Design, Synthesis, and Mode of Action of Thioacetamide Derivatives as the Algicide Candidate Based on Active Substructure Splicing Strategy.

Lakes and reservoirs worldwide are experiencing a growing problem with harmful cyanobacterial blooms (HCBs), which have significant implications for ecosystem health and water quality. Algaecide is an effective way to control HCBs effectively. In this study, we applied an active substructure splicing strategy for rapid discovery of algicides. Through this strategy, we first optimized the structure of the lead compound S5, designed and synthesized three series of thioacetamide derivatives (series A, B, C), and then evaluated their algicidal activities. Finally, compound A3 with excellent performance was found, which accelerated the process of discovering and developing new algicides. The biological activity assay data showed that A3 had a significant inhibitory effect on M. aeruginosa. FACHB905 (EC50 = 0.46 µM) and Synechocystis sp. PCC6803 (EC50 = 0.95 µM), which was better than the commercial algicide prometryn (M. aeruginosa. FACHB905, EC50 = 6.52 µM; Synechocystis sp. PCC6803, EC50 = 4.64 µM) as well as better than lead compound S5 (M. aeruginosa. FACHB905, EC50 = 8.80 µM; Synechocystis sp. PCC6803, EC50 = 7.70 µM). The relationship between the surface electrostatic potential, chemical reactivity, and global electrophilicity of the compounds and their activities was discussed by density functional theory (DFT). Physiological and biochemical studies have shown that A3 might affect the photosynthesis pathway and antioxidant system in cyanobacteria, resulting in the morphological changes of cyanobacterial cells. Our work demonstrated that A3 might be a promising candidate for the development of novel algicides and provided a new active skeleton for the development of subsequent chemical algicides.

[Distribution Characteristics and Environmental Driving Factors of Cyanobacteria Community in Impounded Lakes and Reservoirs in Shandong on the East Route of South-to-North Water Diversion Project].

To investigate the distribution characteristics of the cyanobacteria community and the driving factors in impounded lakes and reservoirs in Shandong on the east route of the South-to-North Water Diversion Project, monthly samples of phytoplankton and the aquatic environment from Nansi Lake, Dongping Lake, Datun Reservoir, Donghu Reservoir, and Shuangwangcheng Reservoir were collected from May to November during 2010 to 2019. A total of 44 planktonic cyanobacteria taxa were identified with 23 filamentous cyanobacteria taxa. Pseudanabaena limnetica, Cylindrospermopsis raciborskii, Microcystis aeruginosa, and Microcystis wesenbergii were the dominant harmful cyanobacteria species, with a high detection frequency and abundance in all lakes and reservoirs. By analyzing the distribution characteristics of the cyanobacteria community in impounded lakes and reservoirs, we found that filamentous cyanobacteria had growth advantages in the water with large hydraulic disturbances, which should be the key points of cyanobacteria prevention and control in the future. Pearson correlation analysis and generalized linear fitting curve results showed that total nitrogen, total phosphorus, water temperature, and water depth played a key role in affecting the growth of P. limnetica, C. raciborskii, M. aeruginosa, and M. wesenbergii. The nitrogen and phosphorus nutrients could promote the growth of harmful cyanobacteria. Due to the good temperature adaptability, P. limnetica could still become the dominant species in early summer and late autumn, and C. raciborskii, M. aeruginosa, and M. wesenbergii had growth advantages when the water temperature was higher than 25℃. In addition, shallow water was more conducive to the growth of C. raciborskii. It was suggested that based on strengthening of the control of nitrogen and phosphorus nutrient input in lakes and reservoirs, the key monitoring of P. limnetica in lakes should be conducted in early summer and late autumn, and the growth of C. raciborskii in shallow water areas should be paid close attention in the high temperature period to ensure the safety of water quality.

Micron-confined microcapturer-triggered Fenton as efficient and environmentally-friendly method for simultaneously capturing bloom-forming cyanobacteria, inhibiting cell-regrowth and degrading microcystins.

