The influence of salinity on copper accumulation and its toxic effects in estuarine animals with differing osmoregulatory strategies

Assessment of Amphibola crenata as a bioindicator of estuarine trace element pollution using biochemical and physiological endpoints

To assess its utility as a bioindicator of estuarine contamination, Amphibola crenata, a pulmonate mud snail, was collected from 17 estuaries in New Zealand. Whole-body soft tissue trace element concentrations were measured via quadrupole inductively coupled plasma mass spectrophotometer (Q-ICP-MS) and were found to be significantly positively correlated with sediment trace element profiles for arsenic, copper and lead. Snails from polluted estuaries generally displayed higher ammonia excretion rates, elevated whole-body soft tissue catalase activity and lipid peroxidation compared to snails from reference sites. Across all sites haemolymph glucose was positively correlated with the tissue burdens of arsenic, copper, nickel and zinc, while haemolymph protein was negatively correlated with arsenic, cadmium and zinc soft tissue concentrations, indicative of altered energy metabolism associated with trace element contamination. Overall, sites were distinguishable by application of the array of measures employed. Our findings suggest that gastropods have significant value as bioindicators of estuarine health.

Comprehensive effects of salinity, dissolved organic carbon and copper on mortality, osmotic regulation and bioaccumulation of copper in Oryzias melastigma

Cu, as an essential and toxic element, has gained widespread attention. Both salinity and dissolved organic carbon (DOC) are known to influence Cu toxicity in marine organisms. However, the intricate interplay between these factors and their specific influence on Cu toxicity remains ambiguous. So, this study conducted toxicity tests of Cu on Oryzias melastigma. The experiments involved three salinity levels (10, 20, and 30 ppt) and three DOC levels (0, 1, and 5 mg/L) to comprehensively investigate the underlying mechanisms of toxicity. The complex toxic effects were analyzed by mortality, NKA activity, net Na+ flux and Cu bioaccumulation in O. melastigma. The results indicate that Cu toxicity is notably influenced by both DOC and salinity. Interestingly, the discernible variation in Cu toxicity across different DOC levels diminishes as salinity levels increase. The presence of DOC enhances the impact of salinity on Cu toxicity, especially at higher Cu concentrations. Additionally, Visual MINTEQ was utilized to elucidate the chemical composition of Cu, revealing that DOC had a significant impact on Cu forms. Furthermore, we observed that fluctuations in salinity lead to the inhibition of Na+/K+-ATPase (NKA) activity, subsequently hindering the inflow of Na+. The effects of salinity and DOC on the bioaccumulation of copper were not significant. The influence of salinity on Cu toxicity is mainly through its effect on the osmotic regulation and biophysiology of O. melastigma. Additionally, DOC plays a crucial role in the different forms of Cu. Moreover, DOC-Cu complexes can be utilized by organisms. This study contributes to understanding the mechanism of copper's biological toxicity in intricate marine environments and serves as a valuable reference for developing marine water quality criteria for Cu.

A comprehensive review of the effects of salinity, dissolved organic carbon, pH, and temperature on copper biotoxicity: Implications for setting the copper marine water quality criteria

In recent years, there has been a growing concern about the ecological hazards associated with copper, which has sparked increased interest in copper water quality criteria (WQC). The crucial factors affecting the bioavailability of copper in seawater are now acknowledged to be salinity, dissolved organic carbon (DOC), pH, and temperature. Research on the influence of these four water quality parameters on copper toxicity is rapidly expanding. However, a comprehensive and clear understanding of the relevant mechanisms is currently lacking, hindering the development of a consistent international method to establish the seawater WQC value for copper. As a response to this knowledge gap, this study presents a comprehensive summary with two key focuses: (1) It meticulously analyzes the effects of salinity, DOC, pH, and temperature on copper toxicity to marine organisms. It takes into account the adaptability of different species to salinity, pH and temperature. (2) Additionally, the study delves into the impact of these four water parameters on the acute toxicity values of copper on marine organisms while also reviewing the methods used in establishing the marine WQC value of copper. The study proposed a two-step process: initially zoning based on the difference of salinity and DOC, followed by the establishment of Cu WQC values for different zones during various seasons, considering the impacts of water quality parameters on copper toxicity. By providing fundamental scientific insights, this research not only enhances our understanding and predictive capabilities concerning water quality parameter-dependent Cu toxicity in marine organisms but also contributes to the development of copper seawater WQC values. Ultimately, this valuable information facilitates more informed decision-making in marine water quality management efforts.

Transgenerational effects of microplastics on Nrf2 signaling, GH/IGF, and HPI axis in marine medaka Oryzias melastigma under different salinities

Little information is available on the toxicity of microplastics (MPs) under different salinities in aquatic organisms. Consequently, the effects of larvae exposure to 180 μg/L MPs with 5.0 μm diameter on growth, antioxidant capacity and stress response were investigated in exposed F1 larvae and unexposed F2 larvae in marine medaka Oryzias melastigma at 5 ‰ and 25 ‰ salinities. Poor growth performance of F1 and F2 larvae and F1 adult fish was merely found under high salinity, as well as changes in the growth hormone/insulin-like growth factor-I (GH/IGF). Although malondialdehyde (MDA) content and antioxidant capacity remained constant in F1 larvae under high salinity, MPs increased MDA content and reduced antioxidant capacity in F2 larvae. Contrarily, MDA and antioxidant capacity increased in F1 and F2 larvae under low salinity. The mRNA expression levels of genes in the NF-E2-related factor 2 (Nrf2) pathway were dysregulated. Cortisol levels in the whole body increased in F1 larvae and recovered to the control level under low salinity while cortisol levels declined in F1 larvae and increased in F2 larvae under high salinity, which was related to the transcriptional regulation of the hypothalamus-pituitary-interrenal (HPI) axis genes. To summary, the present study determined the toxic effects of MPs on growth, antioxidant capacity, and stress response by disturbing Nrf2, HPI, and GH/IGF signaling in exposed larvae and unexposed offspring of marine medaka in a salinity-dependent manner. For the first time, our results highlight the interference effects of salinity on MPs toxicity in fish.

