Using total adenosine triphosphate (tATP) measurements for cyanobacterial bloom monitoring and response assessment during algaecide treatments.

Total adenosine triphosphate (tATP) was investigated for its potential as a rapid indicator of cyanobacterial growth and algaecide effectiveness. tATP and other common bloom monitoring parameters were measured over the growth cycles of cyanobacteria and green algae in laboratory cultures and examined at a drinking water source during an active bloom. Strong correlations (R2>0.78) were observed between tATP and chlorophyll-a in cyanobacteria cultures. tATP offered greater sensitivity by increasing two orders of magnitude approximately 7 d before changes in chlorophyll-a or optical density were observed in Lyngbya sp. and Dolichospermum sp. cultures. Increases in tATP per cell coincided with the onset of exponential growth phases in lab cultures and increase in cell abundance in field samples, suggesting that ATP/cell is a sensitive indicator that may be used to identify the development of blooms. Bench-scale trials using samples harvested during a bloom showed that tATP exhibited a clear dose-response during copper sulfate (CuSO4) and hydrogen peroxide (H2O2) treatment compared to chlorophyll-a and cell counts, indicating that cellular production and storage of ATP decreases even when live and dead cells cannot be distinguished. During Copper (Cu) algaecide application at a reservoir used as a drinking water source, tATP and cell counts decreased following initial algaecide application; however, the bloom rebounded within 10 d showing that the Cu algaecide only has limited effectiveness. In this case, tATP was a sensitive indicator to bloom rebounding after algaecide treatments and correlated positively with cell counts (R2=0.7). These results support the use of tATP as a valuable complementary bloom monitoring tool for drinking water utilities to implement during the monitoring and treatment of cyanobacterial blooms.

Physiological and molecular mechanisms of the inhibitory effects of artemisinin on Microcystis aeruginosa and Chlorella pyrenoidosa.

Artemisinin, a novel plant allelochemical, has attracted attention for its potential selective inhibitory effects on algae, yet to be fully explored. This study compares the sensitivity and action targets of Microcystis aeruginosa (M. aeruginosa) and Chlorella pyrenoidosa (C. pyrenoidosa) to artemisinin algaecide (AMA), highlighting their differences. Results indicate that at high concentrations, AMA displaces the natural PQ at the QB binding site within M. aeruginosa photosynthetic system, impairing the D1 protein repair function. Furthermore, AMA disrupts electron transfer from reduced ferredoxin (Fd) to NADP+ by interfering with the iron-sulfur clusters in the ferredoxin-NADP+ reductases (FNR) domain of Fd. Moreover, significant reactive oxygen species (ROS) accumulation triggers oxidative stress and interrupts the tricarboxylic acid cycle, hindering energy acquisition. Notably, AMA suppresses arginine synthesis in M. aeruginosa, leading to reduced microcystins (MCs) release. Conversely, C. pyrenoidosa counters ROS accumulation via photosynthesis protection, antioxidant defenses, and by regulating intracellular osmotic pressure, accelerating damaged protein degradation, and effectively repairing DNA for cellular detoxification. Additionally, AMA stimulates the expression of DNA replication-related genes, facilitating cell proliferation. Our finding offer a unique approach for selectively eradicating cyanobacteria while preserving beneficial algae, and shed new light on employing eco-friendly algicides with high specificity.

Assessment of soil microbial diversity and soil enzyme activities under inorganic input sources on maize and rice ecosystems.

Background: To increase crop productivity, modern agricultural practices comprises fertilizers, algaecides, herbicides and fungicides. Objective: The purpose of this study was to evaluate the effects of soil microbial population and soil enzyme activity by the use of fertilizer in maize and inorganic input in the rice ecosystem. Methods: A field experiment (2021 to 2023) was carried out using synthetic fertilizer doses with maize crops followed by rice crops using inorganic inputs. Soil microbial population and enzyme activities were examined. Results: Maize field experiment revealed that the plots treated with 75 % Standardized Dose of Fertilizer (SDF) of NPK had the highest populations of diazotrophs (124 × 105cfu / g), Phosphobacteria (66.33 × 105cfu / g), and Azospirillum (0.409 × 105 MPN / g) than 100 % and 150 % SDF of NPK. The soil enzyme activity was higher in the unfertilized control plot than fertilized plot. These experimental results revealed that a low amount of fertilizer and no fertilizers favour the growth of soil microorganisms and soil enzyme activities, respectively. Followed by the rice field experiment, revealed that the soil microbial population was decreased by the application of inorganic inputs viz., fertilizer, algaecide, herbicide and fungicide. However, the maximum soil microbial population was found in algaecide application followed by herbicide and fungicide. Conclusion: The field experiment concluded that soil microbial population and enzyme activity were affected by inorganic amendments. Less inorganic fertilizers and no fertilizers improve soil microbial activities and soil enzyme activities.

