Pseudomonas ZY-1 and Bacillus FY-1 protecting the rice seedlings from the harm of Pseudomonas aeruginosa via indirect seawead lysis.

The local ecosystems, fishery and human health are all threatened by water blooms, so effectively controlling water blooms has become an urgent and challenging issue. Biological control of water blooms is given priority due to its low cost, high efficiency and environmental friendliness. In this study, Pseudomonas ZY-1 and Bacillus FY-1, two highly-effective algicidal bacteria strains which are able to indirectly lyse algae by separating and screening from the vigorous water body in the paddy alga of Northeast China were obtained. The two bacterial strains have stronger ability to lyse alga in the bacterial liquid concentration of 106 CFU/ml, and the alga-lysing rate on 7 d reached 84.03% and 83.11% respectively. The active substance secreted by ZY-1 is not sensitive to the changes of temperature and pH value, while as FY-1 cell-free filtrate is not stable in high temperature above 50 ℃ and pH of 5, it requires the sun light to have the algaecidal effect. The cell-free filtrates of strains ZY-1 and FY-1 had the best lysis effect on Microcystis aeruginosa cells, and the chlorophyll a content of algae decreased to 0.13 ± 0.02 mg/L and 0.14 ± 0.03 mg/L respectively and the Fv/Fm of Microcystis aeruginosa decreased by 97.22% after 7 days. The algaecidal process of ZY-1 and FY-1 may be that the cell-free filtrate inhibits the photosynthesis of Microcystis aeruginosa, and meanwhile it avoids the regeneration and repair of photosynthesis of algal cells by affecting the gene expression and damaging the repair system of algal cells, so the membrane lipid peroxidation is exacerbated and then the membrane of algal cells is broken, the algal cells can't do normal life activities, and finally the algal cell would be killed. The rice seedlings in the algal liquid treatment group are short and show root dysplasia, few roots and brown roots. After treated with cell-free filtrate of ZY-1 and FY-1, the oxidative damage of the rice is obviously reduced, and the harm from Microcystis aeruginosa is reduced, which has the repair effect to the roots of rice seedlings and its aboveground growth. The cell-free filtrate of FY-1 works better than ZY-1. The bacteria strains of ZY-1 and FY-1 have the indirect algaecide trait, which makes them the potential environmentally-friendly algaecidal bacteria and they show broad application in the agricultural production and the control of water blooms.

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.

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.

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.

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.

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.

Influence of mixed antibiotics on Microcystis aeruginosa during the application of glyphosate and hydrogen peroxide algaecides.

Antibiotics regulate various physiological functions in cyanobacteria and may interfere with the control of cyanobacterial blooms during the application of algaecides. In this study, Microcystis aeruginosa was exposed to H2 O2 and glyphosate for 7 d in the presence of coexisting mixed antibiotics (amoxicillin, spiramycin, tetracycline, ciprofloxacin, and sulfamethoxazole) at an environmentally relevant concentration of 100 ng · L-1 . The mixed antibiotics significantly (P < 0.05) alleviated the growth inhibition effect of 15-45 µM H2 O2 and 40-60 mg · L-1 glyphosate. According to the increased contents of chlorophyll a and protein, decreased content of malondialdehyde, and decreased activities of superoxide dismutase and glutathione S-transferase, antibiotics may reduce the toxicity of the two algaecides through the stimulation of photosynthesis and the reduction in oxidative stress. The presence of coexisting antibiotics stimulated the production and release of microcystins in the M. aeruginosa exposed to low concentrations of algaecides and posed an increased threat to aquatic environments. To eliminate the secondary pollution caused by microcystins, high algaecide doses that are ≥45 µM for H2 O2 and ≥60 mg · L-1 for glyphosate are recommended. This study provides insights into the ecological hazards of antibiotic contaminants and the best management practices for cyanobacterial removal under combined antibiotic pollution conditions.

Linalool- and α-terpineol-induced programmed cell death in Chlamydomonas reinhardtii.

