Bioenergetic responses mediate interactive effects of pharmaceuticals and warming on freshwater arthropod populations and ecosystem functioning

Freshwater ecosystems are increasingly impacted by pharmaceutical contaminants (PhACs) and climate change-induced warming. Yet, their joint effects on freshwater taxa remain unclear. This is partly due to poorly understood mechanisms linking the effects on (sub)individual scales to higher levels of ecological organisation. We investigated the responses of two aquatic arthropods, Asellus aquaticus and Cloeon dipterum, to environmentally realistic levels of a 15-PhAC mixture (total concentration: 2.9 µg/L) and warming (+4 °C above ambient) in outdoor pond mesocosms (1000 L) across winter and summer. We measured physiological traits (bioenergetic responses based on quantification of energy consumption and energy stored in proteins, sugars and lipids, and oxidative damage based on malondialdehyde [MDA] levels), population density and ecosystem functions (leaf litter decomposition and insect emergence). In winter, PhACs reduced energy availability and increased MDA levels. In contrast, PhACs increased energy availability and decreased MDA levels in summer. The stressors reduced Asellus abundance, leading to reduced leaf litter decomposition, while Cloeon emergence in summer declined due to a PhAC-induced decline in larval abundance. Warming alone consistently decreased arthropod abundances and emergence, except for Asellus abundance in winter. The stressor effects through changes in bioenergetics were stronger than their direct effects on population abundances and ecosystem functions. Our findings highlight the vulnerability of aquatic arthropods to PhAC pollution and warming, emphasising the need for effective management strategies to mitigate the effects of emerging contaminants and climate change on freshwater biota.

Molecular responses of paddy field carp (Cyprinus carpio) in the agricultural heritage to major environmental factors in paddy fields

As a core element of the Globally Important Agricultural Heritage System (GIAHS), the Qingtian paddy field carp (Cyprinus carpio, PF-carp) has been domesticated for over 1200 years in paddy field environments. This species has successfully adapted to shallow-water conditions in paddy fields. To reveal the adaptation mechanism, we conducted transcriptome sequencing on the hepatopancreas of PF-carp under two temperature conditions (28 °C and 38 °C) and concurrently analysed RNA-seq data from hypoxic conditions in the same tissue. By analysing high-temperature transcriptome data, 3154 differentially expressed genes (DEGs) were identified. KEGG analysis indicated that DEGs involved various pathways, including protein processing in endoplasmic reticulum, circadian rhythm, and HIF-1 signaling pathway. Notably, protein processing in endoplasmic reticulum was significantly enriched with key genes such as HSP70, HSP90, HSP40, CNX, CRT, and Bip. Through concurrent analysis of RNA-seq data from hypoxic conditions, we found that PF-carp regulate their metabolism through multiple pathways and produce almost opposite metabolic regulation to adapt to high temperature and hypoxic environments. The opposite activation state observed in the HIF-1 signaling pathway is particularly intriguing. In conclusion, PF-carp appear to rely on protein processing in endoplasmic reticulum to maintain cell homeostasis at high temperatures. The HIF-1 signaling pathway may emerged as a key player in adapting PF-carps to paddy fields. This study provides valuable insights into the adaptive mechanisms of domesticated fish in paddy fields.

Unraveling the metabolic gene expression and energetic patterns of the seasonally acclimatized gilthead seabream

The aim of the present study was to investigate how seasonal changes in the oxidation of biological energy substrates contribute to the thermal tolerance of farmed fish, as well as to explore the potential relationship between seasonality, metabolic pathways, and the energy reserves of a highly important aquaculture species, i.e., the gilthead sea bream Sparus aurata. In a monthly basis collected tissue samples from a fish farm in Evoikos Gulf in Greece, RNA/DNA ratio was measured, representing a highly informative index of the nutritional condition and growth of fish. Additionally, seasonal variations in glucose and lipid metabolism were assessed through relative gene expressions of key metabolic enzymes and proteins such as glucose transporter (Glu), lactate dehydrogenase (L-LDH), citrate synthase (CS), 3-hydroxyacyl-CoA dehydrogenase (HOAD), pyruvate kinase (PK), AMP-activated protein kinase (AMPK), and peroxisome proliferator-activated receptors (PPARα/γ). Furthermore, the expression of uncoupling proteins, NADH dehydrogenase (NDH-2), hypoxia-inducible factor-1 alpha (Hif-1a), electron transport system activity (ETS), and its components (complex I + III) was also employed as indicators of the respiratory chain activity. The findings reveal two distinct metabolic periods affecting productivity: a cold acclimatization phase marked by significant lipid accumulation and a warm acclimatization phase characterized by elevated carbohydrate metabolic pathways and enhanced corresponding enzymatic activities. However, the decreasing CS enzymatic activity during warm acclimatization may reflect the initiation of mitochondrial dysfunction. These metabolic adjustments underscore the fish adaptive responses to seasonal temperature fluctuations, highlighting their mechanisms of thermal tolerance and energy utilization. This understanding is particularly relevant for sustainability practices under varying thermal conditions.

Impact of hyposalinity on the barrens-forming sea urchin Centrostephanus rodgersii in context with flooding events

The sea urchin Centrostephanus rodgersii is an ecologically important species in southeastern Australia, where its grazing contributes to the formation of macroalgal-free barrens habitat. While climate warming has facilitated this species southward range extension, climate change is also causing an increase in the frequency of storm-driven hyposalinity events. These events can expose marine organisms to acute or gradual decrease salinity stress, depending on the rate and duration of freshwater influx. The tolerance of C. rodgersii to below ambient salinity was investigated using a range of treatments emulating coastal salinity conditions (22-34‰). The response to decreased salinity was quantified in weight change, mortality, and righting time (a measure of muscular coordination) under abrupt salinity decrease and gradual salinity reduction conditions to reflect flash floods and less intense rain events, respectively. Muscular coordination began to decline at 28‰, with prolonged righting times. Acute exposure to 22‰ salinity caused 100% mortality within 72 h. Urchins in the gradual salinity reduction to 22‰ died following a gradual return to ambient conditions. These findings show that C. rodgersii is highly susceptible to climate-driven hyposaline events, which challenge its survival and thereby disrupt local marine community dynamics.

Effects of water-accommodated fractions of crude oil on detoxification and antioxidant mechanisms in Ruditapes philippinarum

To assess the impact of crude oil pollution on Manila clams (Ruditapes philippinarum), we analyzed the effects of exposure to water-accommodated fraction (WAF) at different concentrations (nominal TPH concentrations of 0.5, 1.0 and 3.0 mg/L), including survival rate, histopathology observation and antioxidant enzyme detection. Results demonstrated that the activities of antioxidant enzymes-Catalase (CAT), Superoxide dismutase (SOD), Glutathione peroxidase (GSH-PX) and Malondialdehyde (MDA) in Manila clams was significantly elevated in 3.0 mg/L WAF group compared with the control group (P < 0.05). In addition, RNA-seq was performed to analyze clam hepatopancreas tissue in 0 d (control group, CG), 7 d (exposure group, O7d), 15 d (exposure group, O15d) after the exposure to WAF (3 mg/L) and recovery in clean water for 7 d after 15 d WAF exposure (recovery group, R7d). The results showed that a total of 129 differentially expressed genes (DEGs) were detected in the O7d vs CG group, 123 DEGs were detected in the O15d vs CG group, and 2113 DEGs were detected in the R7d vs CG group. Of these genes, the expression of cytochrome P450 2J2 (6.30-fold), bile salt sulfotransferase (8.06-fold), multidrug resistance-associated protein 1 (8.17-fold) was significantly induced at 15 d under the WAF exposure. DEGs were significantly enriched in pathways such as cysteine and methionine metabolism, as well as glycine, serine and threonine metabolism. Furthermore, eight DEGs, including metabolism-related genes (ABCC1, ABCG2, SULT2A1, CYP2J2), ion transport genes (SLC39a14, RFT2), an immune-related gene (Gvin1), and a cellular structure and signal regulatory gene (Ank3) were selected for qRT-PCR analysis. The results confirmed that DEG expression levels were consistent with RNA-seq findings. This study provides crucial molecular insights into the adaptive responses and recovery processes of marine bivalves in response to oil pollution, thereby contributing a scientific foundation for evaluating and monitoring marine environmental pollution.

Hot and toxic: Accumulation dynamics and ecotoxicological responses of mussel Mytilus galloprovincialis exposed to marine biotoxins during a marine heatwave

Climate change is increasing marine heatwaves (MHWs) frequency and severity worldwide. These extreme events often cause bivalves' mass mortality and facilitate the growth, proliferation and dispersion of toxin-producing microalgae blooms associated with threats to seafood safety. Yet, the interactive effects between MHW and uptake of marine biotoxins by biota are a novel topic still lacking thorough research, from both the ecotoxicological and seafood safety standpoints. This study assessed the effects of a MHW event on the accumulation/elimination dynamics of diarrhetic shellfish toxins in Mytilus galloprovincialis exposed to Prorocentrum lima and the ecotoxicological responses of mussels co-exposed to these two stressors. Results showed that acute exposure to +4 °C reduced toxins accumulation (-49 %) and elimination (-77 %) compared to control temperature. Moreover, exposure to MHW and toxins affected mussels' antioxidant activity, lipid and protein damage, and metabolism in a tissue-specific manner. These findings highlight that M. galloprovincialis can face higher vulnerability to toxins when MHW events strike.

