Tolerance of native and invasive bivalves under herbicide and metal contamination: an ex vivo approach

Unveiling microplastic pollution: Evaluating the role of Sinotaia quadrata (Caenogastropoda, Viviparidae) as a monitoring tool in freshwater ecosystems

Freshwater species play a key role in monitoring microplastics (MPs) pollution, providing insights into its distribution, accumulation, and potential ecological and human health risks in aquatic ecosystems. This study evaluates the invasive snail Sinotaia quadrata as a potential tool for monitoring MPs pollution in freshwater ecosystems heavily impacted by human activities. Specifically, we examined whether the characteristics of MPs (i.e., shape, color, and chemical composition) found in water and sediment were reflected in those accumulated by S. quadrata, and whether MPs accumulation varied across different snail size classes. MPs were detected in all environmental matrices and snail samples, with fragments and filaments as the dominant shapes, blue, white, and black as the most common colors, and polypropylene, polyethylene, and polyethylene terephthalate as the primary polymers. A significant difference in MPs concentration per gram was found across snail size classes, with smaller snails accumulating more MPs than larger individuals, likely due to higher feeding rates during growth. A positive correlation was observed between snail shell length and weight, while MPs concentration per gram showed significant negative correlations with both parameters. These findings suggest that S. quadrata accumulates MPs from the environment, reflecting local contamination levels. While S. quadrata is an invasive species, this study demonstrates its potential utility in MPs monitoring, particularly in the context of eradication efforts. This approach integrates pollution assessment with invasive species management, offering a broader perspective on the role of biological invasions in environmental monitoring.

Assessing of trace elements health risks in the crab Portunus segnis from northern Tunisian lagoons

The current study aims to examine the concentrations of eight trace elements (TE) (nickel, aluminum, copper, cadmium, lead, cobalt, chromium, and zinc) in the edible tissue of the invasive blue crab Portunus segnis in two southern Mediterranean lagoons (i.e., Bizerte Lagoon (BL) and Ghar El-Melh Lagoon (GML)) between 2020 and 2021. The samples were analyzed for TE using inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the mean concentrations in P. segnis muscles were significantly lower in Ghar El-Melh (0.183 mg/kg DW, 1.887 mg/kg DW, and 0.986 mg/kg DW for Cd, Cu, and Al, respectively) compared to Bizerte Lagoon (0.227 mg/kg DW, 8.016 mg/kg DW, and 3.658 mg/kg DW for Cd, Cu, and Al respectively), except for Zn which exhibited similar concentrations in crabs harvested from both lagoons. The recorded concentrations of all TE measured in both lagoons were within acceptable limits per the recommended standards. The highest TE concentrations in P. segnis muscle tissue of crabs from both lagoons were recorded during the summer. The analysis of trace element (TE) levels in P. segnis and the assessment parameters, including estimated daily intake (EDI), target hazard quotient (THQ), and target cancer risk (TCr), revealed values below the acceptable limits for human health. THQ and TCr are commonly utilized in environmental and health risk assessments to gauge the potential impact of contaminants on human health. As a result, we can affirm that the invasive crab P. segnis figures as a secure shellfish product suitable for human consumption in Tunisia. This study provides an opportunity to assess the health risks of consuming blue crabs, with the toxicity risk index aiding decision-making for consumers, policymakers, and stakeholders focused on safety and sustainability. Additionally, it offers fundamental insights to lay the groundwork for forthcoming studies on environmental assessments.

Does temperature influence on biomarker responses to copper exposure? The invasive bivalve Limnoperna fortunei (Dunker 1857) as a model

Biomarkers are useful tools for assessing the early warning effects of pollutants. However, their responses can be influenced by confounding factors. In this study, we investigated the influence of temperature on multiple biomarkers in the invasive freshwater bivalve Limnoperna fortunei exposed to copper (Cu). The mussels were exposed to low and high environmental Cu concentrations at two temperatures (15 °C and 25 °C). After 96 h, the oxidative stress, neurotoxicity, and metabolic parameters were assessed. Our results showed that temperature is a key factor influencing biomarker responses in mussels, with higher glutathione S-transferase activity and lower energy reserves at cold temperature. In addition, the effects of Cu were greater at the highest concentration at 15 °C (increased lipid peroxidation and cholinesterase activity). Overall, these findings suggest that cold stress increases the susceptibility of L. fortunei to metal effects and highlight the importance of including temperature in toxicity testing and biomonitoring. In addition, using the invasive bivalve L. fortunei as a model could prove valuable in its role as a sentinel species for other organisms.