The frequent outbreak and continuous expansion of harmful cyanobacteria blooms (HCBs) have become important environmental concerns and public health issues globally. In this study, the "micron-confined Fe(II)-modified-microcapturer (FMC)-triggered Fenton" technology was established as advanced process adaptable to the HCB treatment. Results show that 95.7-99.4% of cyanobacteria cells were captured and separated from the HCB water at the optimum doses of Fe(II) and H2O2 within only 30 s. The chain-like cyanobacteria of A. flos-aquae were easier to be collected by FMCs compared with the unicellular M. aeruginosa. It was confirmed by scanning electron microscopic observation and fluorescence staining flow cytometry measurement that the FMC-carrying Fe(II) played the roles of both cell-gripper and Fenton catalyst. During the one-step process, the FMC-triggered Fenton effectively inhibited the cyanobacteria regrowth via inactivating the cells, and meanwhile, the microcystins of LR and RR were removed. The analyses by continuous flow chemiluminescence and X-ray photoelectron spectroscopy denote that FMCs performed efficiently in capture and Fe(II)-catalytic oxidation through increasing mass transfer, exposing sufficient active reactive oxygen species active-sites on the FMC surface and accelerating electron transfer. The micron-field-confined cascade processes retained the robust performance of Fenton against the high pH of bulk HCB water. This novel interface-dependent Fenton method is a promising tool for HCB treatment owing to its great efficiency, versatility, rapidness and eco-environmental friendliness.

The unprecedented 2022 extreme summer heatwaves increased harmful cyanobacteria blooms.

Heatwaves are increasing and expected to intensify in coming decades with global warming. However, direct evidence and knowledge of the mechanisms of the effects of heatwaves on harmful cyanobacteria blooms are limited and unclear. In 2022, we measured chlorophyll-a (Chla) at 20-s intervals based on a novel ground-based proximal sensing system (GBPSs) in the shallow eutrophic Lake Taihu and combined in situ Chla measurements with meteorological data to explore the impacts of heatwaves on cyanobacterial blooms and the potential relevant mechanisms. We found that three unprecedented summer heatwaves (July 4-15, July 22-August 16, and August 18-23) lasting a total of 44 days were observed with average maximum air temperatures (MATs) of 38.1 ± 1.9 °C, 38.7 ± 1.9 °C, and 40.2 ± 2.1 °C, respectively, and that these heatwaves were characterized by high air temperature, strong PAR, low wind speed and rainfall. The daily Chla significantly increased with increasing MAT and photosynthetically active radiation (PAR) and decreasing wind speed, revealing a clear promotion effect on harmful cyanobacteria blooms from the heatwaves. Moreover, the combined effects of high temperature, strong PAR and low wind, enhanced the stability of the water column, the light availability and the phosphorus release from the sediment which ultimately boosted cyanobacteria blooms. The projected increase in heatwave occurrence under future climate change underscores the urgency of reducing nutrient input to eutrophic lakes to combat cyanobacteria growth and of improving early warning systems to ensure secure water management.

Identification of Cyanobacteria and Its Potential Toxins in the Joanes I Reservoir, Bahia, Brazil.

The Joanes I Reservoir is responsible for 40% of the drinking water supply of the Metropolitan Region of Salvador, Bahia, Brazil. For water sources such as this, there is concern regarding the proliferation of potentially toxin-producing cyanobacteria, which can cause environmental and public health impacts. To evaluate the presence of cyanobacteria and their cyanotoxins in the water of this reservoir, the cyanobacteria were identified by microscopy; the presence of the genes of the cyanotoxin-producing cyanobacteria was detected by molecular methods (polymerase chain reaction (PCR)/sequencing); and the presence of toxins was determined by liquid chromatography with tandem mass spectrometry (LC-MS/MS). The water samples were collected at four sampling points in the Joanes I Reservoir in a monitoring campaign conducted during the occurrence of phytoplankton blooms, and the water quality parameters were also analysed. Ten cyanobacteria species/genera were identified at the monitoring sites, including five potentially cyanotoxin-producing species, such as Cylindrospermopsis raciborskii, Cylindrospermopsis cf. acuminato-crispa, Aphanocapsa sp., Phormidium sp., and Pseudanabaena sp. A positive result for the presence of the cylindrospermopsin toxin was confirmed at two sampling points by LC-MS/MS, which indicated that the populations are actively producing toxins. The analysis of the PCR products using the HEPF/HEPR primer pair for the detection of the microcystin biosynthesis gene mcyE was positive for the analysed samples. The results of this study point to the worrisome condition of this reservoir, from which water is collected for public supply, and indicate the importance of the joint use of different methods for the analysis of cyanobacteria and their toxins in reservoir monitoring.

Improvement of In Vivo Fluorescence Tools for Fast Monitoring of Freshwater Phytoplankton and Potentially Harmful Cyanobacteria.

