Per- and polyfluoroalkyl substances (PFAS) are persistent, structurally diverse contaminants whose ecological hazard assessment remains challenging, particularly for primary producers. Conventional growth-based algal bioassays often overlook sublethal responses associated with chronic exposure. Here, we developed a 7-day multigenerational bioassay using the freshwater diatom Cyclotella meneghiniana that integrates chlorophyll fluorescence (photosynthetic biomass) and lipid accumulation (oxidative stress and carbon reallocation) as complementary endpoints. Ten PFAS spanning carbon chain lengths from C4 to C11 and representing both perfluoroalkyl carboxylates and sulfonates were evaluated under identical nominal exposure conditions. Distinct structure-dependent toxicity patterns emerged. Long-chain perfluoroalkyl carboxylic acids elicited the strongest responses, whereas short-chain compounds produced no measurable effects. Among the sulfonates, PFHxS reduced chlorophyll fluorescence with limited effects on lipid accumulation, whereas PFOS produced no measurable response. Exploratory species sensitivity distribution analyses indicated compound-specific differences, although predicted no-effect concentrations should be interpreted cautiously because they combine literature-derived growth endpoints with endpoint-specific values generated in this study. This dual-endpoint diatom bioassay provides a proof-of-concept platform for structure-informed PFAS hazard ranking rather than regulatory toxicity assessment.

Root length is increasingly used as a rapid endpoint in duckweed ecotoxicology, yet biologically distinct assays are often treated as equivalent. Two 72 h root-length tests are now in use: root re-growth after excision in mature Lemna aequinoctialis fronds, and root development during germination of rootless Spirodela polyrhiza turions exposed directly to the test solution. Both begin from zero initial root length, but for different biological reasons. We asked whether they produce comparable herbicide responses. Thirteen herbicides were drawn from a screening campaign in which both assays were run under matched exposure conditions. Nine compounds returned quantified EC50 estimates (with the L. aequinoctialis coefficient of variation below 40%) and formed the primary comparison. EC50 ratios (S. polyrhiza/L. aequinoctialis) ranged from 0.75 to 430 (median 2.76). Five compounds agreed within about three-fold, whereas four compounds spanning several target-site classes diverged by 74- to 430-fold, and potency rankings were not significantly correlated (Spearman ρ = 0.43, p = 0.24). For the common reference toxicant, the two assays differed by only about two-fold, and in the opposite direction; comparable reference-toxicant performance therefore did not predict comparable herbicide responses. The two assays should not be treated as interchangeable root-length tests. However, they differ not only in the biological origin of the measured root but also in species and developmental starting condition, and the present design cannot separate these factors; the observed differences therefore demonstrate assay-level non-equivalence without identifying its biological cause.

To investigate the effects of internal and external factors on the growth and development of Griffithsia heteroclada, the optimal culture medium and conditions were first established. Subsequently, individual apical cell (Ca), rhizoid cell (Cr), shoot cell (Cs), and nodal cell (Cn) were cultured under varying light intensities. The findings indicated that the most suitable culture media for G. heteroclada are Provasoli-enriched seawater and Tropic Marin, with optimal culture conditions comprising an irradiance of 60 μmol photons · m-2 · s-1, a salinity of 25, a temperature of 25°C, and a pH of 8. Any single cell could regenerate into a new plant, but regeneration varied by cell type, with the promoting effect being most pronounced in the order of Cn = Cs > Cr ≥ Ca. High light intensity inhibited energy transfer from accessory pigments to reaction centers in Ca and Cr, thereby diminishing their light capture capacity and photosynthetic efficiency. Fresh weight is deemed an appropriate biomass indicator for G. heteroclada, and the cell enlargement rate is considered a suitable growth indicator. Developmental indicators include cell number, division rate, branch number, and branch initiation time, while cell length, branching rate, elongation rate, and area are not suitable.

