Multi-biomarker approach for the (eco)toxicity of UV-filter environmental pollution on the Mediterranean mussel Mytilus galloprovincialis in a multiple stressor context. The case of 4-MBC under salinity shifts

Marine-coastal ecosystems are rapidly transforming because of climate change (CC). At the same time, the impacts of emerging organic contaminants (i.e., organic UV-filters) on these ecosystems are intensifying. In the Mediterranean, the consequences of these disturbances are occurring at a fast pace making this area a potential sentinel site to be investigated. While singular effects of organic UV-filters or CC-related factors on marine biota have been relatively described, their combined impact is still largely unknown. Thus, the objective of this study was to assess the long-term responses of the Mediterranean mussel Mytilus galloprovincialis towards anticipated salinity changes (decreases-S20 or increases-S40) when exposed to environmentally relevant concentrations of the UV-filter 4-methylbenzylidene camphor (4-MBC). An integrated multi-biomarker approach was applied, featuring general and oxidative stress, antioxidant and biotransformation enzyme capacity, energy metabolism, genotoxicity, and neurotoxicity biomarkers. Results showed that both projected salinities, considered separately, exerted non-negligible impacts on mussels' health status, with greater biological impairments found at S 40. Combining both stressors resulted in an evident increase in mussels' susceptibility to the UV-filter, which exacerbated the toxicity of 4-MBC. The dominant influence of salinity in the climate change-contaminant interaction played a crucial role in this outcome. The most severe scenario occurred when S 20 was combined with 4-MBC. In this situation, mussels exhibited a decrease in filtration rate, metabolic capacity and deployment of energy reserves increased, with an upregulation of biotransformation and inhibition of antioxidant enzyme activities. This exposure also led to the observation of cellular and DNA damage, as well as an increase in AChE activity. Furthermore, salinity-dependent bioaccumulation patterns were evaluated revealing that the lowest values in contaminated mussels are found at S 20. Overall, the present findings provide evidence that projected CC/pollutant scenarios may represent high risks for mussels' populations, with global relevant implications for the ecosystem level.

Divergent responses and ecological risks of wheat (Triticum aestivum L.) to cerium oxide nanoparticles in different soil types

Cerium oxide nanoparticles (nCeO₂), as a common component for sustainable agriculture, have been broadly investigated due to their potential threat to the soil biodiversity and health. However, few studies considered the impacts of soil types on response of ecotoxicity of nCeO₂ to plants. This study aimed to explore the effects of soil properties on ecological response of nCeO₂ to wheat (Triticum aestivum L.) and assess the ecological risks of nCeO₂ (0-1000 mg/kg) in red soil, yellow-brown soil, and brown soil by applying a multi-biomarker approach. The results showed that the clay content had the extremely significant correlation with acid solute fraction Ce in soil. Ce accumulation in wheat largely depended on acid-soluble fraction Ce, but not the total Ce. Both urease and invertase activities were highest in brown soil among the three soils, after exposure to diverse concentration nCeO₂. Although wheat has a stronger antioxidant capacity in red soil, integrated biomarker response index proved that nCeO₂ showed least toxicity to wheat in brown soil (IBRv2 = 34.3) among the three soils. These results indicated that the toxicity level of nCeO₂ to wheat was not only related to contaminated concentration, but also greatly depended on soil properties. The soil types are important factors governing ecological risk of nCeO₂ in soil, which needs to be adequately assessed and properly controlled.

The response of bacterial community to UVB was significantly different between immature periphyton and mature periphyton, but not for physiological indicators

Periphyton has important ecological functions. It can even exist in environments with strong ultraviolet radiation. However, knowledge of periphyton under ultraviolet is limited, which limits the understanding and application of periphyton in environments with high ultraviolet radiation. In this study, immature periphyton (IMP) and mature periphyton (MP) under ultraviolet B (UVB) irradiation were investigated and compared in terms of physiological characteristics and bacterial community. Analysis of the physiological characteristics showed that the response patterns of IMP and MP to UVB were similar. IMP and MP could adapt to UVB of 1 W/m² well. However, high-intensity UVB (2 and 3 W/m²) reduced the periphyton biomass, inhibited photosynthesis and antioxidant enzyme activity and caused severe lipid peroxidation in both IMP and MP. Integrated Biological Response (IBR) analysis and toxicological model fitting showed that the ED₅₀ values of UVB for IMP and MP were 1.25 and 1.50 W/m², respectively. 16 S rRNA gene analysis showed that in both IMP and MP, bacterial community composition, assembly and function were affected by UVB. In addition, the response of the bacterial community in IMP to UVB was stronger than that in MP. The diversity of the IMP community was inhibited by UVB, but that of the MP community was not. Proteobacteria and Deinococcus-Thermus are key microorganisms responsible for tolerance to UVB stress. Neutral community model fitting showed that both UVB and the development process caused the determinism of bacterial succession. However, UVB may weaken the deterministic process caused by development. Functional prediction showed that many metabolic functions of periphyton were inhibited by UVB in IMP and MP. However, UVB caused different changes (enhancement or inhibition) of some ecological functions in them. This study provides valuable information for understanding periphyton in environments with UVB radiation, which may be used to improve the application of periphyton in these environments.

