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.

Effects of polymethylmethacrylate nanoplastics on the polychaete Hediste diversicolor: Behavioural, regenerative, and biochemical responses.

Plastics, particularly microplastics (MPs) and nanoplastics (NPs), have been regarded as pollutants of emerging concern due to their effects on organisms and ecosystems, especially considering marine environments. However, in terms of NPs, there is still a knowledge gap regarding the effects of size and polymer on marine invertebrates, such as benthic organisms. Therefore, this study aimed to understand, regarding behavioural, physiological, and biochemical endpoints (neurotransmission, energy metabolism, antioxidant status, and oxidative damage), the effects of 50 nm waterborne polymethylmethacrylate (PMMA) NPs (0.5 to 500 µg/L) on the marine benthic polychaete Hediste diversicolor, a key species in estuarine and coastal ecosystems. Results demonstrated that worms exposed to PMMA NPs had a shorter burrowing time than control organisms. Nevertheless, worms exposed to PMMA NPs (0.5 and 500 µg/L) decreased cholinesterase activity. Energy metabolism was decreased at 50 and 500 µg/L, and glycogen content decreased at all concentrations of PMMA NPs. Enzymes related to the antioxidant defence system (superoxide dismutase and glutathione peroxidase) displayed increased activities in H. diversicolor specimens exposed to concentrations between 0.5 and 500 µg/L, which led to no damage at the cell membrane and protein levels. In this study, polychaetes also displayed a lower regenerative capacity when exposed to PMMA NPs. Overall, the data obtained in this study emphasize the potential consequences of PMMA NPs to benthic worms, particularly between 0.5 and 50 µg/L, with polychaetes exposed to 50 µg/L being the most impacted by the analysed NPs. However, since sediments are considered to be sinks and sources of plastics, further studies are needed to better understand the impacts of different sizes and polymers on marine organisms, particularly benthic species.

A biochemical and lipidomic approach to perceive Halimione portulacoides (L.) response to mercury: An environmental perspective.

The impact of hazardous materials, such as Hg, on life is far from being understood and due to the high number of polluted sites it has generated great concern. A biochemical and lipidomic approach was used to assess the effects of Hg on the saltmarsh halophyte Halimione portulacoides. Plants were collected at two sites of a Hg contaminated saltmarsh. Hg accumulation and distribution in the plant, biochemical parameters (antioxidant and metabolic) and lipid profiles were determined and compared between plant organs and sites (s1 and s2). Hg did not induce antioxidant enzyme activity. Lipid profiles changed under Hg exposure, especially in leaves, decreasing the unsaturation level, the membrane fluidity and stability, and evidencing that membrane lipid remodeling influences plant tolerance to Hg. This knowledge can help select the most appropriate methodologies for the restoration of Hg polluted hotspots, curtailing a serious environmental problem threatening saltmarshes.

Biochemical and Behavioural Alterations Induced by Arsenic and Temperature in Hediste diversicolor of Different Growth Stages.

Contamination with Arsenic, a toxic metalloid, is increasing in the marine environment. Additionally, global warming can alter metalloids toxicity. Polychaetes are key species in marine environments. By mobilizing sediments, they play vital roles in nutrient and element (including contaminants) cycles. Most studies with marine invertebrates focus on the effects of metalloids on either adults or larvae. Here, we bring information on the effects of temperature increase and arsenic contamination on the polychaete Hediste diversicolor in different growth stages and water temperatures. Feeding activity and biochemical responses-cholinesterase activity, indicators of cell damage, antioxidant and biotransformation enzymes and metabolic capacity-were evaluated. Temperature rise combined with As imposed alterations on feeding activity and biochemical endpoints at different growth stages. Small organisms have their antioxidant enzymes increased, avoiding lipid damage. However, larger organisms are the most affected class due to the inhibition of superoxide dismutase, which results in protein damage. Oxidative damage was observed on smaller and larger organisms exposed to As and temperature of 21 °C, demonstrating higher sensibility to the combination of temperature rise and As. The observed alterations may have ecological consequences, affecting the cycle of nutrients, sediment oxygenation and the food chain that depends on the bioturbation of this polychaete.

