Nationwide seasonal monitoring of lipophilic marine algal toxins in shellfish and causative microalgae along the coasts of South Korea.

In this study, lipophilic marine algal toxins (LMATs)-producing microalgae were identified at 23 sites along the coasts of Korea, and distribution characteristics of LMATs in phytoplankton and mussels were investigated. The causative microalgae, including Gonyaulux spinifera, Dinophysis acuminata, D. caudata, and D. fortii, were observed in the study area, with notably higher densities during the summer. Significant correlations were found between the densities of these microalgae and the water temperature. Seasonal distribution patterns of LMATs in phytoplankton closely matched those observed in mussels. Notably, LMAT concentrations in mussels from the Yellow Sea were relatively high. PTX2 was detected predominantly in phytoplankton, and homo-yessotoxin was found mainly in mussels. Overall, LMAT concentrations were elevated in the summer, raising concerns about biotoxin contamination in shellfish. These results provide important insights into the dynamics of unmanaged marine biotoxins in Korea and offer baseline data for future safety management policies and inflow surveillance.

First investigation of the temporal distribution of neurotoxin ß-N-methylamino-L-alanine (BMAA) and the candidate causative microalgae along the South Sea Coast of Korea.

The neurotoxin ß-N-methylamino-L-alanine (BMAA), produced by cyanobacteria and diatoms, has been implicated as an environmental risk factor for neurodegenerative diseases. This study first investigated the occurrence and monthly distributions of BMAA and its isomers, 2,4-diaminobutyric acid (DAB) and N-2-aminoethylglycine (AEG), in phytoplankton and mussels from 11 sites along the South Sea Coast of Korea throughout 2021. These toxins were quantified using LC-MS/MS, revealing elevated BMAA concentrations from late autumn to spring, with phase lags observed between phytoplankton and mussels. The highest concentration of BMAA in phytoplankton was detected in November (mean: 1490 ng g-1 dry weight (dw)), while in mussels, it peaked in December (mean: 1240 ng g-1 dw). DAB was detected in phytoplankton but was absent in mussels, indicating limited bioaccumulation potential. In February, the peak mean DAB concentration in phytoplankton was 89 ng g-1 dw. AEG was not detected in any samples. Chlorophyll-a concentrations consistently showed an inverse correlation with BMAA concentrations in mussels throughout the year. Through correlation analysis, four diatom genera, Bacillaria, Hemiaulus, Odontella, and Pleurosigma, were identified as potential causative microalgae of BMAA. This study offers insights into identifying the causative microalgae for BMAA and informs future regulatory efforts regarding unmanaged biotoxins.

Investigating the Immune-Stimulating Potential of ß-Glucan from Aureobasidium pullulans in Cancer Immunotherapy.

ß-glucan, a polysaccharide found in various sources, exhibits unique physicochemical properties, yet its high polymerization limits clinical applications because of its solubility. Addressing this limitation, we introduce PPTEE-glycan, a highly purified soluble ß-1,3/1,6-glucan derived from Aureobasidium pullulans. The refined PPTEE-glycan demonstrated robust immune stimulation in vitro, activated dendritic cells, and enhanced co-stimulatory markers, cytokines, and cross-presentation. Formulated as a PPTEE + microemulsion (ME), it elevated immune responses in vivo, promoting antigen-specific antibodies and CD8+ T cell proliferation. Intratumoral administration of PPTEE + ME in tumor-bearing mice induced notable tumor regression, which was linked to the activation of immunosuppressive cells. This study highlights the potential of high-purity Aureobasidium pullulans-derived ß-glucan, particularly PPTEE, as promising immune adjuvants, offering novel avenues for advancing cancer immunotherapy.

Chronological distribution and potential sources of persistent toxic substances in soils from the glacier foreland of Midtre Lovénbreen, Svalbard.