Location-dependent effect of microplastic leachates on the respiration rate of two engineering mussel species

Microplastics are ubiquitous in the world's oceans and pose serious environmental concerns, including their ingestion and the release of potentially toxic mixtures of intrinsic and extrinsic chemical compounds (i.e. leachates; MPLs). Mussels, as key intertidal bioengineers and filter-feeders are particularly susceptible to both exposure pathways. While the effects of microplastic ingestion have been widely investigated, research on the impacts of MPLs has only recently begun. This study examined the influence of MPLs derived from beached pellets collected in two separate regions, namely France and Portugal, on the respiration rates of two key ecosystem engineers, Mytilus edulis and Mytilus galloprovincialis. Possibly due to distinct mixtures of leached chemicals, unlike Portuguese-MPLs, exposure to French-MPLs significantly decreased the respiration rate of both mussel species. This research provides new insights into the physiological impacts of MPLs on bioengineer species, highlighting the importance of MP source and potential cascading effects at the ecosystem level. While we reported significant effects on mussel respiration after acute MPL exposure, future research should investigate long-term impacts and potential detoxification mechanisms to clarify the effects of MPs on mussel physiological performance and their potential consequences on specie fitness.

Berberis vulgaris fruit extract mitigated apoptosis in experimentally induced testicular ischemia and reperfusion injury in rats

Aim

The aim was to investigate the possible protective effect of Berberis vulgaris extract, which has anti-inflammatory and antioxidant properties, in the testes in an ischemia-reperfusion (IR) injury model by utilizing molecular, biochemical, histopathological, and immunohistochemical methods.

Methods

A total of 56 male rats were divided in to 7 equal groups. Ischemia was induced by taking the testicles out of the scrotum and rotating them 720° and after 3 h reperfusion was induced. Berberis vulgaris extract was administered 3 h before ischemia. The reperfusion groups were treated by oral gavage 1 h before reperfusion. Following the 3-h reperfusion period, tissue and blood samples were collected.

Results

Histopathologically, H&E staining showed disruption in the seminiferous tubule structure in the ischemia and IR groups SOD levels decreased significantly in the IR group compared to the control group, whereas Berberis vulgaris did not change SOD levels following IR at 300 and 600 mg/kg doses. At the dose of 600 mg/kg, Berberis vulgaris significantly increased SOD levels compared to the ischemia group CAT activity was significantly higher in the BV300 and BV600 groups compared to the ischemia group. CAT activity was significantly lower in the IR group compared to the ischemia group (p < 0.001). When compared to the control group, the ischemia group had a roughly 3-fold increase in caspase-3 expression. In the IR group, this ratio was dramatically increased-roughly 5-fold. However, the antiapoptotic gene Bcl-2 expression was significantly decreased in both the ischemia and IR groups compared to the control group.

Conclusion

B. vulgaris plant extract may have a protective effect against testes IR injury. Further molecular studies are needed to clarify this protective effect.

Diurnal temperature variation exacerbates the effects of phenanthrene on Trochus pyramis Born in a warmer ocean

Under global change scenarios, rising seawater temperature could affect the toxicity of chemical pollutants on marine organisms. Tropical species inhabiting coastal areas are especially vulnerable to diurnal temperature variation (DTV), yet the impacts of DTV on pollutant toxicity remains obscured. This study evaluated how a 4℃ DTV affects the toxicity of phenanthrene (PHE) on the physiological traits of Trochus pyramis, a key herbivorous gastropod in coral reef ecosystems, under both control (28°C) and elevated temperature (31°C) conditions. T. pyramis were exposed to PHE (1 and 10 μg/L) across different temperature scenarios for 14 days. Subsequently, PHE bioaccumulation, heat tolerance, antioxidant responses, and energy budgets of T. pyramis were assessed. The results showed that PHE had minimal effect on T. pyramis under DTV at 28°C, likely due to enhanced antioxidant responses and adaptive energy supply strategies induced by DTV. Conversely, DTV exacerbated the deleterious effect of PHE at 31°C, particularly under exposure to high-concentration PHE (10 μg/L), leading to reduced heat tolerance, suppressed antioxidant responses, and disturbed energy metabolism. These results underscore the necessity of incorporating DTV into PHE risk assessments for coral reef ecosystems in the context of global warming.

Asymmetrical evolution of cross inhibition in zooplankton: insights from contrasting phosphorus limitation and salinization exposure sequences

Understanding the evolutionary responses of organisms to multiple stressors is crucial for predicting the ecological consequences of intensified anthropogenic activities. While previous studies have documented the effects of selection history on organisms' abilities to cope with new stressors, the impact of the sequence in which stressors occur on evolutionary outcomes remains less understood. In this study, we examined the evolutionary responses of a metazoan rotifer species to two prevalent freshwater stressors: nutrient limitation and increased salinization. We subjected rotifer populations with distinct selection histories (salt-adapted, low phosphorus-adapted and ancestral clones) to a reciprocal common garden experiment and monitored their population growth rates. Our results revealed an asymmetric evolutionary response to phosphorus (P) limitation and increased salinity. Specifically, adaptation to low P conditions reduced rotifer tolerance to increased salinity, whereas adaptation to saline conditions did not show such cross-inhibitory effects. Instead, the addition of moderate concentrations of salt enhanced the growth of the salt-adapted population in low P conditions, potentially as a consequence of evolved cross-tolerance. Our findings, therefore, underscore the importance of considering historical stressor regimes to improve our understanding and predictions of organismal responses to multiple stressors and also have significant implications for ecosystem management.

Synergistic effects of elevated temperature with pesticides on reproduction, development and survival of dung beetles

In times of global change, high temperatures can increase the negative effects of pesticides and other stressors. The goal of this study was to evaluate, under controlled laboratory conditions, the effect of a moderate increase in temperature in combination with ivermectin (an antiparasitic medication used in cattle that is excreted in dung), an herbicide, and parasitic pressure, on the reproductive success, development time and adult survival of dung beetles Euoniticellus intermedius. Whereas high temperature increased the number and proportion of emerged offspring, it had synergistic negative effects in combination with the ivermectin, herbicide and parasite treatments. Moreover, high temperature in combination with ivermectin and with parasitism caused a synergistic increase of adult offspring mortality and, in combination with the herbicide, it synergistically accelerated development. These results indicate that high temperatures can enhance the negative effects of other stressors and act synergistically with them, harming dung beetles, a group with high ecological and economic value in natural and productive ecosystems. Although adult sex ratio was not affected by experimental treatments, contrasting responses were found between males and females, supporting the idea that both sexes use different physiological mechanisms to cope with the same environmental challenges. The effects that combined stressors have on insects deepen our understanding of why we are losing beneficial species and their functions in times of drastic environmental changes.

Sex-specific reproductive impairment in Pacific oysters (Magallana gigas) exposed to TiO2 NPs: A focus on gonadal status

Environmentally realistic concentrations of titanium dioxide nanoparticles (TiO2 NPs) are considered reprotoxic for marine bivalves. However, further investigation is needed to understand their impact on gonadal health, particularly concerning sex-specific responses. Thus, this study aimed to understand sex-based effects of TiO2 NPs environmentally realistic concentrations in the gonad of Pacific oysters (Magallana gigas). Oysters were exposed to 10 and 100 μg·L-1 of TiO2 NPs for 3 and 7 days. Morphological parameters (condition index, sex and gametogenic stage), energy-related responses (carbohydrates, lipids, proteins, and electron transport system (ETS) activity), digestive function (alpha-amylase activity), and oxidative stress profile (antioxidants and damage) were assessed to address gonadal status. The results revealed sex-specific responses based on duration and concentration. Females reflected a drop in carbohydrate levels after 3 days at 100 μg·L-1, suggesting mobilization of this energy reserve to counteract TiO2 NP effects, followed by recovery after 7 days. Males showed reduced metabolic activity after 3 days at 10 μg·L-1, marked by ETS depletion, independently of oxidative stress demonstrating a compensatory response to TiO2 NP exposure. After 7 days, both concentrations triggered male lipid peroxidation despite carbohydrate mobilization at 10 μg·L-1, indicating oxidative damage in testes. These findings revealed that TiO2 NPs are reprotoxic for male oysters at 10 μg·L-1, through oxidative stress pathways, while females reflected vulnerability to 100 μg·L-1. This study provides valuable insights into understanding TiO2 NP's reprotoxicity at environmental concentrations, highlighting gonads as a target for these NPs, and their potential risks to marine bivalves.

Physiological energetics of selectively bred oysters (Crassostrea hongkongensis) under marine heatwaves

Marine heatwaves (MHWs) have become more frequent and intense in the context of rapid climate change, causing detrimental effects on marine bivalves and ecosystems they sustain. While selective breeding programs for bivalves can substantially enhance growth performance, their ability to improve thermal stress tolerance remains largely unexplored. Here, we compared physiological energetics of wild and selectively bred Hongkong oysters (Guihao No. 1) under intensifying MHWs conditions. Following two consecutive events of MHWs, selectively bred oysters exhibited around 10% higher survival rate than that of wild oysters. Throughout the course of the experiment, the clearance rate of selectively bred oysters was significantly increased in comparison to wild oysters showing significantly depressed ability to feed. Nevertheless, exposure of selectively bred oysters to MHWs elicited significantly increased oxygen assumption and ammonia excretion rates, which in turn enhanced their O:N ratio. When couched into energetic terms, while MHWs inhibited the individual scope for growth, selectively bred oysters displayed better thermal tolerance than wild oysters. Taken together, our findings highlight the potential of new varieties of selectively bred oysters (such as Guihao No. 2) in coping with intensifying MHWs and guide the future development of selective breeding strategies to enhance the oyster thermal resilience in this era of unprecedented climate change.

