Analía Ale

Marine systems dominate this collection, with five experimental studies spanning contrasting taxa and stressors. Liu et al. examined acute cold stress in juvenile yellowfin tuna (Thunnus albacares), uncovering divergent antioxidant, metabolic and transcriptional trajectories in red and white muscle: antioxidant activities peaked early and then declined, while red muscle sustained induction of hspa1b and acadm and white muscle responded faster but proved more vulnerable to damage. Spencer et al. contrasted 8-hour and 88-day transcriptomic responses of juvenile snow crab (Chionoecetes opilio) to ocean acidification, separating short-term tolerance from chronic stress. The early response mobilized mitochondrial repair, cuticle maintenance and immune modulation; after 88 days, however, sustained upregulation of damage-mitigation pathways under severe acidification revealed a chronic stress state that preceded any outward physiological effect and anticipated later mortality. Their identification of a putative carbonic anhydrase 7 gene as a candidate biomarker illustrates the practical payoff of such designs.Two further contributions show that climate impacts often reach organisms indirectly, and that ontogeny governs who is exposed to the greatest risk. Silva et al. mapped critical thermal maxima across the life cycle of the stenophagous nudibranch Berghia stephanieae, finding juveniles to be the least tolerant stage, thermal tolerance plasticity to be minimal, and embryos to fail under prolonged heatwave conditions. In a companion study, Silva et al. showed that a marine heatwave combined with a diet of bleached prey impaired the cellular stress response, reduced egg output and lowered survival; a performance breakdown driven as much by what the animal ate as by temperature itself. Specialized consumers, rarely included in climate vulnerability assessments, may therefore pay a disproportionate toll.Finally, Mantor et al. confront a persistent constraint: the species of greatest conservation concern are often the least tractable experimentally. Using precision-cut adipose tissue slices from humpback whale blubber, they showed that ex vivo cortisol exposure, alone or combined with epinephrine, upregulated PPARG and downregulated TNF and TLR4, indicating that stress hormones drive blubber towards an anti-inflammatory state with potential immune consequences. Beyond the finding itself, the approach offers a nonlethal, reduction-aligned platform for probing multiple stressors in free-living cetaceans.The two freshwater contributions are reviews, and both converge on the same diagnosis from different starting points: single-stressor designs no longer describe the conditions organisms actually face. Ale et al. synthesized nanoplastic ecotoxicity under pollutant coexposure and climate-derived stressors, finding synergism (frequently mediated by a Trojan horse mechanism) to be the dominant reported interaction, and rising temperature to amplify nanoplastic toxicity across taxonomic groups. The available evidence, however, rests heavily on Chlorella spp., Daphnia magna and Danio rerio, leaving molluscs and macrocrustaceans as critical blind spots under climate change scenarios. Wickramasinghe and Ruvinda reach a parallel conclusion regionally, reviewing morphological, physiological and behavioral biomarker responses in Sri Lankan lotic fishes exposed to complex pollutant mixtures, and identifying the interplay between emerging contaminants (nanoparticles, microplastics, pharmaceuticals and endocrine disruptors) and climate-related physicochemical variation as the principal gap for indigenous species. Both reviews underscore that inland waters concentrate contaminant loads while offering organisms fewer thermal refuges than open marine systems, so interactive effects are likely to be both stronger and less easily escaped.Read together, these contributions point to three priorities. First, temporal design deserves explicit justification. Tolerance measured over hours is not tolerance: both Liu et al. and Spencer et al. show that conclusions invert depending on the exposure window, and studies should state the timescales over which their inferences hold. Second, early-warning biomarkers need cross-taxon validation. Several contributions independently converge on molecular signatures that precede organismal failure; linking these to survival and reproductive endpoints would convert them from descriptive readouts into usable tools for risk assessment. Third, taxonomic and geographic representation must be widened. Model species dominate, ecologically relevant taxa remain largely untested under realistic coexposure, and tropical and Southern Hemisphere freshwater systems are conspicuously underrepresented.Meeting these challenges will require multi-stressor experimental frameworks built on environmentally realistic concentrations and climate scenarios, coupled with predictive approaches capable of anticipating interaction outcomes rather than documenting them case by case. The physiological mechanisms explored here are, ultimately, the currency in which climate change is paid. We thank all authors and reviewers whose work made this Research Topic possible.