Early life stage exposure to cadmium and zinc within hour affected GH/IGF axis, Nrf2 signaling and HPI axis in unexposed offspring of marine medaka Oryzias melastigma

Information on transgenerational effects of cadmium (Cd) and zinc (Zn) within hour of exposure is scarce. To the end, larvae of marine medaka Oryzias melastigma at 0 day-post-hatching (dph) were subjected to LC₅₀ for 96-h of Cd or Zn for 0.5 and 6 h, and then transferred into clear water for 95 days until the generation of offspring larvae at 25 dph. Growth, antioxidant capacity and stress response in offspring larvae were examined. Exposure to Zn for 0.5 h or Cd for 0.5 h and 6 h promoted growth performance and reduced total antioxidant capacity (TAC) and activities of superoxide dismutase (SOD) and catalase (CAT). Malondialdehyde (MDA) and cortisol levels declined in larvae following Zn exposure for 0.5 h, whereas Cd exposure increased MDA content and did not affect cortisol levels. These physiological changes could be partially explained by transcription of genes in the hormone/insulin-like growth factor-I (GH/IGF) axis, NF-E2-related factor 2 (Nrf2) signaling, and hypothalamus-pituitary-interrenal (HPI) axis. For example, Zn exposure for 0.5 h up-regulated genes encoding growth hormone (gh) and insulin-like growth factor binding protein (igfbp1) and down-regulated mRNA levels of nrf2, Kelch-like-ECH-associated protein 1 gene (keap1a), keap1b, sod1, mineralocorticoid receptor (mr), corticotropin-releasing hormone receptor (crhr1), corticotropin-releasing hormone binding protein (crhbp), cytochrome P450 (cyp11a1, cyp17a1) and hydroxysteroid dehydrogenase (hsd3b1). Cd exposure for 0.5 and 6 h up-regulated growth hormone release hormone (ghrh) and igfbp1, down-regulated nrf2 and keap1a, and did not affect mRNA levels of HPI axis genes. Taken together, this study demonstrated that short-term metal exposure during larvae phase had positive and negative effects on offspring even after a long recovery.

Use of non-linear multiple regression models for setting water quality criteria for copper: Consider the effects of salinity and dissolved organic carbon

Cu pollution is a global concern because of its high toxicity and persistence. Few investigations have been conducted on the effects of salinity and dissolved organic carbon (DOC) on Cu toxicity and water quality criteria (WQC). To analyze their impact on the WQC of Cu, non-linear multiple regression (NLMR) models based on salinity and DOC were constructed. The NLMR models demonstrated that when salinity increased, the toxicity values for Cu on fish, mollusca, rotifer, and echinodermata first increased and then declined, whereas those for arthropoda and algae increased. These findings demonstrate that salinity has a substantial impact on Cu toxicity, primarily owing to changes in physiological activity. The original and corrected WQC values in the upper, middle, and outer regions of the Yangtze Estuary were derived based on the species sensitivity distribution method. These values were 1.49, 3.49, 8.86, and 0.87 μg·L^-1. An important finding was that lower Cu concentrations in the outer areas posed the highest ecological risk owing to the effects of salinity and DOC. NLMR models are applicable to other coastal areas worldwide. This provides valuable information for the establishment of an accurate and protective estuary for Cu-related WQC.

Copper exposure does not alter the ability of intertidal sea cucumber Cucumaria miniata to tolerate emersion during low tide

Intertidal animals experience cycles of tidal emersion from water and are vulnerable to copper (Cu) exposure due to anthropogenic toxicant input into marine waters. Both emersion and Cu toxicity can cause damage to physiological processes like aerobic metabolism, ammonia excretion, and osmoregulation, but the interactions of the combination of these two stressors on marine invertebrates are understudied. Mixed effects of 96 h of low and high Cu exposure (20 and 200 μg/L) followed by 6 h of tidal emersion were evaluated on the intertidal sea cucumber Cucumaria miniata. The respiratory tree accumulated the highest concentrations of Cu, followed by the introvert retractor muscle, body wall, and coelomic fluid. Emersion affected accumulation of Cu, perhaps by inhibiting excretion. 200 μg/L of Cu increased lactate production in the respiratory tree, indicative of damaged aerobic metabolism. Cu diminished ammonia excretion, but emersion increased oxygen uptake and ammonia excretion upon re-immersion. The combination of the two stressors did not have any interactive effects on metabolism or ammonia excretion. Neither Cu exposure nor emersion altered ion (sodium, potassium, calcium, magnesium) content of the coelomic fluid. Overall, results of this study suggest that Cu exposure does not alter C. miniata's high tolerance to emersion, and some potential strategies that this species uses to overcome environmental stress are illuminated.

