Lucia De Marchi

The impacts of emergent pollutants on Ruditapes philippinarum : biochemical responses to carbon nanoparticles exposure

Multi-walled carbon nanotubes (MWCNTs) are one of the most important carbon Nanoparticles (NPs). The production and use of these NPs are increasing rapidly and, therefore, the need to assess their presence in the environment and associated risks has become of prime importance. Recent studies demonstrated the impacts of different NPs on bivalves, a taxonomic group where species tolerance to anthropogenic stressors, such as pollutants, is widely variable. The Manila clam Ruditapes philippinarum is one of the most commonly used bivalve species in environmental monitoring studies and ecotoxicology tests, however, to our knowledge, no information is available on biochemical alterations on this species due to MWCNTs exposure. Thus, the present study aimed to assess the toxic effects of different MWCNT concentrations (0.01; 0.10 and 1.00mg/L) in R. philippinarum biochemical (energy reserves, metabolic capacity, oxidative status and neurotoxicity) performance, after 28days of exposure. The results obtained revealed that exposure to MWCNTs altered energy-related responses, with higher metabolic capacity and lower glycogen and protein concentrations in clams exposed to these carbon NPs. Moreover, R. philippinarum exposed to MWCNTs showed oxidative stress expressed in higher lipid peroxidation and lower ratio between reduced and oxidized glutathione, despite the activation of defence mechanisms in exposed clams. Additionally, neurotoxicity was observed by inhibition of cholinesterases activity in organisms exposed to MWCNTs. The present study provides valuable information regarding how these emerging pollutans could become a potential risk for the environment and living organisms.

Physiological and biochemical impacts induced by mercury pollution and seawater acidification in Hediste diversicolor

The present study evaluated the impacts of predicted seawater acidification and Hg pollution, when stressors were acting alone and in combination, on the polychaete Hediste diversicolor. Polychaetes were exposed during 28days to low pH (7.5), Hg (5μg/L) and pH7.5+Hg, and physiological alterations (respiration rate), biochemical markers related to metabolic potential (glycogen and protein content, electron transport system activity) and oxidative status (activity of antioxidant and biotransformation enzymes, lipid peroxidation) were evaluated. The results obtained clearly showed that polychaetes were sensitive to low pH and Hg contamination, both acting alone or in combination. Organisms used their energy reserves under stressful conditions, which decreased by up to half of the control content, probably to fuel defence mechanisms. Our findings further demonstrated that polychaetes exposed to these stressors presented increased antioxidant defence mechanisms (3 fold compared to control). However, organisms were not able to prevent cellular damage, especially noticed at Hg exposure and pH7.5. Overall, although all the tested conditions induced oxidative stress in Hediste diversicolor, the combined effect of seawater acidification and Hg contamination did not induce higher impacts in polychaetes than single stressor exposures. These findings may indicate that predicted climate change scenarios may not increase Hediste diversicolor sensitivity towards Hg and may not significantly change the toxicity of this contaminant to this polychaete species.

Physiological and biochemical responses of two keystone polychaete species: Diopatra neapolitana and Hediste diversicolor to Multi-walled carbon nanotubes.

&NA; Multi‐walled carbon nanotubes (MWCNTs) are one of the most important carbon Nanomaterials (NMs). The production and use of these carbon NMs is increasing rapidly and, therefore, the need to assess their presence in the environment and associated risks has become increasingly important. However, limited literature is available regarding the impacts induced in aquatic organisms by this pollutant, namely in invertebrate species. Diopatra neapolitana and Hediste diversicolor are keystone polychaete species inhabiting estuaries and shallow water bodies intertidal mudflats, frequently used to evaluate the impact of environmental disturbances in these systems. To our knowledge, no information is available on physiological and biochemical alterations on these two species due to MWCNTs exposure. Thus, the present study aimed to assess the toxic effects of different MWCNTs concentrations (0.01; 0.10 and 1.00 mg/L) in both species physiological (regenerative capacity and respiration rate) and biochemical (energy reserves, metabolic activities, oxidative stress related biomarkers and neurotoxicity markers) performance, after 28 days of exposure. The results obtained revealed that exposure to MWCNTs induced negative effects on the regenerative capacity of D. neapolitana. Additionally, higher MWCNTs concentrations induced increased respiration rates in D. neapolitana. MWCNTs altered energy‐related responses, with higher values of electron transport system activity, glycogen and protein concentrations in both polychaetes exposed to this contaminant. Furthermore, when exposed to MWCNTs both species showed oxidative stress with higher lipid peroxidation, lower ratio between reduced and oxidized glutathione, and higher activity of antioxidant (catalase and superoxide dismutase) and biotransformation (glutathione‐S‐transferases) enzymes in exposed organisms. Graphical abstract Figure. No caption available. HighlightsMWCNTs induced negative effects on the regenerative capacity of Diopatra neapolitana.Diopatra neapolitana and Hediste diversicolor exposed to MWCNTs showed oxidative stress.Both species under MWCNTs increased their metabolic capacity.Inhibition of cholinesterases confirmed neurotoxicity of MWCNTs in both species.D. neapolitana and H. diversicolor are potential bioindicators to monitor carbon NMs pollution.

