Biochemical biomarkers in algae and marine pollution: a review

Physiological and toxicological response of Microcystis aeruginosa BCCUSP232 exposed to Salvinia auriculata extracts

Microcystis aeruginosa is one of the most predominant freshwater bloom-forming cyanobacterium found globally which is capable of producing toxic secondary metabolites including microcystins that might intoxicate animals and humans when contaminated water or food is ingested. Salvinia auriculata Aubl is one of the plants that might possess bioactive compounds capable of controlling growth and reproduction of M. aeruginosa. The present study aimed to determine the presence of bioactive compounds in S. auriculata extracts and determine alterations occurred in growth and reproduction of M. aeruginosa when exposed to these plant extracts. In addition, this investigation aimed to examine the influence of S. auriculata on antioxidant enzymes detected in M. aeruginosa. The results obtained demonstrated that the aqueous and ethanolic extracts of S. auriculata presented potential for control of cyanobacteria populations, exhibiting algicidal action on M. aeruginosa as well as interfering in antioxidant enzymes activities and parameters associated with oxidative stress. Phytochemical analyses demonstrated the presence of polyphenols and flavonoids content in both extracts. In addition, application of S. auriculata extracts did not produce cytogenotoxicity and/or mutagenicity utilizing Allium cepa test. Therefore, further studies are needed in order to identify and characterize the compounds responsible for these effects on M. aeruginosa and provide information regarding the possible application of S. auriculata in the treatment of drinking water.

Combined effects of microplastics and pharmaceutical and personal care products on algae: A critical review

Microplastics (MPs) and pharmaceuticals and personal care products (PPCPs) are ubiquitous in aquatic environments. Algae play an important role in aquatic environments. Thus, it is important to study the response of algae to combined exposure of MPs and PPCPs. Here, we review the effects of MPs and PPCPs on algae. First, the individual effects of MPs and PPCPs on algae were summarized. Second, the combined effects of MPs and PPCPs on algae were systematically analyzed. (1) Antagonism: ① when the MPs are too large to enter the algal cells, the adsorption of PPCPs onto MPs results in decreased the contact of MPs and PPCPs with algae; ② PPCPs and MPs have opposing actions on the same biological target; ③ MPs increase the activity of metabolic enzymes in algae, thus promoting the PPCP degradation. (2) Synergy: ① when the MPs are small enough to enter algal cells, the adsorption of PPCPs on MPs promotes the entry of PPCPs; ② when MPs are negatively charged, the adsorption of positively charged PPCPs by MPs decreases the electrostatic repulsion, increasing the interaction between algae and MPs; ③ complementary modes of action between MPs and PPCPs show combined effects on the same biological target. Third, the relative importance of the factors that impact the combined effects are evaluated using the random forest model decreased in the following order: PPCP types > algal species > MP size > MP concentration > MP types > exposure time. Finally, future directions for the combined effects of MPs and PPCPs are proposed, which will facilitate a better understanding of the environmental fate and risks of both MPs and PPCPs.

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.

Microbial recovery of rare earth elements from various waste sources: a mini review with emphasis on microalgae

Rare Earth Elements (REEs) are indispensable in contemporary technologies, influencing various aspects of our daily lives and environmental solutions. The escalating demand for REEs has led to increased exploitation, resulting in the generation of diverse REE-bearing solid and liquid wastes. Recognizing the potential of these wastes as secondary sources of REEs, researchers are exploring microbial solutions for their recovery. This mini review provides insights into the utilization of microorganisms, with a particular focus on microalgae, for recovering REEs from sources such as ores, electronic waste, and industrial effluents. The review outlines the principles and distinctions of bioleaching, biosorption, and bioaccumulation, offering a comparative analysis of their potential and limitations. Specific examples of microorganisms demonstrating efficacy in REE recovery are highlighted, accompanied by successful methods, including advanced techniques for enhancing microbial strains to achieve higher REE recovery. Moreover, the review explores the environmental implications of bio-recovery, discussing the potential of these methods to mitigate REE pollution. By emphasizing microalgae as promising biotechnological candidates for REE recovery, this mini review not only presents current advances but also illuminates prospects in sustainable REE resource management and environmental remediation.

Mechanisms of the novel pesticide sodium dodecyl benzene sulfonate in the mitigation of protozoan ciliated pathogens during microalgal cultivation

Protozoan ciliates represent a common biological contaminant during microalgae cultivation, which will lead to a decline in microalgae productivity. This study investigated the effectiveness of sodium dodecyl benzene sulfonate (SDBS) in controlling ciliate populations within microalgae cultures. SDBS concentrations of 160 mg/L and 100 mg/L were found to effectively manage the representative species of ciliates contamination by Euplotes vannus and Uronema marinum during the cultivation of Synechococcus and Chlorella, and the growth vitality of microalgae has been restored. Additionally, SDBS at these concentrations reduced oxidative stress resistance and induced membrane damage to remove biological pollutants by modulating enzyme activity, affecting lipid, energy, amino acid metabolism pathways, and processes such as translation and protein folding. This research provides insights into the mechanisms through which SDBS effectively combats protozoan ciliates during the microalgal cultivation. This contributes to reduce biological pollution, ensure the overall productivity and healthy and sustainable management of microalgae ecosystems.

Oxidative stress in the bivalve Diplodon chilensis under direct and dietary glyphosate-based formulation exposure

The aim of this study was to evaluate and compare the effects on biochemical parameters and organosomatic indices in the freshwater bivalve Diplodon chilensis exposed to a glyphosate-based formulation under direct and dietary exposures (4 mg a.p./L). After 1, 7, and 14 days of exposure, reduced glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) levels and the activities of glutathione-S- transferase (GST), superoxide dismutase (SOD), and catalase (CAT) were evaluated in the gills and digestive gland. The hepatosomatic (HSI) and branchiosomatic (BSI) indices were also analyzed. Direct and dietary glyphosate-based formulation exposure altered the redox homeostasis in the gills and digestive gland throughout the experimental time, inducing the detoxification response (GST), the antioxidant defenses (SOD, CAT, GSH), and causing lipid peroxidation. After 14 days of exposure, the HSI and BSI increased significantly (43% and 157%, respectively) only in the bivalves under direct exposure. Greater changes in the biochemical parameters were induced by the dietary exposure than by the direct exposure. Furthermore, the gills presented an earlier response compared to the digestive gland. These results suggested that direct and dietary exposure to a glyphosate-based formulation induced oxidative stress in the gills and digestive glands of D. chilensis. Thus, the presence of glyphosate-based formulations in aquatic ecosystems could represent a risk for filter-feeding organisms like bivalves.

Enantioselectivity in ecotoxicity of pharmaceuticals, illicit drugs, and industrial persistent pollutants in aquatic and terrestrial environments: A review

At present, there is a serious concern about the alarming number of recalcitrant contaminants that can negatively affect biodiversity threatening the ecological status of marine, estuarine, freshwater, and terrestrial ecosystems (e.g., agricultural soils and forests). Contaminants of emerging concern (CEC) such as pharmaceuticals (PHAR), illicit drugs (ID), industrial persistent pollutants, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) and chiral ionic solvents are globally spread and potentially toxic to non-target organisms. More than half of these contaminants are chiral and have been measured at different enantiomeric proportions in diverse ecosystems. Enantiomers can exhibit different toxicodynamics and toxicokinetics, and thus, can cause different toxic effects. Therefore, the enantiomeric distribution in occurrence cannot be neglected as the toxicity and other adverse biological effects are expected to be enantioselective. Hence, this review aims to reinforce the recognition of the stereochemistry in environmental risk assessment (ERA) of chiral CEC and gather up-to-date information about the current knowledge regarding the enantioselectivity in ecotoxicity of PHAR, ID, persistent pollutants (PCBs and PBDEs) and chiral ionic solvents present in freshwater and agricultural soil ecosystems. We performed an online literature search to obtain state-of-the-art research about enantioselective studies available for assessing the impact of these classes of CEC. Ecotoxicity assays have been carried out using organisms belonging to different trophic levels such as microorganisms, plants, invertebrates, and vertebrates, and considering ecologically relevant aquatic and terrestrial species or models organisms recommended by regulatory entities. A battery of ecotoxicity assays was also reported encompassing standard acute toxicity to sub-chronic and chronic assays and different endpoints as biomarkers of toxicity (e.g., biochemical, morphological alterations, reproduction, behavior, etc.). Nevertheless, we call attention to the lack of knowledge about the potential enantioselective toxicity of many PHAR, ID, and several classes of industrial compounds. Additionally, several questions regarding key species, selection of most appropriate toxicological assays and ERA of chiral CEC are addressed and critically discussed.