Sediment quality classification in freshwater lakes predicted by the history of treatment with copper-based aquatic algaecides.

Copper-based aquatic algaecides have been widely used in the management of aquatic macrophyte and harmful algal blooms for decades due to their effectiveness and low cost. However, repeated treatment of freshwater lakes results in the accumulation of copper in the sediment, which may adversely affect the ecosystem of the lakes through toxicity to benthic invertebrates and other organisms. Consequently, copper-based aquatic herbicides and algaecides have been frequently subjected to regulations aimed at preventing further ecological deterioration in treated waterbodies. Many states in the US are taking or considering taking an approach that limits or prohibits copper treatment in waterbodies. Freshwater lakes with extensive historical copper treatments typically have significantly higher concentrations of copper in the sediment than untreated lakes. However, the correlation between the extent of the treatments and level of copper accumulation in the sediment has not been quantitatively characterized. In the present study, between 2006 and 2017, copper concentrations were measured in the sediment from selected lakes in New York State with different histories of copper-based aquatic algaecide treatment. Analysis of these data confirmed findings from earlier studies conducted by New York State that lakes with histories of copper treatment have significantly higher copper concentrations in the sediment. It also demonstrated that sediment copper concentrations were significantly higher in the sublittoral zone than the littoral zone in treated lakes. Moreover, a positive correlation was detected between sediment copper concentrations and the total number of treatments with copper-based aquatic algaecide for both littoral and sublittoral zones (p-value = 7.94 × 10-8 and 3.1 × 10-13, respectively). This relationship can be used as a screening tool for regulatory agencies to identify lakes with sediment copper levels possibly higher than the toxicity threshold for aquatic life. Consequently, additional ecological risk assessment may be required before allowing future treatment with copper-based aquatic algaecides. Integr Environ Assess Manag 2024;20:1586-1597. © 2024 SETAC.

In Vitro Activity of Quaternary Ammonium in Prototheca Isolated from Clinical Bovine Mastitis Identified by Mass Spectrometry and PCR Sequencing of the cytb Gene Marker.

The in vitro algaecide activity of quaternary ammonium (QA) against Prototheca isolated from bovine clinical mastitis was investigated, in which the clinical severity was scored, milk samples were subjected to microbiological culture, and algal species were identified by molecular typing. A total of 4275 milk clinical samples of different cows from ten large dairy farms were used. Forty-four (1%) samples of cows from three dairy farms yielded growth of Prototheca, of which 88.6% (39/44) were identified as Prototheca bovis and 11.3% (5/44) as Prototheca sp. by MALDI-TOF MS, whereas 100% of the isolates were identified as P. bovis using PCR sequencing of the cytb gene. Among cows for which clinical severity scoring was available, 78.8% (26/33) and 21.2% (7/33) had mild and moderate infections, respectively, whereas no animal showed severe clinical signs. The algaecide activity of QA in Prototheca was observed in low concentrations among all isolates, in 20.4% (9/44) at 35 ppm, 36.4% (16/44) at 17 ppm, and 43.2% (19/44) at an 8 ppm, in addition to activity on three reference Prototheca strains. Overall, the study highlights the predominance of P. bovis as the causative agent of algal mastitis in bovines. Prototheca induced abnormalities preponderantly in the milk and mammary gland tissue of cows, and to our knowledge, our study is the first to apply clinical severity scoring in protothecal mastitis. In addition, the study underlines the activity of QA in low concentrations against Prototheca, indicating its potential use as an antiseptic/disinfectant in milking facilities and dairy environments.