Thermal modulation of insecticide-induced hormetic and oxidative responses in insect pests

Environmental global changes are dramatically affecting agroecosystems. Insects have been shown to present various responses to multi-stress conditions (i.e., increase in temperature and exposure to contaminants). However, there is a knowledge gap on how temperature can modulate the hormetic effects in individuals sublethally exposed to chemical stressors. Here, we investigated how temperature (15, 20, 25, and 28 °C) modulates the effects of lethal and sublethal exposure to insecticides (imidacloprid) on the longevity, fecundity, and oxidative stress of a pest insect, the aphid Mysus persicae. Our results showed additive and interactive effects of temperature and insecticide on the stimulatory and oxidative responses of the insect pest. Overall, imidacloprid was 2.4-fold less toxic at 15 °C (3.547 μg/ml) than at 20 °C (1.482 μg/ml) and 24.6 to 19.8-fold less toxic than at 25 °C (0.144 μg/ml) and 28 °C (0.179 μg/ml) respectively. Furthermore, although the exposure of female aphids to most sublethal concentrations resulted in a decrease in their longevity and fecundity compared to the control, some of the sublethal concentrations produced positive effects in these parameters for the exposed individuals. The magnitude of induced sublethal effects varied between temperatures and occurred in similar ranges of low concentrations at temperatures 15 °C and 20 °C, and at temperatures 25 °C and 28 °C. Additionally, imidacloprid low concentrations induced a temperature-dependent production of reactive oxygen species in exposed insects at 12 and 24 h after exposure indicating oxidative stress. Our study supplies valuable data on how temperature modulates pesticide-mediated hormesis that can alter ecological interactions and functions within agroecosystems with potential implications in pest management.

Extremely low repeated pyrethroid pulses increase harmful effects on caddisfly larvae (Chaetopteryx villosa) and influence species interactions

Based on effect data, regulatory acceptable concentrations (RACs) are derived for surface waters to avoid unacceptable effects on the environment. RACs often relay on acute tests with single species, which may underestimate the effects under field conditions. Therefore, we applied a higher tier approach with artificial indoor streams (AIS). We exposed representatives of the benthic community in lotic surface waters to varying numbers (one to four times) of 12-hour deltamethrin pulses over a 35-day period with intervening recovery phases, to simulate multiple pesticide peak exposures caused by rain events or spray drift. The deltamethrin concentration of each pulse was equivalent to its RAC value of 0.64 ng/L and consequently should have no unacceptable effects on the tested species. In contrast, we observed that the mortality of caddisfly larvae increased significantly with the number of pulses at the RAC. In addition, larval development was significantly delayed after four deltamethrin pulses, while the gammarids apparently benefited from the toxicity-induced mortality of the larvae. This study underlines the importance of considering higher tier approaches that include species interactions and additional stressors in order to obtain more realistic effect data and optimise regulatory risk assessment. These are not considered in acute tests with single species, which usually leads to an underestimation of the effects. Based on the results of this study, we propose to lower the RAC value for aquatic environments due to the uncertainties mentioned above.

The Benefit of Evolution of Pesticide Tolerance Is Overruled under Combined Stressor Exposure due to Synergistic Stressor Interactions

Despite pleas to consider both evolutionary and multistressor climate change perspectives to improve ecological risk assessment, the much needed combination of both perspectives is largely missing. This is especially important when evaluating the costs of the evolution of genetic tolerance to pollutants as these costs may become visible only under combined exposure to the pollutant and warming due to energetic constraints. We investigated the costs of chlorpyrifos tolerance in Daphnia magna when sequentially exposed to 4-day pesticide treatments and 4-day heat spike treatments. Exposure to chlorpyrifos reduced the fitness of chlorpyrifos-sensitive clones (reduced survival, mass, and reproductive performance), while it had positive (hormetic) effects on clones selected for chlorpyrifos tolerance. We did not find any costs of chlorpyrifos tolerance in the absence of the stressors and only a weak sublethal cost when only exposed to the heat spike. Notably, when sequentially exposed to the pesticide and the heat spike, the benefit of the evolution of chlorpyrifos tolerance was nullified as the chlorpyrifos-tolerant clones experienced (stronger) synergistic interactions between both stressors and stronger thermal costs when preceded by exposure to the pesticide. This highlights the importance of multistressor studies to correctly assess the costs of genetic pesticide tolerance and the potential of evolution of pesticide tolerance to rescue nontarget populations.

Heat Stress, Starvation, and Heat Stress Plus Starvation Cause Unique Transcriptomic Responses in the Economically Important Red Abalone Haliotis rufescens

Although most marine invertebrates are experiencing multiple environmental stressors simultaneously, the transcriptome-wide gene expression responses to multiple stressors remain understudied. We used RNA-sequencing to assess the transcriptomic responses to heat stress, starvation, and heat stress plus starvation in the red abalone Haliotis rufescens. Results indicate that the response to each stressor is distinct and is characterized by unique gene functions. The heat stress plus starvation treatment produced the largest transcriptomic response, including a significant upregulation of genes involved in translation. Overall, this study highlights the importance of multi-stressor experiments that reflect the complex modalities of climate change.

Sediment contamination in two German estuaries: A biomarker-based toxicity test with the ragworm Hediste diversicolor under intermittent oxygenation

Toxicity testing is an important tool for risk assessment of sediment contamination in estuaries. However, there has been a predominant focus on fitness parameters as toxic endpoints and on crustaceans as test organisms, while effects at the sub-organismal level and on other benthic taxa have received less attention. Also, interactions between sediment contamination and natural stressors such as oxygen are often neglected in traditional toxicity tests. Here we conducted a toxicity test of sediments from the Elbe and Oder (Odra) estuaries under three weeks of continuous and intermittent oxygenation, using biomarkers in an annelid, the ragworm Hediste diversicolor. Contaminated sediments affected worm survival and some biomarkers of antioxidant defense, electrophilic stress, and energy status with response ratios of above 20%. Toxic effects were most pronounced in sediments from the upper Elbe estuary, which contained high levels of heavy metals and organic chemicals. Oxygen regimes hardly changed the sediment effects, suggesting the robustness of the biomarker-based toxicity test with ragworms.

Ecophysiological responses to heat waves in the marine intertidal zone

One notable consequence of climate change is an increase in the frequency, scale and severity of heat waves. Heat waves in terrestrial habitats (atmospheric heat waves, AHW) and marine habitats (marine heat waves, MHW) have received considerable attention as environmental forces that impact organisms, populations and whole ecosystems. Only one ecosystem, the intertidal zone, experiences both MHWs and AHWs. In this Review, we outline the range of responses that intertidal zone organisms exhibit in response to heat waves. We begin by examining the drivers of thermal maxima in intertidal zone ecosystems. We develop a simple model of intertidal zone daily maximum temperatures based on publicly available tide and solar radiation models, and compare it with logged, under-rock temperature data at an intertidal site. We then summarize experimental and ecological studies of how intertidal zone ecosystems and organisms respond to heat waves across dimensions of biotic response. Additional attention is paid to the impacts of extreme heat on cellular physiology, including oxidative stress responses to thermally induced mitochondrial overdrive and dysfunction. We examine the energetic consequences of these mechanisms and how they shift organismal traits, including growth, reproduction and immune function. We conclude by considering important future directions for improving studies of the impacts of heat waves on intertidal zone organisms.

Active biomonitoring of river pollution using an ex-situ exposure system with two model species

In the context of increasing pollution pressure on aquatic ecosystems, it is essential to improve our knowledge of habitat quality and its suitability for organisms. It is particularly relevant to better integrate early life stages of fish into pollution biomonitoring programs, as they are reliable indicators of ecosystem integrity and because of their high sensitivity to pollutants. To avoid the influence of environmental parameters on their development, a lab-on-field approach, called the ex-situ exposure method, was developed. Aquatic organisms were exposed to a continuous flux of water under semi-controlled temperature, oxygen, and photoperiod conditions to avoid the influence of these confounding factors when interpreting the results. To investigate the potential role of water contamination, this active biomonitoring method was applied to the Garonne River (Southwest France), where migratory fish populations have declined. Two model species from different taxa were used: embryos of the Japanese medaka (Oryzias latipes) and adults of the crustacean Gammarus fossarum. The results showed a significant impact of water quality on embryo mortality and early hatching in two separate experiments on Japanese medaka. In addition, an induction of feeding rate was observed in exposed gammarids, but no impact on their embryo survival, suggesting differences in sensitivity between the two species selected. Chemical and biological analyses did not identify trace metals, pesticides, or microorganisms as potential sources of toxicity in medaka embryos or G. fossarum. These results raise concerns about the quality of the water in the Garonne River and its toxicity to aquatic organisms.