Despite its reputation as one of the cleanest regions globally, recent studies have identified the presence of various persistent toxic substances (PTSs) in the environmental matrices collected from Svalbard. This study investigated the chronological distribution and potential sources of 81 PTSs in soils from the glacier foreland of Midtre Lovénbreen. Soil samples (n = 45) were categorized by age based on exposure to the atmosphere due to glacier retreat in July 2014 into five age groups: 80-100 years (n = 7), 60-80 years (n = 12), 40-60 years (n = 16), 20-40 years (n = 7), and <20 years (n = 3). Concentrations of polychlorinated biphenyls (PCBs, n = 32) in soils varied with age, ranging from 0.29 to 0.74 ng g-1 dw. In addition, the concentrations of polycyclic aromatic hydrocarbons (PAHs, n = 28), perylene, and alkyl-PAHs (n = 20) in soils ranged from 21 to 80 ng g-1 dw, 2.9-62 ng g-1 dw, and 73-420 ng g-1 dw, respectively. The concentrations of PTSs were observed to be greater in older soils. Principal component analysis revealed that PCBs in soils originated from various product sources. Positive matrix factorization modeling estimated the association of PAHs in soils with potential origins, such as diesel emissions, petroleum and coal combustion, and coal. Potential sources of PAHs were mainly coal in younger soils and diesel emissions and petroleum combustion in older soils. Alkyl-PAH compositions in the soil were similar to those of bituminous coal, with a noteworthy degree of weathering observed in older soils. The accumulation rate and flux of PTSs in soils exhibited compound-specific patterns, reflecting factors such as long-range transport, fate, origin, and recent inputs. These findings can serve as baseline data for protecting and preserving polar environments.

Compound- and element-specific accumulation characteristics of persistent toxic substances and metals in sediments of the Yellow Sea.

This study investigated the large-scale distributions of persistent toxic substances (PTSs) and heavy metals in sediments of the Yellow Sea, collected from six transects between latitudes 32 and 37 degrees north (n = 35). Elevated concentrations of polychlorinated biphenyls (PCBs) were detected near the mainland, with a predominance of low-chlorinated congeners (di to tetra, ∼60%), indicative of atmospheric deposition. Analysis of traditional and emerging polycyclic aromatic hydrocarbons (t-PAHs and e-PAHs) revealed notable enrichment in the Central Yellow Sea Mud Zone (CYSM), attributing fossil fuel combustion as the significant source. Styrene oligomers and alkylphenols exhibited notable accumulation near the Han River Estuary in South Korea and the Yangtze River Estuary in China, respectively. The accumulation of heavy metals was predominantly observed in the CYSM, with element-specific distribution patterns. Cluster analysis revealed distinct distribution patterns for PTSs and metals, highlighting their source-dependent and grain size-dependent behaviors. In addition, the distribution and accumulation of PTSs tended to depend on their partitioning coefficients, such as the octanol-air partition coefficient (log KOA) and octanol-water partition coefficient (log KOW). This study offers valuable insights into the sources, transport, and fate of hazardous substances in the Yellow Sea, emphasizing the necessity for targeted environmental management strategies.

Effect of modification methods on the physical properties and immunomodulatory activity of particulate ß-glucan.

ß-Glucan is an immunoenhancing agent whose biological activities are linked to molecular structure. On that basis, the polysaccharide can be physiochemically modified to produce valuable functional materials. This study investigated the physical properties and immunostimulatory activity of modified ß-glucan. Alkali-treated ß-glucan had a distinct shape and smaller particle size than untreated ß-glucan. The reduced particle size was conducive to the stability of the suspension because the ß-glucan appeared to be completely dissolved by this treatment, forming an amorphous mass. Furthermore, alkali treatment improved the immunostimulating activity of ß-glucan, whereas exposure of macrophages to heat-treated ß-glucan decreased their immune activity. ß-Glucan with reduced particle size by wet-grinding also displayed immunomodulatory activities. These results suggested that the particle size of ß-glucan is a key factor in ß-glucan-induced immune responses of macrophages. Thus, the modification of the ß-glucan particle size provides new opportunities for developing immunoenhancing nutraceuticals or pharmacological therapies in the future.

Integrated assessment of the natural purification capacity of tidal flat for persistent toxic substances and heavy metals in contaminated sediments.