Multi-biomarker approach and IBR index to evaluate the effects of different contaminants on the ecotoxicological status of Apis mellifera

The honeybee, Apis mellifera L. (Hymenoptera: Apidae), a keystone pollinator of wild plant species and agricultural crops, is disappearing globally due to parasites and diseases, habitat loss, genetic constraints, beekeeper management issues and to the widespread use of pesticides. Besides insecticides, widely studied in this species, honeybees are also exposed to herbicides and fungicides and heavy metals whose lethal and sublethal effects need to be investigated. In this context, our study aimed to evaluate the effects of fungicides and of heavy metals on honeybees and to develop and apply a multi-biomarker approach that include an Integrated Biological Index (IBRv2) to assess the toxicological status of this species. Biomarkers of neurotoxicity (AChE and CaE), metabolic alteration (ALP, and GST) and immune system (LYS, granulocytes) were measured, following honeybees' exposure to cadmium or to a crop fungicide, using the genotoxic compound EMS as positive control. A biomarker of genotoxicity (NA assay) was developed and applied for the first time in honeybees. At the doses tested, all the contaminants showed sublethal toxicity to the bees, highlighting in particular genotoxic effects. The data collected were analyzed by an IBRv2 index, which integrated the seven biomarkers used in this study. IBRv2 index increased with increasing cadmium or fungicide concentrations. The IBRv2 represents a simple tool for a general description of honeybees ecotoxicological health status. Results highlight the need for more in-depth investigations on the effects of fungicides on non-target organisms, such as honeybees, using sensitive methods for the determination of sublethal effects. This study contributes to the development of a multi-biomarker approach to be used for a more accurate ecotoxicological environmental monitoring of these animals.

Oxidative stress response mechanism of Scenedesmus obliquus to ionic liquids with different number of methyl-substituents

Ionic liquids (ILs) have become persistent contaminants in water because of their good solubility and low biodegradability. The oxidative stress responses of Scenedesmus obliquus to three imidazole ILs with different number of methyl-substituents, i.e., 1-decyl-imidazolium chloride ([C₁₀IM]Cl), 1-decyl-3-methylimidazolium chloride ([C₁₀MIM]Cl), and 1-decyl-2,3-dimethylimidazolium chloride ([C₁₀DMIM]Cl), were studied. There was a positive correlation between ROS level and IL concentration. The activities of antioxidant enzymes, i.e., superoxide dismutase, catalase, peroxidase, ascorbate peroxidase, and glutathione peroxidase, and the content of antioxidants, i.e., ascorbic acid and glutathione, changed in IL treatment with a concentration-dependent effect. Proline accumulation increased with increasing IL concentration. Integrated biomarker response (IBR) index analysis, based on the eight oxidative stress response indicators, revealed that the toxicity order was: [C₁₀IM]Cl < [C₁₀DMIM]Cl < [C₁₀MIM]Cl. Proteomic analysis showed that IL affect the type and distribution of proteins in S. obliquus. Chloroplast and photosystem II were affected as cellular component, and the proteins related to oxidative stress are annotated in GO categories. IBR index and proteomic analysis indicate that oxidative stress response is one of the main biomarkers of IL stress.

Integrated approach to assess ecosystem health in harbor areas

Harbors are critical environments with strategic economic importance but with potential environmental impact: health assessment criteria are a key issue. An ecosystem health status approach was carried out in Portimão harbor as a case-study. Priority and specific chemical levels in sediments along with their bioavailability in mussels, bioassays and a wide array of biomarkers were integrated in a biomarker index (IBR index) and the overall data in a weight of evidence (WOE) model. Metals, PAHs, PCBs and HCB were not particularly high compared with sediment guidelines and standards for dredging. Bioavailability was evident for Cd, Cu and Zn. Biomarkers proved more sensitive namely changes of antioxidant responses, metallothioneins and vittellogenin-like proteins. IBR index indicated that site 4 was the most impacted area. Assessment of the health status by WOE approach highlighted the importance of integrating sediment chemistry, bioaccumulation, biomarkers and bioassays and revealed that despite some disturbance in the harbor area, there was also an impact of urban effluents from upstream.

CAPSULE ABSTRACT

Environmental quality assessment in harbors.