Developmental plasticity does not improve performance during a species interaction: Implications for species turnover

Species interactions can contribute to species turnover when the outcomes of the interactions are context dependent (e.g., change along environmental gradients). Plasticity may change this dynamic by altering the environmental tolerances of the species interacting. Here, we explored how the competitive interaction between two euryhaline fish, Poecilia reticulata and Poecilia picta, is influenced by acute and developmental responses to salinity. In Trinidad, P. reticulata is confined to freshwater despite being tolerant of brackish water. P. reticulata may fail to occupy brackish water because of reduced tolerance to salinity or because P. picta competitively excludes them, and developing in brackish water could alter the dynamics of either scenario. To test this, we compared the salinity tolerances of both species in the absence of competition, reared P. reticulata individuals in freshwater or brackish water, and tested the consequences of developmental plasticity in experiments in which P. reticulata competed against conspecifics or P. picta during acute exposure to freshwater or brackish water. We found that (1) P. reticulata has a weaker salinity tolerance than P. picta; (2) P. reticulata that developed in freshwater perform best when competing against P. picta in freshwater but perform poorly when competing against P. picta in brackish water, suggesting the species interaction is context dependent; and (3) developing in brackish water did not benefit P. reticulata in brackish water. Our results suggest that P. reticulata's freshwater range limit is in part a product of a lower salinity tolerance leading to a decrease in competitive performance in brackish water. Adaptive plasticity has been suggested to be a crucial part of the colonization process, yet nonadaptive plastic responses as found here can limit range expansion and reinforce range limits.

Environmental signatures and fish proteomics: A multidisciplinary study to identify the major stressors in estuaries located in French agricultural watersheds

Watersheds and estuaries are impacted by multiple anthropogenic stressors that affect their biodiversity and functioning. Assessing their ecological quality has consequently remained challenging for scientists and stakeholders. In this paper, we propose a multidisciplinary approach to identify the stressors in seven small French estuaries located in agricultural watersheds. We collected data from landscape (geography, hydrobiology) to estuary (pollutant chemistry) and fish individual scales (environmental signatures, proteomics). This integrative approach focused on the whole hydrosystems, from river basins to estuaries. To characterize each watershed, we attempted to determine the land use considering geographic indicators (agricultural and urbanised surfaces) and landscape patterns (hedges density and riparian vegetation). Juveniles of European flounder (Platichthys flesus) were captured in September, after an average residence of five summer months in the estuary. Analyses of water, sediments and biota allowed to determine the concentrations of dissolved inorganic nitrogen species, pesticides and trace elements in the systems. Environmental signatures were also measured in flounder tissues. These environmental parameters were used to establish a typology of the watersheds. Furthermore, data from proteomics on fish liver were combined with environmental signatures to determine the responses of fish to stressors in their environments. Differential protein abundances highlighted a dysregulation related to the detoxification of xenobiotics (mainly pesticides) in agricultural watersheds, characterized by intensive cereal and vegetable crops and high livestock. Omics also revealed a dysregulation of proteins associated with the response to hypoxia and heat stress in some estuaries. Furthermore, we highlighted a dysregulation of proteins involved in urea cycle, immunity and metabolism of fatty acids in several systems. Finally, the combination of environmental and molecular signatures appears to be a relevant method to identify the major stressors operating within hydrosystems.

Environmental acidification drives inter-organ energy mobilization to enhance reproductive performance in medaka (Oryzias latipes)

Anthropogenically environmental acidification impacts aquatic organisms, including teleosts, the largest group of vertebrates. Despite its significance, how teleosts allocate nutrient and energy among their organs to cope with acidic stress remains unclear. Our integrated analysis of physiological, metabolic, and gene expression data reveals that Japanese medaka (Oryzias latipes) mobilize energy resources among organs in response to acidic conditions. We found that the muscles lost carbohydrates and proteins and the liver accumulates all macronutrients in both sexes. Notably, female-specific energy mobilization between the liver and ovary were triggered by estrogen signaling, resulting in improved oocyte maturation and ovulation. Female produced more offspring under acidic stress. Furthermore, the offspring embryos exhibited smaller diameters and earlier hatching but demonstrated growth rates and acid tolerance. These metabolic changes suggest a trade-off in energy allocation by suppressing basal maintenance (33 % decrease in oxygen consumption) and growth (25 % decrease in muscle mass) but enhancing energy storage (159 % increase in liver mass in males and 127 % in females) and reproduction (165 % increase in ovary mass). This reallocation may improve medaka fitness and population sustainability in acidic environments. Further investigation into more species is needed to project the survival of aquatic animals in an acidified future.

Effects of metals in sediment under acidification and temperature rise scenarios on reproduction of the copepod Nitokra sp

The potential effects of trace metal pollution in sediment under scenarios of warming and CO2-driven acidification on the fecundity of the copepod Nitokra sp. were assessed. Ovigerous females were exposed to laboratory-spiked sediments at two different concentrations of a mixture of metals (Cu, Pb, Zn, and Hg) and to the control (non-spiked sediments), in combinations of two pH (7.7 and 7.1) and two temperatures (25 °C and 27 °C). The results revealed that CO2-driven acidification affected the fecundity of Nitokra sp. by interacting with temperature rise and metal contamination. While rising temperatures generally increased Nitokra sp. fecundity, when combined with metal addition and a CO2 acidified environment, warming led to a decline in offspring production. This is the first study with copepods to demonstrate the interactive effects of sediment contamination by metals, CO2-driven acidification, and temperature increase. Preliminary experiments are required to understand the complex interactive effects of multiple drivers.

Evaluating the impact of gadolinium contamination on the marine bivalve Donax trunculus: Implications for environmental health

Gadolinium (Gd), commonly used in contrast agents for medical imaging, has been detected in hospital wastewater and aquatic environments, raising environmental concerns. This study examined the accumulation and cellular impacts of Gd in the clam species Donax trunculus, commonly used as bioindicator of contamination. Gadolinium accumulation in clams increased with exposure and over time. Biological responses varied with Gd levels: low concentrations (10 and 50 µg/L) led to low metabolic activity and glycogen content, but high antioxidant activities and lipid peroxidation levels (LPO); high concentrations (250 and 500 µg/L) resulted in increased metabolic activity, while antioxidant enzyme activity was inhibited and LPO levels were the lowest. Metabolic activity decreased after two weeks, suggesting limited long-term metabolic resilience. The study underscores D. trunculus as an effective early warning species for Gd pollution and highlights the ecological risks of rising Gd levels, emphasizing the need for environmental monitoring and regulation.

Heat Hardening Ameliorates Apoptotic and Inflammatory Effects Through Increased Autophagy in Mussels

The severity, frequency, and duration of extreme events, in the context of global warming, have placed many marine ecosystems at high risk. Therefore, the application of methods that can mediate the impacts of global warming on marine organisms seems to be an emerging necessity in the near term. In this context, enhancing the thermal resilience of marine organisms may be crucial for their sustainability. It has been shown that the repeated time-limited exposure of an organism to an environmental stimulus modifies its response mode, thus enhancing resilience and allowing adaptation of the physiological and developmental phenotype to environmental stress. In the present study, we investigated the "stress memory" effect caused by heat hardening on Mytilus galloprovincialis cellular pathways to identify the underlying biochemical mechanisms that enhance mussel thermal tolerance. Heat hardening resulted in increased ETS activity and ATP production and increased autophagic performance at all elevated temperatures (24 °C, 26 °C, and 28 °C). Furthermore, at these increased temperatures, apoptosis and inflammation remain at significantly lower levels in pregnant individuals than in nonhardened individuals. Autophagy, as a negative regulator of apoptosis, may lead to decreased damage to surrounding cells, which in turn alleviates inflammatory effects. In conclusion, the exposure of mussels to heat hardening seems to provide a physiological response that enhances heat tolerance and increases cell survival through increased energy production and reduced cell death and inflammatory responses. The latter can be utilized for the management and conservation of aquatic species of economic value or endangered status.

Temperature-dependent dynamics of energy stores in Drosophila

BACKGROUND

Understanding how ectotherms manage energy in response to temperature is crucial for predicting their responses to climate change. However, the complex interplay between developmental and adult thermal conditions on total energy stores remains poorly understood. Here, we present the first comprehensive quantification of this relationship in Drosophila melanogaster, a model ectotherm, across its entire thermal tolerance range. To account for potential intraspecific variation, we used flies from two distinct populations originating from different climate zones. Utilizing a full factorial design, we assessed the effects of both developmental and adult temperatures on the amount of key energy macromolecules (fat, glycogen, trehalose, and glucose). Importantly, by quantifying these macromolecules, we were able to calculate the total available energy.

RESULTS

Our findings reveal that the dynamic interplay between developmental and adult temperatures profoundly influences the energy balance in Drosophila. The total energy reserves exhibited a quadratic response to adult temperature, with an optimal range of 18-21 °C for maximizing energy levels. Additionally, the temperature during development considerably affected maximum energy stores, with the highest reserves observed at a developmental temperature of approximately 20-21 °C. Deviations from this relatively narrow optimal thermal range markedly reduced energy stores, with each 1 °C increase above 25 °C diminishing energy reserves by approximately 15%.

