Isopropylthiol emission by bloom-forming Microcystis: Biochemistry, ecophysiology and semiochemistry of a volatile organosulfur compound.

Microcystis species not only produce toxic cyanobacterial blooms, but can be a significant source of taste and odour. Previous studies have associated foul-smelling volatile organic sulfur compounds (VOSCs) with Microcystis blooms, but have largely attributed these compounds to bacterial bloom decomposition. However, earlier reports of the production of isopropylthio compounds by several Microcystis strains suggests that these cyanobacteria may themselves be a source of these VOSCs. Sulphur compounds have been shown to play important semiochemical roles in algal cell protection and grazer interactions in marine systems, but little is known about the production and chemical ecology of freshwater cyanobacterial VOSCs. To address this knowledge gap, we undertook the first detailed investigation of the biochemistry, ecophysiology and semiochemistry of these compounds and their production by Microcystis, and tested the hypothesis that they act as multifunctional semiochemicals in processes related to cell protection and grazer defence. Using short-term incubations and an adapted headspace-GC-MS technique, we investigated VOSC production by axenic and non-axenic strains, and verified that isopropylthio compounds are in fact produced by these cyanobacteria, identifying 5 isopropyl moiety-containing VOSCs (isopropylthiol (ISH), isopropylmethyl sulfide, isopropyl methyl disulfide, diisopropyl disulfide (ISSI) and diisopropyl trisulfide) as well as methanethiol in three strains. Further studies with the axenic strain Microcystis PCC 7806 using different light regimes, metabolic inhibitors (sodium azide, DCMU), the antioxidant enzyme catalase and stable labelled precursors (hydrogencarbonate, acetates and sulfate) demonstrated that ISH is a true exo-metabolite, synthesized via the acetate pathway. It is actively produced and continuously excreted by the cyanobacteria during growth, with minimal internal storage or post-lysis catalytic generation. The molar ratios of the redox pair ISH/ISSI are not directly involved in the photosynthetic and respiratory electron transport chains, but dependant on the redox state of the cell - likely mediated by reactive oxygen species (ROS), as shown by a marked effect of catalase. These results, along with toxicological and behavioural assays using the two aquatic invertebrates Thamnocephalus platyurus and Daphnia magna indicate that ISH plays multiple important physiological and ecological roles. It acts as an effective antioxidant against high ROS levels, as often experienced in surface blooms, it elicits avoidance-related behavioural responses in grazer communities and at high levels, it can be toxic to some invertebrates.

Spatio-temporal connectivity of the aquatic microbiome associated with cyanobacterial blooms along a Great Lake riverine-lacustrine continuum.

Lake Erie is subject to recurring events of cyanobacterial harmful algal blooms (cHABs), but measures of nutrients and total phytoplankton biomass seem to be poor predictors of cHABs when taken individually. A more integrated approach at the watershed scale may improve our understanding of the conditions that lead to bloom formation, such as assessing the physico-chemical and biological factors that influence the lake microbial community, as well as identifying the linkages between Lake Erie and the surrounding watershed. Within the scope of the Government of Canada's Genomics Research and Development Initiative (GRDI) Ecobiomics project, we used high-throughput sequencing of the 16S rRNA gene to characterize the spatio-temporal variability of the aquatic microbiome in the Thames River-Lake St. Clair-Detroit River-Lake Erie aquatic corridor. We found that the aquatic microbiome was structured along the flow path and influenced mainly by higher nutrient concentrations in the Thames River, and higher temperature and pH downstream in Lake St. Clair and Lake Erie. The same dominant bacterial phyla were detected along the water continuum, changing only in relative abundance. At finer taxonomical level, however, there was a clear shift in the cyanobacterial community, with Planktothrix dominating in the Thames River and Microcystis and Synechococcus in Lake St. Clair and Lake Erie. Mantel correlations highlighted the importance of geographic distance in shaping the microbial community structure. The fact that a high proportion of microbial sequences found in the Western Basin of Lake Erie were also identified in the Thames River, indicated a high degree of connectivity and dispersal within the system, where mass effect induced by passive transport play an important role in microbial community assembly. Nevertheless, some cyanobacterial amplicon sequence variants (ASVs) related to Microcystis, representing less than 0.1% of relative abundance in the upstream Thames River, became dominant in Lake St. Clair and Erie, suggesting selection of those ASVs based on the lake conditions. Their extremely low relative abundances in the Thames suggest additional sources are likely to contribute to the rapid development of summer and fall blooms in the Western Basin of Lake Erie. Collectively, these results, which can be applied to other watersheds, improve our understanding of the factors influencing aquatic microbial community assembly and provide new perspectives on how to better understand the occurrence of cHABs in Lake Erie and elsewhere.