Natural purification of pollutants is highly recognized as regulating ecosystem services; however, the purification capacity of tidal flats remains largely unknown and/or unquantified. A 60-day mesocosm transplant experiment was conducted in situ to assess the purification capacity of natural tidal flats. We adopted the advanced sediment quality triad approach, monitoring 10 endpoints, including chemical reduction, toxicity changes, and community recoveries. The results indicated that contaminated sediments rapidly recovered over time, particularly > 50% within a day, then slowly recovered up to âˆ¼ 70% in a given period (60 days). A significant early reduction of parent pollutants was evidenced across all treatments, primarily due to active bacterial decomposition. Notably, the presence of benthic fauna and vegetated halophytes in the treatments significantly enhanced the purification of pollutants in both efficacy and efficiency. A forecast linear modeling further suggested additive effects of biota on the natural purification of tidal flats, reducing a full recovery time from 500 to 300 days. Overall, the triad approach with machine learning practices successfully demonstrated quantitative insight into the integrated assessment of natural purification.

Distributed quantum sensing of multiple phases with fewer photons.

Distributed quantum metrology has drawn intense interest as it outperforms the optimal classical counterparts in estimating multiple distributed parameters. However, most schemes so far have required entangled resources consisting of photon numbers equal to or more than the parameter numbers, which is a fairly demanding requirement as the number of nodes increases. Here, we present a distributed quantum sensing scenario in which quantum-enhanced sensitivity can be achieved with fewer photons than the number of parameters. As an experimental demonstration, using a two-photon entangled state, we estimate four phases distributed 3 km away from the central node, resulting in a 2.2 dB sensitivity enhancement from the standard quantum limit. Our results show that the Heisenberg scaling can be achieved even when using fewer photons than the number of parameters. We believe our scheme will open a pathway to perform large-scale distributed quantum sensing with currently available entangled sources.

Phytoplankton assemblage responses to massive freshwater inputs and anthropogenic toxic substances contamination in the Geum River Estuary, South Korea.

This study investigated the relationships between phytoplankton assemblages and water contamination by persistent toxic substances (PTSs) and nutrients in an estuary with an artificial dam over one year. The distribution of PTSs, including 15 polycyclic aromatic hydrocarbons, 6 alkylphenols, and 8 metal(loid)s, along with nutrients, exhibited relatively high concentrations with irregular temporal fluctuations in the inner estuary. During winter and spring, phytoplankton communities showed good ecological quality, with an average of 28 species and a density of 1750 cells L-1. In contrast, during summer, there was a significant increase in the density of freshwater species (max 45,000 cells L-1). These assemblages were categorized into three seasonal groups, featuring dominant taxa like blue-green algae and diatoms. Temperature and nutrient levels were the principal factors influencing phytoplankton assemblages, while PTSs had a minor impact. Overall, phytoplankton assemblages displayed strong seasonal variation, mainly influenced by freshwater input and nutrient availability.

Effect-Directed Analysis Combined with Nontarget Screening to Identify Unmonitored Toxic Substances in the Environment.

Effect-directed analysis (EDA) combined with nontarget screening (NTS) has established a valuable tool for the identification of unmonitored toxic substances in environmental samples. It consists of three main steps: (1) highly potent fraction identification, (2) toxicant candidate selection, and (3) major toxicant identification. Here, we discuss the methodology, current status, limitations, and future challenges of EDA combined with NTS. This method has been applied successfully to various environmental samples, such as sediments, wastewater treatment plant effluents, and biota. We present several case studies and highlight key results. EDA has undergone significant technological advancements in the past 20 years, with the establishment of its key components: target chemical analysis, bioassays, fractionation, NTS, and data processing. However, it has not been incorporated widely into environmental monitoring programs. We provide suggestions for the application of EDA combined with NTS in environmental monitoring programs and management, with the identification of further research needs.

Identification of Mid-Polar and Polar AhR Agonists in Cetaceans from Korean Coastal Waters: Application of Effect-Directed Analysis with Full-Scan Screening.