A systematic review of invasive non-native freshwater bivalves

The introduction of invasive species has become an increasing environmental problem in freshwater ecosystems due to the high economic and ecological impacts it has generated. This systematic review covers publications from 2010 to 2020, focusing on non-native invasive freshwater bivalves, a particularly relevant and widespread introduced taxonomic group in fresh waters. We collected information on the most studied species, the main objectives of the studies, their geographical location, study duration, and type of research. Furthermore, we focused on assessing the levels of ecological evidence presented, the type of interactions of non-native bivalves with other organisms and the classification of their impacts. A total of 397 publications were retrieved. The studies addressed a total of 17 species of non-native freshwater bivalves; however, most publications focused on the species Corbicula fluminea and Dreissena polymorpha, which are recognised for their widespread distribution and extensive negative impacts. Many other non-native invasive bivalve species have been poorly studied. A high geographical bias was also present, with a considerable lack of studies in developing countries. The most frequent studies had shorter temporal periods, smaller spatial extents, and more observational data, were field-based, and usually evaluated possible ecological impacts at the individual and population levels. There were 94 publications documenting discernible impacts according to the Environmental Impact Classification for Alien Taxa (EICAT). However, 41 of these publications did not provide sufficient data to determine an impact. The most common effects of invasive bivalves on ecosystems were structural alterations, and chemical and physical changes, which are anticipated due to their role as ecosystem engineers. Despite a considerable number of studies in the field and advances in our understanding of some species over the past decade, long-term data and large-scale studies are still needed to understand better the impacts, particularly at the community and ecosystem levels and in less-studied geographic regions. The widespread distribution of several non-native freshwater bivalves, their ongoing introductions, and high ecological and economic impacts demand continued research. Systematic reviews such as this are essential for identifying knowledge gaps and guiding future research to enable a more complete understanding of the ecological implications of invasive bivalves, and the development of effective management strategies.

Reductive stress and cytotoxicity in the swollen river mussel (Unio tumidus) exposed to microplastics and salinomycin

Multistress effects lead to unpredicted consequences in aquatic ecotoxicology and are extremely concerning. The goal of this study was to trace how specific effects of the antibiotic salinomycin (Sal) and microplastics (MP) on the bivalve molluscs are manifested in the combined environmentally relevant exposures. Unio tumidus specimens were treated with Sal (0.6 μg L-1), MP (1 mg L-1, 2 μm size), and both at 18 °C (Mix) and 25 °C (MixT) for 14 days. The redox stress and apoptotic enzyme responses and the balance of Zn/Cu in the digestive gland were analyzed. The shared signs of stress included a decrease in NAD+/NADH and Zn/Cu ratios and lysosomal integrity and an increase in Zn-metallothioneins and cholinesterase levels. MP caused a decrease in the glutathione (GSH) concentration and redox state, total antioxidant capacity, and Zn levels. MP and Mix induced coordinated apoptotic/autophagy activities, increasing caspase-3 and cathepsin D (CtD) total and extralysosomal levels. Sal activated caspase-3 only and increased by five times Cu level in the tissue. Due to the discriminant analysis, the cumulative effect was evident in the combined exposure at 18 °C. However, under heating, the levels of NAD+, NADH, GSH, GSH/GSSG and metallothionein-related thiols were decreased, and coordination of the cytosolic and lysosomal death stimuli was distorted, confirming that heating and pollution could exert unexpected synergistic effects on aquatic life.