Plant allelochemicals effectively inhibit and/ or control algal growth, and have potential to use as algaecide. To uncover the lethal mechanism of 2 anti-algal compounds linalool and α-terpineol identified from Cinnamomum camphora extracts, and promote their development as algaecide, the H2O2 production, photosynthetic abilities, caspase-like activities, nuclear changes and DNA degradation were investigated in Chlamydomonas reinhardtii treated with the 2 compounds. H2O2 content burst in linalool treatment at 0.5 h and in α-terpineol treatment at 1 h, with increases of 2.7 folds and 1.3 folds, respectively, compared to that at 0 h. The photosynthetic pigments gradually degraded, and Fv/Fm gradually declined to zero, indicating that the cell death was not a necrosis due to the gradual disappearance of physiological process. In C. reinhardtii cells, the caspase-9-like and caspase-3-like were activated in the treatments with the 2 compounds for 1 h. With prolonging the treatment time, the fluorescent intensity of the cell nucleuses stained by DAPI gradually enhanced and then faded, and the genomic DNA isolated from the cells gradually degraded. These hallmarks indicated that the death of C. reinhardtii cells in linalool and α-terpineol treatments was a programmed cell death (PCD) triggered by the increased reactive oxygen species (ROS). Compared to α-terpineol treatment, linalool treatment showed stronger promoting effects on PCD at the same time point, which may be caused by the higher ROS content inducing higher caspase-9-like and caspase-3-like activities in a short time.

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.

Algicidal properties of extracts from Cinnamomum camphora fresh leaves and their main compounds.

Plant allelochemicals are considered as the source of effective, economic and friendly-environmental algaecides. To uncover the anti-algal activities of Cinnamomum camphora fresh leaves and their main algicidal agents, we investigated the inhibitory effects of water and methanol extracts from C. camphora fresh leaves on Microcystis aeruginosa and Chlamydomonas reinhardtii cell growth, analyzed the composition of the water and methanol extracts, and determined the main compounds in extracts on the growth of the two algae and their anti-algal mechanism from photosynthetic abilities. Water and methanol extracts from C. camphora fresh leaves can inhibit M. aeruginosa and C. reinhardtii cell growth, and methanol extracts showed stronger inhibitory effects, due to their more compounds and higher molar concentration. There were 23 compounds in the water extracts, mainly including terpenoids, esters, alcohols, and ketones. Compared to the water extracts, 9 new compounds were detected in the methanol extracts, and the molar concentration of total compounds in methanol extracts increased by 1.3 folds. Camphor, α-terpineol and linalool were 3 main compounds in the water and methanol extracts. Their mixture (1: 3: 6) and individual compound showed remarkable inhibition on M. aeruginosa and C. reinhardtii cell growth. The degradation of photosynthetic pigments and the reduction of maximum quantum yield of photosystem II (PSII) photochemistry, coefficient of photochemical quenching as well as apparent electron transport rate in C. reinhardtii cells aggravated gradually with increasing the concentration of the mixture and individual compound, while the non-photochemical dissipation of absorbed light energy increased gradually, which led to the decline of photosynthetic abilities. This indicated that camphor, α-terpineol and linalool were 3 main algicidal agents in C. camphora fresh leaf extracts, and they inhibited algal growth by inducing photosynthetic pigment degradation and declining PSII efficiency. Therefore, C. camphora fresh leaf extracts and their main components have potential utilization values as algaecides.

Cell density dependence of Microcystis aeruginosa responses to copper algaecide concentrations: Implications for microcystin-LR release.

Along with mechanistic models, predictions of exposure-response relationships for copper are often derived from laboratory toxicity experiments with standardized experimental exposures and conditions. For predictions of copper toxicity to algae, cell density is a critical factor often overlooked. For pulse exposures of copper-based algaecides in aquatic systems, cell density can significantly influence copper sorbed by the algal population, and consequent responses. A cyanobacterium, Microcystis aeruginosa, was exposed to a copper-based algaecide over a range of cell densities to model the density-dependence of exposures, and effects on microcystin-LR (MC-LR) release. Copper exposure concentrations were arrayed to result in a gradient of MC-LR release, and masses of copper sorbed to algal populations were measured following exposures. While copper exposure concentrations eliciting comparable MC-LR release ranged an order of magnitude (24-h EC50s 0.03-0.3mg Cu/L) among cell densities of 106 through 107 cells/mL, copper doses (mg Cu/mg algae) were similar (24-h EC50s 0.005-0.006mg Cu/mg algae). Comparisons of MC-LR release as a function of copper exposure concentrations and doses provided a metric of the density dependence of algal responses in the context of copper-based algaecide applications. Combined with estimates of other site-specific factors (e.g. water characteristics) and fate processes (e.g. dilution and dispersion, sorption to organic matter and sediments), measuring exposure-response relationships for specific cell densities can refine predictions for in situ exposures and algal responses. These measurements can in turn decrease the likelihood of amending unnecessary copper concentrations to aquatic systems, and minimize risks for non-target aquatic organisms.