Microbes and microbial strategies in carcinogenic polycyclic aromatic hydrocarbons remediation: a systematic review

Degradation, detoxification, or removal of the omnipresent polycyclic aromatic hydrocarbons (PAHs) from the ecosphere as well as their prevention from entering into food chain has never appeared simple. In this context, cost-effective, eco-friendly, and sustainable solutions like microbe-mediated strategies have been adopted worldwide. With this connection, measures have been taken by multifarious modes of microbial remedial strategies, i.e., enzymatic degradation, biofilm and biosurfactant production, application of biochar-immobilized microbes, lactic acid bacteria, rhizospheric-phyllospheric-endophytic microorganisms, genetically engineered microorganisms, and bioelectrochemical techniques like microbial fuel cell. In this review, a nine-way directional approach which is based on the microbial resources reported over the last couple of decades has been described. Fungi were found to be the most dominant taxa among the CPAH-degrading microbial community constituting 52.2%, while bacteria, algae, and yeasts occupied 37.4%, 9.1%, and 1.3%, respectively. In addition to these, category-wise CPAH degrading efficiencies of each microbial taxon, consortium-based applications, CPAH degradation-related molecular tools, and factors affecting CPAH degradation are the other important aspects of this review in light of their appropriate selection and application in the PAH-contaminated environment for better human-health management in order to achieve a sustainable ecosystem.

Hydrogen Peroxide Stress Induced in the Marine Cyanobacterium Synechococcus aeruginosus and Phormidium valdarianum

Biochemical markers against hydrogen peroxide-induced oxidative stress were developed in marine cyanobacteria under standard laboratory conditions. To find out the ability to cope with different concentrations of hydrogen peroxide, two species of marine cyanobacteria including unicellular and filamentous forms were exposed for shorter duration. Synechococcus aeruginosus and Phormidium valderianum tolerated hydrogen peroxide by showing the highest growth of Superoxide dismutase in Synechococcus aeruginosus and Phormidium valderianum, catalase in Synechococcus aeruginosus, peroxidase in Synechococcus aeruginosus and Phormidium valderianum, Glutathione S-transferase in Synechococcus aeruginosus and Phormidium valderianum which were identified as biochemical markers of oxidative stress against H2O2 in marine cyanobacteria. Synechococcus aeruginosus showed new isoforms for Superoxide dismutase, catalase, peroxidase, Glutathione peroxidase, and Glutathione S-transferase and Phormidium valderianum for Superoxide dismutase, peroxidase, and Glutathione S-transferase. Synechococcus aeruginosus is suggested as the indicator species for biochemical markers against hydrogen peroxide in marine cyanobacteria. Peroxidase is suggested as biochemical enzyme marker. The present investigated on these new isoenzymes were identified as biochemical markers for oxidative stress.

Effects of copper and cadmium on stream leaf decomposition: evidence from a microcosm study

We seek to understand how copper and cadmium act on leaf litter decomposition by their effects on microbial conditioning and litter fragmentation by invertebrates. In this study, we evaluated, in an integrated manner, different biological elements responsible for functioning of streams. Thus, we performed a microcosm assay with different concentrations for the two metals and their combination, evaluating their effects on fungi sporulation rate, consumption rate by shredders, and, consequently, the leaf litter decomposition rates. Sporulation rates were affected by all copper concentrations tested 10 ×  = 16 µg L-1 and 25 ×  = 40 µg L-1) but significantly reduced only at the highest concentration of cadmium (25 ×  = 22.5 µg L-1). Increased copper and cadmium concentrations reduced the consumption of leaf litter by Phylloicus at 60%. The concentrations (10 × and 25 ×) of both metals resulted in a reduction in decomposition rates. When combined, copper and cadmium negatively affected microbial conditioning, consumption by shredders, and leaf litter decomposition. Increases in concentrations of copper and cadmium directly affected organic matter decomposition in aquatic environments. Thus, the presence of a high concentration of heavy metals in aquatic environments alters the functioning of ecosystems. As trace-elements occur in a combined manner in environments, our results show that the combined effects of different metals potentiate the negative effects on ecosystem processes.

Plummeting toxic contaminates from water through phycoremediation: Mechanism, influencing factors and future outlook to enhance the capacity of living and non-living algae

Freshwater habitats hold a unique role in the survival of all living organisms and supply water for drinking, irrigation, and life support activities. In recent decades, due to anthropogenic activities, deterioration in the water quality has been a long-lasting problem and challenge to the scientific fraternity. Although, these freshwater bodies have a bearable intrinsic capacity for pollution load however alarming increase in pollution limits the intrinsic capacities and requires additional technological interventions. The release of secondary pollutants from conventional interventions further needs revisiting the existing methodologies and asking for green interventions. Green interventions such as phycoremediation are natural, eco-friendly, economic, and energy-efficient alternatives and provide additional benefits such as nutrient recovery, biofuel production, and valuable secondary metabolites from polluted freshwater bodies. This systemic review in a nut-shell comprises the recent research insights on phycoremediation, technological implications, and influencing factors, and further discusses the associated mechanisms of metal ions biosorption by living and non-living algae, its advantages, and limitations. Besides, the article explores the possibility of future research prospects for applicability at a field scale that will help in the efficient utilization of resources, and improved ecological and health risks.

Potential risk of estrogenic compounds produced by water blooms to aquatic environment

Some freshwater phytoplankton species have been suggested to produce estrogenic compounds in concentrations which could cause adverse effects to aquatic biota, while other studies showed no estrogenic effects after exposure to phytoplankton extracts or pointed out possible sources of the overestimation of the estrogenic activity. This study aimed to clarify these research inconsistencies by investigating estrogenicity of biomass extracts from both environmental freshwater blooms and laboratory cyanobacterial and algae cultures by in vitro reporter bioassay. Biomasses of 8 cyanobacterial and 3 algal species from 7 taxonomic orders were extracted and tested. Next to this, samples of environmental water blooms collected from 8 independent water bodies dominated by phytoplankton species previously assessed as laboratory cultures were tested. The results showed undetectable or low estrogenicity of both freshwater blooms and laboratory cultures with E2 equivalent concentration (EEQ) in a range from LOQ up to 4.5 ng EEQ/g of dry mass. Moreover, the co-exposure of biomass extracts with environmentally relevant concentration of model estrogen (steroid hormone 17β-estradiol; E2), commonly occurring in surface waters, showed simple additive interaction. However, some of the biomass extracts elicited partially anti-estrogenic effects in co-exposure with higher E2 concentration. In conclusion, our study documents undetectable or relatively low estrogenic potential of biomass extracts from both environmental freshwater blooms and studied laboratory cultured cyanobacterial and algae species. Nevertheless, in case of very high-density water blooms, even this low estrogenicity (detected for two cyanobacterial species) could lead to EEQ content in biomass reaching effect-based trigger values indicating potential risk, if recalculated per water volume at field sites. However, these levels would not occur in water under realistic environmental scenarios and the potential estrogenic effects would be most probably minor compared to other toxic effects caused by massive freshwater blooms of such high densities.

Comparison of the microalgae Phormidium tenue and Chlorella vulgaris as biosorbents of Cd and Zn from aqueous environments

Heavy metals are accumulating into sediments and enriching in aquatic food chains. The efficiency of two microalgae, Phormidium tenue and Chlorella vulgaris, to remove zinc and cadmium from aqueous solutions was studied. The microalgae were incubated in different heavy metal concentrations for 18 days. Morphological and anatomical changes in microalgae were investigated using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). Both algae removed both Zn2+ and Cd2+in vitro. C. vulgaris removed Zn2+ almost totally (99%) and Cd2+ slightly less (87%). The concentration factors were 2210 and 1117, respectively. SEM and TEM figures showed some alterations in the form and cellular components of both algae. C. vulgaris appeared to be more tolerant to both Cd and Zn than P. tenue. C. vulgaris is a promising microalgal species used to remove heavy metals from aqueous environments.