Chlorpromazine's impact on Mytilus galloprovincialis: a multi-faceted investigation

The antipsychotic chlorpromazine (Cpz) has raised concern as a pharmaceutical effluent due to its wide medical applications. Moreover, its potent pro-oxidant properties and impact on the cell viability of the marine mollusc Mytilus galloprovincialis, even at low concentrations (ng/L), have been noted. Based on this evidence, in this study, we investigated the physiological effects of Cpz on M. galloprovincialis, to elucidate its fate within the organism, in terms of bioaccumulation, biotransformation, byssus changes and stress responses of the cellular thiolome. Histological and indicators of vitality analyses were also performed to better evaluate the influence of the drug on the morphology and cell viability of the digestive gland. To this end, two different concentrations of Cpz (Cpz I (12 ng/L or 37 pM) and Cpz II (12 μg/L or 37 nM)) were administered to mussels over 14 days. Cpz accumulation in the digestive gland significantly increased with water concentration (BCF of Cpz I and Cpz II). Biochemical analyses indicated lysosomal dysfunction, reflected in elevated total Cathepsin D activity and compromised lysosomal membrane stability. Stress-related and metal-buffering proteins (GST and metallothionein) responded to both Cpz concentrations. Cpz I induced phase I biotransformation activity (CYP450-dependent EROD), while Cpz II triggered caspase-3 activation, indicative of detoxification overload. Histological analysis revealed digestive gland atrophy, epithelial thinning, haemocyte infiltration, and brown cell presence. Byssus analysis showed significant alterations. In conclusion, our study underscores Cpz-induced physiological and histological changes in M. galloprovincialis, posing potential implications for mussel health and confirming the utilisation of this mussel as an indication of Cpz ecotoxicity.

Biochemical basis of resistance to multiple contaminations in the native and invasive populations of Dreissena polymorpha

The zebra mussel Dreissena polymorpha (Pallas, 1771) is an invasive species and a valuable bioindicator in the inland waters. Nevertheless, the biochemical reasons for the unique competitiveness of zebra mussels are not clear. This study aimed to compare the native and invasive populations of D. polymorpha in their ability to withstand the same multiple environmental challenges (i.e. chemical: microplastics and caffeine; physical: temperatures). The specimens from the invasive population in west Ukraine (Tn) and native population at lower streams of river Dnipro (south Ukraine, Kh) were sampled in the August of 2021 y. Molluscs from both populations were treated simultaneously with microplastics (MP, 1 mg L-1, pore size 2 μm); caffeine (Caf, 20.0 μg L-1) at 18 °C, elevated temperature (25 °C) and MP and Caf combinations at 18 °C and 25 °C for 14 days. Untreated molluscs exposed at 18 °C represented control groups. A set of the 20 markers of oxidative stress, biotransformation, detoxification and apoptosis were assayed in the total soft tissues. From the two controls, Kh-group indicated lower stressful impact. However, both populations increased caspase-3 and GST activities and lysosomal instability in most exposures, and cholinesterase and phenoloxidase activities under the heating and combine exposures, indicating the remarkable properties to respond to new challenges and synergistic effect of mixtures. Inter-population differences were related to the metallothionein, cathepsin D, cytochrome P540 and oxidative stress responses that reflect population-dependent adverse outcome pathways. The discriminant analysis separated two populations with a substantially lesser magnitude of responses in the invasive population as a sign of higher resistance.

Long-term sublethal exposure to polyethylene and tire wear particles: Effects on risk-taking behaviour in invasive and native fish

Anthropogenic polymeric particles pollute even the most remote ecosystems and may compromise organisms' behaviour and movement skills. It is expected that invasive species cope better with pollutants than native species (i.e., pollution resistance hypothesis). In this study, invasive gibel carp (Carassius gibelio) and native crucian carp (Carassius carassius) were used as model organisms. Specimens were fed daily with food pellets (1 % body weight) added with 0.1 % polyethylene (PE), tire wear particles (TWPs) and control. Their behavioural parameters were compared before and after 14 and 60 days of exposure. Additionally, we evaluated burst swimming capacity after 60 days of exposure to the treatments. The fishes exposed to the PE and TWPs treatments showed significant trends toward increased boldness scores and, in the PE treatment, higher utilization of the open field, and both behavioural changes are associated with higher risk-taking. Invasive gibel carp had substantially better swimming performance than crucian carp, but the expected trend in relation to the treatments was not found. Fish exposed to sublethal doses of PE and TWPs showed signs of behavioural changes after two months of exposure that may affect risk-taking behaviour, which might impact species interactions with predators.