Application of phosphorus amendments reduces metal uptake and increases yield of Oryza saliva L. (rice) in Cd/Cu-contaminated paddy field

To alleviate worldwide food safety issues caused by metal contamination, an easily available material is urgently needed for extensive application. In this study, calcium magnesium phosphate fertiliser (Pcm) was applied to a Cd/Cu co-contaminated paddy field in comparison with limestone and organic fertiliser. The results showed that only Pcm is effective in simultaneously reducing Cd uptake by 56.7% and Cu uptake by 36.2% in Oryza saliva L. (rice). The rice yield, reduced mainly by Cu, also increased by 30.1% with respect to the enhancement of soil pH, cation exchange capacity and availability of phosphorus, as well as the reduction in availabilities of Cd and Cu. Additionally, Pcm dramatically shaped the bacterial community structure, with Proteobacteria and Firmicutes predominant in the soils. The beneficial genera Exiguobacterium, Citrobacter, and Acinetobacter, which are vital for phosphate dissolution and Cd/Cu immobilisation, were also enriched. The results demonstrated that the application of Pcm at 0.4% (w:w) was able to enhance both crop quantity and quality in Cd/Cu co-contaminated paddy fields by reducing Cu/Cd availability, promoting rice yield, and reshaping bacterial community structures.

Seasonal variation, contribution and dynamics of trace elements in the drainage basin and estuary of the Serinhaém river, BA

In the present study a mass balance calculation was used to quantify trace elements (Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb, Ti, V and Zn) fluxes exported from the Serinhaém River estuary to the Atlantic Ocean. The studied elements exportation in the particulate fraction showed higher fluxes in the first sampling campaign and a high export rate to the Atlantic Ocean during this period. The physical-chemical parameters showed the highest values in sampling campaign 1. These variations are probably the cause of the different trace elements behavior in fluvial and estuarine areas, where removal and addition processes between particulate and dissolved phases took place, affecting distribution coefficient and fluxes to the Atlantic Ocean. EPA ecosystems present values in accordance with Brazilian legislation for pristine areas, however, monitoring programs must be carried out in the region, to avoid future environmental problems.

Physiological and biochemical responses of the estuarine pulmonate mud snail, Amphibola crenata, sub-chronically exposed to waterborne cadmium

Physiological and biochemical responses of the pulmonate mud snail, Amphibola crenata, to waterborne cadmium (Cd) were investigated to determine the mechanisms of toxicity and impacts of a 21-d Cd exposure. Mud snails were exposed to nominal Cd concentrations of 0, 0.2, 4 and 8 mg L ^- 1 and bioaccumulation, whole animal physiological (oxygen consumption, ammonia excretion and oxygen:nitrogen), and tissue level biochemical (catalase activity, lipid peroxidation, glycogen, glucose and protein) endpoints were measured every 7 days. At the two highest Cd exposure concentrations complete mortality was observed over 21-d. In surviving animals, oxygen consumption declined and ammonia excretion rate increased with Cd exposure concentration and duration. The increased ammonia excretion likely reflected enhanced protein metabolism as suggested by a reduced oxygen:nitrogen (O:N). Increasing waterborne Cd concentration and exposure time led to increasing metal accumulation in all tissues. The snail viscera showed the highest Cd accumulation. Both catalase activity and lipid peroxidation in the viscera significantly increased with Cd exposure concentration and time, whereas, the foot muscle and remaining tissues (kidney, mantle, remaining digestive tissues and heart) showed increased catalase activity and lipid peroxidation at higher Cd concentrations (4 and 8 mg L ^- 1), suggestive of an effect of Cd on oxidative stress. Over the course of 21 days, Cd exposure resulted in significantly lower levels of glycogen in viscera relative to Cd-free controls, reflecting an increased energy demand. Haemolymph glucose rose initially and then fell with increased exposure duration, while haemolymph protein generally exhibited an increased concentration in Cd-exposure groups, reflecting the changes in energy substrates noted for somatic tissues. These results suggest that the physiological and biochemical responses of A. crenata to Cd are conserved relative to other aquatic animals, and were tissue-specific, dose- and time-dependant.

Toxic metal and metalloid contamination in seafood from an eutrophic Brazilian estuary and associated public health risks

Guanabara Bay (GB) is a highly contaminated estuarine system and an important fishing area in Southeastern Brazil. In this regard, knowledge concerning the association of certain contaminants in seafood to abiotic factors and human health risk assessments is still understudied. Therefore, this study aimed to quantify nine toxic elements in highly consumed crabs, shrimp, and squid, and associate the results with abiotic factors. A human health risk assessment was also performed. Our findings indicate that crabs are the main bioaccumulators. Transparency and depth were noteworthy for all three taxonomic groups. In general, contaminant concentrations were below the limits established by different international agencies, except for As, which was higher than the Brazilian limit (1 mg kg^-1). However, the Hazard Index identified risks to consumer health for the ingestion of seafood. This study emphasizes the importance of jointly evaluating different toxic elements, for a more accurate health risk assessment.

A Mini-review of the Toxicity of Pollutants to Fish Under Different Salinities

In recent years, with the development of the global economy, water pollution has increased. Pollutants migrate, accumulate, and diffuse in aquatic environments. Most of the pollutants eventually enter aquatic organisms. The accumulation of pollutants affects the development and reproduction of organisms, and many pollutants have teratogenic, carcinogenic, and/or mutagenic effects. Aquatic organisms in estuaries and coastal areas are under pressure due to both salinity and pollutants. Among them, salinity, as an environmental factor, may affect the behavior of pollutants in the aquatic environment, causing changes in their toxic effects on fishes. Salinity also directly affects the growth and development of fishes. Therefore, this paper focuses on metals and organic pollutants and discusses the toxic effects of pollutants on fish under different salinities. This research is of great significance to environmental protection and ecological risk assessment of aquatic environments.

