High Levels of Anabaenopeptins Detected in a Cyanobacteria Bloom from N.E. Spanish Sau-Susqueda-El Pasteral Reservoirs System by LC–HRMS

Authors

Cintia Flores and Josep Caixach

The appearance of a bloom of cyanobacteria in the Sau-Susqueda-El Pasteral system (River Ter, NE Spain) in the autumn of 2015 has been the most recent episode of extensive bloom detected in Catalonia. This system is devoted mainly to urban supply, regulation of the river, irrigation and production of hydroelectric energy. In fact, it is one of the main supply systems for the metropolitan area of cities such as Barcelona and Girona. An assessment and management plan was implemented in order to minimize the risk associated to cyanobacteria. The reservoir was confined and periodic sampling was carried out. Low and high toxicity was detected by cell bioassays with human cell lines. Additionally, analysis studies were performed by enzyme-linked immunosorbent assay (ELISA) and liquid chromatography–high resolution mass spectrometry (LC–HRMS). A microcystin target analysis and suspect screening of microcystins, nodularins, cylindrosperpmopsin and related cyanobacterial peptides by LC–HRMS were applied. The results for the analysis of microcystins were negative (<0.3 μg/L) in all the surface samples. Only traces of microcystin-LR, -RR and -dmRR were detected by LC–HRMS in a few ng/L from both fractions, aqueous and sestonic. In contrast, different anabaenopeptins and oscillamide Y at unusually high concentrations (µg-mg/L) were observed. To our knowledge, no previous studies have detected these bioactive peptides at such high levels. The reliable identification of these cyanobacterial peptides was achieved by HRMS. Although recently these peptides are detected frequently worldwide, these bioactive compounds have received little attention. Therefore, more studies on these substances are recommended, especially on their toxicity, health risk and presence in water resources.

Microbial community successions and their dynamic functions during harmful cyanobacterial blooms in a freshwater lake

Authors

Hanyan Li, Mike Barber, Jingrang Lu, Ramesh Goel

The current study reports the community succession of different toxin and non-toxin producing cyanobacteria at different stages of cyanobacterial harmful algal blooms (CyanoHABs) and their connectivity with nitrogen and phosphorus cycles in a freshwater lake using an ecogenomics framework. Comprehensive high throughput DNA sequencing, water quality parameter measurements, and functional gene expressions over temporal and spatial scales were employed. Among the cyanobacterial community, the lake was initially dominated by Cyanobium during the months of May, June, and early July, and later primarily by Aphanizomenon and Dolichospermum depicting functional redundancy. Finally, Planktothrix appeared in late August and then the dominance switched to Planktothrix in September. Microcystis aeruginosa and Microcystis panniformis; two species responsible for cyanotoxin production, were also present in August and September, but in significantly smaller relative abundance. MC-LR (0.06–1.32 µg/L) and MC-RR (0.01–0.26 µg/L) were two major types of cyanotoxins detected. The presence of MC-LR and MC-RR were significantly correlated with the Microcystis-related genes (16SMic/mcyA/mcyG) and their expressions (r = 0.33 to 0.8, p < 0.05). The metabolic analyses further linked the presence of different cyanobacterial groups with distinct functions. The nitrogen metabolisms detected a relatively higher abundance of nitrite/nitrate reductase in early summer, indicating significant denitrification activity and the activation of N-fixation in the blooms dominated by Aphanizomenon/Dolichospermum (community richness) during nutrient-limited conditions. The phosphorus and carbohydrate metabolisms detected a trend to initiate a nutrient starvation alert and store nutrients from early summer, while utilizing the stored polyphosphate and carbohydrate (PPX and F6PPK) during the extreme ortho-P scarcity period, mostly in August or September. Specifically, the abundance of Aphanizomenon and Dolichospermum was positively correlated with the nitrogen-fixing nif gene and (p < 0.001) and the PPX enzyme for the stored polyphosphate utilization (r = 0.77, p < 0.001). Interestingly, the lake experienced a longer N-fixing period (2–3 months) before non-fixing cyanobacteria (Planktothrix) dominated the entire lake in late summer. The Provo Bay site, which is known to be nutrient-rich historically, had early episodes of filamentous cyanobacteria blooms compared to the rest of the lake.