Copper-Based Aquatic Algaecide Adsorption and Accumulation Kinetics: Influence of Exposure Concentration and Duration for Controlling the Cyanobacterium Lyngbya wollei.

Filamentous mat-forming cyanobacteria are increasingly impairing uses of freshwater resources. To effectively manage, a better understanding of control measures is needed. Copper (Cu)-based algaecide formulations are often applied to reactively control nuisance cyanobacterial blooms. This laboratory research assessed typical field exposure scenarios for the ability of Cu to partition to, and accumulate in Lyngbya wollei. Exposure factors (Cu concentration × duration) of 4, 8, 16, 24, 32 h were tested across three aqueous Cu concentrations (1, 2, 4 ppm). Results indicated that internally accumulated copper correlated with control of L. wollei, independent of adsorbed copper. L. wollei control was determined by filament viability and chlorophyll a concentrations. Similar exposure factors elicited similar internalized copper levels and consequent responses of L. wollei. Ultimately, a "concentration-exposure-time" (CET) model was created to assist water resource managers in selecting an appropriate treatment regime for a specific in-water infestation. By assessing the exposure concentration and duration required to achieve the internal threshold of copper (i.e., critical burden) that elicits control, water management objectives can be achieved while simultaneously decreasing the environmental loading of copper and potential for non-target species risks.

Comparative toxicity of sodium carbonate peroxyhydrate to freshwater organisms.

Sodium carbonate peroxyhydrate (SCP) is a granular algaecide containing H2O2 as an active ingredient to control growth of noxious algae. Measurements of sensitivities of target and non-target species to hydrogen peroxide are necessary for water resource managers to make informed decisions and minimize risks for non-target species when treating noxious algae. The objective of this study was to measure and compare responses among a target noxious alga (cyanobacterium Microcystis aeruginosa) and non-target organisms including a eukaryotic alga (chlorophyte Pseudokirchneriella subcapitata), microcrustacean (Ceriodaphnia dubia), benthic amphipod (Hyalella azteca), and fathead minnow (Pimephales promelas) to exposures of hydrogen peroxide as SCP. Hydrogen peroxide exposures were confirmed using the I3(-) method. SCP margins of safety for these organisms were compared with published toxicity data to provide context for other commonly used algaecides and herbicides (e.g. copper formulations, endothall, and diquat dibromide). Algal responses (cell density and chlorophyll a concentrations) and animal mortality were measured after 96h aqueous exposures to SCP in laboratory-formulated water to estimate EC50 and LC50 values, as well as potency slopes. Despite a shorter test duration, M. aeruginosa was more sensitive to hydrogen peroxide as SCP (96h EC50:0.9-1.0mgL(-)(1) H2O2) than the eukaryotic alga P. subcapitata (7-d EC50:5.2-9.2mgL(-1) H2O2), indicating potential for selective control of prokaryotic algae. For the three non-target animals evaluated, measured 96-h LC50 values ranged from 1.0 to 19.7mgL(-1) H2O2. C. dubia was the most sensitive species, and the least sensitive species was P. promelas, which is not likely to be affected by concentrations of hydrogen peroxide as SCP that would be used to control noxious algae (e.g. M. aeruginosa). Based on information from peer-reviewed literature, other algaecides could be similarly selective for cyanobacteria. Of the algaecides compared, SCP can selectively mitigate risks associated with noxious cyanobacterial growths (e.g. M. aeruginosa), with an enhanced margin of safety for non-target species (e.g. P. promelas).

Effect of the Algaecide Palmitoleic Acid on the Immune Function of the Bay Scallop Argopecten irradians.

Palmitoleic acid (PA), an algicidal compound, is used against the toxin producing dinofagelate Alexandrium tamarense, however, its impact on the edible bay scallop (Argopecten irradians) is still unclear. Therefore, we investigated the impacts of effective algicidal concentrations (20, 40, and 80 mg/L) of PA on immune responses in A. irradians. Various immune parameters including acid phosphatase (ACP) activity, superoxide dismutase (SOD), lysozyme, phagocytic activity, total protein, malondialdehyde (MDA) level, and reactive oxygen species (ROS) production and the expression of immune-related genes (PrxV, CLT-6, MT, and BD) were measured at 3, 6, 12, 24, and 48 h post-exposure (hpe) to PA. Lysozyme activity was lower in scallops at 12-48 hpe to 80 mg/L. SOD, ACP activity, ROS production, the total protein, and MDA level was higher at 12 to 48 hpe with different concentrations of PA. Phagocytic activity increased at 6-12 hpe to 40-80 mg/L of PA, but decreased at 24-48 hpe. The expressions of genes PrxV, CLT-6, MT and BD down-regulated at 3 hpe were observed, while differential expressions from 6-48 hpe with different concentrations of PA. The present study demonstrated that immersing A. irradians in PA at effective concentrations could result in differential effects on non-specific immune responses and expressions of immune-related genes.