A Systematic Review on Metal Dynamics and Marine Toxicity Risk Assessment Using Crustaceans as Bioindicators

Metals, many of which are potentially toxic, are present in the aquatic environment originated from both natural and anthropogenic sources. In these ecosystems, these elements are mostly deposited in the sediment, followed by water dissolution, potentially contaminating resident biota. Among several aquatic animals, crustaceans are considered excellent bioindicators, as they live in close contact with contaminated sediment. The accumulation of metal, whether they are classified as essential, when in excessive quantities or nonessential, not only cause damage to the health of these animals, but also to the man who consumes seafood. Among the main toxic elements to animal and human health are aluminum, arsenic, cadmium, chromium, copper, lead, mercury, nickel and silver. In this context, this systematic review aimed to investigate the dynamics of these metals in water, the main bioaccumulative tissues in crustaceans, the effects of these contaminants on animal and human health, and the regulatory limits for these metals worldwide. A total of 91 articles were selected for this review, and an additional 68 articles not found in the three assessed databases were considered essential and included, totaling 159 articles published between 2010 and 2020. Our results indicate that both chemical speciation and abiotic factors such as pH, oxygen and salinity in aquatic environments affect element bioavailability, dynamics, and toxicity. Among crustaceans, crabs are considered the main bioindicator biological system, with the hepatopancreas appearing as the main bioaccumulator organ. Studies indicate that exposure to these elements may result in nervous, respiratory, and reproductive system effects in both animals and humans. Finally, many studies indicate that the concentrations of these elements in crustaceans intended for human consumption exceed limits established by international organizations, both with regard to seafood metal contents and well as daily, weekly, or monthly intake limits set for humans, indicating consumer health risks.

Interactions between mercury and environmental factors: A chemometric assessment in seafood from an eutrophic estuary in southeastern Brazil

Guanabara Bay (GB) is an estuary in Brazil, constantly the target of pollutants, such as mercury (Hg). Thus, our study aimed to evaluate (i) total mercury (THg) content in shrimp and squid species from GB; (ii) associate THg content to contamination in swimming crabs; (iii) explore potential differences between species, and size; (iv) correlate abiotic water data to the determined THg contents; (v) verify if Hg concentrations are below acceptable limits. Swimming crabs showed greater Hg contamination compared to other species. For shrimp only biometric variables are related to Hg, while for squid, only abiotic. Only squids did not show a correlation between Hg and animal size. Finally, the detected Hg values are below the tolerable limits established by legislations. Our results indicate that the dynamics of Hg contamination differs between groups and that further studies are needed to elucidate the mechanisms that affect bioaccumulation in different species.

Toxic effects of metal copper stress on immunity, metabolism and pathologic changes in Chinese mitten crab (Eriocheir japonica sinensis)

Copper (Cu²⁺), which represents a major physiological challenge for crab culture, is ubiquitous in the aquatic culture environment, and gills are the first organs that come into direct contact with the environment. However, the molecular basis of the response of crabs to Cu²⁺ stress remains unclear. Here, we conducted a transcriptome and differential expression analysis on the gills from Chinese mitten crab unexposed and exposed to Cu²⁺ for 24 h. The comparative transcriptome analysis identified 2486 differentially expressed genes (DEGs). GO functional analysis and KEGG pathway analysis revealed some DEGs, which were mostly related to immunity, metabolism, osmotic regulation, Cu²⁺ homeostasis regulation, antioxidant activity, and detoxification process. Some pathways related to humoral and cellular immunity, such as phagosome, peroxisome, lysosome, mTOR signaling pathway, PI3K-Akt signaling pathway, Toll-like receptor signaling pathway, and T cell receptor signaling pathway were enhanced under Cu²⁺ stress. In addition, Cu²⁺ stress altered the expression patterns of key phagocytosis and apoptosis genes (lectin, cathepsin L, Rab7, and HSP70), confirming that Cu²⁺ can induce oxidative stress and eventually even apoptosis. Histological analysis revealed that the copper can induce damage at the cellular level. This comparative transcriptome analysis provides valuable molecular information to aid future study of the immune mechanism of Chinese mitten crab in response to Cu²⁺ stress and provides a foundation for further understanding of the effects of metal toxicity.

Modelling copper toxicokinetics in the zebra mussel, Dreissena polymorpha, under chronic exposures at various pH and sodium concentrations

The stenohaline zebra mussel, Dreissena polymorpha, is uniquely sensitive to the ionic composition of its aquatic environment. Waterborne copper (Cu) uptake and accumulation in zebra mussels were examined at various conditions in an environmentally relevant range in freshwater, i.e. Cu exposure levels (nominal concentrations of 25 and 50 μg/L), pH (5.8-8.3), and sodium (Na⁺) concentrations (up to 4.0 mM). Copper accumulation was simulated by a kinetic model covering two compartments, the gills and the remaining tissues. The Cu uptake rate constant decreased with decreasing pH from 8.3 down to 6.5, indicating interactions between H⁺ and Cu at uptake sites. The kinetic simulation showed dose-dependent effects of Na⁺ on Cu uptake. At 25 μg/L Cu, addition of Na⁺ at 0.5 mM significantly inhibited the Cu uptake rate, while no significant differences were found in the uptake rate upon further addition of Na⁺ up to a concentration of 4.0 mM. At 50 μg/L Cu, the Cu uptake rate was not influenced by Na⁺ addition. Calibration results exhibited dose-dependent elimination rates with more profound elimination with increasing exposure levels. With kinetic parameters calibrated at environmentally relevant conditions, in terms of pH and Na⁺ concentrations, the model performed well in predicting Cu accumulation based on independent data sets. Estimates of the Cu concentration in mussels were within a factor of 2 of the measurements. This demonstrates potential application of kinetic models that are calibrated in environmentally relevant freshwater conditions.