Effects of combined exposure of PVC and PFOA on the physiology and biochemistry of Microcystis aeruginosa

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs) have drawn significant attention as emerging threats to aquatic ecosystems. There are currently just a few investigations on the combined toxicity of PFAS and MP on freshwater microalgae. In this research, the combined toxicity of polyvinyl chloride (PVC) and perfluorooctanoic acid (PFOA) to Microcystis aeruginosa was investigated. The results indicated that the combination of these pollutants inhibited the growth of M. aeruginosa and promoted the synthesis and release of Microcystin-LR (MC-LR). Individual and combined exposure caused different responses to cellular oxidative stress. Under the Individual exposure of PFOA, when the concentration was greater than 20.0 mg/L, the catalase (CAT) activity increased significantly, and when it was greater than 100.0 mg/L, the malondialdehyde (MDA) content increased significantly, but there is no significant change under combined exposure. PVC and PFOA exposure also caused physical damage to the algal cells and reduced the content of extracellular polymer substances (EPS) based on analysis of cell morphology. Metabolic analysis revealed that carbohydrate metabolism and amino acid metabolism of the algae were affected. The current study offers a fresh theoretical framework for MPs and PFASs environmental risk evaluations.

Antioxidant enzymes of Pseudochlorella pringsheimii under two stressors: variation of SOD Isoforms activity

Algae are always facing the challenge of exposure to different stress conditions, therefore raising challenges of adaptation for survival. In this context, the growth and the antioxidant enzymes of the green stress-tolerant alga Pseudochlorella pringsheimii were investigated under two environmental stresses viz. iron and salinity. The number of algal cells was moderately increased by iron treatment in the range of 0.025-0.09 mM of iron, yet, the number of cells decreased at high iron concentrations (0.18 to 0.7 mM Fe). Furthermore, the different NaCl concentrations (8.5-136.0 mM) had an inhibitory effect on the algal cell number, compared to the control.The superoxide dismutase (SOD) showed three isoforms namely; Mn, Fe, and Cu/Zn SOD. The in gel and in vitro (tube-test) activities of FeSOD were higher compared with the other SOD isoforms. The activity of total SOD and its isoforms increased significantly by the different concentrations of Fe and non-significantly by NaCl. The maximum SOD activity was recorded at 0.7 mM Fe (67.9% above control). The relative expression of FeSOD was high under iron and NaCl at 8.5 and 34 mM, respectively. However, FeSOD expression was reduced at the highest NaCl tested concentration (136 mM). In addition, the antioxidant enzyme activity of catalase (CAT) and peroxidase (POD) were accelerated by increasing iron and salinity stress which indicates the essential role of these enzymes under stress. The correlation between the investigated parameters was also investigated. A highly significant positive correlation between the activity of total SOD and its isoforms, and with the relative expression of FeSOD was observed.

Applying an internal transcribed spacer as a single molecular marker to differentiate between Tetraselmis and Chlorella species

In the realm of applied phycology, algal physiology, and biochemistry publications, the absence of proper identification and documentation of microalgae is a common concern. This poses a significant challenge for non-specialists who struggle to identify numerous eukaryotic microalgae. However, a promising solution lies in employing an appropriate DNA barcoding technique and establishing comprehensive databases of reference sequences. To address this issue, we conducted a study focusing on the molecular characterization and strain identification of Tetraselmis and Chlorella species, utilizing the internal transcribed spacer (ITS) barcode approach. By analyzing the full nuclear ITS region through the Sanger sequencing approach, we obtained ITS barcodes that were subsequently compared with other ITS sequences of various Tetraselmis and Chlorella species. To ensure the reliability of our identification procedure, we conducted a meticulous comparison of the DNA alignment, constructed a phylogenetic tree, and determined the percentage of identical nucleotides. The findings of our study reveal the significant value of the ITS genomic region as a tool for distinguishing and identifying morphologically similar chlorophyta. Moreover, our results demonstrate that both the ITS1 and ITS2 regions are capable of effectively discriminating isolates from one another; however, ITS2 is preferred due to its greater intraspecific variation. These results underscore the indispensability of employing ITS barcoding in microalgae identification, highlighting the limitations of relying solely on morphological characterization.

Marine Pollution and Advances in Biomonitoring in Cartagena Bay in the Colombian Caribbean

Coastal zones sustain extensive biodiversity, support key processes for ocean dynamics, and influence the balance of the global environment. They also provide resources and services to communities, determine their culture, and are the basis for their economic growth. Cartagena Bay in the Colombian Caribbean is the place of the establishment of one of the country's main cities, which has a great historical and tourist attraction, and it is also the location of the main commercial port and a great variety of industries. Historically, it has been affected by several environmental impacts and intense pollution. This situation has gained the attention of different researchers, so herein is presented a literature review with a systematic approach using RStudio's bibliometrix on the presence of pollutants and the impact on biodiversity in recent decades, providing a critical analysis of the state of Cartagena Bay and its future needs to ensure its recovery and conservation. In addition, the socioeconomic dynamics related to the environmental state of Cartagena Bay are presented from the framework drivers, pressures, status, impacts, and responses (DPSIR). The update and critical understanding of the sources, fate, and effects of pollution are important not only for the knowledge of the status of this singular ecosystem but also to encourage future research and entrench evidence to support decision makers' actions. This review highlights that several pollutants that have been detected exceeding sediment quality guidelines, like As, Cd, Hg, and PAH, are also reported to bioaccumulate and cause damage throughout the trophic levels of the coastal environment. In addition, the potential use of sentinel species and biomarkers for their monitoring is discussed. Finally, the factors that cause pollution and threaten the state of the bay continue to exert pressure and impact; thus, there is a call for the further monitoring of this ecosystem and the strengthening of policies and regulations.

Removal of mercury by silica-supported ionic liquids: Efficiency and ecotoxicological assessment

Anthropogenic impacts have affected the coastal environment and contributed to its contamination. Mercury (Hg) is widespread in nature and has been shown to be toxic in even the smallest amounts, negatively affecting not only the marine ecosystem but also the entire trophic chain due to its biomagnification. Mercury ranks third on the Agency for Toxic Substances and Diseases Registry (ATSDR) priority list and it is therefore imperative to develop more effective methods than those currently available to avoid the persistence of this contaminant in aquatic ecosystems. The present study aimed to evaluate the effectiveness of six different silica-supported ionic liquids (SIL) in removing Hg from contaminated saline water, under realistic conditions ([Hg] = 50 µg/L), and to ecotoxicologically evaluate the safety of the SIL-remedied water, using as test model the marine macroalga Ulva lactuca. The results revealed that SIL [Si][C3C1im][SCN] (250 mg/L) was the most effective in removing Hg from solution, with a efficiency up to 99 % in just 6 h, that enable to obtain < 1 µg/L Hg (European guideline in drinking water). U. lactuca exposed to either the SIL and/or the remedied water showed no significant changes in relative growth rate and chlorophyll a and b levels, compared to the control condition. Biomarker analysis (LPO, GSH, GSSG, SOD, GPx, CAT and GRed) also showed no significant changes in the biochemical performance of U. lactuca. Therefore, it could be assumed that water treatment with SIL or its presence in an aqueous environment does not pose toxicity levels that could inhibit the metabolism or cause cell damage to U. lactuca.

Incorporating marine particulate carbon into machine learning for accurate estimation of coastal chlorophyll-a

Accurate predictions of coastal ocean chlorophyll-a (Chl-a) concentrations are necessary for dynamic water quality monitoring, with eutrophication as a critical factor. Prior studies that used the driven-data method have typically overlooked the relationship between Chl-a and marine particulate carbon. To address this gap, marine particulate carbon was incorporated into machine learning (ML) and deep learning (DL) models to estimate Chl-a concentrations in the Yang Jiang coastal ocean of China. Incorporating particulate organic carbon (POC) and particulate inorganic carbon (PIC) as predictors can lead to successful Chl-a estimation. The Gaussian process regression (GPR) model significantly outperforming the DL model in terms of stability and robustness. A lower POC/Chl-a ratio was observed in coastal areas, in contrast to the higher ratios detected in the southern regions of the study area. This study highlights the efficacy of the GPR model for estimating Chl-a and the importance of considering POC in modeling Chl-a concentrations.