Salinity-induced interference remains a persistent challenge in freshwater ecotoxicity assessment because elevated ionic strength can trigger organism-level stress responses that confound the interpretation of chemically mediated toxicity. Such effects may inflate toxicity units (TUs), complicating the separation of intrinsic contaminant toxicity from salinity-driven physiological stress. Here, we present a bioassay-informed machine-learning framework that translates multi-species TU signatures into an interpretable binary classification model based on responses of the salinity-sensitive crustacean Daphnia magna, freshwater macrophyte Lemna minor, and euryhaline macroalga Ulva australis. TU profiling supported the use of U. australis as a salinity-tolerant reference and enabled the construction of biologically grounded interference labels for supervised learning. Among logistic regression, random forest (RF), and gradient boosting models, RF showed balanced performance under repeated stratified five-fold cross-validation (100 repeats). A reduced five-variable RF model (dissolved oxygen, copper, selenium, chromium, and zinc) achieved an AUROC of 0.781 under the same cross-validation protocol (100 repeats); given the limited sample size, this result should be interpreted as evidence that dominant signals can be retained under dimensionality reduction rather than as improved generalization. SHapley Additive exPlanations (SHAP) indicated that dissolved oxygen and selected trace metals contributed most strongly to model predictions within this dataset, consistent with known redox- and metal-associated stress pathways. Overall, this study provides a proof-of-concept explainable framework for flagging salinity-associated interference patterns in ecotoxicity testing, while emphasizing that external validation using larger geographically independent datasets is required before broader operational or regulatory use.

Trace metals are persistent stressors in coastal ecosystems, yet most marine algal toxicity assessments still rely on freshwater model species and growth-based endpoints that provide limited mechanistic resolution. Here, we quantified the sensitivity of two ecologically contrasting marine diatoms—the benthic Cylindrotheca closterium and the planktonic Thalassiosira weissflogii—to ten environmentally relevant metals using a dual-endpoint approach that integrates chlorophyll fluorescence (photosystem function) and Nile Red-based lipid-body fluorescence (metabolic reallocation). Fluorescence-based EC10 values revealed distinct species- and metal-specific patterns, with C. closterium consistently responding at lower concentrations and Hg producing the strongest inhibition in both species (EC10 ≈ 0.04–0.06 mg L−1). Lipid-body accumulation detected earlier metabolic disturbance for several metals, particularly Hg, As, Cr(VI), and Cd, and frequently occurred at concentrations where fluorescence remained minimally affected. These sequential thresholds indicate that pigment impairment and metabolic reallocation represent mechanistically distinct stages of the cellular stress response that differ among metals and between diatom guilds. Comparison with published toxicity data shows that the dual-endpoint sensitivities observed here fall within, or slightly above, the upper range of reported microalgal responses, underscoring the pronounced susceptibility of benthic diatoms to redox-active and thiol-reactive metals. The strong agreement between fluorescence-based EC values and traditional growth-derived benchmarks for key metals further supports fluorescence as an operationally efficient endpoint suitable for integration into emerging ISO marine algal bioassays. Overall, this study demonstrates that pairing a rapid functional marker with a mechanistically informative metabolic biomarker enables metal-specific toxicity fingerprinting and provides an ecologically grounded basis for incorporating benthic diatoms into coastal metal risk assessment frameworks.

Genotoxins cause significant damage to the genetic material of aquatic organisms, requiring rapid and accurate assessment. Fish-derived cells sensitive to genotoxins have proven to be a useful tool for measuring genotoxicity, but the long treatment times required for measurement limit their application in situations requiring rapid testing. Previous studies have shown that fish cells can be kept unstarved for up to 6 h using media containing 1% FBS. In this study, the 1% FBS/6 h parameter was used for genotoxicity assessment. Therefore, genotoxicity assessment was performed after only 6 h of genotoxin treatment in a medium containing 1% FBS. The new genotoxicity assessment method provided faster and more accurate genotoxicity data for climbazole and metolachlor than the existing assessment system using the 15% FBS/96 h parameter. Furthermore, these advantages of the new platform enabled the determination of the genotoxicity of various genotoxins, such as dibenz[a,h]anthracene and ethoprophos. In summary, we have developed a genotoxicity assessment that can generate genotoxicity data rapidly and accurately. This new platform will serve as a foundation for rapid genotoxicity assessment of many genotoxins.