The preparation of calcium phosphate adsorbent from natural calcium resource and its application for copper ion removal

Using the hen eggshells (biowaste) as a source of calcium and an environmentally friendly approach, the nanopowder composed of 74% of hydroxyapatite (HA) and 26% of β-tricalcium phosphate (β-TCP) was obtained. Due to the maximum reduction of the stages associated with the use of chemicals and energy, this method can be considered as economically and environmentally friendly. A well-developed surface area and the negative zeta potential at pH above 3.5 indicate good adsorption properties of this material. The obtained material shows high adsorption capacity towards Cu²⁺ ions, i.e. 105.4 mg/g at pH 5. Good fit of the Langmuir adsorption model and the pseudo-second-order kinetic model may indicate chemical adsorption probably due to the electrostatic interactions between the Cu²⁺ cations and the negatively charged phosphate and hydroxyl groups on the material surface.

Dredging Activities Carried Out in a Brazilian Estuary Affect Mercury Levels in Swimming Crabs

(1) Although suffers from intense pollution inputs, Guanabara Bay, the most socioeconomically and environmentally important estuary in Rio de Janeiro, Brazil, is still home to a diverse fauna, including several fish and crab species consumed by humans. The bay presents high sedimentation rates and sediment contamination, further aggravated by dredging processes carried out in recent years. In this context, this study aimed to verify the effect of the dredging process on total mercury (THg) concentrations at Guanabara Bay through swimming crab assessments sampled before (2016), during (2017), and after (2018) the dredging process, and mainly, if the detected concentrations can be harmful to consumer health; (2) Methods: Swimming crab samplings were carried out at the same time and sampling points in 2016, 2017 and 2018 and the total Hg was determined using a Direct Mercury Analyzer (DMA-80, Milestone, Bergamo, Italy); (3) Results: Increased Hg concentrations were observed during the dredging process, decreasing to lower values, close to the initial concentrations, at the end of the process. Some of the investigated abiotic factors favor Hg dynamics in the aquatic environment, while others were positively altered at some of the assessed sampling areas at the end of the dredging process; (4) Conclusions: Although crab Hg levels were below maximum permissible limits for human consumption, it is important to note that these animals are significantly consumed around Guanabara Bay, which may lead to public health issues in the long term.

Influence of Cu2+ Ions on the Corrosion Resistance of AZ31 Magnesium Alloy with Microarc Oxidation

The objectives of this study were to reduce the corrosion rate and increase the cytocompatibility of AZ31 Mg alloy. Two coatings were considered. One coating contained MgO (MAO/AZ31). The other coating contained Cu²⁺ (Cu/MAO/AZ31), and it was produced on the AZ31 Mg alloy via microarc oxidation (MAO). Coating characterization was conducted using a set of methods, including scanning electron microscopy, energy-dispersive spectrometry, X-ray photoelectron spectroscopy, and X-ray diffraction. Corrosion properties were investigated through an electrochemical test, and a H₂ evolution measurement. The AZ31 Mg alloy with the Cu²⁺-containing coating showed an improved and more stable corrosion resistance compared with the MgO-containing coating and AZ31 Mg alloy specimen. Cell morphology observation and cytotoxicity test via Cell Counting Kit-8 assay showed that the Cu²⁺-containing coating enhanced the proliferation of L-929 cells and did not induce a toxic effect, thus resulting in excellent cytocompatibility and biological activity. In summary, adding Cu ions to MAO coating improved the corrosion resistance and cytocompatibility of the coating.

PET microplastics toxicity on marine key species is influenced by pH, particle size and food variations

This study aims to evaluate effects induced by the exposure of key marine species to leachates and suspensions of different particle-size of PET microparticles, a plastic polymer that is actually considered safe for the environment. Leachates and suspensions of small (5-60 μm); medium (61-499 μm) and large (500-3000 μm) PET were tested on bacteria (V. fischeri; UNI EN ISO 11348-3:2009), algae (P. tricornutum; UNI EN ISO 10253:2016E), and echinoderms (P. lividus; EPA 600/R-95-136/Section 15) species both under standard (8.0) and acidified (7.5) pH conditions. Results obtained show that: i) conversely to larval stage of P. lividus, bacterial and algal tested species are not sensitive to PET pollution under all tested conditions; ii) different tested particle-sizes of PET produce effects that are not always related to their particle-size; iii) differences comparing acidified and standard pH conditions were recorded; iv) concerning echinoderms, food availability produce significant differences compared to fasting conditions; v) special attention on the possible interactions between MPs and other stressors (e.g., food and pH) is needed in order to give a better picture of natural occurring dynamics on marine ecosystems especially in the future frame of global changes.

Does physiological tolerance to acute hypoxia and salinity change explain ecological niche in two intertidal crab species?