Proteomics Reveals Damaging Effect of Alpha-Cypermethrin Exposure in a Non-Target Freshwater Microalga Chlorella sp. NC-MKM

Alpha-cypermethrin, a pyrethroid pesticide, is frequently used on crops to prevent insect attacks. However, occasionally, due to drift, leaching, or with rainwater, it enters the aquatic environment and poses a serious threat to the growth of non-target aquatic organisms. In the current study, we were interested in investigating the damaging effect of alpha-cypermethrin on a local freshwater non-target green alga Chlorella sp. NC-MKM in terms of its protein levels. This was achieved by exposing Chlorella sp. NC-MKM to an EC₅₀ concentration of alpha-cypermethrin for 1 day, followed by the two-dimensional (2-D) gel electrophoresis and MALDI-TOF MS. Fifty-three proteins, which had showed significant differential accumulation (> 1.5 fold, P < 0.05) after exposure to alpha-cypermethrin, were considered as differentially accumulated proteins (DAPs). These DAPs were further divided into several functional categories, and the expressions of each in control and treatment samples were compared. Comparison revealed that alpha-cypermethrin exposure affects the accumulation of proteins related with photosynthesis, stress response, carbohydrate metabolism, signal transduction and transporters, translation, transcription, cell division, lipid metabolism, amino acid and nucleotide biosynthesis, secondary metabolites production, and post-translational modification, and thus rendered the tested algal isolate sensitive toward this pesticide. The overall findings of this research thus offer a fundamental understanding of the possible mechanism of action of the insecticide alpha-cypermethrin on the microalga Chlorella sp. NC-MKM and also suggest potential biomarkers for the investigation of pesticide exposed microalgae.

Methodological advances and future directions of microalgal bioassays for evaluation of potential toxicity in environmental samples: A review

Microalgal bioassays are widely applied to evaluate the potential toxicity of various persistent toxic substances in environmental samples due to multiple advantages, including high sensitivity, short test duration, and cost-effectiveness. Microalgal bioassay is gradually developing in method, and the scope of application to environmental samples is also expanding. Here, we reviewed the published literature on microalgal bioassays for environmental assessments, focusing on types of samples, sample preparation methods, and endpoints, and highlighted key scientific advancements. Bibliographic analysis was performed with the keywords 'microalgae' and 'toxicity' or 'bioassay', and 'microalgal toxicity'; 89 research articles were selected and reviewed. Traditionally, most studies implementing microalgal bioassays focused on water samples (44%) with passive samplers (38%). Studies using the direct exposure method (41%) of injecting microalgae into sampled water mainly evaluated toxic effects by growth inhibition (63%). Recently, various automated sampling techniques, in situ bioanalytical methods with multiple endpoints, and targeted and non-targeted chemical analyses have been applied. More research is needed to identify causative toxicants affecting microalgae and to quantify the cause-effect relationships. This study provides the first comprehensive overview of recent advances in microalgal bioassays performed with environmental samples, suggesting future research directions based on current understanding and limitations.

Effects of erythromycin and roxithromycin on river periphyton: Structure, functions and metabolic pathways

Macrolides have been frequently detected in the surface waters worldwide, posing a threat to the aquatic microbes. Several studies have evaluated the ecotoxicological effects of macrolides on single algal and bacterial strains. However, without considering the species interaction in the aquatic microbial community, these results cannot be extrapolated to the field. Thus, the present study aimed to evaluate the effects of two macrolides (erythromycin and roxithromycin) on the structure, photosynthetic process, carbon utilization capacity, and the antibiotic metabolic pathways in river periphyton. The colonized periphyton was exposed to the graded concentration (0 μg/L (control), 0.5 μg/L (low), 5 μg/L (medium), 50 μg/L (high)) of ERY and ROX, respectively, for 7 days. Herein, high levels of ERY and ROX altered the community composition by reducing the relative abundance of Chlorophyta in the eukaryotic community. Also, the Shannon and Simpson diversity indexes of prokaryotes were reduced, although similar effects were seldomly detected in the low and medium groups. In contrast to the unchanged carbon utilization capacity, the PSII reaction center involved in the periphytic photosynthesis was significantly inhibited by macrolides at high levels. In addition, both antibiotics had been degraded by periphyton, with the removal rate of 51.63-66.87% and 41.85-48.27% for ERY and ROX, respectively, wherein the side chain and ring cleavage were the main degradation pathways. Overall, this study provides an insight into the structural and functional toxicity and degradation processes of macrolides in river periphyton.

To what extent are filter feeder elasmobranchs exposed to marine pollution? A systematic review

Filter feeding elasmobranchs may be considered as biological indicators of marine pollution, despite most of these species are under some degree of extinction risk. Among threats to this taxonomic group, marine pollution might represent an additional concern for their survival. In this review, a comprehensive systematic search of scientific literature on pollutants in filter feeding elasmobranchs was conducted to evaluate the bioaccumulation patterns, and risk for human consumers. We found that, despite an increasing trend in the number of published studies, the geographical coverage is still very limited and most of the studies focused solely on trace elements (70.8%). Among sharks, Rhincodon typus was the most represented species (66.7%), while Mobula mobular the most studied ray species (41.7%). Comparing the levels of pollutants in filter feeders between ocean basins, this review highlighted that Hg, As and Cd levels are mostly higher in those areas affected by both strong natural and anthropogenic source of emissions, such as the Indian Ocean. With regards to OCs, ΣPCB levels in muscle of C. maximus were between 4.3 and 50.5 μg kg^-1 ww, highlighting a persistent contamination of PCB in the Mediterranean Sea. Some species exceeded the maximum allowable limits for foodstuff consumption for As, Cd and Pb. A total of 77.8% of the analyzed species exceeded the Environmental Quality Standards for Hg, while they were always below the EQS_biota for HCB, PBDEs, PFOS and DDT. Given their feeding mechanism that continuously samples the marine environment, further investigations are urgently needed to determine not only the extent of contaminant exposure in different hotspot locations but also the risks posed to the elasmobranch health.

Effects of phosphate on the toxicity and bioaccumulation of arsenate in marine diatom Skeletonema costatum

The effects of nutrient phosphate (P) at environmentally relevant levels on the toxicity of arsenic (As) in marine microalgae have been rarely known. In the present study, we explored the toxicity and bioaccumulation of As in a globally distributed diatom species Skeletonema costatum at different ambient P concentrations. The results showed that As toxicity was suppressed at elevated P concentrations. Intracellular As content ([As]_intra) and the molar ratio of intracellular As to P ([As:P]) were negatively correlated with the ambient P concentrations. The trends of As bioaccumulation were substantially different between the relatively low (0, 0.5 and 1.5 μM) and high P concentrations (7.5 and 37.5 μM). Both [As]_intra and [As:P] suggested that As bioaccumulation was a better factor to explain the As toxicity comparing to the ambient As concentration. The 4 h As uptake kinetics at different P concentrations followed Michaelis-Menten kinetic pattern. The maximum uptake rates (V_max) decreased with the increase in P concentrations, and the half-saturation constants (K_d) remained constant except for that at extremely high P concentration (37.5 μM-P), suggesting the depression of P on As uptake was mainly due to the non-competitive effect. Overall, these results demonstrate that the P concentration in seawater is an important factor affecting As toxicity and bioaccumulation in the marine diatom. This study therefore helps us better understand the effects of eutrophication on the toxicity and biogeochemistry of As in the marine environment.

Cadmium stress interacts with nutrient availability and light condition to affect the growth of Hydrocotyle vulgaris

Heavy metal pollution is becoming a serious problem in wetland and often co-occurs with nutrient availability and light conditions variation. We hypothesized that nutrient availability and light condition can affect the growth of wetland plants under heavy metal stress. To test this hypothesis, single ramets of a common, clonal wetland plant Hydrocotyle vulgaris were grown for four weeks at three levels of cadmium with three levels of nutrient availability under 30% or 100% light conditions. High level of nutrient availability and high light condition overall promoted growth of H. vulgaris under Cd stress. Under the two light conditions, responses of H. vulgaris to Cd treatments differed among three nutrient levels. Under 30% light condition, 2 mg L-1 Cd2+ treatment decreased total mass at the low nutrient level and decreased ramet number at the medium nutrient level; 0.5 and 2 mg L-1 Cd2+ treatments decreased leaf mass ratio at the low and the medium nutrient levels. Under 100% light condition, 2 mg L-1 Cd2+ treatments significantly decreased total mass at the high level of nutrients; 2 mg L-1 Cd2+ treatment decreased ramet number at the medium and the high nutrient levels and decreased leaf mass ratio at the medium nutrient levels. Our results suggested that Cd stress can interact with nutrient availability and light condition to affect the performance of wetland plants such as H. vulgaris.