Sublethal cadmium exposure in the freshwater snail Lymnaea stagnalis meets a deficient, poorly responsive metallothionein system while evoking oxidative and cellular stress

The Great Pond snail Lymnaea stagnalis (Gastropoda, Hygrophila) is a wide-spread freshwater gastropod, being considered as a model organism for research in many fields of biology, including ecotoxicology. The aim of the present study was to explore the Cd sensitivity of L. stagnalis through the measurement of a biomarker battery for oxidative, toxic and cellular stress. The interpretation of biomarker parameters occurred against the background of a truncated metallothionein protein with a limited Cd-binding capacity. Individuals of L. stagnalis were exposed through 14 days to uncontaminated water (controls) or to low (30 μg · L^-1) or high (50 μg · L^-1) Cd concentrations. The digestive gland of control and low-Cd exposed snails was processed for transcriptional analysis of the Metallothionein (MT) gene expression, and for determination of biomarkers for oxidative stress, toxicity and cellular stress. Digestive gland supernatants of high-Cd exposed snails were subjected to chromatography and subsequent analysis by spectrophotometry. It was shown that the MT system of L. stagnalis is functionally deficient, with a poor Cd responsiveness at both, the transcriptional and the protein expression levels. Instead, L. stagnalis appears to rely on alternative detoxification mechanisms such as Cd binding by phytochelatins and metal inactivation by compartmentalization within the lysosomal system. In spite of this, however, traces of Cd apparently leak out of the pre-determined detoxification pathways, leading to adverse effects, which is clearly indicated by biomarkers of oxidative and cellular stress.

Ecosystem services provided by the exotic bivalves Dreissena polymorpha, D. rostriformis bugensis, and Limnoperna fortunei

The ecosystem services approach to conservation is becoming central to environmental policy decision making. While many negative biological invasion-driven impacts on ecosystem structure and functioning have been identified, much less was done to evaluate their ecosystem services. In this paper, we focus on the often-overlooked ecosystem services provided by three notable exotic ecosystem engineering bivalves, the zebra mussel, the quagga mussel, and the golden mussel. One of the most significant benefits of invasive bivalves is water filtration, which results in water purification and changes rates of nutrient cycling, thus mitigating the effects of eutrophication. Mussels are widely used as sentinel organisms for the assessment and biomonitoring of contaminants and pathogens and are consumed by many fishes and birds. Benefits of invasive bivalves are particularly relevant in human-modified ecosystems. We summarize the multiple ecosystem services provided by invasive bivalves and recommend including the economically quantifiable services in the assessments of their economic impacts. We also highlight important ecosystem disservices by exotic bivalves, identify data limitations, and future research directions. This assessment should not be interpreted as a rejection of the fact that invasive mussels have negative impacts, but as an attempt to provide additional information for scientists, managers, and policymakers.

Metal accumulation in relation to size and body condition in an all-alien species community

Metal pollution is one of the main environmental threats in freshwater ecosystems. Aquatic animals can accumulate these substances and transfer them across the food web, posing risks for both predators and humans. Accumulation patterns strongly vary depending on the location, species, and size (which in fish and crayfish is related to age) of individuals. Moreover, high metal concentrations can negatively affect animals' health. To assess the intraspecific relationship between metal accumulation and size and health (proxied by the body condition) of individuals, the concentration of 14 metals (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, Zn) was analyzed in six alien species from the highly anthropogenically altered Arno River (Central Italy): five fish (Alburnus alburnus, Pseudorasbora parva, Lepomis gibbosus, Ictalurus punctatus, and Silurus glanis) and one crayfish (Procambarus clarkii). We found that in P. clarkii, Cu was negatively related to size, as well as Al in L. gibbosus and Mg for adult I. punctatus. Positive size-dependent relationships were found for Hg in L. gibbosus, Fe in S. glanis, and Cr in juvenile I. punctatus. Only Co and Mg in S. glanis were found to negatively correlate with individual health. Since metal concentrations in animal tissue depend on trade-offs between uptake and excretion, the few significant results suggest different types of trade-offs across different species and age classes. However, only predatory fish species (L. gibbosus, I. punctatus, and S. glanis) presented significant relationships, suggesting that feeding habits are one of the primary drivers of metal accumulation.

Does roundup affect zinc functions in a bivalve mollusk in ex vivo exposure?