Interplay of Seasonality, Major and Trace Elements: Impacts on the Polychaete Diopatra neapolitana.

Polychaetes are known to be good bioindicators of marine pollution, such as inorganic contamination. Major and trace elements are commonly present in sediment and may be accumulated by polychaetes such as the tubiculous Diopatra neapolitana. In this study, D. neapolitana individuals were collected in the autumn, winter, spring, and summer of 2018/2019 from the Ria de Aveiro lagoon (western Portugal) to understand how seasonality influences element accumulation. The impact of the interaction of seasonality and elements on oxidative status, energy metabolism, and oxidative damage was also assessed. The obtained results showed that the activity of the antioxidant enzymes catalase, glutathione S-transferases, and non-protein thiol levels were higher in summer and that superoxide dismutase, lipid peroxidation, and electron transport system activity increased in winter. The lowest glycogen levels were observed during spring, and protein carbonylation was the highest during autumn. These results could mainly be related to high temperatures and the bioaccumulation of Al, As, Mn, and Zn. Energy-related parameters increased during spring and autumn, mainly due to the bioaccumulation of the same elements during spring and summer. Lipid damage was higher during winter, which was mainly due to salinity and temperature decreases. Overall, this study demonstrates that seasonality plays a role in element accumulation by polychaetes and that both impact the oxidative status of D. neapolitana.

Graphene oxide influence in soil bacteria is dose dependent and changes at osmotic stress: growth variation, oxidative damage, antioxidant response, and plant growth promotion traits of a Rhizobium strain.

Climate change events, such as drought, are increasing and soil bacteria can be severely affected. Moreover, the accumulation of emerging pollutants is expected to rapidly increase, and their impact on soil organisms, their interactions, and the services they provide is poorly known. The use of graphene oxide (GO) has been increasing due to its enormous potential for application in several areas and it is expected that concentration in soil will increase in the future, potentially causing disturbances in soil microorganisms not yet identified.Here we show the effects that GO nanosheets can cause on soil bacteria, in particular those that promote plant growth, in control and 10% polyethylene glycol (PEG) conditions. Low concentrations of GO nanosheets did not affect the growth of Rhizobium strain E20-8, but under osmotic stress (PEG) GO decreased bacterial growth even at lower concentrations. GO caused oxidative stress, with antioxidant mechanisms being induced to restrain damage, effectively at lower concentrations, but less effective at higher concentrations, and oxidative damage overcame. Under osmotic stress, alginate and glycine betaine osmoregulated the bacteria. Simultaneous exposure to PEG and GO induced oxidative damage. Plant growth promotion traits (indole acetic acid and siderophores production) were increased by osmotic stress and GO did not disturb these abilities. In the context of climate change, our findings might be relevant as they can form the premises for the implementation of crop production methodologies adapted to the new prevailing conditions, which include the presence of nanoparticles in the soil and more frequent and severe drought.

Does parental exposure to nanoplastics modulate the response of Hediste diversicolor to other contaminants: A case study with arsenic.

Plastic pollution is a serious problem in aquatic systems throughout the world. Despite the increasing number of studies addressing the impact of macro- and microplastics on biota, there is still a significant knowledge gap regarding the effects of nanoplastics alone and in combination with other contaminants. Among the aquatic contaminants that may interact with nanoplastics is arsenic (As), a metalloid found in estuarine and coastal ecosystems, pernicious to benthic organisms. This study aimed to understand how a parental pre-exposure to 100 nm polystyrene nanoplastics (PS NPs) would influence the response of Hediste diversicolor to exposure to arsenic in terms of behaviour, neurotransmission, antioxidant defences and oxidative damage, and energy metabolism. The obtained data revealed an increase in burrowing time and a significant inhibition in cholinesterase activity in all polychaetes exposed to As, regardless of the pre-exposure to PS NPs. Oxidative status was altered particularly in parentally exposed organisms, with damage detected in terms of lipid peroxidation at 50 µg/L and protein carbonylation at 50 and 250 µg As/L exposed organisms when compared to control. Overall, data shows that parental pre-exposure to plastics influences the response of aquatic organisms, increasing their susceptibility to other contaminants. Thus, more studies should be performed with other environmental contaminants, to better understand the potential increased risk associated with the presence of nanoplastics to aquatic ecosystems.