Mechanisms and application of microalgae on removing emerging contaminants from wastewater: A review

This study reviews the development of the ability of microalgae to remove emerging contaminants (ECs) from wastewater. Contaminant removal by microalgae-based systems (MBSs) includes biosorption, bioaccumulation, biodegradation, photolysis, hydrolysis, and volatilization. Usually, the existence of ECs can inhibit microalgae growth and reduce their removal ability. Therefore, three methods (acclimation, co-metabolism, and algal-bacterial consortia) are proposed in this paper to improve the removal performance of ECs by microalgae. Finally, due to the high removal performance of contaminants from wastewater by algal-bacterial consortia systems, three kinds of algal-bacterial consortia applications (algal-bacterial activatedsludge, algal-bacterial biofilm reactor, and algal-bacterial constructed wetland system) are recommended in this paper. These applications are promising for ECs removal. But most of them are still in their infancy, and limited research has been conducted on operational mechanisms and removal processes. Extra research is needed to clarify the applicability and cost-effectiveness of hybrid processes.

Ecotoxicological effects of the antidepressant fluoxetine and its removal by the typical freshwater microalgae Chlorella pyrenoidosa

The antidepressant fluoxetine (FLX) has gained increasing attention due to its frequent detection in aquatic environments and negative effects on non-target organisms. However, knowledge on the ecotoxicological effects of FLX and its removal by microalgae is still limited. In this study, the ecotoxicological effects of FLX (10 -1000 μg/L) were assessed using batch cultures of the freshwater microalgae Chlorella pyrenoidosa for 10 days based on changes in growth, antioxidant response, and photosynthetic process. The removal efficiency, removal mechanism, and degradation pathway of FLX by C. pyrenoidosa were also investigated. The results showed that the growth of C. pyrenoidosa was inhibited by FLX with a 4 d EC₅₀ of 0.464 mg/L. Additionally, FLX significantly inhibited photosynthesis and caused oxidative stress on day 4. However, C. pyrenoidosa can produce resistance and acclimatize to FLX, as reflected by the declining growth inhibition rate, recovered photosynthetic efficiency, and disappearance of oxidative stress on day 10. Despite the toxicity of FLX, C. pyrenoidosa showed 41.2%- 100% removal of FLX after 10 days of exposure. Biodegradation was the primary removal mechanism, accounting for 88.2%- 92.8% of the total removal of FLX. A total of five metabolites were found in the degradation processes of FLX, which showed less toxicity than FLX. The main degradation pathways were proposed as demethylation, O-dealkylation, hydroxylation, and N-acylation. Our results not only highlight the potential application of microalgae in FLX purification, but also provide insight into the fate and ecological risk of FLX in aquatic environments.

Copper Effect on Microalgae: Toxicity and Bioremediation Strategies

Microalgae are increasingly recognised as suitable microorganisms for heavy metal (HM) removal, since they are able to adsorb them onto their cell wall and, in some cases, compartmentalise them inside organelles. However, at relatively high HM concentrations, they could also show signs of stress, such as organelle impairments and increased activities of antioxidant enzymes. The main aim of this review is to report on the mechanisms adopted by microalgae to counteract detrimental effects of high copper (Cu) concentrations, and on the microalgal potential for Cu bioremediation of aquatic environments. Studying the delicate balance between beneficial and detrimental effects of Cu on microalgae is of particular relevance as this metal is widely present in aquatic environments facing industrial discharges. This metal often induces chloroplast functioning impairment, generation of reactive oxygen species (ROS) and growth rate reduction in a dose-dependent manner. However, microalgae also possess proteins and small molecules with protective role against Cu and, in general, metal stress, which increase their resistance towards these pollutants. Our critical literature analysis reveals that microalgae can be suitable indicators of Cu pollution in aquatic environments, and could also be considered as components of eco-sustainable devices for HM bioremediation in association with other organisms.

Microalgal Phycoremediation: A Glimpse into a Sustainable Environment

Microalgae are continually exposed to heavy metals and metalloids (HMMs), which stifles their development and reproduction due to the resulting physiological and metabolic abnormalities, leading to lower crop productivity. They must thus change their way of adapting to survive in such a hostile environment without sacrificing their healthy growth, development, reproductive capacity, or survival. The mode of adaptation involves a complex relationship of signalling cascades that govern gene expression at the transcriptional and post-transcriptional levels, which consequently produces altered but adapted biochemical and physiochemical parameters. Algae have been reported to have altered their physicochemical and molecular perspectives as a result of exposure to a variety of HMMs. Hence, in this review, we focused on how microalgae alter their physicochemical and molecular characteristics as a tolerance mechanism in response to HMM-induced stress. Furthermore, physiological and biotechnological methods can be used to enhance extracellular absorption and clean up. The introduction of foreign DNA into microalgae cells and the genetic alteration of genes can boost the bio-accumulation and remediation capabilities of microalgae. In this regard, microalgae represent an excellent model organism and could be used for HMM removal in the near future.

Biotechnology of Microorganisms from Coal Environments: From Environmental Remediation to Energy Production

Simple Summary

Despite the wide perception that coal environments are extreme habitats, they harbor resident microbial communities. Coal-associated habitats, such as coal mine areas/drainages, spoil heaps, and coalbeds, are defined as complex ecosystems with indigenous microbial groups and native microecological networks. Resident microorganisms possess rich functional potentials and profoundly shape a range of biotechnological processes in the coal industry, from production to remediation.

Abstract

It was generally believed that coal sources are not favorable as live-in habitats for microorganisms due to their recalcitrant chemical nature and negligible decomposition. However, accumulating evidence has revealed the presence of diverse microbial groups in coal environments and their significant metabolic role in coal biogeochemical dynamics and ecosystem functioning. The high oxygen content, organic fractions, and lignin-like structures of lower-rank coals may provide effective means for microbial attack, still representing a greatly unexplored frontier in microbiology. Coal degradation/conversion technology by native bacterial and fungal species has great potential in agricultural development, chemical industry production, and environmental rehabilitation. Furthermore, native microalgal species can offer a sustainable energy source and an excellent bioremediation strategy applicable to coal spill/seam waters. Additionally, the measures of the fate of the microbial community would serve as an indicator of restoration progress on post-coal-mining sites. This review puts forward a comprehensive vision of coal biodegradation and bioprocessing by microorganisms native to coal environments for determining their biotechnological potential and possible applications.

Integrated multitrophic aquaculture (IMTA) as an environmentally friendly system for sustainable aquaculture: functionality, species, and application of biofloc technology (BFT)

Aquaculture is one of the fastest-growing industries in the world, and its prominent role has been proven in supplying food for the growing world population. The expected growth of aquaculture requires the development of responsible and sustainable approaches, technologies, culture systems, and practices. The integrated multitrophic aquaculture (IMTA) system has been developed over the past decades. This system is based on the use of all food levels for simultaneous production of some aquaculturally species in a way that contributes to environmental sustainability (biocontrol), economic stability (product diversity and risk reduction), and social acceptance (better management operations). In IMTA, selecting suitable culture species and considering their appropriate population size is absolutely necessary to achieve an optimal biological and chemical process, improving the ecosystem health and sustainability of the industry. Biofloc technology (BFT) is closely related to the IMTA system, where the IMTA potential can be used to control suspended solids in aquaculture systems with limited water exchange. This study reviews the significance of IMTA systems, potential target species for cultivation, the relationship between BFT and IMTA, total suspended solids control, the economics of IMTA farming, and the recent findings in these fields.

The potential of algae and aquatic macrophytes in the pharmaceutical and personal care products (PPCPs) environmental removal: a review

The presence of emerging contaminants, such as pharmaceuticals and personal care products (PPCPs), in aquatic environments has received increasing attention in the last years due to the various possible impacts on the dynamics of the natural environment and human health. In global terms, around 771 active pharmaceutical substances or their transformation products have been detected at levels above their respective detection limit. Additionally, 528 different compounds have been detected in 159 countries. Seeking to overcome potential ecotoxicological problems, several studies have been conducted using different technologies for PPCPs removal. Recently, the use of macro, microalgae, and aquatic macrophytes has been highlighted due to the excellent bioremediation capacity of these organisms and easy acclimatization. Thus, the present review aims to outline a brief and well-oriented scenario concerning the knowledge about the bioremediation alternatives of PPCPs through the use of macro, microalgae, and aquatic macrophytes. The characteristics of PPCPs and the risks of these compounds to the environment and human health are also addressed. Moreover, the review indicates the opportunities and challenges for expanding the use of biotechnologies based on algae and aquatic macrophytes, such as studies dedicated to relate the operational criteria of these biotechnologies with the main PPCPs removal mechanisms. Finally, algae and macrophytes can compose green and ecological biotechnologies for wastewater treatment, having great contribution to PPCPs removal.