Toxins and Other Bioactive Metabolites in Deep Chlorophyll Layers Containing the Cyanobacteria Planktothrix cf. isothrix in Two Georgian Bay Embayments, Lake Huron.

The understanding of deep chlorophyll layers (DCLs) in the Great Lakes-largely reported as a mix of picoplankton and mixotrophic nanoflagellates-is predominantly based on studies of deep (>30 m), offshore locations. Here, we document and characterize nearshore DCLs from two meso-oligotrophic embayments, Twelve Mile Bay (TMB) and South Bay (SB), along eastern Georgian Bay, Lake Huron (Ontario, Canada) in 2014, 2015, and 2018. Both embayments showed the annual formation of DCLs, present as dense, thin, metalimnetic plates dominated by the large, potentially toxic, and bloom-forming cyanobacteria Planktothrix cf. isothrix. The contribution of P. cf. isothrix to the deep-living total biomass (TB) increased as thermal stratification progressed over the ice-free season, reaching 40% in TMB (0.6 mg/L at 9.5 m) and 65% in South Bay (3.5 mg/L at 7.5 m) in 2015. The euphotic zone in each embayment extended down past the mixed layer, into the nutrient-enriched hypoxic hypolimnia, consistent with other studies of similar systems with DCLs. The co-occurrence of the metal-oxidizing bacteria Leptothrix spp. and bactivorous flagellates within the metalimnetic DCLs suggests that the microbial loop plays an important role in recycling nutrients within these layers, particularly phosphate (PO4) and iron (Fe). Samples taken through the water column in both embayments showed measurable concentrations of the cyanobacterial toxins microcystins (max. 0.4 µg/L) and the other bioactive metabolites anabaenopeptins (max. ~7 µg/L) and cyanopeptolins (max. 1 ng/L), along with the corresponding genes (max. in 2018). These oligopeptides are known to act as metabolic inhibitors (e.g., in chemical defence against grazers, parasites) and allow a competitive advantage. In TMB, the 2018 peaks in these oligopeptides and genes coincided with the P. cf. isothrix DCLs, suggesting this species as the main source. Our data indicate that intersecting physicochemical gradients of light and nutrient-enriched hypoxic hypolimnia are key factors in supporting DCLs in TMB and SB. Microbial activity and allelopathy may also influence DCL community structure and function, and require further investigation, particularly related to the dominance of potentially toxigenic species such as P. cf. isothrix.

Dark adaptation and ability of pulse-amplitude modulated (PAM) fluorometry to identify nutrient limitation in the bloom-forming cyanobacterium, Microcystis aeruginosa (Kützing).