The impacts of seawater acidification on Ruditapes philippinarum sensitivity to carbon nanoparticles

In the present study, the impacts of multi-walled carbon nanotubes (MWCNTs), one of the most important NMs used in broad industrial and biomedical applications, on the clam Ruditapes philippinarum were evaluated under actual and predicted ocean acidification conditions. For this, oxidative stress, metabolic capacity and neurotoxicity related biomarkers were measured after a long-term exposure of the clams to different conditions. The results obtained revealed that under low pH conditions the toxicity of MWCNTs was similar to the impacts measured under control pH. In both cases the energy-related responses in contaminated clams were altered with an increase of their metabolism which resulted in the expenditure of their energy reserves (lower glycogen content). Moreover, R. philippinarum showed oxidative stress when exposed to MWCNTs expressed by higher lipid peroxidation activity, a lower ratio between reduced and oxidized glutathione and activation of antioxidant defences and biotransformation mechanisms. Additionally, neurotoxicity was observed by inhibition of cholinesterase activity in organisms exposed to MWCNTs at both pH conditions.

An overview of graphene materials: Properties, applications and toxicity on aquatic environments

Due to unique chemical and physical properties, nanomaterials from the Graphene family are being increasingly introduced in all fields of science. The specific roles they can occupy within different applications are attracting increased attention by several industrial sectors. These carbon nanoparticles are released into the environment especially accumulating in aquatic systems. Since the discovery of graphene, a number of research actives are being conducted to find out the toxic potential of the Graphene family materials to different organisms models. Although their toxicity effects are well described for biomedical applications, few data were produced with the specific aim of assessing the toxic effects of these carbon nanomaterials in the aquatic environment. The purpose of this review is to compile up-to-date information on properties, applications and characterization methods of graphene family materials in aquatic environments and identified biological toxic impacts of these NMs, with special focus on graphene oxide based on the most recent literature.

Physiological and biochemical impacts of graphene oxide in polychaetes: The case of Diopatra neapolitana

Graphene oxide (GO) is an important carbon nanomaterial (NM) that has been used, but limited literature is available regarding the impacts induced in aquatic organisms by this pollutant and, in particular in invertebrate species. The polychaete Diopatra neapolitana has frequently been used to evaluate the effects of environmental disturbances in estuarine systems due to its ecological and socio-economic importance but to our knowledge no information is available on D. neapolitana physiological and biochemical alterations due to GO exposure. Thus, the present study aimed to assess the toxic effects of different concentrations of GO (0.01; 0.10 and 1.00mg/L) in D. neapolitana physiological (regenerative capacity) and biochemical (energy reserves, metabolic activity and oxidative stress related biomarkers) performance, after 28days of exposure. The results obtained revealed that the exposure to GO induced negative effects on the regenerative capacity of D. neapolitana, with organisms exposed to higher concentrations regenerating less segments and taking longer periods to completely regenerate. GO also seemed to alter energy-related responses, especially glycogen content, with higher values in polychaetes exposed to GO which may result from a decreased metabolism (measured by electron transport system activity), when exposed to GO. Furthermore, under GO contamination D. neapolitana presented cellular damage, despite higher activities of antioxidant and biotransformation enzymes in individuals exposed to GO.

