Artificial light at night (ALAN) is a major driver of firefly population declines, but its physiological effects are not well understood. To investigate the impact of ALAN on firefly development, we exposed larval Aquatica ficta fireflies to ALAN for two weeks. High larval mortality was observed in the periods of 1–68 days and 106–134 days post-treatment, which may represent the short- and long-term impacts of ALAN. We then profiled the transcriptome of larval Aquatica ficta fireflies following two weeks of ALAN exposure. A total of 1262 (1.67% out of 75777 unigenes) were differentially expressed in the treatment group: 1157 were down-regulated, and 105 were up-regulated. Up-regulated unigenes were related to regulation of hormone levels, ecdysteroid metabolic process, and response to stimulus; down-regulated unigenes were related to negative regulation of insulin receptor signaling, germ cell development, oogenesis, spermatid development, and regulation of neuron differentiation. Transcriptome results suggest that the endocrine, reproductive, and neural development of firefly larvae could be impaired by even relatively brief period of ALAN exposure. This report contributes a much-needed molecular perspective to the growing body of research documenting the fitness impacts of ALAN on bioluminescent fireflies.

The present study aimed to assess the toxicity of seven UV-filters: zinc oxide nanoparticles (nZnO, particle size <100 nm), titanium dioxide nanoparticles (nTiO₂, primary particle size 21 nm), 2-ethylhexyl-4-methoxycinnamate (EHMC), 4-methylbenzylidene camphor (4-MBC), avobenzone (AVO), octocrylene (OCTO) and benzophenone-3 (BP-3) on three species: Aliivibrio fischeri (inhibition of bioluminescence), Phaeodactylum tricornutum (growth inhibition) and Ficopomatus enigmaticus (larval development success). Results showed nTiO₂ to be the most toxic for P. tricornutum (EC₅₀ 0.043 mg L⁻¹), while no effect was observed in A. fischeri and F. enigmaticus. EHMC was the most toxic to A. fischeri (EC₅₀ 0.868 mg L⁻¹ (15 min) and 1.06 mg L⁻¹ (30 min)) and the second most toxic to P. tricornutum. For F. enigmaticus, the lowest percentages of correct development resulted from 4-MBC exposure, with EC₅₀ of 0.836 mg L⁻¹. Overall, AVO induced low toxicity to every assessed species and OCTO was the least toxic for F. enigmaticus larvae. Considering the results obtained for F. enigmaticus, further larval development assays were performed with nZnO and EHMC under different light (light vs darkness) and temperature (20 and 25 °C) conditions, showing higher percentages of correct development at 25 °C, independently on light/darkness conditions. Under different temperature and photoperiod conditions, nZnO was more toxic than EHMC. Overall, nZnO and EHMC were among the most toxic UV filters tested and, when testing the effects of these UV-filters with temperature the results highlight that the impacts are liable to be lessened at higher temperatures (25 °C compared with 20 °C), in the case of this estuarine polychaete species. Nevertheless, further experiments are necessary to describe the effects of these two UV-filters at different organization levels, to study the toxicity of eventual degradation by-products and to provide more information on the combination of different stressors.

Despite numerous reviews suggesting that microbial biosensors could be used in many environmental applications, in reality they have failed to be used for which they were designed. In part this is because most of these sensors perform in an aqueous phase and a buffered medium, which is in contrast to the nature of genuine environmental systems. In this study, a range of non-exhaustive extraction techniques (NEETs) were assessed for (i) compatibility with a naphthalene responsive biosensor and (ii) correlation with naphthalene biodegradation. The NEETs removed a portion of the total soil naphthalene in the order of methanol > HPCD > βCD > water. To place the biosensor performance to NEETs in context, a biodegradation experiment was carried out using historically contaminated soils. By coupling the HPCD extraction with the biosensor, it was possible to assess the fraction of the naphthalene capable of undergoing microbial degradation in soil. Exposure of microbial biosensors to cyclodextrin solutions allows the assessment of the degradable fraction of contaminants in soil.