Major aryl hydrocarbon receptor (AhR) agonists were identified in extracts of blubber, liver, and muscle from six long-beaked common dolphins (Delphinus capensis) and one fin whale (Balaenoptera physalus) collected from Korean coastal waters using effect-directed analysis. Results of the H4IIE-luc bioassay indicated that the polar fractions of blubber and liver extracts from the fin whale exhibited relatively high AhR-mediated potencies. Based on full-scan screening with high-resolution mass spectrometry, 37 AhR agonist candidates, spanning four use categories: pharmaceuticals, pesticides, cosmetics, and natural products, were selected. Among these, five polar AhR agonists were newly identified through toxicological confirmation. Concentrations of polar AhR agonists in cetaceans were tissue-specific, with extracts of blubber and liver containing greater concentrations than muscle extracts. Polar AhR agonists with great log KOA values (>5) were found to biomagnify in the marine food chain potentially. Polar AhR agonists contributed 8.9% of the observed AhR-mediated potencies in blubber and 49% in liver. Rutaecarpine and alantolactone contributed significantly to the total AhR-mediated potencies of blubber, whereas hydrocortisone was a major AhR contributor in the liver of the fin whale. This study is the first to identify the tissue-specific accumulation of polar AhR agonists in blubber and liver extracts of cetaceans.

Use of molecular composition and compound-specific isotope analysis for source appointment of PAHs in sediments of a highly industrialized area.

This study utilized both conventional molecular analysis and compound-specific isotopic techniques to identify the sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of Ulsan Bay, South Korea. The concentrations of 15 traditional and 11 emerging PAHs were determined in sediments from 21 source sites and 26 bay sites. The concentrations and compositions of traditional and emerging PAHs varied significantly, even at sites close to the source areas. The results obtained from diagnostic ratios and the positive matrix factorization model for source identification were inconsistent in adjacent source areas. The δ13C profiles of PAHs, such as phenanthrene (Phe), fluoranthene (Fl), pyrene (Py), and benz[a]anthracene (BaA) in the sediments showed distinct features depending on the surrounding sources. In urban sediments, lighter δ13CPhe values were observed (mean: -25.1‰), whereas relatively heavier values of δ13CPy were found in petroleum industry areas (mean: -23.4‰). The Bayesian isotope mixing model indicates that the predominant source of PAHs in Ulsan Bay sediments was the petroleum industry (45%), followed by the non-ferrous metals industry (30%), automobile industry (18%), and urban areas (6.3%). These results demonstrated the utility of stable isotopes in assessing the sources and contributions of PAHs in small-scale regions. However, there are still limitations in compound-specific isotope analysis of PAHs, including insufficient end-members for each source, difficulty in analysis, and the influence of non-point sources; thus, further study is needed to expand its application.

Numerical investigation of ultrasound focusing and bubble collapse.

Ultrasound focusing and microbubble collapse are numerically investigated using a level-set interface tracking method for two-phase flows with multiple interfaces. The computations for ultrasound propagating through a spherical lens demonstrate the ultrasound refraction and pressure intensification at the rear of the lens. The focusing of the initial negative pressure wave through the lens induces a converging flow and the focusing of the subsequent positive pressure wave further intensifies the pressure at the lens. Computations are extended to bubble oscillations near the focusing lens and compared with the no-lens case. The lens not only amplifies the bubble expansion and contraction rates significantly but also generates a larger pressure gradient across the bubble. This ultrasound focusing effect contributes to the asymmetric collapse of the bubble and the formation of a liquid jet that penetrates the bubble. The effects of lens size, initial bubble radius and bubble-lens distance on bubble expansion and liquid jet are further investigated.

Monthly distribution of lipophilic marine biotoxins and associated microalgae in the South Sea Coast of Korea throughout 2021.