The use of multi-wavelength spectrofluorometers for the fast detection of algal taxa, based on chlorophyll a (Chl-a) emission spectra, has become a common practice in freshwater water management, although concerns about their accuracy have been raised. Here, inter-laboratory comparisons using monoalgal cultures have been performed to assess the reliability of different spectrofluorometer models, alongside Chl-a extraction methods. Higher Chl-a concentrations were obtained when using the spectrofluorometers than extraction methods, likely due to the poor extraction efficiencies of solvents, highlighting that traditional extraction methods could underestimate algal or cyanobacterial biomass. Spectrofluorometers correctly assigned species to the respective taxonomic group, with low and constant percent attribution errors (Chlorophyta and Euglenophyceae 6-8%, Cyanobacteria 0-3%, and Bacillariophyta 10-16%), suggesting that functioning limitations can be overcome by spectrofluorometer re-calibration with fresh cultures. The monitoring of a natural phytoplankton assemblage dominated by Chlorophyta and Cyanobacteria gave consistent results among spectrofluorometers and with microscopic observations, especially when cell biovolume rather than cell density was considered. In conclusion, multi-wavelength spectrofluorometers were confirmed as valid tools for freshwater monitoring, whereas a major focus on intercalibration procedures is encouraged to improve their reliability and broaden their use as fast monitoring tools to prevent environmental and public health issues related to the presence of harmful cyanobacteria.

Potential Impacts on Treated Water Quality of Recycling Dewatered Sludge Supernatant during Harmful Cyanobacterial Blooms.

Cyanobacterial blooms and the associated release of cyanotoxins pose problems for many conventional water treatment plants due to their limited removal by typical unit operations. In this study, a conventional water treatment process consisting of coagulation, flocculation, sedimentation, filtration, and sludge dewatering was assessed in lab-scale experiments to measure the removal of microcystin-LR and Microcystis aeruginosa cells using liquid chromatography with mass spectrometer (LC-MS) and a hemacytometer, respectively. The overall goal was to determine the effect of recycling cyanotoxin-laden dewatered sludge supernatant on treated water quality. The lab-scale experimental system was able to maintain the effluent water quality below relevant the United States Environmental Protection Agency (US EPA) and World Health Organisation (WHO) standards for every parameter analyzed at influent concentrations of M. aeruginosa above 106 cells/mL. However, substantial increases of 0.171 NTU (Nephelometric Turbidity Unit), 7 × 104 cells/L, and 0.26 µg/L in turbidity, cyanobacteria cell counts, and microcystin-LR concentration were observed at the time of dewatered supernatant injection. Microcystin-LR concentrations of 1.55 µg/L and 0.25 µg/L were still observed in the dewatering process over 24 and 48 h, respectively, after the initial addition of M.aeruginosa cells, suggesting the possibility that a single cyanobacterial bloom may affect the filtered water quality long after the bloom has dissipated when sludge supernatant recycling is practiced.

Microcystinase - a review of the natural occurrence, heterologous expression, and biotechnological application of MlrA.

Microcystinase (MlrA) was first described in 1996. Since then MlrA peptidase activity has proven to be both the most efficient enzymatic process and the most specific catalyst of all known microcystins detoxification pathways. Furthermore, MlrA and the MlrABC degradation pathway are presently the only enzymatic processes with clear genetic and biochemical descriptions available for microcystins degradation, greatly facilitating modern applied genetics for any relevant technological development. Recently, there has been increasing interest in the potential of sustainable, biologically inspired alternatives to current industrial practice, with note that biological microcystins degradation is the primary detoxification process found in nature. While previous reviews have broadly discussed microbial biodegradation processes, here we present a review focused specifically on MlrA. Following a general overview, we briefly highlight the initial discovery and present understanding of the MlrABC degradation pathway, before discussing the genetic and biochemical aspects of MlrA. We then review the potential biotechnology applications of MlrA in the context of available literature with emphasis on the optimization of MlrA for in situ applications including (i) direct modulation of Mlr activity within naturally existing populations, (ii) bioaugmentation of systems with introduced biodegradative capacity via whole cell biocatalysts, and (iii) bioremediation via direct MlrA application.

Oxidative Stress and Antioxidant Responses of Phormidium ambiguum and Microcystis aeruginosa Under Diurnally Varying Light Conditions.

