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

Effects of Carbon Nanoparticles and Chromium Combined Exposure in Native (Ruditapes decussatus) and Invasive (Ruditapes philippinarum) Clams

Studies have described the occurrence of nanoparticles (NPs) in aquatic ecosystems, with particular attention to the widely commercialized carbon nanotubes (CNTs). Their presence in the environment raises concerns, especially regarding their toxicity when co-occurring with other pollutants such as metals. In the present study, changes to the metabolic capacity, oxidative, and neurologic status were evaluated in the presence of carboxylated multi-walled CNTs and chromium (Cr(III)) using two of the most ecologically and economically relevant filter feeder organisms: the clam species Ruditapes decussatus and R. philippinarum. Results indicated that although Cr, either alone or in combination with CNTs, was found in a similar concentration level in both species, a species-specific Cr accumulation was observed, with higher values in R. decussatus in comparison with R. philippinarum. Inhibition of antioxidant defenses and neurotoxic effects were detected only in R. philippinarum. The interaction between contaminants seems to have no effect in terms of antioxidant enzyme activities and neuro status. Nevertheless, synergistic activation of responses to both contaminants may have altered the metabolic capacity of bivalves, particularly evident in R. decussatus. While both clams are tolerant to both contaminants (alone and together), they showed a relevant accumulation capacity, which may represent a possible contaminant transfer to humans.

Interaction between nanomaterials and the innate immune system across evolution

Interaction of engineered nanomaterials (ENMs) with the immune system mainly occurs with cells and molecules of innate immunity, which are present in interface tissues of living organisms. Immuno-nanotoxicological studies aim at understanding if and when such interaction is inconsequential or may cause irreparable damage. Since innate immunity is the first line of immune reactivity towards exogenous agents and is highly conserved throughout evolution, this review focuses on the major effector cells of innate immunity, the phagocytes, and their major sensing receptors, Toll-like receptors (TLRs), for assessing the modes of successful versus pathological interaction between ENMs and host defences. By comparing the phagocyte- and TLR-dependent responses to ENMs in plants, molluscs, annelids, crustaceans, echinoderms and mammals, we aim to highlight common recognition and elimination mechanisms and the general sufficiency of innate immunity for maintaining tissue integrity and homeostasis.

The influence of salinity on the toxicity of remediated seawater

Mercury (Hg) is one of the most hazardous pollutants, due to its toxicity, biological magnification and worldwide persistence in aquatic systems. Thus, new efficient nanotechnologies (e.g. graphene oxide functionalized with polyethyleneimine (GO-PEI)) have been developed to remove this metal from the water. Aquatic environments, in particular transitional systems, are also subjected to disturbances resulting from climate change, such as salinity shifts. Salinity is one of the most relevant factors that influences the distribution and survival of aquatic species such as mussels. To our knowledge, no studies assessed the ecotoxicological impairments induced in marine organisms exposed to remediate seawater (RSW) under different salinity levels. For this, the focus of the present study was to evaluate the effects of seawater previously contaminated with Hg and remediated with GO-PEI, using the species Mytilus galloprovincialis, maintained at three different salinities (30, 20 and 40). The results obtained demonstrated similar histopathological and metabolic alterations, oxidative stress and neurotoxicity in mussels under RSW treatment at stressful salinity conditions (20 and 40) in comparison to control salinity (30). On the other hand, the present findings revealed toxicological effects including cellular damage and histopathological impairments in mussels exposed to Hg contaminated seawater in comparison to non-contaminated ones, at each salinity level. Overall, these results confirm the high efficiency of GO-PEI to sorb Hg from water with no noticeable toxic effects even under different salinities, leading to consider it a promising eco-friendly approach to remediate contaminated water.

Biochemical response of Ficopomatus enigmaticus adults after exposure to organic and inorganic UV filters

With the increase of UV filters usage and consequent release into aquatic environments, the concerns about their potential ecological risks are also increasing. According to this, in the present study, adult polychaetes of the species Ficopomatus enigmaticus were chronically exposed to three concentrations (0.01, 0.1 and 0.5 mg/L) of organic and inorganic filters (Ethylhexyl methoxycinnamate (EHMC) and nanoparticulate Zinc oxide (nZnO), respectively) in order to analyse biochemical responses related to cellular damage, antioxidant defence, biotransformation mechanisms and, lastly, neurotoxicity. Despite major lipid peroxidation caused by EHMC was observed, both UV filters have produced the same response patterns. In details, a clear concentration-dependent activation of glutathione S-transferases and a significant decrease of acetylcholinesterase levels defined an important neurotoxic effect was observed for both contaminants. These results become important to expand the limited scientific literature on biochemical responses of marine and brackish water invertebrates to organic and inorganic UV filters.