Harmful algal blooms in inland waters are widely linked to excess phosphorus (P) loading, but increasing evidence shows that their growth and formation can also be influenced by nitrogen (N) and iron (Fe). Deficiency in N, P, and Fe differentially affects cellular photosystems and is manifested as changes in photosynthetic yield (Fv/Fm). While Fv/Fm has been increasingly used as a rapid and convenient in situ gauge of nutrient deficiency, there are few rigorous comparisons of instrument sensitivity and ability to resolve specific nutrient stresses. This study evaluated the application of Fv/Fm to cyanobacteria using controlled experiments on a single isolate and tested three hypotheses: i) single Fv/Fm measurements taken with different PAM fluorometers can distinguish among limitation by different nutrients, ii) measurements of Fv/Fm made by the addition of DCMU are comparable to PAM fluorometers, and iii) dark adaptation is not necessary for reliable Fv/Fm measurements. We compared Fv/Fm taken from the bloom-forming Microcystis aeruginosa (UTEX LB 3037) grown in nutrient-replete treatment (R) and N-, P-, and Fe-limited treatments (LN, LP, LFe, respectively), using three pulse-amplitude modulated (PAM) fluorometers and the chemical photosynthesis inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), and evaluated the effects of dark adaptation prior to PAM measurement. There were significant differences in Fv/Fm estimates among PAM fluorometers for light- versus dark-adapted cell suspensions over the whole experiment (21 days), which were all significantly higher than the DCMU-based measurements. However, dark adaptation had no effect on Fv/Fm when comparing PAM-based values across a single nutrient treatment. All Fv/Fm methods could distinguish LN and LP from R and LFe treatments but none were able to resolve LFe from R, or LN from LP cultures. These results indicated that for most PAM applications, dark adaptation is not necessary, and furthermore that single measurements of Fv/Fm do not provide a robust measurement of nutrient limitation in Microcystis aeruginosa UTEX LB 3037, and potentially other, common freshwater cyanobacteria.

The Ecobiomics project: Advancing metagenomics assessment of soil health and freshwater quality in Canada.

Transformative advances in metagenomics are providing an unprecedented ability to characterize the enormous diversity of microorganisms and invertebrates sustaining soil health and water quality. These advances are enabling a better recognition of the ecological linkages between soil and water, and the biodiversity exchanges between these two reservoirs. They are also providing new perspectives for understanding microorganisms and invertebrates as part of interacting communities (i.e. microbiomes and zoobiomes), and considering plants, animals, and humans as holobionts comprised of their own cells as well as diverse microorganisms and invertebrates often acquired from soil and water. The Government of Canada's Genomics Research and Development Initiative (GRDI) launched the Ecobiomics Project to coordinate metagenomics capacity building across federal departments, and to apply metagenomics to better characterize microbial and invertebrate biodiversity for advancing environmental assessment, monitoring, and remediation activities. The Project has adopted standard methods for soil, water, and invertebrate sampling, collection and provenance of metadata, and nucleic acid extraction. High-throughput sequencing is located at a centralized sequencing facility. A centralized Bioinformatics Platform was established to enable a novel government-wide approach to harmonize metagenomics data collection, storage and bioinformatics analyses. Sixteen research projects were initiated under Soil Microbiome, Aquatic Microbiome, and Invertebrate Zoobiome Themes. Genomic observatories were established at long-term environmental monitoring sites for providing more comprehensive biodiversity reference points to assess environmental change.

Mastery learning in a bachelor's of nursing program: the Roseman University of Health Sciences experience.

BACKGROUND: Roseman University of Health Sciences (RUHS) developed and delivers a mastery learning curriculum designed for students to acquire the knowledge and skills to become competent nurses. Despite a trend in nursing education to adopt competency-based education (CBE) models, there is little in the nursing literature about programs based on a mastery model. The aim of this study is to describe an undergraduate nursing program built on a mastery learning model and to report on program outcome measures. METHODS: The 18-month BSN nursing program is divided into blocks, varying in length and focusing on a single subject. Students must demonstrate mastery, defined as ≥90% on an assessment, to pass a block. Recognizing the critical nature of health care, educators seek methods to assure that practitioners become competent to perform the services they provide.Program outcomes reported include comparisons to national standards and RUHS student exit survey data. RESULTS: From 2013 to 2017 the RUHS College of Nursing students' pass rates ranged from 82 to 97% for the National Council Licensure Examination exam compared to national pass rates between 81.8-84.5% during the same time frame. The program completion rate ranged from 86 to 100% and employment rates exceeded accreditation standards. Students reported overall satisfaction with their education as 4.38 and with the block system as 4.74 (5 point Likert scale). CONCLUSIONS: Roseman University's mastery learning model appears successful as measured by high levels of student satisfaction, outcomes on exams, and degree completion when compared to national averages. The results suggest that other nursing and health profession's programs can develop a successful mastery based learning model.