Toxic benthic freshwater cyanobacterial proliferations: Challenges and solutions for enhancing knowledge and improving monitoring and mitigation

Authors

Susanna A. Wood Laura T. Kelly Keith Bouma‐Gregson Jean‐François Humbert Haywood Dail Laughinghouse IV James Lazorchak Tara G. McAllister Andrew McQueen Kaytee Pokrzywinski Jonathan Puddick Catherine Quiblier Laura A. Reitz Ken G. Ryan Yvonne Vadeboncoeur Arthur Zastepa Timothy W. Davis

1. This review summarises knowledge on the ecology, toxin production, and impacts of toxic freshwater benthic cyanobacterial proliferations. It documents monitoring, management, and sampling strategies, and explores mitigation options.
2. Toxic proliferations of freshwater benthic cyanobacteria (taxa that grow attached to substrates) occur in streams, rivers, lakes, and thermal and meltwater ponds, and have been reported in 19 countries. Anatoxin‐ and microcystin‐containing mats are most commonly reported (eight and 10 countries, respectively).
3. Studies exploring factors that promote toxic benthic cyanobacterial proliferations are limited to a few species and habitats. There is a hierarchy of importance in environmental and biological factors that regulate proliferations with variables such as flow (rivers), fine sediment deposition, nutrients, associated microbes, and grazing identified as key drivers. Regulating factors differ among colonisation, expansion, and dispersal phases.
4. New ‐omics‐based approaches are providing novel insights into the physiological attributes of benthic cyanobacteria and the role of associated microorganisms in facilitating their proliferation.
5. Proliferations are commonly comprised of both toxic and non‐toxic strains, and the relative proportion of these is the key factor contributing to the overall toxin content of each mat.
6. While these events are becoming more commonly reported globally, we currently lack standardised approaches to detect, monitor, and manage this emerging health issue. To solve these critical gaps, global collaborations are needed to facilitate the rapid transfer of knowledge and promote the development of standardised techniques that can be applied to diverse habitats and species, and ultimately lead to improved management.

 

Vertical heterogeneities of cyanobacteria and microcystin concentrations in lakes using a seasonal In situ monitoring station

Authors

A.A. Wilkinson, M. Hondzo, M. Guala

A high frequency, high resolution, seasonal research station was deployed to quantify a wide range of local meteorological conditions, water temperature, and water chemistry, including phycocyanin, in two different eutrophic stratified Minnesota lakes. The monitoring effort was coupled with discrete weekly sampling measuring nutrients, cyanobacteria composition, and microcystin concentrations. Our objective was to describe the vertical and seasonal distributions of cyanobacteria biovolume (BV) and microcystin concentrations (MC) using physical lake variables. Two types of BV distributions were observed above the thermocline upward in the water column. The first distribution depicted BV uniformly distributed over the diurnal surface layer (h_SL), and the second BV distribution displayed local BV maxima. A quantitative relationship was developed to determine the anticipation of observing a uniform distribution as a function of the surface layer Reynolds number (Re_SL), the dimensionless ratio of inertial to viscous forces. The uniform distribution was observed systematically for Re_SL > 50,000. MC was observed to accumulate above the thermocline and have a vertical distribution similar to BV, thus depending on Re_SL. This is important for directing sampling efforts, because it narrows the range of BV and MC heterogeneity above the thermocline, and suggests a vertical sampling protocol to detect potential maxima and compute representative depth-average concentrations. We explored the temporal variability of the MC to BV ratio, spatially averaged in the epilimnion (MC_ep/BV_ep). The maximum MC_ep/BV_ep occurred before the maximum BV_ep and specifically, during the onset of significant biomass growth in both lakes. This observation is notable because the maximum MC_ep occurs before the visual signs of enhanced cyanobacterial accrual are less recognizable to the public and to monitoring efforts. Our findings could have important implications for predicting MC distribution and guiding monitoring strategies for quantifying MC concentrations in small stratified lakes.

Improved detection of mcyA genes and their phylogenetic origins in harmful algal blooms

Authors

Jaejin Lee, Jinlyung Choi, Micah Fatka, Elizabeth Swanner, Kaoru Ikuma, Xuewei Liang, Tania Leung, Adina Howe