Aquaculture farms have been established along the South Sea Coast of Korea, supplying most of the seafood consumed domestically. However, annual harmful algal blooms pose a potential threat to seafood safety. This study aimed to determine the spatial and seasonal distributions of 12 lipophilic marine biotoxins (LMTs) in phytoplankton and mussels in the region in 2021. Solid-phase adsorption toxin tracking (SPATT) was used to monitor the cumulative compositions of LMTs in seawater. LMT concentrations were also determined in twelve commercially available species of domestic shellfish to evaluate the potential risks to human health. Gonyaulux spinifera and Dinophysis acuminata, causative microalgae of yessotoxins (YTXs) and pectenotoxins (PTXs), respectively, showed high densities in the region from May to July. This period corresponded to high LMT concentrations in phytoplankton and mussels. Phytoplankton mainly contained PTX-2 and homo-YTX, with a maximum concentration of 2300 ng g-1 wet weight (ww) in May. In contrast, mussels mainly contained homo-YTX and YTX, with a maximum concentration of 1300 ng g-1 ww in July. LMTs-producing microalgae showed low densities and concentrations after July, whereas mussels accumulated toxins until September. In the SPATT sampler, more diverse LMTs were detected than in seawater, phytoplankton, and mussels. For example, dinophysistoxin-1 and azaspiracid-2 were detected only in SPATT. YTXs were detected in domestic seafood samples, including mussels, red scallops, and pen shells, but the concentrations were below the European Food Safety Agency recommended standard of 3.75 mg YTX-eq. kg-1. Moreover, the hazard quotient was less than 100 in all scenarios, indicating that the human health risk was not significant. This study provides valuable data on monthly distribution patterns of LMTs in the South Sea Coast of Korea and can serve as baseline data for future management policies of marine biotoxins.

Historical trends of traditional, emerging, and halogenated polycyclic aromatic hydrocarbons recorded in core sediments from the coastal areas of the Yellow and Bohai seas.

Historical trends of polycyclic aromatic hydrocarbons (PAHs) contamination were reconstructed from eleven sediment cores located in intertidal zones of the Yellow and Bohai seas for a period encompassing the last 80 years. The analysis encompassed 15 traditional PAHs (t-PAHs), 9 emerging PAHs (e-PAHs), and 30 halogenated PAHs (Hl-PAHs), including 10 chlorinated PAHs (Cl-PAHs) and 20 brominated PAHs (Br-PAHs). Concentrations of target PAHs were highest in industrial and municipal areas situated along the coast of the Bohai Sea, including Huludao, Yingkou, Tianjin, and Dandong, constituting a substantial mass inventory. All target PAHs showed increasing trends since the 1950s, reflecting the development history of South Korea and China. High molecular weight PAHs accumulated in sampling sites more than low molecular weight PAHs. A positive matrix factorization model showed that the PAH sources were coal and gasoline combustion (35%), diesel combustion (33%), and biomass combustion (32%). Over the last 80 years, the contribution of coal and gasoline combustion increased in all regions, while diesel combustion and biomass combustion varied across regions and over time. Toxicity equivalence values were highest for t-PAHs (>99% contribution), followed by Cl-PAHs, Br-PAHs, and e-PAHs. Concentrations of t-PAHs in Eastern Asia seas have increased since the 1900s, particularly in intertidal areas compared to subtidal areas. The intertidal zone removed 83% of the total flux of PAHs originating from land and thus appears to serve as a buffer zone against marine pollution. Overall, this study provides novel knowledge on the historical trends and sources of PAHs on a large scale, along with insights for future coastal management.

Legacy and novel perfluoroalkyl substances in raw and cooked squids: Perspective from health risks and nutrient benefits.

Perfluoroalkyl substance (PFAS) existed ubiquitously in the environment and could be ingested unconsciously with food which posed a disease risk to human health. Swordtip squid (Uroteuthis edulis) is one of the most popular and highly consumed seafood worldwide, with wide distribution and abundant biomass. Therefore, it is of great importance to the health of the public by reducing the health risks of squid consumption while preserving the benefits of squid to humans. In this study, the PFAS and fatty acids in squids were tested from the southeast coastal regions of China, a major habitat for squids. Relative higher concentrations of PFAS in squid were found in the subtropical zone of southern China (mean: 15.90 ng/g·dw) compared to those of the temperate zone of northern China (mean: 11.77 ng/g·dw). The digestive system had high tissue/muscle ratio (TMR) values, and the pattern of TMR among the same carbon-chain PFAS was similar. Cooking methods have a significant contribution to eliminating PFAS (in squids). PFAS were transferred from squids to other mediums after cooking, so juice and oil should be poured out to minimize PFAS exposure into body. The result showed that squids can be regarded as a healthy food by health benefits associated with fatty acids. Estimated daily intake (EDI) had the highest level in Korea via consuming squids through cooking processes compared with other countries. Based on the assessment of the hazard ratios (HRs), there was a high exposure risk of perfluoropentanoic acid (PFPeA) via taking squids for human health. This research provided the theoretical guidance of aquatic product processing in improving nutrition and reducing harmful substances.