Two harmful cyanobacteria species (Phormidium ambiguum and Microcystis aeruginosa) were exposed to diurnal light-intensity variation to investigate their favorable and stressed phases during a single day. The photosynthetically active radiation (PAR) started at 0 µmol·m-2·s-1 (06:00 h), increased by ~25 µmol·m-2·s-1 or ~50 µmol·m-2·s-1 every 30 min, peaking at 300 µmol·m-2·s-1 or 600 µmol·m-2·s-1 (12:00 h), and then decreased to 0 µmol·m-2·s-1 (by 18:00 h). The H2O2 and antioxidant activities were paralleled to light intensity. Higher H2O2 and antioxidant levels (guaiacol peroxidase, catalase (CAT), and superoxidase dismutase) were observed at 600 µmol·m-2·s-1 rather than at 300 µmol·m-2·s-1. Changes in antioxidant levels under each light condition differed between the species. Significant correlations were observed between antioxidant activities and H2O2 contents for both species, except for the CAT activity of P. ambiguum at 300 µmol·m-2·s-1. Under each of the conditions, both species responded proportionately to oxidative stress. Even under maximum light intensities (300 µmol·m-2·s-1 or 600 µmol·m-2·s-1 PAR intensity), neither species was stressed. Studies using extended exposure durations are warranted to better understand the growth performance and long-term physiological responses of both species.

Inhibitory Effects of Cu2O/SiO2 on the Growth of Microcystis aeruginosa and Its Mechanism.

In this study, a novel nanomaterial Cu2O/SiO2 was synthesized based on nano-SiO2, and the inhibitory effects of different concentrations of Cu2O/SiO2 on the growth of Microcystis aeruginosa (M. aeruginosa) were studied. At the same time, the mechanism of Cu2O/SiO2 inhibiting the growth of M. aeruginosa was discussed from the aspects of Cu2+ release, chlorophyll a destruction, oxidative damage, total protein, and the phycobiliprotein of algae cells. The results showed that low doses of Cu2O/SiO2 could promote the growth of M. aeruginosa. When the concentration of Cu2O/SiO2 reached 10 mg/L, it exhibited the best inhibitory effect on M. aeruginosa, and the relative inhibition rate reached 294% at 120 h. In terms of the algae inhibition mechanism, Cu2O/SiO2 will release Cu2+ in the solution and induce metal toxicity to algae cells. At the same time, M. aeruginosa might suffer oxidative damage by the free radicals, such as hydroxyl radicals released from Cu2O/SiO2, affecting the physiological characteristics of algae cells. Moreover, after the addition of Cu2O/SiO2, a decrease in the content of chlorophyll a, total soluble protein, and phycobiliprotein was found, which eventually led to the death of M. aeruginosa. Therefore, Cu2O/SiO2 can be used as an algaecide inhibitor for controlling harmful cyanobacteria blooms.

Growth inhibition of harmful cyanobacteria by nanocrystalline Cu-MOF-74: Efficiency and its mechanisms.

Metal-organic Frameworks (MOFs) as a new type of nanomaterials are extensively used in various fields of environment pollution remediation. However, the MOFs are rarely applied in the removal of cyanobacterial blooms, and more fundamental investigation is warrant for more insights into mechanisms for algae inhibition. In this study, Cu-MOF-74 was synthesized by a simple hydrothermal method, and its inhibitory effect on the growth of Microcystis aeruginosa was studied. Furthermore, its mechanisms were explored with respect to metal ion release, agglomeration, shading and algal cell membrane breakage, production of extracellular hydroxyl radical and intracellular reactive oxygen species. The results showed that the inhibition rate of M. aeruginosa was 372% after 24-h exposure when the concentration of Cu-MOF-74 exceeded 1 mg/L. However, the addition of Cu-MOF-74 at the concentration lower than 0.1 mg/L promoted the algal growth. The inhibition of algal growth by Cu-MOF-74 was basically attributed to the presence of hydroxyl radical and intracellular reactive oxygen species, with the released Cu2+ and cell aggregation involved to some extent. Overall, nanocrystalline Cu-MOF-74 is of great potential in the control of harmful cyanobacterial blooms and the inhibition is specific to the concentration of Cu-MOF-74.

Unexpected population response to increasing temperature in the context of a strong species interaction.