Roundup (Rn), a glyphosate-based formulation, is one of the most commonly used herbicides in the world. It affects non-targeted organisms in several ways, including adhesive activity towards metal ions. Zinc (Zn) plays a crucial role in a number of biochemical processes. In this study, we aim to elucidate the direct impact of Rn on Zn accumulation and Zn-dependent activities in the ex vivo system. To this end, we exposed the samples of the digestive gland of a bivalve mollusk Unio tumidus to 3 µM of Rn (calculated as 3 µM of glyphosate), Zn, Zn chelator (N,N,N',N'-Tetrakis(2-pyridylmethyl)ethylenediamine) (TPEN, Tp), and their combinations ZnTp and ZnRn for 17 h. We determined the levels of Zn in the tissue (Zn t) and metallothioneins (Zn-MT), metallothioneins (MTSH), and glutathione (GSH & GSSG), total antioxidant capacity (TAC), lysosomal membrane integrity, and caspase-3 activity. Our study demonstrated that Rn and Tp had different effects on the accumulation and functionality of Zn. Rn did not affect the accumulation of Zn (Zn t, Zn-MT) in the Zn- and ZnRn-groups. On the contrary, Tp produced effects antagonistic to Zn on caspase-3 activity, lysosomal stability, and MTSH concentration. Rn caused particular pro-oxidative effect that decreased GSH level (Rn- and ZnRn-groups) and lysosomal stability (Rn-group). The shared affected index was the GSH/GSSG ratio, which decreased by 2-8 times in each exposure. As the first experience with the application of Tp to indicate Zn activity in mollusks, the study concluded that the ex vivo approach could be useful in the study of numeral aquatic pollutants.

Environmental concentrations of Roundup in combination with chlorpromazine or heating causes biochemical disturbances in the bivalve mollusc Unio tumidus

Bivalve molluscs represent the most recognized bioindicators of freshwater pollution. However, their ability to indicate specific xenobiotics in complex exposures is unclear. In this study, we aimed to track the particular effects of the pesticide Roundup (Rnd) and the antipsychotic drug chlorpromazine (Cpz) on the mussel Unio tumidus at the simpler environmentally relevant models. We treated the mussels by Rnd (17 μg L-1), Cpz (18 μg L-1), the mixture of Rnd and Cpz at 18 °C (RndCpz), and Rnd at 25 °C (RndT) and examined their digestive glands after 14 days of exposure. We analyzed total antioxidant capacity, glutathione (GSH&GSSG) and protein carbonyls levels, total and Zn-related concentrations of metallothioneins (MT and Zn-MT, respectively), the activities of CYP450-related EROD, glutathione S-transferase, cholinesterase, caspase-3, citrate synthase (CS), lysosomal membrane integrity (NRR), and Zn level in the tissue. Shared responses were indicated as the increase of the antioxidant, Zn-MT, and EROD levels, whereas the changes of Zn concentration, NRR, and caspase-3 activity were most diverse compared to control. According to discriminant analysis, complex exposures abolished the individual response traits and intensified the harmful effects that caused a decrease in the Zn level in the RndCpz- and RndT-groups and the loss of lysosomal integrity in the RndT-group. We concluded that multi-marker expertise with the application of integrated indices had benefits when evaluating the effects of complex exposures.

Molecular Impacts of Dietary Exposure to Nanoplastics Combined or Not with Arsenic in the Caribbean Mangrove Oysters (Isognomon alatus)

Nanoplastics (NPs) are anthropogenic contaminants that raise concern, as they cross biological barriers. Metals' adsorption on NPs' surface also carries ecotoxicological risks to aquatic organisms. This study focuses on the impacts of three distinct NPs on the Caribbean oyster Isognomon alatus through dietary exposure. As such, marine microalgae Tisochrysis lutea were exposed to environmentally weathered mixed NPs from Guadeloupe (NPG), crushed pristine polystyrene nanoparticles (PSC), and carboxylated polystyrene nanoparticles of latex (PSL). Oysters were fed with NP-T. lutea at 10 and 100 µg L-1, concentrations considered environmentally relevant, combined or not with 1 mg L-1 pentoxide arsenic (As) in water. We investigated key gene expression in I. alatus' gills and visceral mass. NP treatments revealed significant induction of cat and sod1 in gills and gapdh and sod1 in visceral mass. As treatment significantly induced sod1 expression in gills, but once combined with any of the NPs at both concentrations, basal mRNA levels were observed. Similarly, PSL treatment at 100 µg L-1 that significantly induced cat expression in gills or sod1 in visceral mass showed repressed mRNA levels when combined with As (reduction of 2222% and 34%, respectively, compared to the control). This study suggested a protective effect of the interaction between NPs and As, possibly by decreasing both contaminants' surface reactivity.