Herbicide contamination of aquatic ecosystems poses a critical risk to biodiversity. Bioassays provide useful ecological insights on responses to herbicides; however, they require a model organism. Ulva australis is an ideal candidate for herbicide toxicity evaluations. Conventional monitoring methods have certain limitations, necessitating innovative approaches for ecological risk assessment. We evaluated the toxicity of six herbicides (atrazine, chlorimuron-ethyl, diuron, hexazinone, simazine, and pendimethalin) to U. australis by integrating experimental bioassays with advanced machine learning models. Three key endpoints were measured-reproduction, relative growth rate, and photosynthetic efficiency. Species sensitivity distribution modelling was employed to determine the hazardous concentration values for 5 % of species (HC5) and the predicted no-effect concentration (PNEC). The derived values aligned well with regulatory benchmarks. For diuron, the PNEC (0.37 ± 0.25 μg L-1) closely matched the value of the European Chemicals Agency (0.32 μg L-1). In contrast, the HC5 for hexazinone (26.8 ± 28.7 μg L-1) was lower than that specified by the Australian/New Zealand guideline (75 μg L-1). Machine learning models showed high predictive accuracy, with gradient boosting outperforming random forest (R2 = 0.933, RMSE = 0.0036 mg L-1 vs R2 = 0.878 and RMSE = 0.0048 mg L-1). Sensitivity analysis confirmed the robustness of gradient boosting to input variability, highlighting its suitability for ecological risk assessment. This approach establishes a scalable framework for ecological risk evaluation by integrating experimental and computational methodologies. The resulting data can also generate adaptive strategies to mitigate herbicide impacts and protect aquatic ecosystems.

This study investigates how selected environmental variables affect growth and total (poly)phenolic content (TPC) in the gametophyte stage of the brown kelp, Ecklonia cava, in controlled laboratory settings. In three multivariate cultivation experiments, we explored the effect of irradiance, aeration and temperature on the growth and TPC of both male and female gametophytes. Temperature did not cause significant changes in TPC content of female gametophytes, while for males grown at 15 °C significantly higher TPC levels were observed. We observed significant differences in TPC levels in both female and male gametophytes grown under different irradiances, while no effect of aeration was observed. In addition to their cytotoxicity, antioxidant activity of the polyphenolic extracts of female gametophytes was evaluated via two in vitro assays. First, all evaluated extracts displayed DPPH radical scavenging activity, ranging from approximately 22 – 59

Following World Wars I and II, extensive dumping of conventional and chemical munitions in the marine environment has left a lasting impact on coastal areas, particularly those directly involved in the conflicts. Over the decades, corrosion of munition shells has resulted in the release and subsequent detection of a range of hazardous chemicals in environmental samples. These include conventional explosives and related compounds (E&RC), as well as chemical warfare agents and related compounds (CWA&RC). Despite this legacy, significant data gaps persist concerning the persistence, bioaccumulation, and toxicity of these chemicals to human and environmental health. In this study, we applied an updated and expanded suite of (quantitative) structure-activity relationship, or (Q)SAR, tools-Ecological Structure-Activity Relationships Program Version 2.2, Estimation Program Interface Suite Version 4.11, and Organisation for Economic Co-operation and Development (Q)SAR Toolbox Version 4.5-to comprehensively and simultaneously screen and prioritize a broad range of E&RC and CWA&RC detected in environmental samples from global munition dumpsites. To our knowledge, this is the first application of this combined, up-to-date toolchain to field-detected munition compounds. Our results demonstrate that (Q)SAR models can generate conservative estimations useful for the prioritization of munition-related chemicals for further investigation, although the reliability for specific endpoints may vary by the available empirical data. We underline that trinitrotoluene and its metabolites, followed by tetryl and picric acid (all E&RC), require urgent monitoring in the environment and seafood, alongside defined human health safety thresholds in key exposure sources. In addition, sulfur mustard, arsenical CWA, and their metabolites should be prioritized for targeted human health and long-term environmental studies. This comprehensive screening approach addresses long-standing data gaps, providing a valuable framework for decision makers engaged in the management and remediation of munition dumpsites.