Plastics in scene: A review of the effect of plastics in aquatic crustaceans.

Plastic pollution in aquatic environments is present in all compartments from surface water to benthic sediment, becoming a topic of emerging concern due to the internalization, retention time, and its effects on aquatic biota. Crustacea with nearly 70,000 species, broad distribution and different roles in the trophic webs is a significant target of the increasing plastic pollution. At least 98 publications in the last 10 years report the impact of plastics in crustaceans, all suggesting that this taxon is at high risk for ecosystem disadvantage by plastic contamination loads. This review compiles the current knowledge on physiological effects (endpoints) by plastic contamination analyzed in crustaceans in the last 10 years, highlighting their use as model species for ecotoxicological tests, sentinels species and bioindicators. Plastic contamination analyzed in this review includes macroplastic, microplastic, and nanoplastic, in a wide variety of types. The studies were focused on 38 marine species with an economic interest in fisheries and aquaculture; 14 freshwater with a higher frequency in standard test species and 4 estuarial and 3 mangrove species with ecological interest. The publications reviewed were divided into studies describing plastic presence in crustaceans without reporting toxic effects and those with analysis of plastic toxicity. Publications describing the plastic presence in the organisms show that the ingestion in individual effects and food-web transfer in ecological effects were the most frequent endpoints. The publications that analyzed plastic toxicity through survival, nutrition-metabolism-assimilation, and reproduction in individual effects, and bioaccumulation in ecological effects were the most frequent endpoints. This review gathers the available information on the use of crustaceans as model species in environmental impact for toxicity screening and hazard assessment. Besides, identifying knowledge gaps will let us propose some future directions in research and the effects on target fisheries species which involves a possible effect on human health.

Micro(nano)plastics and plastic additives effects in marine annelids: A literature review.

Plastic debris are dispersed in the marine environment and are consequently available to many organisms of different trophic levels, including sediment-dwelling organisms such as polychaetae. Plastic degradation generates micro (MPs) and nanoplastics (NPs) and as well as releases bounded plastic additives, increasing the ecotoxicological risk for marine organisms. Therefore, this review summarizes current knowledge on the accumulation and effects of MPs and NPs and plastic additives in polychaetes, derived from laboratory and field evidences. Thirty-six papers (from January 2011 to September 2021) were selected and analysed: about 80% of the selected works were published since 2016, confirming the emerging role of this topic in environmental sciences. The majority of the analysed manuscripts (68%) were carried out in the laboratory under controlled conditions. These studies showed that polychaetes accumulate and are responsive to this contaminant class, displaying behavioural, physiological, biochemical and immunological alterations. The polychaetes Hediste diversicolor and Arenicola marina were the most frequent used species to study MPs, NPs and plastic additive effects. The consideration of field studies revealed that MP accumulation was dependent on the plastic type present in the sediments and on the feeding strategy of the species. Polychaetes are known to play an important role in coastal and estuarine food webs and exposure to MPs, NPs and plastic additives may impair their behavioural, physiological, biochemical and immunological responses. Thus, the estimated global increase of these contaminants in the marine environment could affect the health of these benthic organisms, with consequences at population and ecosystem levels.

Studying Annelida Body Regeneration Under Environmental Stress in Diopatra neapolitana.