Diquat associated with copper sources for algae control: Efficacy and ecotoxicology.

The aims of this research were to evaluate the efficacy of copper oxychloride (CuCl2.3Cu(OH)2), copper hydroxide (Cu(OH)2) and diquat (1.1'-ethylene-2.2'-bipyridyldiylium dibromide), isolated and in association with 0.1% of both copper sources, in the control of the unicellular algae Ankistrodesmus gracilis and the filamentous algae Pithophora kewesis, and to determine the acute toxicity of the tested chemicals in Hyphressobrycon eques, Pomacea canaliculata, Lemna minor and Azolla caroliniana. The efficacy was estimated by the methods of chlorophyll a and pheophytin a readings, changed into growth inhibition percentage. Both algae were exposed to the following concentrations: 0.2; 0.4; 0.8; 1.2 mg L(-1) of diquat and its association with the copper sources; and 0.1; 0.3; 0.5; 0.7; 1.0 and 1.5 mg L(-1) in the isolated applications of copper hydroxide and copper oxychloride. An untreated control was kept. The acute toxicity was estimatedby 50% lethal concentration (LC50). The copper sources were effective for A. gracilis control, at rates as high as 0.1 mg L(-1) (>95% efficacy). Isolated diquat and its association with copper hydroxide were both effective at rates as high as 0.4 mg L(-1), with 95 and 88% control efficacy, respectively. The copper oxychloride was effective at 0.2 mg L(-1), with 93% efficacy. None of the tested chemicals and associations was effective on P. kewesis control. The most sensitive non target organism to the tested chemicals was L. minor; the less sensitive was H. eques.

Differential response of orthologous L,L-diaminopimelate aminotransferases (DapL) to enzyme inhibitory antibiotic lead compounds.

L,L-Diaminopimelate aminotransferase (DapL) is an enzyme required for the biosynthesis of meso-diaminopimelate (m-DAP) and L-lysine (Lys) in some bacteria and photosynthetic organisms. m-DAP and Lys are both involved in the synthesis of peptidoglycan (PG) and protein synthesis. DapL is found in specific eubacterial and archaeal lineages, in particular in several groups of pathogenic bacteria such as Leptospira interrogans (LiDapL), the soil/water bacterium Verrucomicrobium spinosum (VsDapL) and the alga Chlamydomonas reinhardtii (CrDapL). Here we present the first comprehensive inhibition study comparing the kinetic activity of DapL orthologs using previously active small molecule inhibitors formerly identified in a screen with the DapL of Arabidopsis thaliana (AtDapL), a flowering plant. Each inhibitor is derived from one of four classes with different central structural moieties: a hydrazide, a rhodanine, a barbiturate, or a thiobarbituate functionality. The results show that all five compounds tested were effective at inhibiting the DapL orthologs. LiDapL and AtDapL showed similar patterns of inhibition across the inhibitor series, whereas the VsDapL and CrDapL inhibition patterns were different from that of LiDapL and AtDapL. CrDapL was found to be insensitive to the hydrazide (IC50 >200 µM). VsDapL was found to be the most sensitive to the barbiturate and thiobarbiturate containing inhibitors (IC50 ∼5 µM). Taken together, the data shows that the homologs have differing sensitivities to the inhibitors with IC50 values ranging from 4.7 to 250 µM. In an attempt to understand the basis for these differences the four enzymes were modeled based on the known structure of AtDapL. Overall, it was found that the enzyme active sites were conserved, although the second shell of residues close to the active site were not. We conclude from this that the altered binding patterns seen in the inhibition studies may be a consequence of the inhibitors forming additional interactions with residues proximal to the active site, or that the inhibitors may not act by binding to the active site. Compounds that are specific for DapL could be potential biocides (antibiotic, herbicide or algaecide) that are nontoxic to animals since animals do not contain the enzymes necessary for PG or Lys synthesis. This study provides important information to expand our current understanding of the structure/activity relationship of DapL and putative inhibitors that are potentially useful for the design and or discovery of novel biocides.

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.

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.