Identification of a Shewanella halifaxensis Strain with Algicidal Effects on Red Tide Dinoflagellate Prorocentrum triestinum in Culture.

The dinoflagellate Prorocentrum triestinum forms high biomass blooms that discolor the water (red tides), which may pose a serious threat to marine fauna and aquaculture exploitations. In this study, the algicidal effect of a bacterial strain (0YLH) belonging to the genus Shewanella was identified and evaluated against P. triestinum. The algicidal effects on the dinoflagellate were observed when P. triestinum was exposed to cell-free supernatant (CFS) from stationary-phase cultures of the 0YLH strain. After 24 h exposure, a remarkable reduction in the photosynthetic efficiency of P. triestinum was achieved (55.9%), suggesting the presence of extracellular bioactive compounds produced by the bacteria with algicidal activity. Furthermore, the CFS exhibited stability and maintained its activity across a wide range of temperatures (20-120 °C) and pH values (3-11). These findings highlight the algicidal potential of the bacterium Shewanella halifaxensis 0YLH as a promising tool for the environmentally friendly biological control of P. triestinum blooms.

Residential swimming pools maintenance under an environmental perspective.

Swimming pools provides various benefits for users, but their owners need to carry out constant maintenance to ensure water quality and user safety. This paper goal was to assess the maintenance process of residential swimming pools, through Life Cycle Assessment based on NBR ISO 14040:2014 and NBR 14044:2014. The standard steps were followed and primary data on materials and quantities for the treatments were collected during 2022. The purchase costs of the treatment process were obtained, which based the cost analysis. The Impact Assessment Method used was the ReCiPe Endpoint (H) 2016, which assesses damage across three categories. The water, electricity and hypochlorite production processes were the most impactful in the categories of damage to human health, ecosystems and resources availability. These inputs production have an intense natural resources consumption and causes emissions into the environment. The highest expenses in pool maintenance were associated to human resources (worker) and chlorine purchase, followed by electricity. Scenarios were created to identify feasible changes to reduce the impacts. The waiver of water for replacement in the rainy season had greater potential for reducing impacts than the consumption changes in electricity and chlorine.

Magnetic biochar with Mg/La modification for highly effective phosphate adsorption and its potential application as an algaecide and fertilizer.

In this study, a highly efficient phosphate adsorbent (MBC/Mg-La) based on magnetic biochar was successfully synthesized through Mg-La modification. The phosphate adsorption capacity of biochar was significantly enhanced after Mg-La modification. The adsorbent exhibited an excellent phosphate adsorption performance, particularly for treating low-concentration phosphate wastewater. Within a wide pH range, the adsorbent maintained a stable phosphate adsorption capacity. Furthermore, it showed a high adsorption selectivity for phosphate. Therefore, given the excellent phosphate adsorption performance, the adsorbent could effectively inhibit algae growth by removing phosphate from water. Furthermore, the adsorbent after phosphate adsorption can be easily recycled through magnetic separation, which can serve as a phosphorus fertilizer to promote the growth of Lolium perenne L.

Evaluation of algaecide effectiveness of five different oxidants applied on harmful phytoplankton.

Harmful algal blooms (HABs) in coastal areas similarly impact both ecosystems and human health. The translocation of phytoplankton species via maritime transport can potentially promote the growth of HABs in coastal systems. Accordingly, ballast water must be disinfected. The main goal of this study is to assess the effectiveness of different emerging biocides, including H2O2, peracetic acid (PAA), peroxymonosulfate (PMS), and peroxydisulfate (PDS). The effectiveness of these biocides is compared with that of conventional chlorination methods. Their effects on two ichthyotoxic microalgae with worldwide distribution, i.e., Prymnesium parvum and Heterosigma akashiwo, are examined. To ensure the prolonged effectiveness of the different reagents, their concentration-response curves for 14 days are constructed and examined. The results suggest a strong but shorter effect by PMS (EC50 = 0.40-1.99 mg·L-1) and PAA (EC50 = 0.32-2.70 mg·L-1), a maintained effect by H2O2 (EC50 = 6.67-7.08 mg·L-1), and a negligible effect by PDS. H. akashiwo indicates higher resistance than P. parvum, except when H2O2 is used. Based on the growth inhibition performance and consumption of the reagents as well as a review of important aspects regarding their application, using H2O2, PAA, or PMS can be a feasible alternative to chlorine-based reagents for inhibiting the growth of harmful phytoplankton.