The polychaete Diopatra neapolitana is a cosmopolitan annelid that can robustly regenerate both its anterior and posterior body part depending on the position of the amputation. Previous studies demonstrated that body regeneration represents a sensitive and unspecific response to environmental stresses, including contaminants and climate alterations.The posterior body regeneration of D. neapolitana is thus a suitable, ecological and relevant biomarker in ecotoxicological and ecological risk assessment assays. Here we describe the amputation process, the monitoring of the regeneration process of the polychaete D. neapolitana and the quantification of the impact of environmental stresses on its regenerative capacity.

Effects of graphene oxide nanosheets in the polychaete Hediste diversicolor: Behavioural, physiological and biochemical responses.

Numerous applications exist for graphene-based materials, such as graphene oxide (GO) nanosheets. Increased concentrations of GO nanosheets in the environment have the potential to have a large negative effect on the aquatic environment, with consequences for benthic organisms, such as polychaetes. The polychaete Hediste diversicolor mobilises the sediments, hence altering the availability of contaminants and the nutrients biogeochemical cycle. As such, this study proposes to assess the effects of different GO nanosheet concentrations on the behaviour, feeding activity, mucus production, regenerative capacity, antioxidant status, biochemical damage and metabolism of H. diversicolor. This study evidenced that H. diversicolor exposed to GO nanosheets had a significantly lower ability to regenerate their bodies, took longer to feed and burrow into the sediment and produced more mucus. Membrane oxidative damage (lipid peroxidation) increased in exposed specimens. The increased metabolic rate (ETS) evidenced a higher energy expenditure in exposed organisms (high use of ready energy sources - soluble sugars) to fight the toxicity induced by GO nanosheets, such as SOD activity. The increase in SOD activity was enough to reduce reactive oxygen species (ROS) induced by GO on cytosol at the lowest concentrations, avoiding the damage on proteins (lower PC levels), but not on membranes (LPO increase). This study revealed that the presence of GO nanosheets, even at the lower levels tested, impaired behavioural, physiological, and biochemical traits in polychaetes, suggesting that the increase of this engineered nanomaterial in the environment can disturb these benthic organisms, affecting the H. diversicolor population. Moreover, given the important role of this group of organisms in coastal and estuarine food webs, the biogeochemical cycle of nutrients, and sediment oxygenation, there is a real possibility for repercussions into the estuarine community.

Effects of ocean acidification on the biochemistry, physiology and parental transfer of Ampelisca brevicornis (Costa, 1853).

Ocean acidification (OA) has received more attention in the marine research community in recent years than any other topic. Excess carbon dioxide makes the ocean more acidic, threatening marine ecosystems. There has been little research on the impact of OA on crustaceans, particularly on their physiological and potential ecosystem-level consequences. Thus, we investigated the impacts of OA on the physiological and biochemical characteristics of the estuarine amphipod Ampelisca brevicornis. Ovigerous amphipods were harvested from nature and maintained in the laboratory to produce juveniles, which were then further reared to obtain the mature adults (F0) and successive offspring (F1). For this study, four pH treatments (pH 8.1, 7.5, 7.0, and 6.5) mimicking future OA were evaluated to understand the physiological and biochemical effects on the organisms. The findings of this study suggest that A. brevicornis is more vulnerable to OA than was previously established in short-term trials. The survival was significantly reduced as pH decreased over time and a significant interaction between pH and time was observed. Survival was higher in F1 than in F0 juveniles and vice versa in terms of growth. Animal's physiological responses such as growth, burrowing behavior, locomotor activity, swimming speed, ventilation rate and reproductive performance were negatively influenced by acidification. These physiological characteristics can be linked to the oxidative stress induced by global change conditions because excess of free radicals degrade cell functioning, affecting species' biochemical and physiological performance. These alterations may have long-term negative impacts, with ecological consequences. The results of this study provide baseline information regarding the effect of OA on this keystone crustacean that may be useful in simulating the impacts of OA to develop different conceptual models for a better understanding of the consequences and implications of climate change in the future for managing marine ecosystems.