Bioaccumulation and ecotoxicological responses of clams exposed to terbium and carbon nanotubes: Comparison between native (Ruditapes decussatus) and invasive (Ruditapes philippinarum) species

In the last decades the use of rare earth elements (REEs) increased exponentially, including Terbium (Tb) which has been widely used in newly developed electronic devices. Also, the production and application of nanoparticles has been growing, being Carbon Nanotubes (CNTs) among the most commonly used. Accompanying such development patterns, emissions towards the aquatic environments are highly probable, with scarce information regarding the potential toxicity of these pollutants to inhabiting species, especially considering their mixture. In the present study the effects of Tb and CNTs exposure (acting alone or as a mixture) on native and invasive clams' species (Ruditapes decussatus and Ruditapes philippinarum, respectively) were evaluated, assessing clams' accumulation and metabolic capacities, oxidative status as well neurotoxic impacts. Results obtained after a 28-days exposure period showed that the accumulation of Tb in both species was not affected by the presence of the CNTs and similar Tb concentrations were found in both species. The effects caused by Tb and CNTs, acting alone or as a mixture induced greater alterations in R. philippinarum antioxidant capacity in comparison to native R. decussatus, but no cellular damages were observed in both species. Nevertheless, although metabolic impairment was only observed in clams exposed to Tb, loss of redox balance and neurotoxicity were evidenced by both species regardless the exposure treatment. These findings highlight the potential impacts caused by CNTs and Tb, which may affect clams' normal physiological functioning, impairing their reproduction and growth capacities. The obtained results point out the need for further investigation considering the mixture of pollutants.

Do the graphene nanoflakes pose a potential threat to the polychaete Hediste diversicolor?

Graphene is a promising material with a wide range of future applications that could potentially lead to its transfer from numerous water and terrestrial sources to the sea, thus fate and effects of graphene in the marine ecosystem deserve attention. Within this work, the impact of the short- and long-term exposure (36 h and 24 days) of the marine benthic polychaete Hediste diversicolor to various concentrations (36 h: 0.4, 4, 40 and 400 mg L^-1; 24 days: 4 and 40 mg L^-1) of the pristine graphene multilayer nanoflakes (of thickness 8-12 nm) was investigated. Experiments revealed a limited toxic effect of graphene on H. diversicolor. Although the polychaetes ingested graphene, no impact on their total energy content was found. The toxic effect expressed by significant elevation of catalase activity indicating activation of defence mechanisms was recorded but only at the early stage of exposure. Activities of other antioxidant and cellular damage biomarkers (SOD, GST, GSH, MDA, CBO) remained unaffected. Moreover, no neurotoxic effect expressed by inhibition of acetylcholinesterase (AChE) activity was observed. Substantial inter-individual variability in the activities of some biomarkers at the end of the long-term experiment was found. Polychaetes were buried deeper in the sediment with graphene than in the controls indicating an escape reaction and avoidance behaviour. The latter may lead to the transfer of graphene from the sediment surface to deeper sediment layers with unknown consequences for the benthic ecosystem.

Nanomaterials and Annelid Immunity: A Comparative Survey to Reveal the Common Stress and Defense Responses of Two Sentinel Species to Nanomaterials in the Environment

Simple Summary

Nanotechnology is a dynamically developing field producing large amounts of nanocompounds that are applied in industry, daily life, and health care. During production, use, and waste these materials could end up in water or soil. Large scale contaminations of our environment are a threat to public health. Pollution can have harmful effects on the immune system, as revealed by numerous studies in humans and other vertebrates. The relative simplicity of invertebrate immune functions offers potentially sensitive and accessible means of monitoring the effects and complex interactions of nanoparticles which ultimately affect host resistance. Among terrestrial and freshwater invertebrates, earthworms and leeches are the “keystone” species to evaluate the health of our ecosystems. In this review we compare the conserved stress and immune responses of these invertebrate model organisms toward nanoparticles. The obtained knowledge provides exciting insights into the conserved molecular and cellular mechanisms of nanomaterial-related toxicity in invertebrates and vertebrates. Understanding the unique characteristics of engineered nanoproducts and their interactions with biological systems in our environment is essential to the safe realization of these materials in novel biomedical applications.