Plastics pose a significant threat to marine ecosystems, owing to their slow biodegradability. Microplastics (MPs), in particular, affect marine life and maricultural organisms and can enter the food chain via ingestion by marine organisms, leading to bioaccumulation in predators, including humans. This study assessed the toxic interactions between polystyrene microplastic particles (PSMPs) and cadmium (Cd) and phenanthrene (Phe) using marine bivalves. While PSMPs were non-toxic to Pacific oysters (Crassostrea gigas), the toxicity of Cd and Phe was concentration-dependent. In most conditions, PSMPs reduced the toxicity of Cd and Phe, but in simultaneous exposure, they acted as Cd messengers, altering the toxicity during the adult stage. This study confirms that PSMPs can interact with coastal environmental pollutants, thereby accelerating biotoxicity and posing a significant threat to marine wildlife, mariculture, and human health. It also highlights the need to assess MP toxicity in coastal environments and their interactions with pollutants.

Toxic substances can cause serious harm to aquatic organisms and humans who consume them. Rapid ecotoxicity assessment and genotoxicity assessment should be performed simultaneously to detect potential harm caused by toxic substances. In a previous study, an ecotoxicity and genotoxicity assessment system was established by treating fish cells derived from Cyprinus carpio (C. carpio) with toxic substances in a medium containing 1

Macroalgal growth and yield are key to sustainable aquaculture. Although light and water turbulence are two important factors that affect algal productivity, research on their interaction is limited. Therefore, in this study, we investigated the effects of different wavelengths of light and the presence or absence of water turbulence on the growth of the green macroalga Ulva australis. Water turbulence was found to enhance the growth of U. australis irrespective of photosynthetic performance, but only in blue light cultures. The quantum dose of blue light required to induce 50% growth promotion was 1.02 mol m−2, which is comparable to the reported values for cryptochrome-mediated effects in other macroalgae. The combined effect of blue light and water turbulence led to the accumulation of photosynthesis-related proteins that support plastid differentiation and facilitate efficient photosynthesis and growth. Our findings thus highlight the potential of harnessing blue light and water turbulence to maximise macroalgal cultivation for sustainable and profitable algal aquaculture.

Trace heavy metals have a tendency to persist in the effluent of industrial wastewater treatment facilities, leading to toxic effects on downstream water bodies. Traditional assessment methods relied on animal testing, but ethical concerns have rendered them unacceptable. An alternative solution is to evaluate wastewater toxicity using trophic-level aquatic organisms as bioassays. However, these bioassay methods involve costly and time-consuming chemical and biological analytical experiments. In this study, an artificial intelligence-powered water quality assessment (AiWA) approach is proposed for predicting industrial effluent ecotoxicity to further enhance the quick and cost-effective ecotoxicity assessment process. Initially, 99 samples were collected from industrial wastewater treatment plants representing 21 different industries in the Republic of Korea. Fourteen parameters were measured, encompassing both physicochemical and ecotoxicological aspects. Boosting algorithms, especially extreme gradient boosting (XGBoost) and adaptive boosting (AdaBoost), were employed for model development. XGBoost outperformed AdaBoost in terms of model performance. Feature selection analysis revealed that conductivity, copper, lead, selenium, pH, and zinc concentrations were the most suitable inputs for training the boosting model. The innovated XGBoost-based AiWA model demonstrated significantly higher performance (i.e., up to 80%) compared to conventional models with an R2 value of exceeding 0.94 and root mean square error of 3.5 toxicity unit for predicting the integrated toxicity unit (ITU). Additionally, pH and conductivity emerged as crucial indicators for reflecting ecotoxicity levels. Specially, this case study indicated that non-toxic/directly dischargeable levels (TU ≤ 1) were achieved when the pH ranged from 6.8 to 8.4 and the conductivity remained below 1651 μS/cm. These findings are expected to facilitate rapid and cost-effective detection of heavy metal ecotoxicity in industrial wastewater effluents, aiding decision-making in wastewater management.