A Multiplex Analysis of Potentially Toxic Cyanobacteria in Lake Winnipeg during the 2013 Bloom Season.

Lake Winnipeg (Manitoba, Canada), the world's 12th largest lake by area, is host to yearly cyanobacterial harmful algal blooms (cHABs) dominated by Aphanizomenon and Dolichospermum. cHABs in Lake Winnipeg are primarily a result of eutrophication but may be exacerbated by the recent introduction of dreissenid mussels. Through multiple methods to monitor the potential for toxin production in Lake Winnipeg in conjunction with environmental measures, this study defined the baseline composition of a Lake Winnipeg cHAB to measure potential changes because of dreissenid colonization. Surface water samples were collected in 2013 from 23 sites during summer and from 18 sites in fall. Genetic data and mass spectrometry cyanotoxin profiles identified microcystins (MC) as the most abundant cyanotoxin across all stations, with MC concentrations highest in the north basin. In the fall, mcyA genes were sequenced to determine which species had the potential to produce MCs, and 12 of the 18 sites were a mix of both Planktothrix and Microcystis. Current blooms in Lake Winnipeg produce low levels of MCs, but the capacity to produce cyanotoxins is widespread across both basins. If dreissenid mussels continue to colonize Lake Winnipeg, a shift in physicochemical properties of the lake because of faster water column clearance rates may yield more toxic blooms potentially dominated by microcystin producers.

Denisovan, modern human and mouse TNFAIP3 alleles tune A20 phosphorylation and immunity.

Resisting and tolerating microbes are alternative strategies to survive infection, but little is known about the evolutionary mechanisms controlling this balance. Here genomic analyses of anatomically modern humans, extinct Denisovan hominins and mice revealed a TNFAIP3 allelic series with alterations in the encoded immune response inhibitor A20. Each TNFAIP3 allele encoded substitutions at non-catalytic residues of the ubiquitin protease OTU domain that diminished IκB kinase-dependent phosphorylation and activation of A20. Two TNFAIP3 alleles encoding A20 proteins with partial phosphorylation deficits seemed to be beneficial by increasing immunity without causing spontaneous inflammatory disease: A20 T108A;I207L, originating in Denisovans and introgressed in modern humans throughout Oceania, and A20 I325N, from an N-ethyl-N-nitrosourea (ENU)-mutagenized mouse strain. By contrast, a rare human TNFAIP3 allele encoding an A20 protein with 95% loss of phosphorylation, C243Y, caused spontaneous inflammatory disease in humans and mice. Analysis of the partial-phosphorylation A20 I325N allele in mice revealed diminished tolerance of bacterial lipopolysaccharide and poxvirus inoculation as tradeoffs for enhanced immunity.

Quantitative evaluation of variables to student success in a mastery learning baccalaureate nursing programme.

AIM: This study evaluated the relationship of student input and throughput variables in a mastery learning baccalaureate nursing programme to licensure success. DESIGN: This study used a quantitative, correlational design. METHODS: Retrospective analysis of records of 367 graduates over a 6-year period tested the relationship of pass rate on the licensing examination to six variables: overall pre-admission grade point average, entrance assessment scores, interview scores, remediation, programme length and exit assessment using point-biserial correlations, and chi-square analysis and logistic regression analysis. RESULTS: Overall pre-admission grade point average, entrance assessment scores, interview scores and exit assessment scores were positively correlated with student success. Although remediation and programme length were not correlated with success, 87% of the students participated in remediation. Most students (95%) successfully passed the Registered Nurse licence examination on their first attempt. While specific criteria were related to student success, further research is needed to determine the role of remediation.

A Bayesian risk assessment framework for microcystin violations of drinking water and recreational standards in the Bay of Quinte, Lake Ontario, Canada.