Climate change is driving large changes in the spatial and temporal distributions of species, with significant consequences for individual populations. Community- and ecosystem-level implications of altered species distributions may be complex and challenging to anticipate due to the cascading effects of disrupted interactions among species, which may exhibit threshold responses to extreme climatic events. Toxic, bloom-forming cyanobacteria like Microcystis are expected to increase worldwide with climate change, due in part to their high temperature optima for growth. In addition, invasive zebra mussels (Dreissena polymorpha) have caused an increase in Microcystis aeruginosa, a species typically associated with eutrophication, in low-nutrient lakes. We conducted a 13-yr study of a M. aeruginosa population in a low-nutrient lake invaded by zebra mussels. In 10 of the 13 years, there was a significant positive relationship between M. aeruginosa biomass and accumulated degree days, which are projected to increase with climate change. In contrast, Microcystis biomass was up to an order of magnitude lower than predicted by the above relationship during the other three years, including the warmest in the data set, following repeated heat-induced mass mortality of D. polymorpha. Thus, the positive relationship between Microcystis biomass and temperature was negated when its facilitating species was suppressed during a series of exceptionally warm summers. Predicting the net response of a species to climate change may therefore require, at minimum, quantification of responses of both the focal species and species that strongly interact with it over sufficiently long time periods to encompass the full range of climatic variability. Our results could not have been predicted from existing data on the short-term responses of these two interacting species to increased temperature.

Improvement of cyanobacterial-killing biologically derived substances (BDSs) using an ecologically safe and cost-effective naphthoquinone derivative.

In previous studies, naphthoquinone (NQ) compounds have been shown to be effective, selective, and ecologically safe algicides for controlling harmful algal blooming species (HABs) or winter bloom species, such as Stephanodiscus hantzschii. However, there are no reports on NQ-based algicides for use with cyanobacterial blooming species. In this study, we developed 31 NQ compounds to investigate algicides for mitigating cyanobacterial blooms. In addition, to better apply these compounds in the field, we reduced the number of production steps to develop a cost-effective algicide. In preliminary testing, we screened NQ compounds that showed the best algicidal activity on target cyanobacteria, including Aphanizomenon, Dolichospermum, Microcystis, Oscillatoria, and Nostoc species. The compound NQ 2-0 showed the highest algicidal activity (90%) at a low concentration (≥1µM) on target algae. These were very limiting algicidal effects of 1µM NQ 2-0 observed against non-target algae, such as diatoms (Stephanodiscus hantzschii, Cyclotella meneghiniana, Synedra acus, and Aulacoseira granulata) or green algae (Cosmarium bioculatum and Scenedesmus quadricauda), and the effect did not exceed 15-25% (except against S. quadricauda). NQ 2-0 (1µM) showed no eco-toxicity, as represented by the survival rates of Pseudokirchneriella subcapitata (100%), Daphnia magna (100%), and Danio rerio (100%). Additionally, a chronic eco-toxicity assessment showed no toxicity toward the survival, growth or reproduction of D. magna. Moreover, NQ 2-0 quickly dissipated from field water samples and had a half-life of approximately 3.2 days. These results suggest that NQ 2-0 could be a selective and ecologically safe algicide to mitigate harmful cyanobacterial blooms.

Fenced cultivation of water hyacinth for cyanobacterial bloom control.

To achieve the goals of harmful cyanobacterial bloom control and nutrient removal, an eco-engineering project with water hyacinth planted in large-scale enclosures was conducted based on meteorological and hydrographical conditions in Lake Dianchi. Water quality, cyanobacteria distribution, and nutrient (TN, TP) bioaccumulation were investigated. Elevated concentrations of N and P and low Secchi depth (SD) were relevant to large amount of cyanobacteria trapped in regions with water hyacinth, where biomass of the dominant cyanobacteria Microcystis (4.95 × 10(10) cells L(-1)) was more than 30-fold compared with values of the control. A dramatic increase of TN and TP contents in the plants was found throughout the sampling period. Results from the present study confirmed the great potential to use water hyacinth for cyanobacterial bloom control and nutrient removal in algal lakes such as Lake Dianchi.

Mitigating cyanobacterial harmful algal blooms in aquatic ecosystems impacted by climate change and anthropogenic nutrients.

Mitigating the global expansion of cyanobacterial harmful blooms (CyanoHABs) is a major challenge facing researchers and resource managers. A variety of traditional (e.g., nutrient load reduction) and experimental (e.g., artificial mixing and flushing, omnivorous fish removal) approaches have been used to reduce bloom occurrences. Managers now face the additional effects of climate change on watershed hydrologic and nutrient loading dynamics, lake and estuary temperature, mixing regime, internal nutrient dynamics, and other factors. Those changes favor CyanoHABs over other phytoplankton and could influence the efficacy of control measures. Virtually all mitigation strategies are influenced by climate changes, which may require setting new nutrient input reduction targets and establishing nutrient-bloom thresholds for impacted waters. Physical-forcing mitigation techniques, such as flushing and artificial mixing, will need adjustments to deal with the ramifications of climate change. Here, we examine the suite of current mitigation strategies and the potential options for adapting and optimizing them in a world facing increasing human population pressure and climate change.