Cyanobacteria control using Cu-based metal organic frameworks derived from waste PET bottles.

Copper sulfate (CuSO4) is actively used to control the proliferation of harmful algal blooms because of its fast and effective killing mechanism. However, its use unintentionally harms innocuous aquatic organisms. Therefore, there is a need to find non-toxic solutions for controlling algal blooms. In this study, Cu-based metal-organic framework (Cu-BDC MOF) chips (ca. 2 × 2 cm) were synthesized using waste polyethylene terephthalate (PET) bottles. The as-synthesized Cu-BDC MOF chips efficiently inhibited the cyanobacteria species Microcystis aeruginosa, which was comparable to the conventional dose of CuSO4 algaecide (1.00 mg L-1). Moreover, unlike the CuSO4 algaecide, Cu-BDC MOF chips did not cause any acute toxicity (48 h) to the water flea Daphnia magna. Both Cu-BDC MOF and Cu2O seemed to be responsible for the generation of reactive oxygen species, which resulted in the aggregation, photosynthesis disruption, and eventually growth inhibition of M. aeruginosa. This study suggests that the environmentally safe Cu-BDC MOF chip is a promising agent to sustainably control harmful algal blooms.

Complex effects of dissolved organic matter, temperature, and initial bloom density on the efficacy of hydrogen peroxide to control cyanobacteria.

Harmful cyanobacterial blooms plague reservoirs and lakes used for a variety of purposes, such as recreation and drinking water. Chemical controls are frequently used to mitigate the occurrence of cyanobacterial blooms given that many are fast-acting and effective at reducing cyanobacterial abundance. Recent research has identified hydrogen peroxide (H2O2) as an environmentally friendly alternative to algaecides that have typically been used, such as copper sulfate. To build on past studies, these experiments sought to further understand how well H2O2 treatments reduce cyanobacteria in complex eutrophic conditions, as well as to assess treatment effects on a non-target phytoplankter, a green alga. We assessed the effectiveness of H2O2 (at treatments of 2-16 mg L-1) under varying environmental conditions in a controlled laboratory setting, including (1) dissolved organic matter (DOM) concentrations (humic acid; 0-60 mg L-1), (2) temperature (20, 25, and 32 °C), and (3) initial algal biomass (chlorophyll-a; 82-371 µg L-1). In contrast to our expectations, neither DOM concentration nor temperature meaningfully impacted the effectiveness of H2O2 at reducing cyanobacteria. However, initial algal biomass as well as H2O2 treatment dose greatly influenced the effectiveness of the algaecide on cyanobacteria. Treatments of ≥ 8 mg H2O2 L-1 on algal biomass were significantly buffered with higher DOM and lower temperature, and the biological significance of these findings should be explored further. Across all experiments, H2O2 concentrations of 0.03-0.12 mg H2O2 L-1 µg chlorophyll L-1 were effective at significantly reducing cyanobacteria with varying effects on algal biomass. Thus, water resource managers are encouraged to consider how ambient levels of phytoplankton biomass may affect the ability of H2O2 to control cyanobacterial blooms prior to treatment.

Inhibitory effects of Ipomoea cairica extracts on the harmful algae Phaeocystis globosa.

Ipomoea cairica (L.) Sweet is an invasive plant that cause serious invasion and damage in South China. Phaeocystis globosa is a common harmful algal bloom species on the southeast coast of China. Both species cause great environmental disturbances and serious economic damage to the localregion. This study explored the potential inhibitory effects of I. cairica leaf extracts on P. globosa. The results showed that solitary cells growth was inhibited at extract concentrations higher than 0.25 % (v/v). Although the colony diameter did not change, and the colony number increased rapidly in the first 36 h, we found that cells in the colonies had been damaged using scanning electron microscope and SYTOX-Green staining at 48 h. In addition, the rapid light-response curve of cells treated with extracts decreased, along with down-regulation of photosynthesis-related genes (psbA, psbD, and rbcL), suggesting damage to the photosynthetic system. Finally, the activities of antioxidant enzymes including superoxide dismutase, peroxidase, and catalase increased with increasing treatment time, indicating that cells activate antioxidant enzyme defense systems to alleviate the production of reactive oxygen species (ROS). Increased ROS levels disrupt cell membranes, alter cellular ultrastructures, and ultimately lead to cell death. This study not only achieved the reuse of invasive plant resources, but also demonstrated that I. cairica leaf extract has potential value as an algaecide.