CONCLUSIONS

This study highlights the critical and interacting roles of both developmental and adult thermal conditions in shaping Drosophila energy reserves, with potentially profound implications for fitness, survival, and ecological interactions under future climate scenarios.

Assessment of extracellular polymeric substances production and antioxidant defences in periphytic communities exposed to effluent contaminants

Periphyton is frequently used in the evaluation of the ecological status of aquatic ecosystems using diatoms as a proxy. However, periphyton has a particularity, the production of extracellular polymeric substances (EPS), which might play a protective role against exposure to harmful environmental contaminants. Effluents originating in wastewater treatment plants (WWTPs) constitute some of the most complex mixtures of contaminants, to which aquatic ecosystems are frequently exposed, often containing tens to hundreds of different chemicals. In such challenging scenarios, a putative protective role of EPS may obscure the bioindicator value of diatoms. To address this problem, we sampled periphyton upstream and downstream of the effluent outfall from three different WWTPs, quantifying EPS production and simultaneously evaluating general stress responses in the community (protein and sugar content, photosynthetic pigments, antioxidant enzyme activity and oxidative damage). By combining these endpoints with a characterization of the sediments of the riverine systems receiving the effluents made in a previous study (metals, polycyclic aromatic hydrocarbons, pharmaceuticals and personal care products), we aimed to elucidate whether effluent contaminants trigger negative effects, which may be mitigated by EPS layers protecting the communities. Our results indicated that under a comparatively milder contamination burden, EPS production is enhanced in samples collected downstream of the effluent outfall; under a higher contamination burden, EPS production is hampered. Stress-coping mechanisms were activated by environmental contaminants, including the antioxidant defense, particularly through catalase and superoxide dismutase activity. The findings support the generally assumed protective effect of EPS, but also suggest that EPS production depends on the contamination burden and that protective effects should be in place under specific scenarios of, for example, relatively low contamination levels. Overall, the integrative approach used in this study contributes to a better understanding of the complex interplay of interactions between effluent-driven contamination and thriving periphytic communities inhabiting recipient waterways, including evolved protection mechanisms.

Coral larvae increase nitrogen assimilation to stabilize algal symbiosis and combat bleaching under increased temperature

Rising sea surface temperatures are increasingly causing breakdown in the nutritional relationship between corals and algal endosymbionts (Symbiodiniaceae), threatening the basis of coral reef ecosystems and highlighting the critical role of coral reproduction in reef maintenance. The effects of thermal stress on metabolic exchange (i.e., transfer of fixed carbon photosynthates from symbiont to host) during sensitive early life stages, however, remains understudied. We exposed symbiotic Montipora capitata coral larvae in Hawai'i to high temperature (+2.5°C for 3 days), assessed rates of photosynthesis and respiration, and used stable isotope tracing (4 mM 13C sodium bicarbonate; 4.5 h) to quantify metabolite exchange. While larvae did not show any signs of bleaching and did not experience declines in survival and settlement, metabolic depression was significant under high temperature, indicated by a 19% reduction in respiration rates, but with no change in photosynthesis. Larvae exposed to high temperature showed evidence for maintained translocation of a major photosynthate, glucose, from the symbiont, but there was reduced metabolism of glucose through central carbon metabolism (i.e., glycolysis). The larval host invested in nitrogen cycling by increasing ammonium assimilation, urea metabolism, and sequestration of nitrogen into dipeptides, a mechanism that may support the maintenance of glucose translocation under thermal stress. Host nitrogen assimilation via dipeptide synthesis appears to be used for nitrogen limitation to the Symbiodiniaceae, and we hypothesize that nitrogen limitation contributes to retention of fixed carbon by favoring photosynthate translocation to the host. Collectively, our findings indicate that although these larvae are susceptible to metabolic stress under high temperature, diverting energy to nitrogen assimilation to maintain symbiont population density, photosynthesis, and carbon translocation may allow larvae to avoid bleaching and highlights potential life stage specific metabolic responses to stress.

Metabolomic and microbiomic resilience of Hong Kong oysters to dual stressors: Zinc oxide nanoparticles and low salinity

Zinc oxide nanoparticles, increasingly used in industrial and consumer products, and low salinity, exacerbated by climate change-induced alterations in precipitation patterns, represent significant environmental pressures in estuarine and coastal environments. This study advances previous research on their impacts on Hong Kong oysters (Crassostrea hongkongensis) by integrating metabolomics of hepatopancreas and gills with intestinal microbiomics. Employing advanced multi-omics integration methods, our analysis reveals novel insights into metabolic resilience under combined stress conditions. This resilience is characterized by coordinated, organ-specific adjustments in energy metabolism (d-glucose 1-phosphate in hepatopancreas, cytidine in gills), antioxidant defenses (glutathione, meso-2,6-diaminoheptanedioate, pimelic acid in hepatopancreas; indole, 3-(3-hydroxyphenyl)propanoic acid in gills), immune function (l-glutamine, ergocalciferol in hepatopancreas; argininosuccinic acid in gills), and membrane stability (lanosterin in hepatopancreas, allantoin in gills). Notably, under dual stressors, we observed a previously undescribed stabilization of microbial alpha diversity and certain phyla, an absence of distinctive biomarkers, and certain metabolic activity stabilization within the intestinal microbiota. These findings suggest robust compensatory mechanisms that maintain physiological homeostasis and microbial balance under stress, contrasting with primarily negative impacts reported in previous studies. Integration of metabolomic and microbiomic data revealed coordinated responses between microbial community changes and metabolic adjustments, particularly in osmoregulation, energy metabolism and antioxidant defenses, under dual stressors. This comprehensive approach provides a more realistic model of environmental challenges, revealing sophisticated adaptive strategies in Hong Kong oysters. Our study offers critical insights for understanding bivalve resilience, informing conservation strategies, and managing marine ecosystems in the face of increasing anthropogenic pressures.

How water acidification influences the organism antioxidant capacity and gill structure of Mediterranean mussel (Mytilus galloprovincialis, Lamarck, 1819) at normoxia and hypoxia

The effect of water acidification in combination with normoxia or hypoxia on the antioxidant capacity and oxidative stress markers in gills and hemolymph of the Mediterranean mussel (Mytilus galloprovincialis), as well as on gill microstructure, has been evaluated through an in vivo experiment. Mussels were exposed to a low pH (7.3) under normal dissolved oxygen (DO) conditions (8 mg/L), and hypoxia (2 mg/L) for 8 days, and samples were collected on days 1, 3, 6, and 8 to evaluate dynamic changes of physiological responses. Cytoplasmic concentrations of reactive oxygen species (ROS) and levels of DNA damage were measured in hemocytes, while the activity of catalase (CAT) and superoxide dismutase (SOD) and histopathological changes were assessed in gills. The results revealed that while water acidification did not significantly affect the activity of SOD and CAT in gills under normoxic and hypoxic conditions, there was a trend towards suppression of CAT activity at the end of the experimental period (day 8). Similarly, we did not observe increased formation of ROS in hemocytes or changes in the levels of DNA damage during the experimental period. These results strongly suggest that the oxidative stress response system in mussels is relatively stable to experimental conditions of acidification and hypoxia. Experimental acidification under normoxia and hypoxia caused changes to the structure of the gills, leading to various histopathological alterations, including dilation, hemocyte infiltration into the hemal sinuses, intercellular edema, vacuolization of epithelial cells in gill filaments, lipofuscin accumulation, changes in the shape and adjacent gill filaments, hyperplasia, exfoliation of the epithelial layer, necrosis, swelling, and destruction of chitinous layers (chitinous rods). Most of these alterations were reversible, non-specific changes that represent a general inflammatory response and changes in the morphology of the gill filaments. The dynamics of histopathological alterations suggests an active adaptive response of gills to environmental stresses. Taken together, our data indicate that Mediterranean mussels have a relative tolerance to water acidification and hypoxia at tissue and cellular levels.

Microplastics and low tide warming: Metabolic disorders in intertidal Pacific oysters (Crassostrea gigas)

Sessile intertidal organisms live in a harsh environment with challenging environmental conditions and increasing anthropogenic pressure such as microplastic (MP) pollution. This study focused on effects of environmentally relevant MP concentrations on the metabolism of intertidal Pacific oyster Crassostrea gigas, and its potential MP-induced vulnerability to warming during midday low tide. Oysters experienced a simulated semidiurnal tidal cycle based on their natural habitat, and were exposed to a mixture of polystyrene microbeads (4, 7.5 and 10 µm) at two environmentally relevant concentrations (0.025 µg L-1 and 25 µg L-1) for 16 days, with tissue samplings after 3 and 12 days to address dose-dependent effects over time. On the last day of exposure, the remaining oysters were additionally exposed to low tide warming (3 °C h-1) to investigate possible MP-induced susceptibility to aerial warming. Metabolites of digestive gland and gill tissues were analysed by using untargeted 1H nuclear magnetic resonance (NMR) based metabolomics. For the digestive gland metabolite profiles were comparable to each other independent of MP concentration, exposure time, or warming. In contrast, gill metabolites were significantly affected by high MP exposure and warming irrespective of MP, initiating the same cellular stress response to counteract induced oxidative stress. The activated cascade of antioxidant defence mechanisms required energy on top of the general energy turnover to keep up homeostasis, which in turn may lead to subtle, and likely sub-lethal, effects within intertidal oyster populations. Present results underline the importance of examining the effects of environmentally relevant MP concentrations not only alone but in combination with other environmental stressors.