Plastic-waste pollution has become one of the major threats to the entire environment, including the aquatic ecosystems. Vast literature is available on microplastics ecotoxicity; however, further degradation leads to nano-sized plastics, or nanoplastics (NP), which were reported to be more reactive and even more toxic for the aquatic biota despite the fact that they were studied to a lesser extent. In a context of a changing world, where freshwater systems are particularly sensitive, and the ecotoxicology of plastic as a nanopollutant has been poorly addressed in comparison with the marine environment, the objective of this study is to evaluate the physiological effects in case of NP co-exposures with other pollutants and/or stressors, and also provide further insights into in a context of climate change (CC) based on peer-reviewed literature published between 2020 and 2025. The most represented groups were freshwater algae, microinvertebrate and fish; however, they were predominantly represented by a few model species: Chlorella spp. alga, Daphnia magna microcrustacean, and Danio rerio fish, respectively. Metals and pesticides were the most frequently studied co-stressors. Synergistic interactions emerged as particularly relevant, often linked to NP acting as pollutant vectors through Trojan horse-derived mechanism. Regarding CC, rising temperature was the most assessed variable, generally enhancing NP toxicity in freshwater organisms. Our findings highlight the complexity of realistic co-exposure scenarios and emphasize the need for ecotoxicological studies that address multiple stressors in a changing world.

Silver nanoparticles (AgNPs) have been widely employed across various industrial, medical, and consumer applications due to their unique biocidal properties, raising concerns about their potential impact on biota such as planktonic microinvertebrates, which, in turn, necessitates the rapid development of in vivo nanotoxicological bioassays. Here, we combined physicochemical particle characterization with organismal responses to assess the in vivo nanotoxicity of chemically synthesized AgNPs in the marine rotifer Brachionus plicatilis (Ploimida, Brachionidae). Particles were fully characterized by dynamic light scattering (hydrodynamic diameter and polydispersity), zeta potential, transmission electron microscopy, and UV–Vis spectroscopy in both stock and exposure media. Rotifers were exposed to low AgNP concentrations: 0 (control), 2, and 20 µg/L. After a 24 h exposure, in vivo metabolic activity was quantified via resazurin reduction. Reactive oxygen species (ROS) were measured using the fluorescent probe H₂DCF-DA (excitation 485 nm, emission 530 nm), quantified by fluorimeter and fluorescence microscopy. Results showed that AgNP exposure decreased ROS levels at both tested concentrations, a finding that can be linked to reduced aerobic metabolic activity in the rotifers. These findings demonstrate that B. plicatilis provides a rapid and sensitive in vivo toxicity assessment that integrates metabolic and ROS endpoints for nano-ecotoxicity evaluations.

Zinc oxide nanoparticles (ZnONP) are among the most widely produced nanomaterials worldwide given their unique properties, despite their nanotoxicity has been poorly addressed. In parallel, environmental concern has risen because of increasing amounts of them reaching the environmental matrices, whereas the aquatic ones are one of the main final sinks. As key non-target species, we aimed to expose the invasive freshwater bivalve Limnoperna fortunei to sublethal concentrations of ZnONP (0, 0.025, 0.25, and 2.5 mg/L) to evaluate tissue damage and oxidative stress-related markers in the soft tissue. After a 96 h-exposure, the alkaline phosphatase enzyme activity increased after 0.025 mg/L, and the alanine aminotransferase activity decreased at 2.5 mg/L. Aspartate aminotransferase enzyme activity also decreased at 0.25 and 2.5 mg/L. In terms of oxidative stress, only superoxide dismutase activity increased after exposure to the lowest nanozinc concentration. We concluded that nanozinc may pose a threat to the aquatic biota in a context that lacks proper regulation and control for nanopollutants, and that the toxicity mechanisms in this species are mainly related to tissue damage, even at environmentally relevant concentrations, as the lowest one tested.