Development of a Potentially New Algaecide for Controlling Harmful Cyanobacteria Blooms Which is Ecologically Safe and Selective.

Harmful cyanobacterial blooms (HCBs) caused by Microcystis aeruginosa are of great concern as they negatively affect the aquatic environment and human health. Chemical methods could rapidly eradicate HCBs and have been used for many decades. However, many chemical reagents are not recommended to eliminate HCBs in the long term, given the possible destructive and toxic effects of the chemicals employed on non-target aquatic organisms. We developed a new algaecide, 2-((1,3,4-thiadiazol-2-yl)thio)-N-(4-chlorophenyl) acetamide (Q2), to control harmful cyanobacteria while being environmentally friendly and selective. In our study, Q2 effectively inhibited cyanobacterial growth, especially of M. aeruginosa, but did not affect eukaryotic algae in test concentrations. A critical mechanism was revealed by transcriptome and metagenomic results showing that Q2 affects multiple cellular targets of cyanobacteria for HCB control, including the destruction of organelles, damage in the photosynthesis center, as well as inhibition of gas vesicle growth, and these changes can be highly relevant to the decrease of quorum-sensing functional KEGG pathways. Furthermore, Q2 did not affect the microbial composition and could recover the disrupted aquatic functional pathways in a short period. This is different from the impact on ecosystem functioning of the traditionally used harmful algaecide diuron. All these results verified that Q2 could be friendly to the aquatic environment, providing a new directional choice in managing HCBs in the future.

Using hydrogen peroxide to control cyanobacterial blooms: A mesocosm study focused on the effects of algal density in Lake Chaohu, China.

The application of hydrogen peroxide (H2O2) to control harmful algal blooms is affected by algal density and species. In the present study, a simulation field study was carried out to evaluate the removal of cyanobacteria with high algal density (chlorophyll a of approximately 220-250 µg/L) and low algal density (chlorophyll a of approximately 30-50 µg/L) using 10, 20 mg/L H2O2 and 5 mg/L H2O2. The dynamics of algal biomass, nutrients, microcystins, phytoplankton, and zooplankton were measured within 7 d. The results showed that 5 mg/L H2O2 effectively eliminated algal biomass (measured as chlorophyll a and phycocyanin) and inhibited 50% of the photosynthetic activity of the cyanobacteria at 7 d in the low algal cell density group, while the same inhibition rate was observed in the high algal cell density group when the H2O2 was 20 mg/L. However, using a high dosage of H2O2, such as 10 mg/L, to suppress cyanobacteria with high biomass could result in a dramatic increase in nutrients and microcystins in the water column. The portion of eukaryotic algae, such as Chlorophyta, Bacillariophyta and Euglenophyta, in the phytoplankton community increased with increasing H2O2 concentrations; moreover, the dominant species of cyanobacteria changed from the nontoxic genus Dactylococcopsis to the toxic genus Oscillatoria, which may result in acute toxicity to zooplankton. Our results demonstrated that the application of H2O2 to control cyanobacterial blooms at the early stage when algal cell density was low posed less potential ecological risks and may have increased the diversity of the phytoplankton community.

Identification of compounds from terrestrial dissolved organic matter toxic to cyanobacteria.

