Emerging Lyngbya wollei toxins: A new high resolution mass spectrometry method to elucidate a potential environmental threat

Algae impacted drinking water: Does switching to chloramination produce safer drinking water?

Harmful algal (cyanobacterial) blooms (HABs) are increasing throughout the world. HABs can be a direct source of toxins in freshwater sources, and associated algal organic matter (AOM) can act as precursors for the formation of disinfection by-products (DBPs) in drinking water. This study investigated the impacts of algae on DBP formation using treatment with chloramine, which has become a popular disinfectant in the U.S. and in several other countries because it can significantly lower the levels of regulated DBPs formed. Controlled laboratory chloraminations were conducted using live field-collected algal biomass dominated by either Phormidium sp. or Microseira wollei (formerly known as Lyngbya wollei) collected from Lake Wateree and Lake Marion, SC. Sixty-six priority, unregulated or regulated DBPs were quantified using gas chromatography (GC)-mass spectrometry (MS). The presence of HAB-dominated microbial communities in source waters led to significant increases in more toxic nitrogen-containing DBPs (1.5-5 fold) relative to lake waters collected in HAB-free waters. Compared to chlorinated Phormidium-impacted waters, chloraminated waters yielded lower total DBP levels (up to 123 μg/L vs. 586 μg/L for low Br^-/I^- waters), but produced a greater number of brominated, iodinated, and mixed halogenated DBPs in high Br^-/I^- waters. Among the DBPs formed in Phormidium-impacted chloraminated waters, dichloroacetic acid, trichloromethane, chloroacetic acid, chloropropanone, and dichloroacetamide were dominant. For Microseira wollei-impacted chloraminated waters, total DBP concentrations ranged from 33 to 145 μg/L (approximately 3-5 times lower than chlorination), with dichloroacetic acid, dichloroacetamide, and trichloromethane dominant. Overall, chloramination significantly reduced calculated cytotoxicity and genotoxicity in low Br^- and I^- waters, but produced 1.3 fold higher calculated cytotoxicity (compared to chlorine) with high Br^-/I^- waters due to increased formation of more toxic iodo- and mixed halogenated DBPs.

Shoreline Drying of Microseira (Lyngbya) wollei Biomass Can Lead to the Release and Formation of Toxic Saxitoxin Analogues to the Water Column

The harmful, filamentous cyanobacteria Microseira (Lyngbya) wollei produces several toxic analogues of saxitoxin (Lyngbya wollei toxins 1-6, or LWTs 1-6), grows in shallow water, and can deposit significant biomass on nearby shorelines. Here, we show that the LWTs are stable in the biomass during subsequent drying but that the process facilitates the later release of LWTs upon return to the water column. Under basic conditions, LWTs hydrolyzed to generate products that were significantly more neurotoxic than the initial toxins. Aqueous LWTs were subjected to conditions of covarying temperature and pH, and their degradation rates and products were determined at each condition. LWTs 1, 5, and 6 degraded faster at pH ≥ 8 at all temperatures. Their degradation products, which included decarbamoyl saxitoxin and LWT 4, were consistent with a base-catalyzed hydrolysis mechanism and represented a net increase in total biomass toxicity normalized against the equivalent toxicity of saxitoxin. The corresponding pre-exponential terms and activation energies for hydrolysis were obtained for pH 6-10 over the temperature range 10-40 °C. A locally weighted scatterplot smoothing (LOWESS) regression was developed to predict the loss of parent toxins and subsequent products in the water column under conditions corresponding to those commonly encountered in cyanobacterial blooms.

Growth of the harmful benthic cyanobacterium Microseira wollei is driven by legacy sedimentary phosphorous

Models for cyanobacterial harmful algae blooms (cHABs) in fresh waters are usually predicated on the relationship between cyanobacterial ecology and dissolved nutrients, particularly phosphorous. Here we show legacy sediment-associated phosphorous as the primary driver of a benthic cHAB, not phosphorous in the water column. Biogeographical surveys by teams of citizen science volunteers working with the University of South Carolina identified over 200 distinct mats of Microseira wollei in Lake Wateree, SC based on toxin characterization. In sum these were estimated to affect approximately 175 km of the lake's shoreline. This growth occurred under water quality conditions that were near or below the regulatory total maximum daily load for phosphorous and nitrogen. A series of established predictive models for cyanobacterial biomass growth were applied retroactively to match the measured growth with measured water quality parameters. The only component of the system that successfully predicted microbial biomass was sedimentary phosphorous. Concentrations of the Lyngbya wollei toxins (LWTs) 1, 4, 5, and 6 were determined at multiple sites over an 18-month period and a toxin inventory for the lake was calculated. Toxin profiles between sites differed at the 95% level of confidence, establishing each site as a unique mat. An empirical model of toxin production potential based on sedimentary phosphorous was developed.