Detection of landscape species as a low-cost biomonitoring study: Cr, Mn, and Zn pollution in an urban air quality

Urban air pollution in cities, among the world's most critical problems, has escalated to such an extent that it threatens human health in many urban centers and causes the death of millions every year. Trace metals are significant among the components of air pollution. Trace metals can endure long without undergoing biodegradation and bioaccumulation in living organisms. Moreover, their concentration in the air increases gradually. Therefore, monitoring metal concentration is extremely important for reliable indicators of environmental pollution. Biomonitoring is an effective method for describing metal concentrations in urban areas. Chromium, manganese, and zinc, selected within the present study, have various adverse effects on plants in high concentrations. Their identification is highly critical for monitoring the pollution level in their regions. This study aimed to determine the Cr, Mn, and Zn concentration changes according to organ, and age in Elaeagnus angustifolia L., Platanus orientalis L., Koelreuteria paniculata Laxm, Ailanthus altissima (Mill.) Swingle, and Cedrus atlantica (Endl.) Manetti ex Carr is 30 years old. The accumulation of metals in the outer bark can be found as follows Zn > Mn > Cr in all species, although Ailanthus altissima (Mill.) Swingle and Platanus orientalis L. can be suitable for biomonitoring tools because concentrations change significantly depending on the airborne metal.

Physiological changes and rate of resistance of Acrosiphonia arcta (Dillwyn) Gain upon exposure to diesel fuel

The changes in the morpho-physiological state of green alga Acrosiphonia arcta upon exposure to diesel fuel (DF) at concentrations of 20; 100; 1,000; 2,000; 3,000 of maximum permissible concentrations (MPC) were studied. The main physiological stress markers, such as enzymes of the antioxidant system (AOS), non-enzymatic antioxidants (carotenoids) and free amino acids (as components of plant metabolome) were measured. In general, all concentrations of the petroleum product used changed the activity of the antioxidant system, changed the intensity of physiological processes (photosynthesis, free amino acid synthesis) and also affected the structure of microbiomes inhabiting the surface of algae.

It was shown that the concentration of DF within 1 mg/l (20 MPC) was not lethal as plants were able to maintain physiological activity and the observed changes were reversible.

Although DF exposure caused decreases in superoxide dismutase (SOD) activity, proline concentration and photosynthetic rate, increases in catalase activity and pigment concentration were observed. After the effects of stress disappeared, most physiological parameters were restored, except for carotenoid content.

Higher DF concentrations (100 MPC and higher) caused injury to cell structures and damage to the pigment apparatus. The restoration of functions after the termination of exposure to stress was not achieved. Epiphytic bacterial communities actively responded both to the introduction of a toxicant and to the changing physiological parameters of algae by the change in the numbers of cultured heterotrophic bacteria. The results of this study showed that the concentration of petroleum products in the water decreased to values not exceeding MPC in the presence of algae in the environment.

Species-specific bioaccumulation and health risk assessment of heavy metal in seaweeds in tropic coasts of South China Sea

Seaweeds are widely known superfood in coasts where most anthropogenic heavy metal discharges are inputted and stored. The present study analyzed 11 seaweed species and 13 heavy metals to test the hypothesis that the species-specific capacity of heavy metal bioaccumulation had great significance to health risk of human. The seaweeds were collected from tropic coasts of Hainan Island. We comparatively determined the bioaccumulation level of metals in different species. The results revealed that the red algae mainly concentrated V, Se, Mn, Ni, and Ag. The brown algae mainly concentrated Cr, Co, Cu, Cd, As and Fe, while the green algae mainly concentrated Zn and Pb. The cluster analysis, principal component analysis and metal pollution index indicated that Padina crassa, Sargassum thunbergii, Caulerpa racemosa and Asparagopsis taxiformis showed similar metal bioaccumulation behavior. The health risk assessment revealed that the overall hazard index (HI) of seaweeds consumption to adults was less than 1, while the HI of Sargassum oligocystum, Turbinaria ornate, Sargassum polycystum and Sargassum thunbergii consumption to children was greater than 1, suggesting a moderate or high risk to children. Moreover, the exposure amount and the carcinogenic risk parameter indicated that As and Cr were the limiting factor for seaweeds consumption. Overall, our findings here largely supported our hypothesis that the heavy metal bioaccumulation behavior and health risk was highly variable and complex among different species. We thus suggested that the species-specific health risk of heavy metals in seaweeds should be cautiously evaluated in natural environments.

Sulfamethoxazole removal from mariculture wastewater in moving bed biofilm reactor and insight into the changes of antibiotic and resistance genes

Antibiotics are widely dosed in mariculture sector, resulting in substantial antibiotics residues. Hence, mariculture wastewater is urgent to be treated before discharging. In this study, the anoxic/oxic moving bed biofilm reactor (A/O-MBBR) was used to treat the wastewater containing sulfamethoxazole (SMX) from mariculture, SMX removal mechanism and the variation of antibiotic-resistant genes (ARGs) were investigated. The results showed that 22%-33% of SMX was removed by the bioreactor, where a small amount of SMX was adsorbed and stored by the extracellular polymers and most of SMX (>80%) was biodegraded in the anoxic tank. Occurrence of nitrate in anoxic condition was conducive to SMX degradation. Pseudomonas, Desulfuromusa, and Methanolobus species, as well as microbial catalase contributed to the SMX biotransformation. Quantitative PCR analysis of ARGs (sul1, sul2 and int1) and mRNA (sul1, sul2) showed that SMX enriched SMX-related ARGs and enhanced the expression of corresponding genes. Most of ARGs finally were discharged with effluent. Hence, the effluent from biologically based processes treating mariculture wastewater still contained antibiotics residue and resistance genes, which should be further controlled by suitable techniques.

Toxicity Effects of Combined Mixtures of BDE-47 and Nickel on the Microalgae Phaeodactylum tricornutum (Bacillariophyceae)

Nickel and 2,2’,4,4’-tetrabromodiphenyl ether (BDE-47) are two environmental pollutants commonly and simultaneously present in aquatic systems. Nickel and BDE-47 are individually toxic to various aquatic organisms. However, their toxicity mechanisms are species-dependent, and the toxic effects of combined mixtures of BDE-47 and nickel have not yet been investigated. The present study investigated the toxic effects of combined mixtures of BDE-47 and nickel in the diatom Phaeodactylum tricornutum. BDE-47 and nickel mixtures significantly decreased cell abundance and photosynthetic efficiency, while these cells’ reactive oxygen species (ROS) production significantly increased. The EC₅₀-72 h for BDE-47 and mixtures of BDE-47 and nickel were 16.46 ± 0.93 and 1.35 ± 0.06 mg/L, respectively. Thus, combined mixtures of the two pollutants enhance their toxic effects. Interactions between BDE-47 and nickel were evaluated, revealing synergistic interactions that contributed to toxicity in P. tricornutum. Moreover, transcriptomic analyses revealed photosynthesis, nitrogen metabolism, the biosynthesis of amino acids, the biosynthesis of secondary metabolites, oxoacid metabolism, organic acid metabolism, carboxylic acid metabolism, and oxidation-reduction processes were considerably affected by the mixtures. This study provides evidence for the mechanisms of toxicity from combined BDE-47 and nickel exposure while also improving our understanding of the ecological risks of toxic chemicals on microalgae.