Freshwater ecosystems can experience harmful algal blooms, which negatively impact recreational uses, aesthetics, taste, and odor in drinking water. Cyanobacterial toxins can have dire repercussions on aquatic wildlife and human health, and the most ubiquitous worldwide are the hepatotoxic compounds known as microcystins. The factors that influence the occurrence and magnitude of cyanobacteria blooms and toxin production vary in space and time and remain poorly understood. It is within this context that we present a suite of statistical models, parameterized with Bayesian inference techniques, to link the retrospective analysis of important environmental factors with the probability of exceedance of threshold microcystin levels. Our modelling framework is applied to the Bay of Quinte, Lake Ontario, Canada; a system with a long history of eutrophication problems. Collectively, 16.1% of the samples of the system collected during the study period (2003-2016) exceeded the drinking water guideline of 1.5 µgL-1, while approximately 3% of recorded values exceeded the recommended recreational threshold of 20 µgL-1. Using a segmented regression model with a stochastic breakpoint of microcystin concentrations estimated at 0.54 µg L-1, we demonstrate that the environmental conditions associated with increased probability of exceedance of the drinking water standard are chlorophyll a concentration ≥7 µg L-1, water temperature ≥20 °C, ammonium concentration ≤40 µgL-1, total phosphorus concentration ≥25 µg L-1, and wind speed ≤37 km h-1. Considering the multitude of factors that can influence the ambient levels of toxins, our study argues that the adoption of probabilistic water quality criteria offers a pragmatic approach to accommodate the associated uncertainty by permitting a realistic frequency of violations. In this context, we present a framework to evaluate the confidence of compliance with probabilistic standards that stipulate less than 10% violations of microcystin threshold ambient levels.

Estimating the economic costs of algal blooms in the Canadian Lake Erie Basin.

Over the past two decades there has been a re-emergence of regular harmful algal blooms in Lake Erie due to increasing phosphorus loading, mainly from non-point agricultural sources. The Canadian and United States governments have jointly agreed to reduce phosphorus loadings to the lake in order to control the extent and severity of the blooms. Citizens on both sides of the border face a number of economic costs, both market and non-market, as a result of the blooms. This study values these costs for the Canadian portion of the Lake Erie basin economy using standard economic approaches that are widely applied within the world of cost-benefit analysis. The results suggest that algal blooms will impose equivalent annual costs equal to $272 million in 2015 prices over a 30-year period if left unchecked. The largest market costs will be imposed on the tourism industry ($110 million in equivalent annual costs) and the largest non-market costs will be borne by recreational users and those who place inherent value on the lake's quality ($115 million in equivalent annual costs). Management action to reduce phosphorus loadings is found to be justified on economic grounds if the 30-year net present value of the reduction program is less than $1294 million (2015 Canadian dollars).

A closely-related clade of globally distributed bloom-forming cyanobacteria within the Nostocales.

In order to better understand the relationships among current Nostocales cyanobacterial blooms, eight genomes were sequenced from cultured isolates or from environmental metagenomes of recent planktonic Nostocales blooms. Phylogenomic analysis of publicly available sequences placed the new genomes among a group of 15 genomes from four continents in a distinct ADA clade (Anabaena/Dolichospermum/Aphanizomenon) within the Nostocales. This clade contains four species-level groups, two of which include members with both Anabaena-like and Aphanizomenon flos-aquae-like morphology. The genomes contain many repetitive genetic elements and a sizable pangenome, in which ABC-type transporters are highly represented. Alongside common core genes for photosynthesis, the differentiation of N2-fixing heterocysts, and the uptake and incorporation of the major nutrients P, N and S, we identified several gene pathways in the pangenome that may contribute to niche partitioning. Genes for problematic secondary metabolites-cyanotoxins and taste-and-odor compounds-were sporadically present, as were other polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) gene clusters. By contrast, genes predicted to encode the ribosomally generated bacteriocin peptides were found in all genomes.

Complement-Dependent Cytotoxicity Assay.

A useful feature of therapeutic antibodies is the ability to kill the cells to which they bind. Antibodies are capable of mediating cell killing in a variety of ways. Apoptosis, complement-mediated mechanisms, and antibody-dependent cellular cytotoxicity are all effects that can be assayed to characterize lead antibody candidates. Extensive, multidose characterizations of a series of candidates can be performed in a short amount of time using assays developed for high-throughput flow cytometry systems. Antibodies that contain the Fc portion of the human IgG1 can activate complement-mediated cell death. One way in which they do this is via direct complement killing of tumor cells by the membrane attack complex, a process usually called complement-dependent cytotoxicity.