Animal personality in multiple stressor environments: the evolutionary ecology of among-individual differences in responses to stressor suites

Animal personality differences may have evolved as alternative strategies for negotiating multiple stressor landscapes. Indeed, ecologists are increasingly recognizing that interactions among multiple stressors can transform selective landscapes and behavioural and physiological responses to stress regimes. Yet, evaluating this hypothesis poses challenges, as most studies involving relationships between personality variation and the environment consider single stressors. Here, we review the literature to explore the theory and evidence that multiple stressor environments may mediate personality variation. We consider effects on evolution of personality variation, as influenced by life-history, energetic and behavioural trade-offs, and effects on phenotypic expression of personality traits. We then explore how personality variation may modulate behavioural and physiological responses to multiple stressors, and how differential responses may be affected by personality-dependent movement ecology and cognitive strategies. Among-individual differences in responses to multiple stressors are critical to elucidate, as multi-stress interactions may transform animal behavioural and physiological responses relative to those predicted under single stressor scenarios, and because among-individual variation comprises the basis for evolutionary shifts in stress responsiveness and population resiliency to global environmental change.

Temperature-dependent responses and trophic interaction strengths of a predatory marine gastropod and rock oyster under ocean warming

Predator-prey interactions are important in shaping ecosystem structure. Consequently, impacts of accelerating global warming on predators will have notable implications. Effects are likely to be particularly marked for tropical organisms which are anticipated to be sensitive to further thermal stress. Here, we investigated effects of future ocean warming on the predatory dogwhelk Reishia clavigera and its predation of Saccostrea cucullata. Mortality of the predators rapidly increased under the extreme elevated temperature, while those exposed to moderate elevated temperature displayed similar mortality as the ambient. Predators that survived moderate temperature increases altered their oxygen consumption patterns, increased average feeding rates, and functional responses, although condition index and energy reserves were unchanged. Overall, we show extreme ocean warming scenarios can remove predators and their consumption of prey from an ecosystem, whereas moderate warming can intensify predator-prey interactions. Such temperature-dependent alterations to predator-prey interactions would lead to fundamental changes of ecosystem structure as the ocean warms.

When the Going Gets Tough, the Females Get Going: Sex-Specific Physiological Responses to Simultaneous Exposure to Hypoxia and Marine Heatwave Events in a Ubiquitous Copepod

The existence of sex-specific differences in phenotypic traits is widely recognized. Yet they are often ignored in studies looking at the impact of global changes on marine organisms, particularly within the context of combined drivers that are known to elicit complex interactions. We tested sex-specific physiological responses of the cosmopolitan and ecologically important marine copepod Acartia tonsa exposed to combined hypoxia and marine heatwave (MHW) conditions, both of which individually strongly affect marine ectotherms. Females and males were acutely exposed for 5 days to a combination of either control (18°C) or a high temperature mimicking a MHW (25°C), and normoxia (100% O2 sat.) or mild hypoxia (35% O2 sat.). Life-history traits, as well as sex-specific survival and physiological traits, were measured. Females had overall higher thermal tolerance levels and responded differently than males when exposed to the combined global change drivers investigated. Females also showed lower metabolic thermal sensitivity when compared to males. Additionally, the MHW exerted a dominant effect on the traits investigated, causing a lower survival and higher metabolic rate at 25°C. However, egg production rates appeared unaffected by hypoxia and MHW conditions. Our results showed that MHWs could strongly affect copepods' survival, that combined exposure to hypoxia and MHW exerted an interactive effect only on CTmax, and that sex-specific vulnerability to these global change drivers could have major implications for population dynamics. Our results highlight the importance of considering the differences in the responses of females and males to rapid environmental changes to improve the implementation of climate-smart conservation approaches.

Unravelling biochemical responses in the species Mytilus galloprovincialis exposed to the antineoplastics ifosfamide and cisplatin under different temperature scenarios

This study investigates the chronic impact of two of the most widely consumed antineoplastic drugs, Ifosfamide (IF) and Cisplatin (CDDP), on the bivalve species Mytilus galloprovincialis under current (17 °C) and predicted warming conditions (21 °C). Accompanying the expected increase in worldwide cancer incidence, antineoplastics detection in the aquatic environment is also expected to rise. Mussels were exposed to varying concentrations of IF (10, 100, 500 ng/L) and CDDP (10, 100, 1000 ng/L) for 28 days. Biochemical analyses focused on metabolic, antioxidant and biotransformation capacities, cellular damage, and neurotoxicity. Results showed temperature-dependent variations in biochemical responses. Metabolic capacity remained stable in mussels exposed to IF, while CDDP exposure increased it at 1000 ng/L for both temperatures. Antioxidant enzyme activities were unaffected by IF, but CDDP activated them, particularly at 21 °C. Biotransformation capacity was unchanged by IF but enhanced by CDDP. Nevertheless, cellular damage occurred at CDDP concentrations above 100 ng/L, regardless of temperature. Integrated biomarker responses highlighted CDDP's greater impact, emphasizing the critical role of temperature in shaping organismal responses and underscoring the complexity of environmental stressor interactions.

Aspirin exposure coupled with hypoxia interferes energy metabolism, antioxidant and autophagic processes and causes liver injury in estuarine goby Mugilogobius chulae

Toxicity assessments of pollutants often overlook the impact of environmental factors like hypoxia, which can alter chemical toxicity with unexpected consequences. In this study, Mugilogobius chulae, an estuarine fish, was used to investigate the effects of hypoxia (H), aspirin (ASA), and their combination (H_ASA) exposure over 24, 72, and 168 h. We employed RNA-seq analysis, expression of key gene expression profiling, enzymatic activity assays, and histopathological and ultrastructural examinations of liver tissue to explore the effects and mechanisms of ASA-coupled hypoxia exposure in fish. Results showed that glycolysis was inhibited, and lipolysis was enhanced in ASA/H_ASA groups. The PPAR signaling pathway was activated, increasing fatty acid β-oxidation and lipophagy to mitigate energy crisis. Both ASA and H_ASA exposures induced p53 expression and inhibited the TOR pathway to combat environmental stress. However, a greater energy demand and heightened sensitivity to ASA were observed in H_ASA compared to ASA exposure. Disruptions in energy and detoxification pathways led to increased stress responses, including enhanced antioxidant activities, autophagy, and apoptotic events, as observed in organelle structures. Overall, sub-chronic H_ASA exposure caused liver injury in M. chulae by affecting energy metabolism, antioxidant regulation, and autophagy processes. This study highlights the influence of hypoxia on ASA toxicity in fish, providing valuable insights for ecological risk assessment of NSAIDs.

Interactive effects of temperature and salinity on metabolism and activity of the copepod Tigriopus californicus

In natural environments, two or more abiotic parameters often vary simultaneously, and interactions between co-varying parameters frequently result in unpredictable, non-additive biological responses. To better understand the mechanisms and consequences of interactions between multiple stressors, it is important to study their effects on not only fitness (survival and reproduction) but also performance and intermediary physiological processes. The splash-pool copepod Tigriopus californicus tolerates extremely variable abiotic conditions and exhibits a non-additive, antagonistic interaction resulting in higher survival when simultaneously exposed to high salinity and acute heat stress. Here, we investigated the response of T. californicus in activity and oxygen consumption under simultaneous manipulation of salinity and temperature to identify whether this interaction also arises in these sublethal measures of performance. Oxygen consumption and activity rates decreased with increasing assay salinity. Oxygen consumption also sharply increased in response to acute transfer to lower salinities, an effect that was absent upon transfer to higher salinities. Elevated temperature led to reduced rates of activity overall, resulting in no discernible impact of increased temperature on routine metabolic rates. This suggests that swimming activity has a non-negligible effect on the metabolic rates of copepods and must be accounted for in metabolic studies. Temperature also interacted with assay salinity to affect activity, and with acclimation salinity to affect routine metabolic rates upon acute salinity transfer, implying that the sublethal impacts of these co-varying factors are also not predictable from experiments that study them in isolation.

Heat hardening improves thermal tolerance in abalone, without the trade-offs associated with chronic heat exposure

Marine animals are challenged by chronically raised temperatures alongside an increased frequency of discrete, severe warming events. Exposure to repeated heat shocks could result in heat hardening, where sub-lethal exposure to thermal stress temporarily enhances thermotolerance, and may be an important mechanism by which marine species will cope with future thermal challenges. However, we have relatively little understanding of the effects of heat hardening in comparison to chronic exposure to elevated temperatures. Therefore, we compared the effects of heat hardening from repeated exposure to acute heat shocks and chronic exposure to elevated temperatures on thermal tolerance in the European abalone, Haliotis tuberculata. Adult abalones were exposed to either control temperature (15 °C), chronic warming (20 °C) or a regime of two events of repeated acute heat shock cycles (23-25 °C) during six months, and their thermal tolerance and performance, based upon cardiac activity, compared using a dynamic ramping assay. The cost associated with each treatment was also estimated via measurements of condition index (CI). Abalone exposed to both temperature treatments had higher upper thermal limits than the control, but heat-hardened individuals had significantly higher CI values, indicating an enhancement in condition status. Differences in the shape of the thermal performance curve suggest different mechanisms may be at play under different temperature exposure treatments. We conclude that heat hardening can boost thermal tolerance in this species, without performance trade-offs associated with chronic warming.