Suitability of cholinesterase of polychaete Diopatra neapolitana as biomarker of exposure to pesticides: In vitro characterization

Cholinesterases of Diopatra neapolitana were characterized for their activity in whole body and different body segments (apical, intermediate, posterior), substrate affinity (acetyl-, butyryl-, propionylthiocholine), kinetic parameters (Km and Vmax) and in vitro response to model inhibitors (eserine hemisulfate, isoOMPA, BW284C51) and carbamates (carbofuran, methomyl, aldicarb and carbaryl). Results showed that the rate of hydrolysis for acetyl- and propionylthiocholine was higher in the posterior segment than the apical/intermediate segments and whole body. Cholinesterases of D. neapolitana showed a substrate preference for acetylthiocholine followed by propionylthiocholine; butyrylthioline was poorly hydrolyzed indicating, together with the absence of inhibition by the specific inhibitor and the absence of reactive bands in native electrophoresis, a lack of an active butyrylcholinesterase, differently than that observed in other Annelida species. The degree of inhibition by selected carbamates of cholinesterase activity with propionylthiocholine as substrate was higher than that observed with ATChI-ChE activity; aldicarb showed the highest inhibitory effect.

The influence of salinity on the effects of Multi-walled carbon nanotubes on polychaetes

Salinity shifts in estuarine and coastal areas are becoming a topic of concern and are one of the main factors influencing nanoparticles behaviour in the environment. For this reason, the impacts of multi-walled carbon nanotubes (MWCNTs) under different seawater salinity conditions were evaluated on the common ragworm Hediste diversicolor, a polychaete species widely used as bioindicator of estuarine environmental quality. An innovative method to assess the presence of MWCNT aggregates in the sediments was used for the first time. Biomarkers approach was used to evaluate the metabolic capacity, oxidative status and neurotoxicity of polychaetes after long-term exposure. The results revealed an alteration of energy-related responses in contaminated polychaetes under both salinity conditions, resulting in an increase of metabolism and expenditure of their energy reserves (lower glycogen and protein contents). Moreover, a concentration-dependent toxicity (higher lipid peroxidation, lower ratio between reduced and oxidized glutathione and activation of antioxidant defences and biotransformation mechanisms) was observed in H. diversicolor, especially when exposed to low salinity. Additionally, neurotoxicity was observed by inhibition of Cholinesterases activity in organisms exposed to MWCNTs at both salinities.

The influence of Arsenic on the toxicity of carbon nanoparticles in bivalves

Although an increasing number of studies have been published on the effects of emergent pollutants such as carbon nanoparticles, there is still scarce information on the impact of these contaminants on marine organisms when acting in combination with classical pollutants such as meta(loid)s. The present study evaluated the impacts of Arsenic and Multi-Walled Carbon Nanotubes (MWCNTs) in the clam Ruditapes philippinarum, assessing the effects induced when both contaminants were acting individually (As, NP) and as a mixture (As + NP). Metabolic capacity (electron transport system activity), oxidative stress (antioxidant and biotransformation enzymes activity and cellular damage) and neurotoxicity (Acetylcholinesterase activity) biomarkers were evaluated in clams after a 28 days exposure period. The results obtained showed that the accumulation of As was not affected by the presence of the NPs. Our results demonstrated that higher injuries were noticed in clams exposed to NPs, with higher metabolic depression and oxidative stress, regardless of the presence of As. Furthermore, higher neurotoxicity was observed in clams exposed to the combination of both contaminants in comparison to the effects of As and NPs individually.

Effects of multi-walled carbon nanotube materials on Ruditapes philippinarum under climate change: the case of salinity shifts

The toxicity of carbon nanotubes (CNTs) is closely related to their physico-chemical characteristics as well as the physico-chemical parameters of the media where CNTs are dispersed. In a climate change scenario, changes in seawater salinity are becoming a topic of concern particularly in estuarine and coastal areas. Nevertheless, to our knowledge no information is available on how salinity shifts may alter the sensitivity (in terms of biochemical responses) of bivalves when exposed to different CNTs. For this reason, a laboratory experiment was performed exposing the Manila clam Ruditapes philippinarum, one of the most dominant bivalves of the estuarine and coastal lagoon environments, for 28 days to unfunctionalized multi-walled carbon nanotube MWCNTs (Nf-MWCNTs) and carboxylated MWCNTs (f-MWCNTs), maintained at control salinity (28) and low salinity 21. Concentration-dependent toxicity was demonstrated in individuals exposed to both MWCNT materials and under both salinities, generating alterations of energy reserves and metabolism, oxidative status and neurotoxicity compared to non-contaminated clams. Moreover, our results showed greater toxic impacts induced in clams exposed to f-MWCNTs compared to Nf-MWCNTs. In the present study it was also demonstrated how salinity shifts altered the toxicity of both MWCNT materials as well as the sensitivity of R. philippinarum exposed to these contaminates in terms of clam metabolism, oxidative status and neurotoxicity.