Assessment of Antibody-Dependent Cellular Cytotoxicity by Flow Cytometry.

A useful feature of therapeutic antibodies is the ability to kill the cells to which they bind. Antibodies are capable of mediating cell killing in a variety of ways. Apoptosis, complement-mediated mechanisms, and antibody-dependent cellular cytotoxicity (ADCC) are all effects that can be assayed to characterize lead antibody candidates. Extensive, multidose characterizations of a series of candidates can be performed in a short amount of time using assays developed for high-throughput flow cytometry systems. Antibodies that contain the Fc portion of the human IgG1 can activate complement-mediated killing. In the ADCC method described here, cytotoxicity is mediated mostly by natural killer (NK) cells. Thus, if an antibody binds to its target on the surface of a tumor cell, Fc receptors on the surface of the NK cells (effector cells) recognize the bound antibody. This leads to the release of cytotoxic granules containing perforin, granzymes, and interferon γ, a cytokine that can stimulate other cells of the immune system such as T cells.

Simple Multiplexed Antibody-Binding Assay.

This simple protocol tests antibody binding to target antigens on the surface of cells. This assay is powerful because negative controls are built into each well of the screening plates. It can be used to screen crude supernatants from hybridomas, as well as bacterial periplasmic extracts when screening phage libraries. Using cell-permeant dyes allows the negative and positive cell lines to be color-coded and screened in the same well. A variant enzyme-linked immunosorbent assay can be performed where the target antigen is presented on beads.

Assessment of Apoptosis (Programmed Cell Death) by Flow Cytometry.

A useful feature of therapeutic antibodies is the ability to kill the cells to which they bind. Antibodies are capable of mediating cell killing in a variety of ways. Apoptosis, complement-mediated mechanisms, and antibody-dependent cellular cytotoxicity are all effects that can be assayed to characterize lead antibody candidates. Extensive, multidose characterizations of a series of candidates can be performed in a short amount of time using assays developed for high-throughput flow cytometry systems. Here, we describe a simple multiplexed flow assay performed using Annexin V and propidium iodide that measures an early marker of apoptosis. When cells enter apoptosis, phosphatidyl serine (PS), which is normally found on the inside of the cytoplasmic membrane, is found on the extracellular surface of the membrane, thus revealing Annexin V-binding sites. Because binding of Annexin V to PS is calcium dependent, the buffers used for this assay must contain 1 mm calcium. The calcium dependence can also be used to test whether the Annexin V staining is specific. Thus, if the staining is performed in the presence of 1 mm EDTA, binding of Annexin V should be inhibited. The addition of propidium iodide allows subsequent stages of apoptosis and eventual cell death to be distinguished. For flow cytometry, this assay is best performed on suspension cells.

Antibody Screening Using High-Throughput Flow Cytometry.

Because molecular targets addressable with antibody therapeutics are present on the surface of cells or in circulation, they are ideal for screening by cell- or bead-based assays using flow cytometry, a powerful, high-content analysis technique for cells, beads, and other particles in suspension. The ability to analyze thousands of cells per second, combined with multiplexing capabilities, has made this technology indispensable for laboratories performing antibody development work. Advances in this field, particularly in the areas of plate-based sampling and high-throughput flow cytometry, are enabling the use of this technology earlier in the antibody development and discovery process.

Genome sequences of lower Great Lakes Microcystis sp. reveal strain-specific genes that are present and expressed in western Lake Erie blooms.