Common and particular biochemical responses of Unio tumidus to herbicide, pharmaceuticals and their combined exposure with heating

The priority list of freshwater pollutants is increasingly amended by pharmaceuticals. Their impact on the aquatic biota can be modulated by the presence of typical pollutants, like pesticides, and/or abnormal heating. The aim of this study was to elucidate potentially hazardous impact of combined environmental factors on the freshwater mussels by analyzing various sets of biochemical markers. We treated the bivalve molluscs of Unio tumidus with non-steroidal anti-inflammatory drug diclofenac (Dc, 2 nM), calcium antagonist and antihypertensive drug nifedipine (Nf, 2 nM) or organophosphonate glyphosate-based herbicide Roundup MAX (Rn, 79 nM of glyphosate) at 18 °C as well as with the mixture of these substances at 18 °C (Mix) or 25 °C (MixT) during 14 days. The concentrations used were correspondent to the environmentally relevant levels. The biomarkers of stress and toxicity were evaluated in digestive gland, except the lysosomal membrane stability measured in hemocytes. Exposures caused an oxidative stress due to the decreased SOD and GST activities and GSH/GSSG ratio, increased levels of thiobarbituric acid-reactive substances and protein carbonyls (with some exceptions). Dc increased cathepsin D activity in lysosomes. Nf increased lysosomal membrane stability and caspase-3 activity. Rn caused a dramatic distortion of metallo-thiolome due to increased levels of GSH and metallothionein-related thiols (MTSH) as well as depletion of Zn, Cu and Cd in the composition of metallothioneins, and decreased Zn/Cu molar ratio in the tissue. The particular toxicity of Rn was also attested by decreased lysosomal membrane stability and cholinesterase activity. Canonical discriminant analysis separated Rn-, Mix- and MixT-groups from the joint set of C-, Dc- and Nf-groups. Generally, compound-specific effects were expressed in U. tumidus responses to the mixtures, but in MixT-group some effects were particular or extremely strong. Multi-marker approach and integrative analysis proved to be a useful tool for understanding possible future risks to freshwater mussels under a combination of xenobiotics and warming climate.

Combining metal and stable isotope analyses to disentangle contaminant transfer in a freshwater community dominated by alien species

Freshwater ecosystems are negatively impacted by various pollutants, from agricultural, urban and industrial wastewater, with metals being one of the largest concerns. Moreover, freshwater ecosystems are often affected by alien species introductions that can modify habitats and trophic relationships. Accordingly, the threat posed by metals interacts with those by alien species, since the latter can accumulate and transfer these substances across the food web to higher trophic levels. How metals transfer within such communities is little studied. We analysed the concentration of 14 metals/metalloids (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb, Se, Zn, hereafter 'metal(s)') of eight fish and three crustacean species co-existing in the Arno River (Central Italy), most of which were alien. To assess the pathway of contaminants within the community, we coupled metal analysis with carbon and nitrogen stable isotope analysis derived from the same specimens. Crustaceans showed higher metal concentration than fish, except for Cd, Hg and Se that were higher in fish. We found evidence of trophic transfer for six metals (Cd, Cr, Hg, Mg, Se, Zn). Additionally, ontogenetic differences and differences among various fish tissues (muscle, liver, and gills) were found in metals concentration. Considerable biomagnification along the trophic chain was found for Hg, while other metals were found to biodilute. Using stable isotopes and Hg as a third diet tracer, we refined the estimations of consumed preys in the diet previously reconstructed with stable isotope mixing models. Alien species reach high biomass and can both survive to and accumulate high pollutants concentrations, potentially posing a risk for their predators and humans. A combined effect of environmental filtering and increased competition may potentially contribute to the disappearance of native species with lower tolerances.