Intertidal biota is subjected to significant fluctuations in environmental parameters such as salinity and dissolved oxygen (DO). In the current study, the effects of salinity and DO on metabolic rate, critical oxygen partial pressure (P crit), heart rate and osmoregulation in two intertidal crab species commonly found on New Zealand coastlines, Hemigrapsus crenulatus and Hemigrapsus sexdentatus, were measured. Based on its habitation of burrows in the lower intertidal zone, H. crenulatus was predicted to be more resilient to these environmental stressors than H. sexdentatus, which is distributed in the mid to high tidal zone. However, relative to the full-strength seawater control, there were no consistent salinity-dependent changes in respiratory or cardiovascular endpoints in either species following acute 6-h exposures mimicking a tidal cycle. Analysis of haemolymph osmolality and ions determined that both crab species were strong osmotic and ionic regulators over the 6-h exposure period. However, the threshold salinities at which significant changes in osmotic and ionic regulation occurred did differ and generally indicated that H. crenulatus was the better regulator. Respiratory and cardiovascular responses to DO were prominent, with a strong bradycardia observed in both species. Changes in osmolality and sodium ion regulation were also seen as DO declined. The effect on sodium ion levels had its onset at a higher oxygen partial pressure in H. sexdentatus than in H. crenulatus, indicative of a relatively poorer hypoxia tolerance in the former species. The relative resilience of respiratory, cardiovascular and osmoregulatory processes to salinity and DO variations likely contribute to distinct habitat distributions of the two crab species on New Zealand shorelines, although behaviour and inter-specific interactions may also play important roles. Environmental change, in the form of coastal erosion and anthropogenic contamination of estuaries, has the potential to disturb the delicate niche separation that exists between these species.

Genotoxic Response and Mortality in 3 Marine Copepods Exposed to Waterborne Copper

Copper (Cu) is an essential trace metal, but may also be toxic to aquatic organisms. Although many studies have investigated the cytotoxicity of Cu, little is known about the in vivo genotoxic potential of Cu in marine invertebrates. We investigated the genotoxicity of Cu in 2 pelagic calanoid copepods, Acartia tonsa and Temora longicornis, and the intertidal harpacticoid copepod Tigriopus brevicornis by exposing them for 6 and 72 h to waterborne Cu (0, 6, and 60 µg Cu/L). A subsequent 24-h period in filtered seawater was used to investigate delayed effects or recovery. Genotoxicity was evaluated as DNA strand breaks in individual copepods using the comet assay. Copper did not increase DNA strand breaks in any of the species at any concentration or time point. The treatment did, however, cause 100% mortality in A. tonsa following exposure to 60 µg Cu/L. Acartia tonsa and T. longicornis were more susceptible to Cu-induced mortality than the benthic harpacticoid T. brevicornis, which appeared to be unaffected by the treatments. The results show major differences in Cu susceptibility among the 3 copepods and also that acute toxicity of Cu to A. tonsa is not directly associated with genotoxicity. We also show that the comet assay can be used to quantify genotoxicity in individual copepods. Environ Toxicol Chem 2019;38:2224-2232. © 2019 SETAC.

Increased sensitivity of subantarctic marine invertebrates to copper under a changing climate - Effects of salinity and temperature

Stressors associated with climate change and contaminants, resulting from the activities of humans, are affecting organisms and ecosystems globally. Previous studies suggest that the unique characteristics of polar biota, such as slower metabolisms and growth, and the generally stable conditions in their natural environment, cause higher susceptibility to contamination and climate change than those in temperate and tropical areas. We investigated the effects of increased temperature and decreased salinity on copper toxicity in four subantarctic marine invertebrates using realistic projected conditions under a future climatic change scenario for this region. We hypothesised that these relatively subtle shifts in environmental stressors would impact the sensitivity of cold-adapted species to copper. The four test species were: a copepod Harpacticus sp.; isopod Limnoria stephenseni; flatworm Obrimoposthia ohlini; and bivalve Gaimardia trapesina. These species occupy a range of ecological niches, spanning intertidal and subtidal nearshore zones. We predicted that species would differ in their tolerance to stressors, depending on where they occurred within this ecological gradient. Organisms were exposed to the multiple stressors in a factorial design in laboratory based toxicity tests. Sensitivity estimates for copper (LC50) were calculated using a novel statistical approach which directly assessed the impacts of the multiple stressors. In three of the four species tested, sensitivity to copper was amplified by small increases in temperature (2-4 °C). The effects of salinity were more variable but a decrease of as little as 2 ppt caused a significant effect in one species. This study provides some of the first evidence that high latitude species may be at increased risk from contaminants under projected future climate conditions. This interaction, between contaminants and the abiotic environment, highlights a potential pathway to biodiversity loss under a changing climate.

Comparative copper sensitivity between life stages of common subantarctic marine invertebrates

The development of environmental guidelines in the Antarctic and subantarctic is essential, because expansion of research, tourism, and fishing is placing these regions at increasing risk of contamination. Data are currently insufficient to create the region-specific guidelines needed for the unique conditions in these areas. To develop the most appropriate environmental guidelines, data from the most sensitive life stages of a species should be included to ensure effective protection throughout its life cycle. It is generally accepted that early life stages are more sensitive to contaminants. We compared the toxicity of copper between juvenile and adult life stages of 4 subantarctic marine invertebrates using sublethal and lethal endpoints. For 2 of the species tested, juveniles were more sensitive than adults. (The 7-d median effect concentration [EC50] values for the gastropod Laevilittorina caliginosa were 79 μg/L at the juvenile stage and 125 μg/L at the adult; for the flatworm Obrimoposthia ohlini, values were 190 μg/L at the juvenile stage and 300 μg/L at the adult.) For the isopod Limnoria stephenseni, juveniles were either more sensitive or of equal sensitivity to adults (7-d EC50 values: juvenile 278 μg/L and adult 320 μg/L). In contrast, for the bivalve Gaimardia trapesina, adults appeared to be more sensitive than young adults (7-d EC50 values: juvenile 23 μg/L and adult <10-20 μg/L). Although no consistent trend in the sensitivity of life history stages was observed, the present study contributes important information for the development of water quality guidelines in polar regions. Environ Toxicol Chem 2018;37:807-815. © 2017 SETAC.

