describing water physico-chemistry, stream habitats, and sub-watershed structure. Water physico-chemistry and local watershed-scale descriptors differed significantly between algal communities from sites in the Selwyn Mountain ecoregion compared to sites in the Nahanni-Hyland ecoregions. Distinct differences in algal community types between ecoregions were apparent irrespective of whether algal community structure was defined using all algal taxa, diatom taxa, or photosynthetic pigments. Two algal community types were highly predictable using environmental variables, a core consideration in the development of Reference Condition Approach (RCA) models. These results suggest that assessments of environmental impacts could be completed using RCA models for each ecoregion. We suggest that use of algal pigments, a high through-put analysis, is a promising alternative compared to more labor-intensive and costly taxonomic approaches for defining algal community structure.

Evaluating the use of algal pigments to assess the biological condition of streams.

Assessments of stream condition using benthic algal communities have traditionally relied on taxonomy-based approaches to compare community structure at sites exposed to a stressor versus reference sites. Taxonomy-based methods are often effective, but they require high levels of training and are relatively time consuming and expensive. We examined the utility of assessing stream biological condition using algal pigments. We used gradient and control-impact study designs in 2008 and 2009 to compare the extent that algal pigments versus taxonomic descriptors of algal community structure varied along a 10.5-km stretch of the Flat River (South Nahanni River watershed, NWT, Canada) encompassing a gradient of nutrients and metals at sites upstream, adjacent to and downstream of a northern metals mine. We also calculated costs to quantify algal pigments relative to taxonomy-based methods. Multivariate analyses (ANOSIM tests, redundancy analysis) identified that pigment concentrations from benthic algal samples differed significantly (p < 0.05) between non-exposed and exposed river sites and were related to variations in water physico-chemical conditions. By contrast, community composition determined from taxonomy-based enumeration to the Order and Family levels did not differ significantly between non-exposed and exposed sites, and relations with water physico-chemical conditions were weaker and inconsistent between the study years. In-house costs to quantify algal pigments were lower than commercial rates to describe community structure using taxonomy. Thus, our data suggests that analysis of benthic algal pigments represents a viable and cost-effective bio-monitoring method for assessing anthropogenic effects on stream condition that merits further evaluation.

Colon perforation secondary to porphyria.

Acute intermittent porphyria (AIP) is a rare, inherited metabolic disorder of the haem biosynthesis pathway. The diagnosis is well known to cause significant diagnostic challenge due to its broad range of symptoms that may mimic many other conditions. We report a case of AIP that presented with caecal perforation, a clinical scenario that has not previously been reported in the literature.

Conversion diversion: participation in a social HMO reduces the likelihood of converting from short-stay to long-stay nursing facility placement.

OBJECTIVES: To determine the effect of a Social Health Maintenance Organization (S/HMO) on diverting older adults admitted into a nursing facility from converting to long-stay placement. DESIGN: Members of the SCAN S/HMO and those in Medicare Fee-For-Service were compared on successful discharge to the community after being admitted to nursing facilities between January 1, 2001, and December 31, 2003. SETTING: Skilled nursing facilities in 4 counties in Southern California (Los Angeles, Orange, San Bernardino, Riverside). PARTICIPANTS: Data (N = 4635) were extracted from Minimum Data Set (MDS) 2.0 records for nursing facility residents in the S/HMO or the Medicare Fee-for-Service 5% sample who were aged 65 and older with an episode of care greater than 14 days. MEASUREMENTS: Predisposing, enabling, and need measures were used to predict successful discharge to the community within 90 days. RESULTS: After controlling for selected sociodemographics, comorbidities, behavioral issues, mental health conditions, and other risk factors, being enrolled in the S/HMO increased the likelihood of successful discharge by 26%. CONCLUSION: With systemic increases in short-stay patients, research on diversion must look past the avoidance of unnecessary entry to nursing facilities, to the successful transition of short-stay residents to the community. As described in this study, the S/HMO model is an important but largely unaddressed method of avoiding the conversion to long-stay.