There is emerging evidence for the phytotoxicity of terrestrial dissolved organic matter (DOM), however its sources, transformations and ecological effects in aquatic ecosystems are poorly understood. DOM characterization by Nuclear Magnetic Resonance (NMR) spectroscopy has typically involved solid-state techniques, but poor resolution has often precluded identification of individual components. This study is the first to directly identify individual phytotoxic components using a novel combined approach of preparative HPLC fractionation of DOM (obtained from leaves of two common riparian trees, Casuarina cunninghamiana and Eucalyptus tereticornis). This was followed by chemical characterization of fractions, using one-dimensional (1D) and two-dimensional (2D) solution-state 1H NMR analyses. Additionally, the phytotoxic effect of the fractions was determined using cultures of the cyanobacteria Raphidiopsis (Cylindrospermopsis) raciborskii. The amino acid, proline, from Casuarina leachate was identified as phytotoxic, while for Eucalyptus leachate, it was gallic acid and polyphenols. These phytotoxicants remained in the leachates when they were incubated in sunlight or the dark conditions over 5 days. Our study identifies phytotoxic compounds with the potential to affect algal species composition, and potentially control nuisance R. raciborskii blooms.

Biomass of the Cyanobacterium Lyngbya wollei Alters Copper Algaecide Exposure and Risks to a Non-target Organism.

Nuisance algal infestations are increasing globally in distribution and frequency. Copper-based algaecides are routinely applied to control these infestations, though there is an ever-present concern of risks to non-target species. This research evaluated risks associated with a commonly applied chelated copper algaecide (Captain® XTR; SePRO Corporation) to a sentinel non-target species (Daphnia magna) and further assessed alteration of the exposure and toxicity when a nuisance mat-forming cyanobacterium, Lyngbya wollei, was present in exposures. Aqueous copper concentrations in treatments with algae significantly decreased within 1 h after treatment and averaged 57.5% of nominal amended Cu through the experiment duration. The 48 h LC50 values were 371 µg Cu/L with no algae present in exposures and increased significantly to 531 µg Cu/L when L. wollei was simultaneously exposed. This research provides information on the short-term fate of copper and hazard assessment by incorporating targeted binding ligands, as present in operational treatments.

Identification of novel disinfection byproducts in pool water: Chlorination of the algaecide benzalkonium chloride.

The maintenance of public swimming pools requires numerous technological steps. One of the most important issues involves microbiological safety. Benzalkonium chloride (BAC) encompasses homologous alkylbenzyldimethylammonium chlorides with various alkyl chains, in particular C12 and C14, and is known as a popular algaecide for keeping water clean. In addition to BAC, NaOCl and UV-irradiation are also used to treat pool water as additional technological steps. Therefore, BAC itself can become a precursor of disinfection byproducts (DBPs). High-performance liquid chromatography - tandem mass spectrometry (HPLC-MS/MS), with accurate mass measurements, has allowed the discovery of several groups of DBPs that are related to BAC in public pool water in Arkhangelsk (Russia). These DBPs include numerous isomeric monochlorinated derivatives ([C21H37ClN]+ and [C23H41ClN]+), hydroxyl derivatives ([C21H38NO]+ and [C23H42NO]), carbonyl ([C21H36NO]+ and [C23H40NO]+), and dicarbonyl derivatives ([C21H34NO2]+ and [C23H38NO2]+). In addition, chlorinated alcohols, ketones and ketoalcohols of BAC were also detected, including [C21H35ClNO]+, [C21H37ClNO]+ and [C21H35ClNO2]+ for BAC-12; and [C23H39ClNO]+, [C23H41ClNO]+ and [C23H39ClNO2]+ for BAC-14. MS/MS allowed reliable elucidation of the structures of novel DBPs, proving that chlorination starts via radical substitution in the long aliphatic chains of BAC. UV-irradiation dramatically accelerates the reaction completely destroying the original compounds in less than an hour, while the array of the intermediate products remains the same as in the dark. The formation of other DBPs proceeds due to further reactions of these primary products. The concentrations of novel DBPs in pool water reach µg L-1 levels. These conclusions were proved by conducting model reactions of BAC with NaOCl.

Effect of the Algicide Thiazolidinedione 49 on Immune Responses of Bay Scallop Argopecten Irradians.