Pollutants in real aquatic systems commonly occur as chemical mixtures. Yet, the corresponding risk assessment is still mostly based on information on single-pollutant toxicity, accepting the assumption that pollutant mixtures exhibit additive toxicity effect which is often not the case. Therefore, it is still better to use the experimental approach. Unfortunately, experimental determination of toxicity for each mixture is practically unfeasible. In this study, quantitative structure-activity relationship (QSAR) models for the prediction of toxicity of binary mixtures towards bioluminescent bacteria Vibrio fischeri were developed at three toxicity levels (EC₁₀, EC₃₀ and EC₅₀). For model development, experimentally determined toxicity values of 14 pollutants (pharmaceuticals and pesticides) were correlated with their structural features, applying multiple linear regression together with genetic algorithm. Statistical analysis, internal validation and external validation of the models were carried out. The toxicity is accurately predicted by all three models. EC₃₀ and EC₅₀ values are mostly influenced by geometrical distances between nitrogen and sulfur atoms. Furthermore, the simultaneous presence of oxygen and chlorine atoms in mixture can induce the increase in toxicity. At lower effect levels (EC₁₀), nitrogen atom bonded to different groups has the highest impact on mixture toxicity. Thus, the analysis of the descriptors involved in the developed models can give insight into toxic mechanisms of the binary systems.

Environment can be affected by a variety of micropollutants. In this paper, we develop a system to assess the toxicity on an environmental sample, based on the expression of a nanoluciferase under the control of the STB5 promotor in a yeast. The STB5 gene encodes for a transcription factor involved in a pleiotropic drug resistance and in the oxidative stress response. The response of the modified yeast was assessed using 42 micropollutants belonging to different families (antibiotics, pain killers, hormones, plasticizers, pesticides, etc.). Among them, 26 induced an increase of the bioluminescence for concentration ranges from pg.L⁻¹ to ng.L⁻¹. Surprisingly, for concentrations higher than 100 ng.L⁻¹, no response can be observed, suggesting that other mechanisms are involved when the stress increases. Analyzing the different responses obtained, we highlighted six nonmonotonic types of responses. The type of response seems to be independent of the properties of the compounds (polarity, toxicology, molecular weight) and of their family. In conclusion, we highlighted that a cellular response exists for very low exposition to environmental concentration of micropollutants and that it was necessary to explore the cellular mechanisms involved at very low concentration to provide a better risk assessment.

Transformation products (TPs) of micropollutants contaminating our water resources have become an emerging issue due to the potential threats they pose to environmental and human health. This study investigated the transformation chemistry, toxicity, physicochemical properties and environmental behavior resulting from photocatalytic transformation of organic UV filters as model micropollutants. 3-Benzylidene camphor (3-BC), 4-hydroxybenzophenone (4-HB) and octocrylene (OC) were effectively degraded by UV-A/TiO₂ treatment, with TPs identified and characterized with high resolution mass spectrometry. Nitrated-TPs were observed to be formed in the presence of nitrite and nitrate for 3-BC and 4-HB, suggesting that the transformation process could be altered by components in the water matrix. Vibrio fischeri bioluminescence inhibition assay revealed an increase in toxicity of TPs derived from photocatalytic treatment, with quantitative structure-activity relationship model (ECOSAR) predicted an enhanced toxicity of individual TPs' after transformation. Assessment of physicochemical properties and environmental behavior suggested that TPs as compared to parent organic UV filters, may represent even greater hazards due to their increased water solubility, persistence and mobility – in addition to retaining the parent organic UV filter's toxicity. The results provide important information relevant to the potential risks for the selected organic UV filters, and their corresponding transformation products.