Microcystins, a group of cyanotoxins produced by cyanobacterial strains, have become a significant microbial hazard to human and animal health due to increases in the frequency and intensity of cyanobacterial harmful algal blooms (CyanoHABs). Many studies have explored the correlation between microcystin concentrations and abundances of toxin-producing genes (e.g., mcyA genes) measured using quantitative PCR, and discrepancies between toxin concentrations and gene abundances are often observed. In this study, the results show that these discrepancies are at least partially due to primer sets that do not capture the phylogenetic diversity of naturally present toxin-producers. We designed three novel primer gene probes based on known mcyA genes to improve the detection and quantification of these genes in environmental samples. These primers were shown to improve the identification of mcyA genes compared to previously published primers in freshwater metagenomes, cyanobacterial isolates, and lake water samples. Unlike previously published primers, our primer sets could selectively amplify and resolve Microcystis, Anabaena, and Planktothrix mcyA genes. In lake water samples, abundance estimations of mcyA genes were found to correlate strongly with microcystin concentrations. Based on our results, these primers offer significant improvements over previously published probes to accurately identify and quantify mcyA genes in the environment. There is an increasing need to develop models based on microbial information and environmental factors to predict CyanoHABs, and improved primers will play an important role in aiding monitoring efforts to collect reliable and consistent data on toxicity risks.

Strong turbulence benefits toxic and colonial cyanobacteria in water: A potential way of climate change impact on the expansion of Harmful Algal Blooms

Authors

Mengzi Liu, Jianrong Ma, Li Kang, Yanyan Wei, Qiang He, Xuebin Hu, Hong Li

Extreme natural events such as typhoons can amplify the effect of hydrodynamics on the lake ecosystems. Here we presented data on the effect of typhoons on algal cell size based on field observation. Then turbulence simulation systems were used to decipher the response of natural phytoplankton communities to a range of turbulence regimes (linked to typhoon-induced turbulence intensity) under laboratory conditions. Turbulence intensities of 6.17 × 10−3, 1.10 × 10−2 and 1.80 × 10−2 m2/s3 benefited algal growth and triggered abrupt switches from unicellular Chlorella dominated to colonial Microcystis dominance, and the abundance of colonial algae depended on the turbulence intensity. Under the influence of elevated turbulence, Microcystis dominated biomass increased by 2.60–6.58 times compared with that of Chlorella. At a given phytoplankton density and community composition, we observed a significant increase in extracellular microcystins (MCs) and a 47.5-fold increase in intracellular MCs with intensified turbulent mixing, suggesting that the damage of algal cells concomitantly the stimulation of toxin-producing Microcystis. Our results confirmed that the formation of large colonial algal cells, enhancement of the succession of algal species, and most importantly, the induction of toxin-producing Microcystis, were the active adaption strategy when phytoplankton were impacted by strong turbulence. The result implies that the ongoing climates changes and typhoon events are likely to contribute to undesirable outcomes concerning phytoplankton populations.

Perspective: Advancing the research agenda for improving understanding of cyanobacteria in a future of global change

Authors

M.A. Burford, C.C. Carey, D.P. Hamilton, J. Huisman, H.W. Paerl, S.A. Wood, A. Wulff

Harmful cyanobacterial blooms (=cyanoHABs) are an increasing feature of many waterbodies throughout the world. Many bloom-forming species produce toxins, making them of particular concern for drinking water supplies, recreation and fisheries in waterbodies along the freshwater to marine continuum. Global changes resulting from human impacts, such as climate change, over-enrichment and hydrological alterations of waterways, are major drivers of cyanoHAB proliferation and persistence. This review advocates that to better predict and manage cyanoHABs in a changing world, researchers need to leverage studies undertaken to date, but adopt a more complex and definitive suite of experiments, observations, and models which can effectively capture the temporal scales of processes driven by eutrophication and a changing climate. Better integration of laboratory culture and field experiments, as well as whole system and multiple-system studies are needed to improve confidence in models predicting impacts of climate change and anthropogenic over-enrichment and hydrological modifications. Recent studies examining adaptation of species and strains to long-term perturbations, e.g. temperature and carbon dioxide (CO₂) levels, as well as incorporating multi-species and multi-stressor approaches emphasize the limitations of approaches focused on single stressors and individual species. There are also emerging species of concern, such as toxic benthic cyanobacteria, for which the effects of global change are less well understood, and require more detailed study. This review provides approaches and examples of studies tackling the challenging issue of understanding how global changes will affect cyanoHABs, and identifies critical information needs for effective prediction and management.