Toxicity mechanism of Nylon microplastics on Microcystis aeruginosa through three pathways: Photosynthesis, oxidative stress and energy metabolism

Nylon has been widely used all over the world, and most of it eventually enters the aquatic environment in the form of microplastics (MPs). However, the impact of Nylon MPs on aquatic ecosystem remains largely unknown. Thus, the long-term biological effects and toxicity mechanism of Nylon MPs on Microcystis aeruginosa (M. aeruginosa) were explored in this study. Results demonstrated that Nylon MPs had a dose-dependent growth inhibition of M. aeruginosa at the initial stage, and the maximum inhibition rate reached to 47.62% at the concentration of 100 mg/L. Meanwhile, Nylon MPs could obstruct photosynthesis electron transfer, reduce phycobiliproteins synthesis, destroy algal cell membrane, enhance the release of extracellular polymeric substances, and induce oxidative stress. Furthermore, transcriptomic analysis indicated that Nylon MPs dysregulated the expression of genes involved in tricarboxylic acid cycle, photosynthesis, photosynthesis-antenna proteins, oxidative phosphorylation, carbon fixation in photosynthetic organisms, and porphyrin and chlorophyll metabolism. According to the results of transcriptomic and biochemical analysis, the growth inhibition of M. aeruginosa is inferred to be regulated by three pathways: photosynthesis, oxidative stress, and energy metabolism. Our findings provide new insights into the toxicity mechanism of Nylon MPs on freshwater microalgae and valuable data for risk assessment of MPs.

Perspectivas de una producción sostenible en acuicultura multitrófica integrada (IMTA): Una revisión

La acuicultura tradicional se enfrenta a serios problemas medioambientales, particularmente por el uso de grandes volúmenes de agua, con las consecuentes descargas de efluentes ricos en nutrientes inorgánicos y partículas orgánicas. Un ejemplo claro de esto está en que del 20 al 30% del nitrógeno presente en la proteína del alimento suministrado es aprovechado por los peces, el restante 70-80% es desechado en el cuerpo de agua producto de la excreción y el alimento no consumido, lo que favorece la eutrofización de aguas receptoras y su entorno. Por lo anterior, se requiere el desarrollo de tecnologías y prácticas de producción innovadoras, responsables, sostenibles y rentables. Una de las alternativas que está generando interés, debido a sus implicaciones ambientales, económicas y sociales, es la producción en sistemas de acuicultura multitrófica integrada (IMTA). Este concepto se basa en la integración de diferentes niveles tróficos en un mismo sistema, lo que resulta en una conversión de los residuos de cultivo de unas especies en alimentos o fertilización para otras especies. Aplicada, la producción IMTA puede mejorar la sostenibilidad de la acuicultura al reducir el impacto de los efluentes y generar mayor rentabilidad económica, debido a la producción simultanea de dos o más productos finales y al uso mínimo de fertilizantes. El objetivo de la presente revisión es presentar los fundamentos básicos de los sistemas de IMTA, como una alternativa a los sistemas de producción en piscicultura.

Early molecular markers for retrospective biodosimetry and prediction of acute health effects

Radiation-induced biological changes occurring within hours and days after irradiation can be potentially used for either exposure reconstruction (retrospective dosimetry) or the prediction of consecutively occurring acute or chronic health effects. The advantage of molecular protein or gene expression (GE) (mRNA) marker lies in their capability for early (1-3 days after irradiation), high-throughput and point-of-care diagnosis, required for the prediction of the acute radiation syndrome (ARS) in radiological or nuclear scenarios. These molecular marker in most cases respond differently regarding exposure characteristics such as e.g. radiation quality, dose, dose rate and most importantly over time. Changes over time are in particular challenging and demand certain strategies to deal with. With this review, we provide an overview and will focus on already identified and used mRNA GE and protein markers of the peripheral blood related to the ARS. These molecules are examined in light of 'ideal' characteristics of a biomarkers (e.g. easy accessible, early response, signal persistency) and the validation degree. Finally, we present strategies on the use of these markers considering challenges as their variation over time and future developments regarding e.g. origin of samples, point of care and high-throughput diagnosis.

Determination of veterinary drugs in microalgae biomass from photobioreactors fed with piggery wastewater

Concentration data of veterinary drugs in microalgae biomass collected from photobioreactors fed with piggery wastewaters are presented for the first time in this work. To this aim, a QuEChERS methodology and an ultrasound-assisted solid-liquid extraction have been assessed as sample preparation procedures with the purpose of determining 20 veterinary drugs, mainly antibiotics of different physico-chemical properties in addition to dexamethasone, fenbendazole and progesterone. Some critical operation parameters of the QuEChERS procedure were optimized by an experimental design but tetracycline, oxytetracycline, doxycycline, marbofloxacin and ciprofloxacin were not detected by the QuEChERS sample preparation. The use of a longer and thorough approach, a solid-liquid extraction with water/methanol in presence of primary secondary amine as a clean-up agent followed by solid-phase extraction on Oasis HLB cartridges, is recommended to monitor all intended analytes. The determination in extracts is carried out by ultra-high performance liquid chromatography-tandem mass spectrometry in selected reaction monitoring mode. Limits of detection about 0.2-42 ng per g of lyophilized microalgae sample, and repeatabilities about 6-46% (n = 5, RSDs) are reached. The solid-liquid extraction method was applied to microalgae biomass samples collected from a photobioreactor. Nine drugs were detected in the samples at relatively low concentration and a proportional relationship between the found concentrations and the octanol/water partition coefficients of the drugs has been outlined. Moreover, a linear ratio between the concentrations measured in biomass and effluent has been observed for most of the drugs.

A review on the enzymes and metabolites identified by mass spectrometry from bacteria and microalgae involved in the degradation of high molecular weight PAHs

High molecular weight PAHs (HMW PAHs) are dangerous pollutants widely distributed in the environment. The use of microorganisms represents an important tool for HMW PAHs bioremediation, so, the understanding of their biochemical pathways facilitates the development of biodegradation strategies. For this reason, the potential role of species of microalgae, bacteria, and microalga-bacteria consortia in the degradation of HMW PAHs is discussed. The identification of their metabolites, mostly by GC-MS and LC-MS, allows a better approach to the enzymes involved in the key steps of the metabolic pathways of HMW PAHs biodegradation. So, this review intends to address the proteomic research on enzyme activities and their involvement in regulating essential biochemical functions that help bacteria and microalgae in the biodegradation processes of HMW PAHs. It is noteworthy that, given that to the best of our knowledge, this is the first review focused on the mass spectrometry identification of the HMW PAHs metabolites; whereby and due to the great concern of the presence of HMW PAHs in the environment, this material could help the urgency of developing new bioremediation methods. The elucidation of the metabolic pathways of persistent pollutant degrading microorganisms should lead to a better knowledge of the enzymes involved, which could contribute to a very ecological route to the control of environmental contamination in the future.

Effect of calcium peroxide pretreatment on the remediation of sulfonamide antibiotics (SMs) by Chlorella sp

This study investigated the effect of CaO₂ pretreatment on sulfonamide antibiotics (SMs) remediation by Chlorella sp. Results showed that a CaO₂ dose ranging from 0.05 to 0.1 g/g biomass was the best and led to higher SMs removal efficacy 5-10% higher than the control. The contributions made by cometabolism and CaO₂ in SMs remediation were very similar. Bioassimilation could remove 24% of sulfadiazine (SDZ) and sulfamethazine (SMZ), and accounted for 38% of sulfamethoxazole (SMX) remediation. Pretreatment by CaO₂ wielded a positive effect on microalgae. The extracellular polymeric substances (EPS) level of the CaO₂ pretreatment microalgae was three times higher when subjected to non-pretreatment. For the long-term, pretreatment microalgae removed SMs 10-20% more than the non-pretreatment microalgae. Protein fractions of EPS in continuous operation produced up to 90 mg/L for cometabolism. For bioassimilation, SMX intensity of the pretreatment samples was 160-fold less than the non-treatment one. It indicated the CaO₂ pretreatment has enhanced the biochemical function of the intracellular environment of microalgae. Peroxidase enzyme involved positively in the cometabolism and degradation of SMs to several metabolites including ring cleavage, hydroxylation and pterin-related conjugation.