A bioflocculant-producing bacterial strain, designated MSI021, was isolated from the marine sponge Dendrilla nigra and demonstrated 94% flocculation activity in a kaolin clay suspension. MSI021 was identified as Bacillus cereus based on phylogenetic affiliation and biochemical characteristics. The purified extra-cellular bioflocculant was chemically elucidated as a polysaccharide molecule. The polysaccharide bioflocculant was stable under both acidic and alkaline conditions (pH 2.0–10.0) and temperatures up to 100 °C. The purified bioflocculant efficiently nucleated the formation of silver nanoparticles which showed broad spectrum antibacterial activity. The ability of the bioflocculant to remediate heavy metal toxicity was evaluated by measuring the inhibition of bioluminescence expression in Vibrio harveyi. Enrichment of heavy metals such as zinc, mercury and copper at concentrations of 1, 2 and 3 mM in culture media showed significant reduction of bioluminescence in Vibrio, whereas media enriched with heavy metals and bioflocculant showed dose dependent improvement in the expression of bioluminescence. The assay results demonstrated that the polysaccharide bioflocculant effectively mitigates heavy metal toxicity, thereby improving the expression of bioluminescence in Vibrio. This bioluminescence reporter assay can be developed into a high-throughput format to monitor and evaluate of heavy metal toxicity. The findings of this study revealed that a novel polysaccharide bioflocculant produced by a marine B. cereus demonstrated strong flocculating performance and was effective in nucleating the formation antibacterial silver nanoparticles and removing heavy metals. These results suggest that the MSI021 polysaccharide bioflocculant can be used to develop greener waste water treatment systems.

Bacteria based ecotoxicology assessment of manufactured nanoparticles is largely restricted to Escherichia coli bioreporters in laboratory media. Here, toxicity effects of model OECD nanoparticles (Ag NM-300K, ZnO NM-110 and TiO2 NM-104) were assessed using the switch-off luminescent Pseudomonas putida BS566::luxCDABE bioreporter in Luria Bertani (LB) medium and artificial wastewater (AW). IC50 values ∼4 mg L−1, 100 mg L−1 and >200 mg L−1 at 1 h were observed in LB for Ag NM-300K, ZnO NM-110 and TiO2 NM-104, respectively. Similar results were obtained in AW for Ag NM-300K (IC50 ∼5 mg L−1) and TiO2 NM-104 (IC50 >200 mg L−1) whereas ZnO NM-110 was significantly higher (IC50 >200 mg L−1). Lower ZnO NM-110 toxicity in AW compared to LB was associated with differences in agglomeration status and dissolution rate. This work demonstrates the importance of nanoecotoxicological studies in environmentally relevant matrices.

In this study, the acute toxicity of microplastics (MPs) on unicellular organisms as marine decomposers and microalgae was assessed, by evaluating standards endpoints included in International Standard Organization (ISO) protocols. The bacteria Vibrio fischeri and the diatom Phaeodactylum tricornutum were exposed to different sizes (1–500 μm) of polyethylene MPs in order to evaluate bioluminescence inhibition and microalgal growth. No acute toxicity was found on bacteria or microalgae in an order of magnitude above environmentally relevant concentrations, suggesting that tested MPs did not affect the investigated biological processes. In conclusion, standard ecotoxicological endpoints are not sufficiently sensitive to assess the potential effects of MPs on decomposers and primary producers, conversely to nanoplastics. These findings highlight that the current approach for MP risk assessment in unicellular species should be revised, by providing alternative endpoints to be included in standardized protocols, able to monitor the fate and biological effects of MPs.

A dinoflagellate under the ambit of Harmful Algal Blooms (HAB), the bioluminescent Noctiluca scintillans (NS), has been infesting the northern Arabian Sea increasingly over the last few decades during late winter. Their occurrence is found to be due to seasonal oscillations in the coastal currents. The physical and biogeochemical parameters associated with the seasonal blooms are reasonably well known. But accurate quantitative estimation capability using remote sensing sensors over the extensive oceanic regime is still lacking. This is especially due to a lack of information on bio-optical properties associated with cell density measurements. We attempted to show that remote sensing reflectance and chl-a show significant relationship e.g., Rᵣₛ(531)/Rᵣₛ(510) = 0.8261 + 6.06 × 10⁻⁶NS + 0.02323chl-a (N = 19, R²ₐdⱼ = 0.99, p = 2.5 × 10⁻¹⁷, RMSE = 0.1083) which is applicable over diverse areas of the northeastern Arabian Sea e.g., coastal, shelf and offshore regions. The model is supported by a second dataset with an RMSE of 0.022893 (N = 8) for the Rᵣₛ(531)/Rᵣₛ(510) ratio. The NS cell densities were derived from the Rrs(510)/Rrs(531) band ratio within reasonable error and accuracy limits. Including sensor capability at 510 nm is suggested in future satellite launches.