The influence of temperature on the impacts of caffeine in mussels: Evaluating subcellular impacts and model predictions

In aquatic ecosystems, the presence of pharmaceuticals, particularly caffeine (CAF), has been linked to wastewater discharge, hospital waste, and the disposal of expired pharmaceutical products containing CAF. Additionally, rising temperatures due to climate change are anticipated in aquatic environments. This study aimed to assess the toxicity of various CAF concentrations under current (17 °C) and projected (21 °C) temperature conditions, using the mussel Mytilus galloprovincialis as a bioindicator species. Subcellular impacts were evaluated following 28 days of exposure to four CAF concentrations (0.5; 1.0; 5.0; 10.0 μg/L) at the control temperature (17 °C). Only effects at an environmentally relevant CAF concentration (5.0 μg/L) were assessed at the highest temperature (21 °C). The overall biochemical response of mussels was evaluated using non-metric Multidimensional Scaling (MDS) and the Integrated Biomarker Response (IBR) index, while the Independent Action (IA) model was used to compare observed and predicted responses. Results showed that at 17 °C, increased CAF concentrations were associated with higher metabolism and biotransformation capacity, accompanied by cellular damage at the highest concentration. Conversely, under warming conditions (21 °C), the induction of antioxidant enzymes was observed, although insufficient to prevent cellular damage compared to the control temperature. Regarding neurotoxicity, at 17 °C, the activity of the acetylcholinesterase enzyme was inhibited up to 5.0 μg/L; however, at 10.0 μg/L, activity increased, possibly due to CAF competition for adenosine receptors. The IA model identified a synergistic response for most parameters when CAF and warming acted together, aligning with observed results, albeit with slightly lower magnitudes.

Genetics and ontogeny are key factors influencing thermal resilience in a culturally and economically important bivalve

Increasing seawater temperatures coupled with more intense and frequent heatwaves pose an increasing threat to marine species. In this study, the New Zealand green-lipped mussel, Perna canaliculus, was used to investigate the effect of genetics and ontogeny on thermal resilience. The culturally and economically significant mussel P. canaliculus (Gmelin, 1971) has been selectively-bred in New Zealand for two decades, making it a unique biological resource to investigate genetic interactions in a temperate bivalve species. Six selectively-bred full sibling families and four different ages, from early juveniles (6, 8, 10 weeks post-fertilisation) to sub-adults (52 weeks post-fertilisation), were used for experimentation. At each age, each family was exposed to a three-hour heat challenge, followed by recovery, and survival assessments. The shell lengths of live and dead juvenile mussels were also measured. Gill tissue samples from sub-adults were collected after the thermal challenge to quantify the 70 kDa heat shock protein gene (hsp70). Results showed that genetics, ontogeny and size influence thermal resilience in P. canaliculus, with LT50 values ranging between 31.3 and 34.4 °C for all studied families and ages. Juveniles showed greater thermotolerance compared to sub-adults, while the largest individuals within each family/age class tended to be more heat sensitive than their siblings. Sub-adults differentially upregulated hsp70 in a pattern that correlated with net family survival following heat challenge, reinforcing the perceived role of inducible HSP70 protein in molluscs. This study provides insights into the complex interactions of age and genotype in determining heat tolerance of a key mussel species. As marine temperatures increase, equally complex selection pressure responses may therefore occur. Future research should focus on transcriptomic and genomic approaches for key species such as P. canaliculus to further understand and predict the effect of genetic variation and ontogeny on their survival in the context of climate change.

Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793)

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

Elevated temperature and decreased salinity impacts on exogenous Vibrio parahaemolyticus infection of eastern oyster, Crassostrea virginica

Anthropogenic carbon emissions have resulted in drastic oceanic changes, including increased acidity, increased temperature, and decreased salinity. Anthropogenic carbon emissions have resulted in drastic oceanic changes, including increased acidity, increased temperature, and decreased salinity. Few studies have directly assessed the compounded impact of alterations to oceanic conditions on oyster physiology and the relation to the presence of V. parahaemolyticus. This project investigated the relationship between projected climate scenarios and their influence on both eastern oyster, Crassostrea virginica, and the aquatic bacteria, Vibrio parahaemolyticus. Specifically, we examined whether an increase in water temperature and/or decrease in salinity would impair oyster resistance to V. parahaemolyticus, a human food and waterborne pathogen. Using a culture-dependent approach, our data revealed that the alterations in environmental conditions did not significantly impact the numbers of V. parahaemolyticus numbers within oyster hemolymph or tissues. However, we did observe a dramatic increase in the total amount of bacteria and pathogenic native Vibrio species, Vibrio aestuarianus and Vibrio harveyi. Despite detecting V. parahaemolyticus in most tissues at 7 days post-challenge, oysters were able to reduce bacterial levels below our limit of detection by 28 days of exposure. Furthermore, in our second experimental trial exploring single vs. multiple inoculation of bacteria, we observed that oysters were either able to reduce total bacterial levels to pre-treatment burdens (i.e., below our limit of detection) or die. This study demonstrates that the synergistic effects of elevated temperature and decreased salinity do not inhibit oysters from preventing the long-term colonization of exogenous V. parahaemolyticus. However, our data do show these environmental stressors impact oyster physiology and the native microbiota. This can lead to the proliferation of opportunistic pathogens, which could have impacts on oyster population numbers and ecosystem and human health.

Rapid evolution of consumptive and non-consumptive predator effects on prey population densities, bioenergetics and stoichiometry

Predators can strongly influence prey populations not only through consumptive effects (CE) but also through non-consumptive effects (NCE) imposed by predation risk. Yet, the impact of NCE on bioenergetic and stoichiometric body contents of prey, traits that are shaping life histories, population and food web dynamics, is largely unknown. Moreover, the degree to which NCE can evolve and can drive evolution in prey populations is rarely studied. A 6-week outdoor mesocosm experiment with Caged-Fish (NCE) and Free-Ranging-Fish (CE and NCE) treatments was conducted to quantify and compare the effects of CE and NCE on population densities, bioenergetic and stoichiometric body contents of Daphnia magna, a keystone species in freshwater ecosystems. We tested for evolution of CE and NCE by using experimental populations consisting of D. magna clones from two periods of a resurrected natural pond population: a pre-fish period without fish and a high-fish period with high predation pressure. Both Caged-Fish and Free-Ranging-Fish treatments decreased the body size and population densities, especially in Daphnia from the high-fish period. Only the Free-Ranging-Fish treatment affected bioenergetic variables, while both the Caged-Fish and Free-Ranging-Fish treatments shaped body stoichiometry. The effects of CE and NCE were different between both periods indicating their rapid evolution in the natural resurrected population. Both the Caged-Fish and Free-Ranging-Fish treatments changed the clonal frequencies of the experimental Daphnia populations of the pre-fish as well as the high-fish period, indicating that not only CE but also NCE induced clonal sorting, hence rapid evolution during the mesocosm experiment in both periods. Our results demonstrate that CE as well as NCE have the potential to change not only the body size and population density but also the bioenergetic and stoichiometric characteristics of prey populations. Moreover, we show that these responses not only evolved in the studied resurrected population, but that CE and NCE also caused differential rapid evolution in a time frame of 6 weeks (ca. four to six generations). As NCE can evolve as well as can drive evolution, they may play an important role in shaping eco-evolutionary dynamics in predator-prey interactions.

Impact of anthropogenic global hypoxia on the physiological response of bivalves

Dissolved oxygen (DO) is an important parameter that affects the biology, physiology, and immunology of aquatic animals. In recent decades, DO levels in the global oceans have sharply decreased, partly due to an increase in atmospheric carbon dioxide, temperature, and anthropogenic nutrient loads. Although there have been many reports on the effects of hypoxia on the survival, growth, behavior, and immunity of bivalves, this information has not been well organized. Therefore, this article provides a comprehensive review of the effects of hypoxia on bivalves. In general, hypoxia negatively impacts the food consumption rate and assimilation efficiency, as well as increasing respiration rates in many bivalves. As a result, it reduces the energy allocation for bivalve growth, shell formation, and reproduction. In severe cases, prolonged exposure to hypoxia can result in mass mortality in bivalves. Moreover, hypoxia also has adverse effects on the immunity and response of bivalves to predators, including decreased burial depths, sensitivity to predators, impairment of byssus production, and negatively impacts on the integrity, strength, and composition of bivalve shells. The tolerance of bivalves to hypoxia largely depends on size and species, with larger bivalves being more susceptible to hypoxia and intertidal species being relatively more tolerant to hypoxia. The information in this article is very useful for elucidating the current research status of hypoxia on bivalves and determining future research directions.