Abstract

Earthworms and leeches are sentinel animals that represent the annelid phylum within terrestrial and freshwater ecosystems, respectively. One early stress signal in these organisms is related to innate immunity, but how nanomaterials affect it is poorly characterized. In this survey, we compare the latest literature on earthworm and leeches with examples of their molecular/cellular responses to inorganic (silver nanoparticles) and organic (carbon nanotubes) nanomaterials. A special focus is placed on the role of annelid immunocytes in the evolutionarily conserved antioxidant and immune mechanisms and protein corona formation and probable endocytosis pathways involved in nanomaterial uptake. Our summary helps to realize why these environmental sentinels are beneficial to study the potential detrimental effects of nanomaterials.

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.

The influence of temperature and salinity on the impacts of lead in Mytilus galloprovincialis

Mussels, such as the marine bivalve Mytilus galloprovincialis are sentinels for marine pollution but they are also excellent bioindicators under laboratory conditions. For that, in this study we tested the modulation of biochemical responses under realistic concentrations of the toxic metal Lead (Pb) in water for 28 days under different conditions of salinity and temperature, including control condition (temperature 17 ± 1.0 °C and salinity 30 ± 1.0) as well as those within the range expected to occur due to climate change predictions (± 5 in salinity and + 4 °C in temperature). A comprehensive set of biomarkers was applied to search on modulation of biochemical responses in terms of energy metabolism, energy reserves, oxidative stress and damage occurrence in lipids, proteins as well as neurotoxicity signs. The application of an integrative Principal Coordinates Ordination (PCO) tool was successful and demonstrated that Pb caused an increase in the detoxification activity mainly evidenced by glutathione S-transferases and that the salinities 25 and 35 were, even in un-exposed mussels, responsible for cell damage seen as increased levels of lipid peroxidation (at salinity 25) and oxidised proteins (at salinity 35).

The influence of Climate Change on the fate and behavior of different carbon nanotubes materials and implication to estuarine invertebrates

The widespread use of Carbon nanotubes (CNTs) has been increasing exponentially, leading to a significant potential release into the environment. Nevertheless, the toxic effects of CNTs in natural aquatic systems are related to their ability to interact with abiotic compounds. Considering that salinity variations are one of the main challenges in the environment and thus may influence the behavior and toxicity of CNTs, a laboratory experiment was performed exposing the tube-building polychaete Diopatra neapolitana (Delle Chiaje 1841) for 28 days to pristine multi-walled carbon nanotube (MWCNTs) and carboxylated MWCNTs, maintained at control salinity 28 and low salinity 21. An innovative approach based on thermogravimetric analysis (TGA) was adopted for the first time to assess the presence of MWCNTs aggregates in the organisms. Both CNTs generated toxic impacts in terms of regenerative capacity, energy reserves and metabolic capacity as well as oxidative and neuro status, however greater toxic impacts were observed in polychaetes exposed to carboxylated MWCNTs. Moreover, both CNTs maintained under control salinity (28) generated higher toxic impacts in the polychaetes compared to individuals maintained under low salinity (21), indicating that exposed polychaetes tend to be more sensitive to the alteration induced by salinity variations on the chemical behavior of both MWCNTs in comparison to salt stress.

Does the exposure to salinity variations and water dispersible carbon nanotubes induce oxidative stress in Hediste diversicolor?

Salinity plays a fundamental role in naturally fluctuating environments such as estuaries influencing physiological and biochemical performance of inhabiting biota. Moreover salinity is considered one of the main factors influencing nanoparticles' stability. Thus, the aim of the present paper was to show the impacts induced by different salinities (control-28 and 21) on the chemical behavior of water dispersible multi-walled carbon nanotube (MWCNTs-COOH) and the consequent toxicity in the common ragworm Hediste diversicolor, after long term exposure. Results showed a concentration-dependent toxicity in terms of energy reserves and metabolism, oxidative status and neurotoxicity. In addition, under low salinity (21), the toxicity of the carbon NMs was similar to the impacts measured under control (28), although under salinity 28 the concentrations of MWCNTs-COOH used generated greater alterations in LPO levels and antioxidant enzymes (SOD and GPx). These results demonstrate that higher salinity caused the formation of large-size aggregates, which increased the chance of physical retention, such as gravitational sedimentation, interception and straining of f-MWCNTs generating higher cell injuries than the impacts induced in polychaetes sensitivity to these contaminates due to low salinity.