Encapsulation of Clofazimine by Cyclodextran: Preparation, Characterization, and In Vitro Release Properties.

This study aimed to evaluate and compare the efficacy of cyclodextrans (CIs) and cyclodextrins (CDs) in improving the water solubility of a poorly water-soluble drug, clofazimine (CFZ). Among the evaluated CIs and CDs, CI-9 exhibited the highest percentage of drug inclusion and the highest solubility. Additionally, CI-9 showed the highest encapsulation efficiency, with a CFZ:CI-9 molar ratio of 0.2:1. SEM analysis indicated successful formation of inclusion complexes CFZ/CI and CFZ/CD, accounting for the rapid dissolution rate of the inclusion complex. Moreover, CFZ in CFZ/CI-9 demonstrated the highest drug release ratio, reaching up to 97%. CFZ/CI complexes were found to be an effective means of protecting the activity of CFZ against various environmental stresses, particularly UV irradiation, compared to free CFZ and CFZ/CD complexes. Overall, the findings provide valuable insights into designing novel drug delivery systems based on the inclusion complexes of CIs and CDs. However, further studies are needed to investigate the effects of these factors on the release properties and pharmacokinetics of encapsulated drugs in vivo, in order to ensure the safety and efficacy of these inclusion complexes. In conclusion, CI-9 is a promising candidate for drug delivery systems, and CFZ/CI complexes could be a potential formulation strategy for the development of stable and effective drug products.

Cooking methods effectively alter perfluoroalkyl substances and nutrients in cultured and wild bullfrogs.

The ubiquitous distribution of perfluoroalkyl substances (PFASs) poses a threat to the health of aquatic organisms and humans. Bullfrogs are considered a popular aquatic food product in South China, providing high protein and tasty cuisine; however bullfrogs have been shown to contain significant concentrations of PFASs. However, the risk-benefit ratios of PFASs and nutrient contents in cooked bullfrogs are not well understood. PFASs and nutrients were investigated in raw and cooked specimens of cultured and wild bullfrogs in this study. Novel PFASs showed higher detection levels and accumulation in wild bullfrogs than in cultured bullfrogs. Potential factors such as fat and fatty acid ratio affected PFASs accumulation in different tissues and by different cooking methods of bullfrogs. All cooking methods can reduce PFASs in edible tissues while significantly enhancing the nutritive value index (NVI) compared to raw bullfrogs. Steaming was the most effective way to reduce PFASs (rate of reduction was over 66%) and resulted in a lower risk of contributing to arteriosclerosis than other cooking methods assessed by atherogenicity index (AI) values. Cultured bullfrogs instead of wild bullfrogs were recommended for human consumption, and steaming was regarded as a better cooking method in terms of risk-benefit concerns. Overall, this work provides quantitative analysis of cooking methods that alter PFASs and nutrients in bullfrogs.

Distribution, compositional characteristics, and historical pollution records of microplastics in tidal flats of South Korea.

Studies on distribution of microplastics (MPs) in sediments of tidal flats are relatively scarce compared to other coastal areas. In this study, spatial and vertical distributions and compositions of MPs in tidal flat sediments along the west coast of Korea were investigated. The abundance of MPs in surface and core sediments ranged from 20 to 325 and 14 to 483 particles per 50 g dry weight, respectively. Polypropylene (51%) and polyethylene (36%) were the most dominant MPs; the size was <0.3 mm, and the shape was mostly fragments followed by fibers. The abundance of MPs in sediments has increased rapidly since the 1970s, and recently showed a slight decrease. Surface morphology of MPs analyzed using a scanning electron microscope revealed that the MPs in tidal flats were highly weathered mechanically and/or oxidatively. The results of this study provide valid baseline data on distributions of MPs in tidal flats.

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.