The Role of Life Stages in the Sensitivity of Hediste diversicolor to Nanoplastics: A Case Study with Poly(Methyl)Methacrylate (PMMA)

The presence of plastic particles in oceans has been recognized as a major environmental concern. The decrease in particle size increases their ability to directly interact with biota, with particles in the nanometer size range (nanoplastics-NPs) displaying a higher ability to penetrate biological membranes, which increases with the decrease in particle size. This study aimed to evaluate the role of life stages in the effects of poly(methyl)methacrylate (PMMA) NPs on the polychaete Hediste diversicolor, a key species in the marine food web and nutrient cycle. Thus, behavioral (burrowing activity in clean and spiked sediment) and biochemical endpoints (neurotransmission, energy reserves, antioxidant defenses, and oxidative damage) were assessed in juvenile and adult organisms after 10 days of exposure to spiked sediment (between 0.5 and 128 mg PMMA NPs/Kg sediment). Overall, the results show that H. diversicolor is sensitive to the presence of PMMA NPs. In juveniles, exposed organisms took longer to burrow in sediment, with significant differences from the controls being observed at all tested concentrations when the test was performed with clean sediment, whereas in PMMA NP-spiked sediment, effects were only found at the concentrations 8, 32, and 128 mg PMMA NPs/Kg sediment. Adults displayed lower sensitivity, with differences to controls being found, for both sediment types, at 8, 32, and 128 mg PMMA NPs/Kg sediment. In terms of Acetylcholinesterase, used as a marker of effects on neurotransmission, juveniles and adults displayed opposite trends, with exposed juveniles displaying increased activity (suggesting apoptosis), whereas in adults, overall decreased activity was found. Energy-related parameters revealed a generally similar pattern (increase in exposed organisms) and higher sensitivity in juveniles (significant effects even at the lower concentrations). NPs also demonstrated the ability to increase antioxidant defenses (higher in juveniles), with oxidative damage only being found in terms of protein carbonylation (all tested NPs conditions) in juveniles. Overall, the data reveal the potential of PMMA NPs to affect behavior and induce toxic effects in H. diversicolor, with greater effects in juveniles.

Perfluorooctanoate and nano titanium dioxide impair the byssus performance of the mussel Mytilus coruscus

Perfluorooctanoate (PFOA) is widely used as a surfactant and has metabolic, immunologic, developmental, and genetic toxicity on marine organisms. However, the effects of PFOA on individual defense functions in mussels in the presence of titanium dioxide nanoparticles (nano-TiO2) are poorly understood. To investigate the defense strategies and regulatory mechanisms of mussels under combined stressors, the thick-shell mussels Mytilus coruscus were exposed to different PFOA concentrations (0, 2 and 200 μg/L) and nano-TiO2 (0 and 0.1 mg /L, size: 25 nm) for 14 days. The results showed that, compared to the control group, PFOA and nano-TiO2 significantly reduced the number of byssal threads (NBT), byssal threads length (BTL), diameter of proximal threads (DPB), diameter of middle threads (DMB), diameter of distal byssal threads (DDB), adhesive plaque area (BPA), and breaking force of byssal threads (N). Under the influence of PFOA and nano-TiO2, the morphological surface smoothness of the fractured byssal threads surface increased, concurrently inducing an increased surface roughness in the adhesive plaques. Additionally, under the presence of PFOA and nano-TiO2, the foot displayed dispersed tissue organization and damaged villi, accompanied by an increased incidence of cellular apoptosis and an upregulation of the apoptosis gene caspase-8. Expression of the adhesion gene mfp-3 and byssal threads strength genes (preCOL-D, preCOL-NG) was upregulated. An interactive effect on the performance of byssal threads is observed under the combined influence of PFOA and nano-TiO2. Under co-exposure to PFOA and nano-TiO2, the performance of the byssal threads deteriorates, the foot structure is impaired, and the genes mRNA expression of byssal thread secretory proteins have compensated for the adhesion and byssal threads strength by up-regulation. Within marine ecosystems, organic and particulate contaminants exert a pronounced effect on the essential life processes of individual organisms, thereby jeopardizing their ecological niche within community assemblages and perturbing the dynamic equilibrium of the overarching ecosystem. ENVIRONMENTAL IMPLICATION: Perfluorooctanoic acid (PFOA) is prone to accumulate in marine organisms. TiO2 nanoparticles (nano-TiO2) are emerging environmental pollutants frequently found in marine environment. The effects of PFOA and nano-TiO2 on marine mussels are not well understood, and their toxic mechanisms remain largely unknown. We investigated the impacts of PFOA and nano-TiO2 on mussel byssus defense mechanisms. By assessing byssus performance indicators, morphological structures of the byssus, subcellular localization, and changes in byssal secretion-related genes, we revealed the combined effects and mechanisms through which these two types of pollutants may affect the functional capabilities and survival of mussels in the complex marine ecosystem.

A systematic review of approaches to assess fish health responses to anthropogenic threats in freshwater ecosystems

Anthropogenic threats such as water infrastructure, land-use changes, overexploitation of fishes and other biological resources, invasive species and climate change present formidable challenges to freshwater biodiversity. Historically, management of fish and fishery species has largely been based on studies of population- and community-level dynamics; however, the emerging field of conservation physiology promotes the assessment of individual fish health as a key management tool. Fish health is highly sensitive to environmental disturbances and is also a fundamental driver of fitness, with implications for population dynamics such as recruitment and resilience. However, the mechanistic links between particular anthropogenic disturbances and changes in fish health, or impact pathways, are diverse and complex. The diversity of ways in which fish health can be measured also presents a challenge for researchers deciding on methods to employ in studies seeking to understand the impact of these threats. In this review, we aim to provide an understanding of the pathway through which anthropogenic threats in freshwater ecosystems impact fish health and the ways in which fish health components impacted by anthropogenic threats can be assessed. We employ a quantitative systematic approach to a corpus of papers related to fish health in freshwater and utilize a framework that summarizes the impact pathway of anthropogenic threats through environmental alterations and impact mechanisms that cause a response in fish health. We found that land-use changes were the most prolific anthropogenic threat, with a range of different health metrics being suitable for assessing the impact of this threat. Almost all anthropogenic threats impacted fish health through two or more impact pathways. A robust understanding of the impact pathways of anthropogenic threats and the fish health metrics that are sensitive to these threats is crucial for fisheries managers seeking to undertake targeted management of freshwater ecosystems.

Hues of risk: investigating genotoxicity and environmental impacts of azo textile dyes

The textile industry, with its extensive use of dyes and chemicals, stands out as a significant source of water pollution. Exposure to certain textile dyes, such as azo dyes and their breakdown products like aromatic amines, has been associated with health concerns like skin sensitization, allergic reactions, and even cancer in humans. Annually, the worldwide production of synthetic dyes approximates 7 × 107 tons, of which the textile industry accounts for over 10,000 tons. Inefficient dyeing procedures result in the discharge of 15-50% of azo dyes, which do not adequately bind to fibers, into wastewater. This review delves into the genotoxic impact of azo dyes, prevalent in the textile industry, on aquatic ecosystems and human health. Examining different families of textile dye which contain azo group in their structure such as Sudan I and Sudan III Sudan IV, Basic Red 51, Basic Violet 14, Disperse Yellow 7, Congo Red, Acid Red 26, and Acid Blue 113 reveals their carcinogenic potential, which may affect both industrial workers and aquatic life. Genotoxic and carcinogenic characteristics, chromosomal abnormalities, induced physiological and neurobehavioral changes, and disruptions to spermatogenesis are evident, underscoring the harmful effects of these dyes. The review calls for comprehensive investigations into the toxic profile of azo dyes, providing essential insights to safeguard the aquatic ecosystem and human well-being. The importance of effective effluent treatment systems is underscored to mitigate adverse impacts on agricultural lands, water resources, and the environment, particularly in regions heavily reliant on wastewater irrigation for food production.

Differential intestinal effects of water and foodborne exposures of nano-TiO2 in the mussel Mytilus coruscus under elevated temperature

With the wide use of nanomaterials in daily life, nano-titanium dioxide (nano-TiO2) presents potential ecological risks to marine ecosystems, which can be exacerbated by ocean warming (OW). However, most previous studies have only centered around waterborne exposure, while there is a scarcity of studies concentrating on the impact of trophic transfer exposure on organisms. We investigated the differences in toxic effects of 100 μg/L nano-TiO2 on mussels via two pathways (waterborne and foodborne) under normal (24 °C) and warming (28 °C) conditions. Single nano-TiO2 exposure (waterborne and foodborne) elevated the superoxide dismutase (SOD) and catalase (CAT) activities as well as the content of glutathione (GSH), indicating activated antioxidatant response in the intestine. However, depressed antioxidant enzymes and accumulated peroxide products (LPO and protein carbonyl content, PCC) demonstrated that warming in combination with nano-TiO2 broke the prooxidant-antioxidant homeostasis of mussels. Our findings also indicated that nano-TiO2 and high temperature exhibited adverse impacts on amylase (AMS), trypsin (PS), and trehalase (THL). Additionally, activated immune function (lysozyme) comes at the cost of energy expenditure of protein (decreased protein concentration). The hydrodynamic diameter of nano-TiO2 at 24 °C (1693-2261 nm) was lower than that at 28 °C (2666-3086 nm). Bioaccumulation results (range from 0.022 to 0.432 μg/g) suggested that foodborne induced higher Ti contents in intestine than waterborne. In general, the combined effects of nano-TiO2 and warming demonstrated a more pronounced extent of interactive effects and severe damage to antioxidant, digestive, and immune parameters in mussel intestine. The toxicological impact of nano-TiO2 was intensified through trophic transfer. The toxic effects of nano-TiO2 are non-negligible and can be exerted together through both water- and foodborne exposure routes, which deserves further investigation.