Effects of volatile sulfur compounds on growth and oxidative stress of Rhizobium leguminosarum E20-8 exposed to cadmium.

Volatile sulfur compounds (VSCs) have been reported to be produced by many bacterial species. Depending on the compound, they can negatively influence some organisms (fungi, nematodes and insects) or promote plant growth. Some of these compounds have also been hypothesized to play a role in bacterial response to cadmium (Cd) induced stress. This study aimed to assess the potential effects of four VSCs (dimethyl sulfide - DMS, dimethyl disulfide - DMDS, dimethyl trisulfide - DMTS and methyl thioacetate - MTA) on the growth and oxidative status of Rhizobium sp. strain E20-8 via airborne exposure, in order to test the hypothesis that these volatile compounds can influence growth and tolerance to cadmium. Our results show that, overall, the tested compounds triggered similar antioxidant mechanisms in Rhizobium in the presence of Cd. The protective effect at the membrane level by DMDS and DMTS particularly demonstrates the antioxidant effect of these volatiles, with reductions of up to 50% (DMS) and 80% (DMTS) in lipid peroxidation levels. Due to the volatile nature of these compounds, the low concentrations tested (1 nM to 100 mM), and considering that they are released by bacteria and other organisms such as plants, it is possible that these effects also occur in the soil ecosystem.

Experimental evidence of uncertain future of the keystone ragworm Hediste diversicolor (O.F. Müller, 1776) under climate change conditions.

It is currently assumed that climate change related factors pose severe challenges to biodiversity maintenance. This paper assesses the multi-stressor effects of elevated temperature (15 °C as control, 25 °C as elevated) and CO2 levels (pH 8.1 as control, 7.5 and 7.0 representing acidifying conditions) on the physiological (survival and regenerative capacity), behavioral (feeding and burrowing activities), and biochemical changes (metabolic capacity, oxidative status and biotransformation mechanisms) experienced by the keystone polychaete Hediste diversicolor. Temperature rise enlarged the adverse effect of marine acidification on the survival of H. diversicolor, delayed the beginning of the excavation activity, enhancing the negative effects that pH decrease had in the burrowing behavior of this polychaete. Additionally, regardless of the temperature, exposure of H. diversicolor to acidification results in a reduction in the feeding rate. It is the first time that this decreased feeding capacity is found related to seawater acidification in this species. The healing of the wound and the blastemal formation were retarded due to these two climatic factors which hinder the regenerative process of polychaetes. These vital physiological functions of H. diversicolor can be related to the oxidative stress induced by climate change conditions since free radicals overproduced will impair cells functioning, affecting species biochemical and physiological performance, including feeding and tissue regeneration. The present results also demonstrated that although polychaetes' metabolic capacity was enhanced under stress conditions, organisms were still able to increase or maintain their energy reserves. Our findings are of major environmental relevance considering that predicted climate change conditions will affect species vital and ecological and physiological capacities. These can be translated into shrinking not only at the individual and population level but also in microbial and endofaunal diversities, in the detritus processing in estuaries and biogeochemical cycles at the ecosystem level. Thus the conservation of H. diversicolor populations is vital for the normal functioning of estuarine mudflat ecosystems.

Relationship between wild-caught organisms for bioassays and sampling areas: Widespread serpulid early-development comparison between two distinct populations after trace element exposure.