The thiazolidinedione 49 (TD49) is an effective algaecide against harmful algae; however, its potential effects on the immune function of the edible bay scallop are unclear. Therefore, the present work studied the effects of TD49 on the immune response in bay scallop by evaluating activities of acid phosphatase (ACP), alkaline phosphatase (ALP), and superoxide dismutase (SOD), as well as nitric oxide (NO) levels, total protein content, and expression of immune genes (CTL-6, PGRP, PrxV, MT, and Cu/Zn-SOD) at 3-48 h post-exposure (hpe) to TD49. The activities of ACP and ALP significantly increased in TD49-treated groups at 3-24 hpe, whereas NO levels decreased significantly in 0.58 and 0.68 µM of TD49 at 6-24 hpe, after which the level was similar to that in the untreated control. Moreover, SOD activity significantly increased in all three concentration groups at 3-6 hpe, while it decreased at 12 hpe in the 0.68 µM TD49 treatment group. Notably, total protein content increased with TD49 treatment at each time interval. The results revealed that variable effects on the expression of immune-related genes were observed after treatment with TD49. The findings demonstrate that exposure of scallops to TD49 changes immune responses and expression of immune-related genes. We hypothesize that TD49 may disrupt immune system in bay scallop. The current investigation highlights the potential negative effects of using TD49 as an algaecide on marine economic bivalves to control harmful algal blooms in marine environments.

Ozonation of the algaecide irgarol: Kinetics, transformation products, and toxicity.

The degradation of irgarol, a frequently detected algaecide in the aquatic environment, by ozonation was investigated in this study. The second-order rate constants for the reaction of irgarol with ozone (O3) and hydroxyl radical (OH) were determined to be 505 M-1 s-1 and 4.96 × 109 M-1 s-1, respectively. During ozonation, sixteen transformation products (TPs) of irgarol were proposed using an electrospray ionization quadrupole time-of-flight mass spectrometer. Most of the TPs are ozone-refractory compounds and therefore could only be further transformed by oxidation with OH generated from O3 decomposition during ozonation. Toxicity analysis using the ecological structure activity relationship class program indicates that some of the TPs (e.g., irgarol sulfoxide) still exhibit high acute or chronic toxicity to aquatic organisms (fish, daphnia, and algae) as the parent compound. With a typical ozone dose applied in water treatment (2 mg/L, corresponding to a specific ozone dose of 0.8 mg O3/mg dissolved organic carbon), irgarol could be completely abated in a selected surface water by ozonation. However, most of the TPs persisted in the ozonation effluent because of their low ozone reactivity. The results of this study suggest that ozonation with typical ozone doses applied in water treatment may not be able to sufficiently reduce the ecotoxicological effects of irgarol on aquatic organisms. More effective treatment processes such as ozone-based advanced oxidation processes may be required to enhance the removal of toxic TPs of irgarol in water treatment.

Evaluating the treatment effectiveness of copper-based algaecides on toxic algae Microcystis aeruginosa using single cell-inductively coupled plasma-mass spectrometry.

Single cell-inductively coupled plasma-mass spectrometry (SC-ICP-MS) is an emerging technology. In this work, we have developed a novel SC-ICP-MS method to quantify metal ions in individual cells of a toxic cyanobacterial species, Microcystis aeruginosa (M. aeruginosa), without complicated post-dosing sample preparation, and applied this method to study the treatment effectiveness of copper-based algaecides (cupric sulfate and EarthTec®) on the toxic algae M. aeruginosa. The developed SC-ICP-MS method uses new intrinsic metal element magnesium to determine real transport efficiency and cell concentration. The cell viability and microcystin-LR release by algaecide treatment were studied by flow cytometry and ultra-fast liquid chromatography-tandem mass spectrometry, respectively. The results showed that this novel method was very rapid, highly sensitive (detection limits of intracellular copper and magnesium were 65 ag/cell and 98 ag/cell, respectively), and reproducible (relative standard deviation within 12%). The algaecide effectiveness study further demonstrated that copper in the forms of cupric sulfate and copper-based algaecide EarthTec® successfully diminished M. aeruginosa populations. The higher the copper concentration used to treat the cells, the faster the speeds of copper uptake and cell lysis in the copper concentrations ranged from 0 to 200 µg/L of copper-based algaecide. The cells exhibit obvious heterogeneity in copper uptake. The result suggests that M. aeruginosa cells uptake and cumulate copper followed by cellular lysis and microcystin-LR release. These novel results indicated that though the copper-based algaecides could control this type of harmful algal bloom, further treatment to remove the released algal toxin from the treated water would be needed. Graphical abstract.