Combatting cyanobacteria with hydrogen peroxide: a laboratory study on the consequences for phytoplankton community and diversity.

Experiments with different phytoplankton densities in lake samples showed that a high biomass increases the rate of hydrogen peroxide (HP) degradation and decreases the effectiveness of HP in the selective suppression of dominant cyanobacteria. However, selective application of HP requires usage of low doses only, accordingly this defines the limits for use in lake mitigation. To acquire insight into the impact of HP on other phytoplankton species, we have followed the succession of three phytoplankton groups in lake samples that were treated with different concentrations of HP using a taxa-specific fluorescence emission test. This fast assay reports relatively well on coarse changes in the phytoplankton community; the measured data and the counts from microscopical analysis of the phytoplankton matched quite well. The test was used to pursue HP application in a Planktothrix agardhii-dominated lake sample and displayed a promising shift in the phytoplankton community in only a few weeks. From a low-diversity community, a change to a status with a significantly higher diversity and increased abundance of eukaryotic phytoplankton species was established. Experiments in which treated samples were re-inoculated with original P. agardhii-rich lake water demonstrated prolonged suppression of cyanobacteria, and displayed a remarkable stability of the newly developed post-HP treatment state of the phytoplankton community.

Stoichiometric regulation of phytoplankton toxins.

Ecological Stoichiometry theory predicts that the production, elemental structure and cellular content of biomolecules should depend on the relative availability of resources and the elemental composition of their producer organism. We review the extent to which carbon- and nitrogen-rich phytoplankton toxins are regulated by nutrient limitation and cellular stoichiometry. Consistent with theory, we show that nitrogen limitation causes a reduction in the cellular quota of nitrogen-rich toxins, while phosphorus limitation causes an increase in the most nitrogen-rich paralytic shellfish poisoning toxin. In addition, we show that the cellular content of nitrogen-rich toxins increases with increasing cellular N : P ratios. Also consistent with theory, limitation by either nitrogen or phosphorus promotes the C-rich toxin cell quota or toxicity of phytoplankton cells. These observed relationships may assist in predicting and managing toxin-producing phytoplankton blooms. Such a stoichiometric regulation of toxins is likely not restricted to phytoplankton, and may well apply to carbon- and nitrogen-rich secondary metabolites produced by bacteria, fungi and plants.

Identification of harmful cyanobacteria in the Sacramento-San Joaquin Delta and Clear Lake, California by DNA barcoding.

Accurate identification of cyanobacteria using traditional morphological taxonomy is challenging due to the magnitude of phenotypic plasticity among natural algal assemblages. In this study, molecular approach was utilized to facilitate the accurate identification of cyanobacteria in the Sacramento-San Joaquin Delta and in Clear Lake in Northern California where recurring blooms have been observed over the past decades. Algal samples were collected from both water bodies in 2011 and the samples containing diverse cyanobacteria as identified by morphological taxonomy were chosen for the molecular analysis. The 16S ribosomal RNA genes (16S rDNA) and the adjacent internal transcribed spacer (ITS) regions were amplified by PCR from the mixed algal samples using cyanobacteria generic primers. The obtained sequences were analyzed by similarity search (BLASTN) and phylogenetic analysis (16S rDNA) to differentiate species sharing significantly similar sequences. A total of 185 plasmid clones were obtained of which 77 were successfully identified to the species level: Aphanizomenon flos-aquae, Dolichospermum lemmermannii (taxonomic synonym: Anabaena lemmermannii), Limnoraphis robusta (taxonomic synonym: Lyngbya hieronymusii f. robusta) and Microcystis aeruginosa. To date, Dolichospermum and Limnoraphis found in Clear Lake have only been identified to the genus lavel by microscopy. During the course of this study, morphological identification and DNA barcoding confirmed A. flos-aquae as the predominant cyanobacterium in the Sacramento-San Joaquin Delta indicating a shift from M. aeruginosa that have dominated the blooms in the past decade. Lastly, the species-specific identification of Limnoraphis robusta in Clear Lake is another significant finding as this cyanobacterium has, thus far, only been reported in Lake Atitlan blooms in Guatemala.