Microseira wollei and Phormidium algae more than doubles DBP concentrations and calculated toxicity in drinking water

Warm weather and excess nutrients from agricultural runoff trigger harmful algal blooms, which can affect drinking water safety due to the presence of algal toxins and the formation of disinfection by-products (DBPs) during drinking water treatment. In this study, 66 priority, unregulated and regulated DBPs were quantified in chlorinated controlled laboratory reactions of harmful algae Microseira wollei (formerly known as Lyngbya wollei) and Phormidium using gas chromatography (GC)-mass spectrometry (MS). Live algae samples collected from algae-impacted lakes in South Carolina were chlorinated in both ultrapure water and real source waters containing natural organic matter. DBPs were also measured in finished water from a real drinking water plant impacted by a Microseira bloom. Results show that the presence of Microseira and Phormidium more than doubles total concentrations of DBPs formed by chlorination, with levels up to 586 μg/L formed in natural lake waters. Toxic nitrogen-containing DBPs also more than doubled in concentration, with levels up to 36.1, 3.6, and 37.9 μg/L for haloacetamides, halonitromethanes, and haloacetonitriles, respectively. In ultrapure water, DBPs also formed up to 314 μg/L when algae was chlorinated, demonstrating their ability to serve as direct precursors for these DBPs. When environmentally relevant levels of bromide and iodide were added to chlorination reactions, total DBPs increased 144, 51, and 24% for drinking water reservoir, Lake Marion and Lake Wateree Microseira respectively and 29% for Phormidium. Iodo-DBPs, bromochloroiodomethane, chloroiodoacetic acid, bromoiodoacetic acid, and diiodoacetic acid were observed in finished water from a drinking water plant impacted by Microseira, and bromochloroiodomethane and dibromoiodomethane were observed in chlorinated ultrapure water containing algae, bromide, and iodide. Notably, total calculated cytotoxicity tripled in Microseira-impacted waters and doubled for Phormidium-impacted waters. Calculated genotoxicity doubled for Microseira-impacted waters and more than doubled in Phormidium-impacted waters. Haloacetonitriles were major drivers of calculated cytotoxicity in algae-impacted waters, while haloacetic acids were major drivers of calculated genotoxicity in algae-impacted waters. These results provide the most extensive assessment of DBPs formed from chlorination of algae-impacted waters and highlight potential impacts to drinking water and human health. Results from this study are particularly applicable to drinking water treatment plants that employ pre-chlorination, which can cause the release of algal organic matter (AOM) precursors to form DBPs.

Substratum-associated microbiota

Highlights of new, interesting, and emerging research findings on substratum-associated microbiota covered from a survey of 2019 literature from primarily freshwaters provide insight into research trends of interest to the Water Environment Federation and others interested in benthic, aquatic environments. Coverage of topics on bottom-associated or attached algae and cyanobacteria, though not comprehensive, includes new methods, taxa new-to-science, nutrient dynamics, auto- and heterotrophic interactions, grazers, bioassessment, herbicides and other pollutants, metal contaminants, and nuisance, and bloom-forming and harmful algae. Coverage of bacteria, also not comprehensive, focuses on the ecology of benthic biofilms and microbial communities, along with the ecology of microbes like Caulobacter crescentus, Rhodobacter, and other freshwater microbial species. Bacterial topics covered also include metagenomics and metatranscriptomics, toxins and pollutants, bacterial pathogens and bacteriophages, and bacterial physiology. Readers may use this literature review to learn about or renew their interest in the recent advances and discoveries regarding substratum-associated microbiota. PRACTITIONER POINTS: This review of literature from 2019 on substratum-associated microbiota presents highlights of findings on algae, cyanobacteria, and bacteria from primarily freshwaters. Coverage of algae and cyanobacteria includes findings on new methods, taxa new to science, nutrient dynamics, auto- and heterotrophic interactions, grazers, bioassessment, herbicides and other pollutants, metal contaminants, and nuisance, bloom-forming and harmful algae. Coverage of bacteria includes findings on ecology of benthic biofilms and microbial communities, the ecology of microbes, metagenomics and metatranscriptomics, toxins and pollutants, bacterial pathogens and bacteriophages, and bacterial physiology. Highlights of new, noteworthy and emerging topics build on those from 2018 and will be of relevance to the Water Environment Federation and others interested in benthic, aquatic environments.