Heavy metals have serious negative effects on various aquatic organisms, and therefore rapid and accurate ecotoxicological assessments of heavy metals are necessary. Fish-derived cells sensitive to heavy metals have been used as valuable tools for ecotoxicological assessments. However, this method requires a minimum toxicity treatment time of 96 h, which limits its use when rapid ecotoxicological assessments are required or ecotoxicological assessments of a large number of toxicants are performed. In this study, these limitations were overcome by adjusting parameters including the concentration of fetal bovine serum (FBS) in the medium and the treatment time of the toxicant. Specifically, we found that the maximum time for fish cells to remain unstarved was 6 h when using a medium containing 1% FBS. We applied both parameters to the ecotoxicological assessment (using a medium containing 1% FBS for the toxicity assessment and treating the toxicant for only 6 h). Surprisingly, these adjusted parameters allowed us to obtain faster and more accurate data than the traditional assessment. This improvement was due to the new assessment conditions that minimized the possibility that the growth-inducing effects of nutrients present in excess in the medium could interfere with the cellular response to the toxicant. The accuracy of this assessment was not limited to measuring the toxicity of heavy metals. In conclusion, we have established an ecotoxicity assessment that can generate rapid and accurate data on heavy metals. This new platform will become the cornerstone of rapid and accurate ecotoxicity assessments of heavy metals.

Microalgal growth-based tests are international standards for ecotoxicity assessment; however, their long exposure times, large sample volumes, and reliance on a single growth-endpoint make them inadequate for rapid toxicity screening. Here, we aimed to develop a rapid and simple ecotoxicological test using the fast-growing green alga Mychonastes afer, with multiple endpoints-growth, lipid content, and photosynthesis. We exposed M. afer to two metals-silver and copper-and two herbicides-atrazine and diuron-for 24 h and identified the most sensitive and reliable endpoints for each toxicant: the maximum electron transport rate (ETRmax) for Ag, Cu and atrazine, and the lipid content for diuron. Lipid content was found to be both a sensitive and reliable biomarker, meeting the effluent limit guidelines in both the Republic of Korea and the USA. The sensitivity of M. afer to Ag and atrazine also closely matched the HC5 values derived from the species sensitivity distribution approach, confirming its reliability for setting regulatory concentrations of these contaminants. Our calculated predicted no-effect concentration (PNEC) values were similar to established European Union PNECs for Ag, Cu, atrazine, and diuron, underlining the utility of these biological endpoints for ecological risk assessment and regulatory decision making. This method required lower sample volume (2 mL vs 100 mL) and exposure time (24 h vs 72-120 h) than conventional green algal tests, and eliminated the need for labour-intensive cell counting, expensive equipment, and chlorophyll fluorescence measurement expertise. Overall, this M. afer test can be a valuable tool for the rapid screening of wastewater for metals and herbicides, contributing to environmental protection and management practices.

Red phycoerythrin (R-PE) is a highly valuable protein found in an edible seaweed, Pyropia yezoensis. It is used extensively in biotechnological applications due to its strong fluorescence and stability in diverse environments. However, the current methods for extracting and purifying R-PE are costly and unsustainable. The aim of the present study was to enhance the financial viability of the process by improving the extraction and purification of R-PE from dried P. yezoensis and to further enhance R-PE value by incorporating it into a tandem dye for molecular biology applications. A combination of ultrafiltration, ion exchange chromatography, and gel filtration yielded concentrated (1 mg·mL–1) R-PE at 99% purity. Using purified PE and Cyanine5 (Cy5), an organic tandem dye, phycoerythrin-Cy5 (PE-Cy5), was subsequently established. In comparison to a commercially available tandem dye, PE-Cy5 exhibited 202.3% stronger fluorescence, rendering it suitable for imaging and analyzes that require high sensitivity, enhanced signal-to-noise ratio, broad dynamic range, or shorter exposure times to minimize potential damage to samples. The techno-economic analysis confirmed the financial feasibility of the innovative technique for the extraction and purification of R-PE and PE-Cy5 production.