Cu, Ni, and Zn effects on basic physiological and stress parameters of Raphidocelis subcapitata algae

The submitted work observed Cu, Ni, and Zn effects on selected physiological and stress parameters of the alga Raphidocelis (Pseudokirchneriella) subcapitata. In 96-h experiments, EC50 values for algal specific growth rates (SGR) inhibition in Cu, Ni, and Zn presence were estimated as 0.15, 0.50, and 0.20 mg l^-1. In addition to growth inhibition, the effect of metals at various concentrations on algal SGR was also monitored. While these experiments confirmed approximately the same toxicity of Zn and Cu on SGR, Ni toxicity on this parameter was observed as the lowest. In terms of the effect of metals on the level of selected photosynthetic pigments, chlorophyll a, chlorophyll b, and carotenoids, the following inhibition orders can be established: Zn > Cu > Ni, Ni > Cu > Zn, and Ni > Cu ≥ Zn, respectively. As a novelty of our research, we included monitoring and evaluation of the intensity of stress, which was the response of algal cells to the presence of Cu, Ni, and Zn, and its correlation with respect to production factors and metal accumulation in algal cells. As stress factors, thiol (-SH) group and TBARS (thiobarbituric acid reactive substances) as significant indicators of lipid level peroxidation were determined. The content of -SH groups depended on the concentration of metal, and its level was the most stimulated by Zn, less by Cu and Ni. The TBARS content was 2 to 5 times higher in Cu than in Zn or Ni presence. In the presence of Zn and Ni, TBARS content reached approximately the same levels. For this parameter, the following rank order can be arranged: Cu >> Ni ≥ Zn. While Cu and Ni accumulation in R. subcapitata was confirmed, Zn accumulation was not determined or was below the detectable limit. Regression analyses revealed significant positive correlation between Cu accumulation and TBARS while carotenoids as possible antioxidants confirmed with TBARS mostly negative correlations.

Characterization of allelochemicals from Pistia stratiotes extracts and their effects on the growth and physiology of Microcystis aeruginosa

Due to the public and environmental health impact of cyanotoxins, investigations have been focused on finding environmental friendly algaecides from aquatic plants. The present study had the objective to evaluate the population control and physiological response of Microcystis aeruginosa (Kützing) Kützing (strain BCCUSP232) exposed to Pistia stratiotes L. extracts. Aqueous and ethanolic extracts of P. stratiotes at different concentrations (10, 25, and 50 mg L^-1) were submitted to M. aeruginosa and reduced significantly (p<0.05) the cyanobacterium cell density. The ethanolic extract presented the greatest growth inhibition of the strain at the highest concentration. During exposure to P. stratiotes extracts, intracellular hydrogen peroxide levels, malondialdehyde content, and antioxidant enzymes (peroxidase, catalase, and glutathione S-transferase) activities increased in M. aeruginosa, while total protein concentration decreased when compared to the control group. Superoxide dismutase (SOD) activities presented a sharp decline, suggesting superoxide radical and peroxide accumulation. This implied that SOD was a target for bioactive substance(s) from aqueous and ethanolic extracts of P. stratiotes. Phytochemical screening of the extracts revealed that the ethanolic extract presented 93.36 mg gallic acid equivalent (GAE) per gram dry weight (g^-1 DW) total polyphenols and 217.33 mg rutin equivalent (RE) per gram dry weight total flavonoids, and for the aqueous extract, 5.19 mg GAE g^-1 DW total polyphenols and 11.02 mg RE g^-1 DW total flavonoids were detected. Gas chromatography (GC)/mass spectrometry (MS) analyses of the ethanolic and aqueous extracts presented palmitic acid ethyl ester as major allelochemical. In view of these results, it can be concluded that P. stratiotes showed potential in controlling M. aeruginosa populations.

Algae-mediated processes for the treatment of antiretroviral drugs in wastewater: Prospects and challenges

The prevalence of pharmaceuticals (PCs), especially antiretroviral (ARV) drugs in various aquatic ecosystems has been expansively reported, wherein wastewater treatment plants (WWTPs) are identified as the primary point source. Consequently, the occurrence, ecotoxicity and treatment of ARV drugs in WWTPs have drawn much attention in recent years. Numerous studies have shown that the widely employed activated sludge-based WWTPs are incapable of removing ARV drugs efficiently from wastewater. Recently, algae-based wastewater treatment processes have shown promising results in PCs removal from wastewater, either completely or partially, through different processes such as biosorption, bioaccumulation, and intra-/inter-cellular degradation. Algal species have also shown to tolerate high concentrations of ARV drugs than the reported concentrations in the environmental matrices. In this review, emphasis has been given on discussing the current status of the occurrence of ARV drugs in the aquatic environment and WWTPs. Besides, the current trends and future perspectives of PCs removal by algae are critically reviewed and discussed. The potential pathways and mechanisms of ARV drugs removal by algae have also been discussed.

Impact of heavy metals in the microalga Chlorella sorokiniana and assessment of its potential use in cadmium bioremediation

The chlorophyte microalga Chlorella sorokiniana was tested for the bioremediation of heavy metals pollution. It was cultured with different concentrations of Cu²⁺, Cd²⁺, As (III) and As (V), showing a significant inhibition on its growth at concentrations of 500 µM Cu²⁺, 250 µM Cd²⁺, 750 µM AsO₃^3- and 5 mM AsO₄^3- or higher. Moreover, the consumption of ammonium was also studied, showing significant differences for concentrations higher than 1 mM of Cu²⁺ and As (III), and 5 mM of As (V). The determination of intracellular heavy metals concentration revealed that Chlorella sorokiniana is an outstanding Cd accumulator organism, able to accumulate 11,232 mg kg^-1 of Cd, and removing 65% of initial concentration of this heavy metal. Finally, antioxidant enzymes, such as catalase (CAT) and ascorbate peroxidase (APX), and enzymes involved in the production of glutamate and cysteine, such as glutamine syntethase (GS), glutamate dehydrogenase (GDH), O-acetylserine (thiol) lyase (OASTL) and NAD-isocitrate dehydrogenase (NAD-IDH) were studied both at gene expression and enzymatic activity levels. These enzymes exhibited different grades of upregulation, especially in response to Cd and As stress. However, GS expression was downregulated when Chlorella sorokiniana was cultured in the presence of these heavy metals.

Tylosin toxicity in the alga Raphidocelis subcapitata revealed by integrated analyses of transcriptome and metabolome: Photosynthesis and DNA replication-coupled repair

Tylosin (TYN) is widely used in veterinary prophylactic as a macrolide and frequently detected in the surface water. Previous studies showed that exposure to TYN caused suppression of chlorophyll biosynthesis and inhibition of photosynthesis at the physiological level, associated with reduced growth performances in algae, but the molecular mechanisms remain unknown, especially at environmental exposure levels. The present study elucidated the underlying molecular mechanism(s) of TYN toxicity in a model green alga Raphidocelis subcapitata using approaches of transcriptomics and metabolomics. Following a 7-day exposure, algal growth performances were reduced by 26.3% and 58.3% in the 3 (an environmentally realistic level) and 400 μg L^-1 TYN treatment group, respectively. A total of 577 (99) and 5438 (180) differentially expressed genes (differentially accumulated metabolites) were identified in algae treated with 3 and 400 μg L^-1 TYN, respectively. Signaling pathways including photosynthesis - antenna protein, porphyrin and chlorophyll metabolism, carbon fixation in photosynthetic organisms, and DNA replication were altered in the 400 μg L^-1 TYN treatment, while photosynthesis and DNA replication were the shared pathways in both TYN treatments. The metabolomic data further suggest that molecular pathways related to photosynthesis, DNA replication-coupled repair and energy metabolism were impaired. Photosynthesis was identified as the most sensitive target of TYN toxicity in R. subcapitata, in contrast to protein synthesis inhibition caused by TYN in bacteria. This study provides novel mechanistic information of TYN toxicity in R. subcapitata.

Microalgae-based technology for antibiotics removal: From mechanisms to application of innovational hybrid systems

Antibiotics contamination is an emerging environmental concern, owing to its potential risks to ecosystems and human health. Microalgae-based technology has been widely reported as a promising alternative to conventional wastewater treatment, since it is a solar-power driven, ecologically friendly, cost-effective, and sustainable reclamation strategy. This review provides fundamental insights into the major mechanisms underpinning microalgae-based antibiotics removal, including bioadsorption, bioaccumulation, and biodegradation. The critical role of extracellular polymeric substances on bioadsorption and extracellular biodegradation of antibiotics are also covered. Moreover, this review sheds light on the important factors affecting the removal of antibiotics by microalgae, and summarizes several novel approaches to improve the removal efficiency, including acclimation, co-metabolism and microbial consortium. Besides, hybrid systems (such as, microalgae-based technologies combined with the conventional activated sludge, advanced oxidation processes, constructed wetlands, and microbial fuel cells), and genetic engineering are also recommended, which will be feasible for enhanced removal of antibiotics. Finally, this review also highlights the need for further studies aimed at optimizing microalgae-based technology, with emphasis on improving performance and expanding its application in large-scale settings, especially in terms of technical, environmental-friendly and economically competitiveness. Overall, this review summarizes current understanding on microalgae-based technologies for removal of antibiotics and outlines future research directions.