Previous studies suggested the suitability of the brackish-water serpulid (Ficopomatus enigmaticus) to be used as model organism for both marine and brackish waters monitoring, by the performance of sperm toxicity and larval development assays. The present study focused on larval development after the exposure of two F. enigmaticus populations (Mediterranean and Atlantic, collected in Italy and Portugal, respectively) to different trace elements (copper, mercury, arsenic, cadmium, and lead) at different concentrations. Results of larval development assays were presented as the percentage of abnormal developed larvae. The effect, measured in terms of EC50 for all toxicants tested, showed that mercury was the most toxic metal for larvae of both populations. Specifically, the tested trace elements may be racked in the following order from the highest to the lowest toxicity: Mediterranean: mercury > copper > lead > arsenic > cadmium; Atlantic: mercury > copper > cadmium > arsenic > lead. Responses of both populations were similar for arsenic. Lead was the least toxic element for the Atlantic population, while cadmium showed the least toxicity for the Mediterranean population. These preliminary results demonstrate the sensitivity and suitability of the organisms to be used in ecotoxicological bioassays and monitoring protocols. Moreover, chemical analyses on soft tissues and calcareous tubes of collected test organisms and their sampling site water were performed, to identify and quantify the concentration of the tested trace elements in these 3 matrices. Populations exhibited less sensitivity to a certain element together with a relevantly higher concentration of the same element in soft tissues. This may indicate a certain resistance to particular contaminant toxic effects by organisms that tend to accumulate the same toxicant. This highlights the potential correlation between wild-caught test organisms' responses and a deep characterization of the sampling site to identify putative abnormalities or differences in model organism response during bioassay execution.

The use of Hediste diversicolor in the study of emerging contaminants.

The contamination of aquatic environments has been the focus of research to understand effects on ecosystems and its species. Benthic organisms are considered potential targets since sediments act as sources and sinks for environmental contaminants. This review presents information on the effects of three types of emerging contaminants: pharmaceuticals (tested concentrations between 0.1 ng/L - 250 mg/L and 0.01 ng/g - 2.5 µg/g), metal-based nanoparticles (<100 nm) (tested concentrations between 10 µg/L - 1 mg/L and 5 - 140 µg/g) and micro(nano)plastics (tested concentrations between 5 µg/L - 50 mg/L and 10 - 50 mg/kg), on the polychaete Hediste diversicolor, a key species in estuarine/coastal ecosystems. Data shows that these contaminants promote alterations in burrowing activity (lowest concentration inducing effects: 10 ng/L), neurotransmission and damage related parameters (lowest concentration inducing effects: 100 ng/L). The characteristics of this polychaete, such as regenerative capacity, make the use of this species in biomedical studies involving environmental contaminants valuable.

Rhizobium sensing of airborne saturated aldehydes of different sizes modulates the response to Cd exposure.

α,ß-unsaturated aldehydes are generally reported as being toxic, however for saturated aldehydes information is scarce. Here we report the effects on growth and biochemical endpoints related to oxidative stress of Rhizobium colonies under airborne exposure to C6 to C13 saturated aliphatic aldehydes and exposed or not to Cd. Smaller aldehydes (C6 to C10) and larger aldehydes (C11 to C13) had distinct effects on cell biochemistry. Smaller aldehydes reduced and larger ones increased lipid peroxidation. The activity of superoxide dismutase was also decreased by smaller aldehydes and increased by the larger ones. Thus, even an exposure at a distance to saturated aldehydes is able to influence the biochemical status of bacterial cells, and the effects appear to be dependent on the size and thus on distinct properties (e.g. volatility and liposolubility). Moreover, some aldehydes (the smaller saturated ones) may even have a beneficial effect, that switches when cells are in oxidative stress (exposed to Cd). This influence can be used in different contexts, by increasing the resilience of bacterial communities to environmental contaminants with oxidizing effect or by sensitizing bacteria to antimicrobial agents.

Can Palythoa cf. variabilis biochemical patterns be used to predict coral reef conservation state in Todos Os Santos Bay?