Alterations of larval photo-dependent swimming responses (PDR): New endpoints for rapid and diagnostic screening of aquatic contamination

Detection and toxicity assessment of waterborne contaminants are crucial for protecting human health and the environment. Development of easy-to-implement, rapid and cost-effective tools to measure anthropogenic effects on watersheds are critical for responsible management, particularly in times of increasing development and urbanization. Traditionally, environmental toxicology has focused on limited endpoints, such as lethality and fertility, which are directly affecting population levels. However, more sensitive readings are needed to assess sub-lethal effects. Monitoring of contaminant-induced behavior alterations was proposed before, but is difficult to implement in the wild and performing it in aquatic laboratory models seem more suited. For this purpose, we adapted a photo-dependent swimming response (PDR) that was previously described in zebrafish larva. We first asked if PDR was present in other aquatic animals. We measured PDR in larvae from two freshwater prawn species (Macrobrachium rosenbergii, MR, and Macrobrachium carcinus, MC) and from another fish the fathead minnow (FHM, Pimephales promelas). In all, we found a strong and reproducible species-specific PDR, which is arguing that this behavior is important, therefore an environmental relevant endpoint. Next, we measured PDR in fish larvae after acute exposure to copper, a common waterborne contaminant. FHM larvae were hyperactive at all tested concentrations in contrast to ZF larvae, which exhibited a concentration-dependent hyperactivity. In addition to this well-accepted anxiety-like behavior, we examined two more: photo-stimulated startle response (PSSR) and center avoidance (CA). Both were significantly increased. Therefore, PDR measures after acute exposure to this waterborne contaminant provided as sensitive readout for its detection and toxicity assessment. This approach represents an opportunity to diagnostically examine any substance, even when present in complex mixtures like ambient surface waters. Mechanistic studies of toxicity using the extensive molecular tool kit of ZF could be a direct extension of such approaches.

Copper-induced metabolic variation of oysters overwhelmed by salinity effects

In estuarine environments, Cu (copper) contamination is simultaneously coupled with salinity variation. In this study, ¹H NMR was applied to investigate the metabolic disturbance of estuarine oysters Crassostrea hongkongensis under both Cu and salinity stresses. Oysters were exposed to dissolved Cu (50 μg L^-1) at different salinities (10, 15 and 25 psu) for six weeks, and the Cu accumulation in the oyster tissues was higher at lowered salinity. Based on the NMR-metabolomics results, disturbances induced by Cu and salinity was mainly related to osmotic regulation, energy metabolism and glycerophospholipid metabolism, as indicated by the alteration of important metabolic biomarkers such as alanine, citrate, glucose, glycogen, betaine, taurine, hypotaurine and homarine in the gills. At lower salinity, oysters accumulated higher energy related compounds (e.g., glucose and glycogen) and amino acids (e.g., aspartate, dimethylglycine and lysine), with the enhancement of ATP/ADP production and accumulation of oxidizable amino acids catabolized from protein breakdown. With Cu exposure, the synthesis from glycine to dimethylglycine was observed to cope with severe osmotic stress, together with the elevation of lysine and homarine. The effects induced by Cu were much similar for each salinity treatment, but the combination of Cu and salinity turned out to be consistent with the singular salinity effects. Therefore, salinity played a dominant role in affecting the metabolites of oysters when combined with Cu exposure. This study indicated that salinity should be taken into consideration in order to predict the Cu toxicity in estuarine organisms.

Revealing the complex effects of salinity on copper toxicity in an estuarine clam Potamocorbula laevis with a toxicokinetic-toxicodynamic model

The effects of salinity on metal toxicity are complex: not only affecting metal bioaccumulation, but also altering the physiology and sensitivity of organisms. In this study, we used a toxicokinetic-toxicodynamic (TK-TD) model to separate and quantify the dual effects of salinity on copper (Cu) toxicity in a euryhaline clam Potamocorbula laevis. The toxicokinetics of Cu was determined using the stable isotope ⁶⁵Cu as a tracer at concentrations (10-500 μg L^-1) realistic to contaminated environments and at salinities ranging from 5 to 30. At low Cu concentrations (ca. 10 μg L^-1), Cu bioaccumulation decreased monotonically with salinity, and the uptake rate constant (k_u, 0.546 L g^-1 h^-1 to 0.213 L g^-1 h^-1) fitted well with an empirical equation, k_u = 1/(1.35 + 0.116·Salinity), by treating salinity as a pseudo-competitor. The median lethal concentrations (LC₅₀s) of Cu were 269, 224, and 192 μg L^-1 at salinity 5, 15, and 30, respectively. At high Cu concentrations (ca. 500 μg L^-1), elevating salinity were much less effective in decreasing Cu bioaccumulation; whereas Cu toxicity increased with salinity. The increased toxicity could be explained by the increases in Cu killing rates (k_ks), which were estimated to be 0.44-2.08 mg μg^-1 h^-1 and were presumably due to the osmotic stress caused by the deviation from the optimal salinity of the clams. The other toxicodynamic parameter, internal threshold concentration (C_IT), ranged from 79 to 133 μg^-1 g^-1 and showed no clear trend with salinity.