Ecological meta-analysis of bloom-forming planktonic Cyanobacteria in Argentina

Authors

Inés O’Farrell, Carolina Motta, Marina Forastier, Wanda Polla, Silvia Otaño, Norma Meichtry, Melina Devercelli, Ruben Lombardo

The aim of the present research was to summarize the main reasons that explain the distribution of harmful blooms of cyanobacteria in Argentina. It is a large territory with climates ranging from humid tropical to cold temperate. We performed a meta-analysis of the published data and information in technical reports published from 1945 to 2015, and included additional data from personal non-published studies. A total of 122 water bodies affected by planktonic cyanobacterial blooms were recorded and geo-referenced. The analysis showed that blooms, defined as events exceeding 5000 cells/mL, occurred in different types of water bodies, including shallow lakes, rivers, streams, reservoirs, estuaries and storage facilities. Maximum bloom abundance and species and ecological strategies (dispersive, scum-forming, nitrogen fixer) responsible for each event were related to the geographic and climatologic characteristics and type and origin of water bodies. The Puna and the Andean Patagonia eco-regions were mostly free of blooms. The most impaired aquatic systems were shallow lakes and reservoirs (46.7 and 24.6%, respectively). Deep lakes had no reports of blooms and rivers were mainly affected at the regulated reaches, with intensities generally decreasing downstream the dams. Besides, 74.3% of the blooms reported in Argentina exceeded WHO Alert Level 2 for drinking and bathing waters (100,000 cells/mL). Thirty-nine species, identified by Komárek’s polyphasic approach to taxonomy, were responsible for the blooms. Microcystis aeruginosa, Dolichospermum spiroides, Dolichospermum circinale, Raphidiopsis mediterranea and Cylindrospermopsis raciborskii were frequently found participating in either mixed or single species blooms. The species distribution was associated with the eco-region and aquatic system typologies and affected by seasonality and climatological and geographic variables. The eco-strategies of cyanobacterial species showed stronger associations with the qualitative and quantitative indicators used in the meta-analysis, and appeared as useful tools for management measures.

Evaluating putative ecological drivers of microcystin spatiotemporal dynamics using metabarcoding and environmental data

Authors

A. Banerji, M.J. Bagley, J.A. Shoemaker, D.R. Tettenhorst, C.T. Nietch, H.J. Allen, J.W. Santo Domingo

Microcystin is a cyanobacterial hepatotoxin of global concern. Understanding the environmental factors that cause high concentrations of microcystin is crucial to the development of lake management strategies that minimize harmful exposures. While the literature is replete with studies linking cyanobacterial production of microcystin to changes in various nutrients, abiotic stressors, grazers, and competitors, no single biotic or abiotic factor has been shown to be reliably predictive of microcystin concentrations in complex ecosystems. We performed random forest regression analyses with 16S and 18S rRNA gene sequencing data and environmental data to determine which putative ecological drivers best explained spatiotemporal variation in total microcystin and several individual congeners in a eutrophic freshwater reservoir. Model performance was best for predicting concentrations of the congener MC-LR, with ca. 88% of spatiotemporal variance explained. Most of the variance was associated with changes in the relative abundance of the cyanobacterial genus Microcystis. Follow-up RF regression analyses revealed that factors that were the most important in predicting MC-LR were also the most important in predicting Microcystis population dynamics. We discuss how these results relate to prevailing ecological hypotheses regarding the function of microcystin.

The influence of nutrients limitation on phytoplankton growth and microcystins production in Spring Lake, USA

Authors

Xiaomei Su, Alan D. Steinman, Maggie Oudsema, Michael Hassett, Liqiang Xie

Due to excessive loadings of nitrogen (N) and phosphorus (P), frequent blooms of harmful cyanobacteria and their associated cyanotoxins pose serious threats to recreational usage and human health. However, whether cyanobacteria growth and toxin production are limited by N, P, or both N + P is still not clear. Thus, we conducted a nutrient enrichment bioassay in situ in Spring Lake, a eutrophic lake in west Michigan, USA, to examine the influence of nutrient limitation on the proliferation of algal blooms and the production of microcystins (MC). N or P addition alone resulted in a slight increase in the concentration of chlorophyll-a(Chl-a), suggesting a positive effect on phytoplankton growth, but alone, neither were sufficient to induce algal blooms. In contrast, the combination of N and P had a significant and positive influence on phytoplankton growth and MC production. Compared to controls, the N + P treatment resulted in high concentrations of Chl-aand MC, as well as high pH and dissolved oxygen. In addition, significant increases were observed in different MC analogues for each treatment; the highest concentrations of intracellular MC-LR, -RR, -YR, and TMC (total MC) were found in the N + P treatment with values of 9.16, 6.10, 2.57, and 17.82 μg/L, respectively. This study suggests that at least in this temperate coastal lake, cyanobacterial blooms and associated MC are influenced more by combined N and P enrichment than by N or P alone, indicating that managing both nutrients is important for effectively reducing algal blooms and MC production.