In approximately one decade, global temperatures will likely exceed a warming level that a United Nations Intergovernmental Panel on Climate Change report considers a "red alert for humanity". We propose exploring tidal flat diatoms to address climate change challenges. Tidal flats are extensive coastal ecosystems crucial to the provisioning and regulation of aquatic environments. Diatoms contribute to tidal flat biomass production and account for 20% of global primary productivity and 40% of annual marine biomass production, making them crucial for nutrient cycling and sediment stabilization. Potential CO2 removal from Korean tidal flats by diatoms is estimated to be 598,457-683,171 t CO2 equivalents (CO(2)e) annually, with the economic value of blue carbon (BC) resulting from diatom activity being approximately US$ 17.95-20.50 million. Dissemination of this potential could incentivize coastal wetland protection and climate change mitigation measures. The global estimated CO(2)e removal potential of tidal flat diatoms is 40,957,346-46,754,961 t CO(2)e, representing 0.11-0.13% of the annual global greenhouse gas emissions, even though tidal flats cover 0.0025% of the Earth's surface and diatoms represent less than 0.5% (by weight) of all photosynthetic plants. Researchers should combine ecology and economics to develop standardized approaches for carbon input monitoring and quantification. Further, spatiotemporal analyses of environmental threats to tidal flat diatoms are necessary for conserving their biodiversity and function as a critical BC source. Land-based cultivation for large-scale biomass production and biorefinery processes can contribute to a greener, more prosperous future for humanity and the marine ecosystems upon which we rely.

Green tides, characterised by massive blooms of the seaweed Ulva, pose a significant threat to coastal economies and marine ecosystems. This review explores the potential repurposing of harmful Ulva blooms for carbon sequestration, addressing the critical global issue of CO2 emission. We conducted a comprehensive literature review and examined the conversion of shoreline Ulva biomass into biochar through pyrolysis, a process that can be implemented directly at biorefineries. This approach not only facilitates carbon sequestration but also mitigates greenhouse gas emissions and enhances soil quality through soil amendments. Our review covers data from 2008 to 2022, focusing on the carbon sequestration potential of Ulva during green tide episodes in China and Korea. Our assessment indicates that Ulva biomass has the potential to sequester approximately 3.85 million tons of CO2 equivalent (CO2e), with about 1.93 million tons of CO2e potentially stabilised through biochar conversion. Furthermore, we conducted a hypothetical techno-economic analysis assessing the sustainability and economic viability of Ulva cultivation and biochar production for CO2 sequestration. These findings suggest that the combined biomass and biochar production could be financially viable and profitable. Despite the challenges posed by green tides, our review highlights their potential role in mitigating global climate change.

Toxicity tests represent a rapid, user-friendly and cost-effective means to assess the impact of wastewater quality on aquatic ecosystems. There are not many cases where wastewater management standards are set based on various bio-based ecotoxicity values. Here, we tested a novel multitaxon approach to compare standard water quality indices to toxicity metrics obtained from ecotoxicity tests, conducted using aquatic organisms representing several trophic levels (Aliivibrio, Ulva, Daphnia, and Lemna), for 99 industrial wastewater samples from South Korea. For five wastewater samples, the concentrations of Se, Zn, or Ni exceeded the permissible limits (1, 5, and 3 mg L-1, respectively). All the four physiochemical water quality indices tested were positively correlated with Se and Pb concentrations. The toxicity unit (TU) scores indicated a declining sensitivity to pollutants, in the order Lemna (2.87) >Daphnia (2.24) >Aliivibrio (1.78) >Ulva (1.42). Significant correlations were observed between (1) Cd and Ni, and Aliivibrio, (2) Cu and Daphnia, (3) Cd, Cu, Zn, and Cr and Lemna, and (4) Cu, Zn, and Ni and Ulva. Daphnia-Lemna and Lemna-Ulva were found to be good indicators of ecologically harmful Se and Ni contents in wastewater, respectively. We suggest that regulatory thresholds based on these bioassays should be set at TU = 1 for all the species or at TU = 1 for Aliivibrio and Ulva and TU = 2 for Daphnia and Lemna, if the number of companies whose wastewater discharge exceeds the allowable TU levels is <1 % or 5 % of the total number of industries, respectively. Taken together, these findings could help in establishing a rapid, ecologically relevant wastewater quality assessment system that would be useful for developing strategies to protect aquatic ecosystems.

Metals and metalloids are toxic, persistent, and non-biodegradable and can be biomagnified (e.g., Hg), and therefore pose a serious threat to the algal flora of aquatic ecosystems. This laboratory study tested the effects of metals (Zn, Fe, and Hg) and a metalloid (As) on the cell wall morphology and protoplasmic content of living cells of six widespread diatom genera over 28 days. Diatoms exposed to Zn and Fe had a higher frequency of deformed diatom frustules (> 1