Coral reefs are one of the most diverse, complex and productive marine ecosystems on the planet. Global climate change and other anthropogenic impacts have had a strong impact on the equilibrium of these ecosystems and causing the denominated "coral reef crisis". One consequence of coral reef crisis is the phase shift in reef communities, where scleractinian corals responsible for the bioconstruction of the coralline building are replaced by macroalgae or soft corals. In Todos os Santos Bay (TSB) there is a rare case of phase shift caused by the soft coral Palythoa cf. variabilis. When in population outbreak, this coral species becomes dominant and leads to loss of scleractinian coral cover. Palythoa genus establishes a symbiotic relationship with dinoflagellate algae of the genus Symbiodinium, that is changed in phase shift coral reefs, but other alterations remain unknown. In this study, the metabolism (oxidative damage, antioxidant and biotransformation enzymes, electron transport chain activity and photosynthetic pigments) of P. cf. variabilis from reefs in different conservation states was studied to identify and relate if changes that may occur in the biochemical and metabolism of the coral might trigger the population outbreak, identify parameters recognizing if corals are in stress and assess if one or more parameters can reflect the level of stress organisms are experiencing. The results obtained evidenced a clear distinction in the biochemistry and metabolism of corals from conserved sites and sites in phase shift, and these changes may be the trigger for population outbreak. Some of the parameters were able to discriminate the level of stress corals are experiencing and may allow to recognize the most at-risk coral reefs that need immediate intervention and prevent the entry into or revert P. cf. variabilis outbreak and phase shift in coral reefs. Actions like these can be of vital importance for the preservation of TSB coral reefs and possibly for other threatened reefs worldwide.

Airborne exposure of Rhizobium leguminosarum strain E20-8 to volatile monoterpenes: Effects on cells challenged by cadmium.

Volatile organic compounds (VOCs) are produced by plants, fungi, bacteria and animals. These compounds are metabolites originated mainly in catabolic reactions and can be involved in biological processes. In this study, the airborne effects of five monoterpenes (α-pinene, limonene, eucalyptol, linalool, and menthol) on the growth and oxidative status of the rhizobial strain Rhizobium leguminosarum E20-8 were studied, testing the hypothesis that these VOCs could influence Rhizobium growth and tolerance to cadmium. The tested monoterpenes were reported to have diverse effects, such as antibacterial activity (linalool, limonene, α-pinene, eucalyptol), modulation of antioxidant response or antioxidant properties (α-pinene and menthol). Our results showed that non-stressed cells of Rhizobium E20-8 have different responses (growth, cell damage and biochemistry) to monoterpenes, with α-pinene and eucalyptol increasing colonies growth. In stressed cells the majority of monoterpenes failed to minimize the detrimental effects of Cd and increased damage, decreased growth and altered cell biochemistry were observed. However, limonene (1 and 100 mM) and eucalyptol (100 nM) were able to increase the growth of Cd-stressed cells. Our study evidences the influence at-a-distance that organisms able to produce monoterpenes may have on the growth and tolerance of bacterial cells challenged by different environmental conditions.

Behavior and biochemical responses of the polychaeta Hediste diversicolor to polystyrene nanoplastics.

Plastic debris has been reaching the world's oceans since it started being used. Multiple studies have been addressing the effects of microplastics in various organisms but, despite the increased scientific awareness, there is still a significant gap in knowledge when it comes to small-sized plastic particles of sizes below 100 nm. The aim of this study was to understand the effect of waterborne 100 nm polystyrene nanoplastics (PS NPs) on the marine polychaeta Hediste diversicolor, a keystone species in intertidal and coastal environments, in terms of behavior, neurotransmission, oxidative status, energy metabolism and oxidative damage. Results of PS NPs characterization showed an aggregation along the time and with increasing concentrations. Results also revealed a considerable impact of PS NPs on ecologically relevant endpoints like cholinesterase (ChE) and burrowing, but no increases in most of the parameters associated with oxidative stress. Protein carbonylation was found to be more sensitive to PS NPs effects than lipid peroxidation. Behavioral alterations induced by PS NPs may affect nutrient cycling and (endo-)benthic fauna. The data revealed in this study highlighted the potential consequences of NPs to benthic organisms and the need for further studies.