In a changing world where temperature is expected to increase, emerging nanopollutants could affect the biota in complex ways. With zinc oxide nanoparticles (ZnONP) being one of the most applied nanomaterials, we exposed the freshwater invasive bivalve Limnoperna fortunei to 0 (control), 25, and 250 µg/L of ZnONP at 27 or 31 °C for 96 h. In parallel, a 24 h bioassay was performed to calculate filtration rate. After 96 h, in soft tissue of the bivalves, tissue-damage-related enzyme activities (aspartate aminotransferase and alkaline phosphatase) were inhibited at both concentrations and temperatures. Oxidative stress was observed through increased superoxide dismutase activity after both ZnONP concentrations at 27 °C and decreased catalase activity after 250 µg/L at 31 °C, while glutathione-S-transferase activity showed opposing significant tendencies depending on temperature. After 6 h, the filtration rate differed significantly between control groups, as it was higher at 31 °C. However, in case of 31 °C, bivalves exposed to ZnONP drastically decreased their filtration rate compared to control. Our study highlights nanotoxicological implications of ZnONP; as even at environmentally relevant concentrations (such as the lowest applied in this study), they exert deleterious effects on freshwater organisms, which could be worsened in a climate-change scenario.

With the increasing use of manufactured nanomaterials in consumer products, especially silver nanoparticles (AgNPs), concerns about their environmental impact are rising. Two AgNP formulations were tested, the commercial nanosilver product nanArgen™ and a newly eco-designed bifunctionalized nanosilver (AgNPcitLcys), using marine organisms across three trophic levels, microalgae, microcrustaceans, and bivalves. Acute toxicity was assessed on the diatom Phaeodactylum tricornutum, brine shrimp larvae Artemia franciscana, and bivalve Mytilus galloprovincialis. The behavior of the formulations in marine media, including stability across a concentration range (0.001–100 mg/L), was also evaluated. Results showed that nanArgen™ was less stable compared to AgNpcitLcys, releasing more silver ions and exhibiting higher toxicity to microalgae (100% growth inhibition at 1 mg/L) and microcrustaceans (>80% mortality at 10 mg/L). Conversely, AgNPcitLcys (10 µg/L) was more toxic to bivalves, possibly due to the smaller nanoparticle size affecting lysosomal membrane stability. This study highlights how eco-design, such as surface coating, influences AgNP behavior and toxicity. These findings emphasize the importance of eco-design in minimizing environmental impacts and guiding the development of safer, more sustainable nanomaterials.

This review summarizes how salinity and temperature, two key global factors driven by climate change in freshwater systems, interact with other stressors on organisms in controlled small-scale factorial experiments at the population, individual, or subindividual level (excluding mesocosm and field studies). Despite the growing interest, research following all these criteria remains limited with 156 publications of which 50% analyzed stressors + salinity, 46% stressors + temperature, and only 4% involved the triple combination. Research on the combined effect of temperature and salinity predominantly focused on metals, pesticides, and, to a lesser extent, emergent contaminants, such as microplastics and nanomaterials, encompassing various biological models and responses. In general, increased temperature amplifies the single effect of stressors, whereas salinity leads to a higher diversity of responses, with similar proportions of synergisms and antagonisms. Fish (Salmoniformes, Perciformes, and Cypriniformes) were the most studied organisms. Among Crustacea, only cladocerans of the genera Daphnia and Ceriodpahnia were considered. The present review highlights the need to include other species that play key roles in freshwater food webs and to increase triple combination studies to understand complex interactions and develop adaptation and mitigation strategies to preserve the environment and its services in this changing world. Graphical Abstract