Blooms of the potentially toxic cyanobacterium Microcystis are increasing worldwide. In the Laurentian Great Lakes they pose major socioeconomic, ecological, and human health threats, particularly in western Lake Erie. However, the interpretation of "omics" data is constrained by the highly variable genome of Microcystis and the small number of reference genome sequences from strains isolated from the Great Lakes. To address this, we sequenced two Microcystis isolates from Lake Erie (Microcystis aeruginosa LE3 and M. wesenbergii LE013-01) and one from upstream Lake St. Clair (M. cf aeruginosa LSC13-02), and compared these data to the genomes of seventeen Microcystis spp. from across the globe as well as one metagenome and seven metatranscriptomes from a 2014 Lake Erie Microcystis bloom. For the publically available strains analyzed, the core genome is ~1900 genes, representing ~11% of total genes in the pan-genome and ~45% of each strain's genome. The flexible genome content was related to Microcystis subclades defined by phylogenetic analysis of both housekeeping genes and total core genes. To our knowledge this is the first evidence that the flexible genome is linked to the core genome of the Microcystis species complex. The majority of strain-specific genes were present and expressed in bloom communities in Lake Erie. Roughly 8% of these genes from the lower Great Lakes are involved in genome plasticity (rapid gain, loss, or rearrangement of genes) and resistance to foreign genetic elements (such as CRISPR-Cas systems). Intriguingly, strain-specific genes from Microcystis cultured from around the world were also present and expressed in the Lake Erie blooms, suggesting that the Microcystis pangenome is truly global. The presence and expression of flexible genes, including strain-specific genes, suggests that strain-level genomic diversity may be important in maintaining Microcystis abundance during bloom events.

Algal bloom response and risk management: On-site response tools.

Harmful algal blooms caused by cyanobacteria can present a risk to the safety of drinking- and recreational waters and beachfronts through the production of toxins, particularly microcystin, which are highly resilient to degradation. These blooms are difficult to predict, vary in appearance and toxicity, and can show significant spatial heterogeneity: wind- and current-borne scums can produce an order of magnitude range in toxin levels along shorelines. The growing demand for reliable, cost-effective and rapid methods to detect toxins in bloom material and reduce the risk of public exposure cannot be met by most analytical lab turnaround times. Commercial microcystin test kits are now available, but few have been rigorously field-tested or incorporated into monitoring programmes. Working with a local health agency, we evaluated two kits with different operative ranges of detection, applied to samples covering a wide range of water quality, sample matrices, and bloom composition. We compared their performance against lab analyses using Enzyme-Linked Immunosorbent and Protein Phosphatase Inhibition assays. Both kits could resolve samples with high (<10 µg/L microcystin equivalents (MCequiv)) and low/no toxins, but failed to reliably detect toxin levels between 1 and 5 µg/L, at which threshold there were few false negatives (8%) but âˆ¼ one third of the samples (32%) yielded false positives. We conclude that these kits are potentially useful for screening and informed risk management decisions e.g. on beach closures, but should be followed up with more rigorous tests where needed. We describe how, based on these results, the kits have been successfully incorporated into the routine municipal beach monitoring and advisory programme by the Hamilton Public Health Services (Ontario).

Malodorous volatile organic sulfur compounds: Sources, sinks and significance in inland waters.

Volatile Organic Sulfur Compounds (VOSCs) are instrumental in global S-cycling and greenhouse gas production. VOSCs occur across a diversity of inland waters, and with widespread eutrophication and climate change, are increasingly linked with malodours in organic-rich waterbodies and drinking-water supplies. Compared with marine systems, the role of VOSCs in biogeochemical processes is far less well characterized for inland waters, and often involves different physicochemical and biological processes. This review provides an updated synthesis of VOSCs in inland waters, focusing on compounds known to cause malodours. We examine the major limnological and biochemical processes involved in the formation and degradation of alkylthiols, dialkylsulfides, dialkylpolysulfides, and other organosulfur compounds under different oxygen, salinity and mixing regimes, and key phototropic and heterotrophic microbial producers and degraders (bacteria, cyanobacteria, and algae) in these environs. The data show VOSC levels which vary significantly, sometimes far exceeding human odor thresholds, generated by a diversity of biota, biochemical pathways, enzymes and precursors. We also draw attention to major issues in sampling and analytical artifacts which bias and preclude comparisons among studies, and highlight significant knowledge gaps that need addressing with careful, appropriate methods to provide a more robust understanding of the potential effects of continued global development.