Toxicity of copper to three common subantarctic marine gastropods

Investigating the impacts of contamination on high latitude ecosystems includes determining the sensitivity of key taxa to contaminants. Unique characteristics, arising from adaption to cold and stable temperatures has likely resulted in marine biota at the poles being particularly sensitive to contamination in comparison to related species at lower latitudes. We aimed to determine the sensitivity of three species of common and ecologically important subantarctic gastropods to copper. This is the first study to investigate the sensitivity of subantarctic marine gastropods to contamination. We determined sensitivity by exposing each species to a range of copper concentrations by establishing mortality and sublethal endpoints. Sensitivity to copper was highly species specific. Laevilittorina caliginosa was relatively tolerant, with no response at Cu concentrations up to 1488µg/L following 7 d of exposure, while two species (Cantharidus capillaceus coruscans and Macquariella hamiltoni) were highly sensitive with 7 d Cu LC50 estimates of 33µg/L and 78µg/L respectively. In a global comparison of gastropod sensitivity data, these two species were highly sensitive to copper, highlighting the vulnerability of polar ecosystems to contamination.

Assessment of the effects of Cu and Ag in oysters Crassostrea gigas (Thunberg, 1793) using a battery of cell and tissue level biomarkers

Oysters are considered sentinel organisms in environmental water quality monitoring programs in which cell and tissue level biomarkers are reliable tools. Copper (Cu) and silver (Ag) are present in relatively high concentrations in several estuaries, potentially affecting environmental and human health. Crassostrea gigas oysters were exposed during 28 days to a range of environmentally relevant concentrations of Cu and Ag alone or in mixture. Effects were studied through cell and tissue level biomarkers approach. Results indicated: changes in the Condition Index (CI), altered digestive gland epithelium and presence of histopathological alterations in the gonad and digestive gland of exposed oysters. A time-dependent increase in lipofuscin contents in exposed oysters and an increase in intralysosomal metal accumulation in digestive cells through the experiment were also recorded. The Integrative Biological Response (IBR) Index showed that even at low exposure levels, Ag and Cu can produce alterations on oysters' health status.

Effects of salinity on short-term waterborne zinc uptake, accumulation and sub-lethal toxicity in the green shore crab (Carcinus maenas)

Waterborne zinc (Zn) is known to cause toxicity to freshwater animals primarily by disrupting calcium (Ca) homeostasis during acute exposure, but its effects in marine and estuarine animals are not well characterized. The present study investigated the effects of salinity on short-term Zn accumulation and sub-lethal toxicity in the euryhaline green shore crab, Carcinus maenas. The kinetic and pharmacological properties of short-term branchial Zn uptake were also examined. Green crabs (n=10) were exposed to control (no added Zn) and 50μM (3.25mgL(-1)) of waterborne Zn (∼25% of 96h LC50 in 100 seawater) for 96h at 3 different salinity regimes (100%, 60% and 20% seawater). Exposure to waterborne Zn increased tissue-specific Zn accumulation across different salinities. However, the maximum accumulation occurred in 20% seawater and no difference was recorded between 60% and 100% seawater. Gills appeared to be the primary site of Zn accumulation, since the accumulation was significantly higher in the gills relative to the hepatopancreas, haemolymph and muscle. Waterborne Zn exposure induced a slight increase in haemolymph osmolality and chloride levels irrespective of salinity. In contrast, Zn exposure elicited marked increases in both haemolymph and gill Ca levels, and these changes were more pronounced in 20% seawater relative to that in 60% or 100% seawater. An in vitro gill perfusion technique was used to examine the characteristics of short-term (1-4h) branchial Zn uptake over an exposure concentration range of 3-12μM (200-800μgL(-1)). The rate of short-term branchial Zn uptake did not change significantly after 2h, and no difference was recorded in the rate of uptake between the anterior (respiratory) and posterior (ion transporting) gills. The in vitro branchial Zn uptake occurred in a concentration-dependent manner across different salinities. However, the rate of uptake was consistently higher in 20% seawater relative to 60% or 100% seawater - similar to the trend observed with tissue Zn accumulation during in vivo exposure. The short-term branchial Zn uptake was found to be inhibited by lanthanum (a blocker of voltage-independent Ca channels), suggesting that branchial Zn uptake occurs via the Ca transporting pathways, at least in part. Overall, our findings indicate that acute exposure to waterborne Zn leads to the disruption of Zn and Ca homeostasis in green crab, and these effects are exacerbated at the lower salinity.

Salinity-dependent mechanisms of copper toxicity in the galaxiid fish, Galaxias maculatus

The euryhaline galaxiid fish, inanga (Galaxias maculatus) is widely spread throughout the Southern hemisphere occupying near-coastal streams that may be elevated in trace elements such as copper (Cu). Despite this, nothing is known regarding their sensitivity to Cu contamination. The mechanisms of Cu toxicity in inanga, and the ameliorating role of salinity, were investigated by acclimating fish to freshwater (FW), 50% seawater (SW), or 100% SW and exposing them to a graded series of Cu concentrations (0-200μgL(-1)) for 48h. Mortality, whole body Cu accumulation, measures of ionoregulatory disturbance (whole body ions, sodium (Na) influx, sodium/potassium ATPase activity) and ammonia excretion were monitored. Toxicity of Cu was greatest in FW, with mortality likely resulting from impaired Na influx. In both FW and 100% SW, ammonia excretion was significantly elevated, an effect opposite to that observed in previous studies, suggesting fundamental differences in the effect of Cu in this species relative to other studied fish. Salinity was protective against Cu toxicity, and physiology seemed to play a more important role than water chemistry in this protection. Inanga are sensitive to waterborne Cu through a conserved impairment of Na ion homeostasis, but some effects of Cu exposure in this species are distinct. Based on effect concentrations, current regulatory tools and limits are likely protective of this species in New Zealand waters.

Co-contamination of Cu and Cd in paddy fields: Using periphyton to entrap heavy metals

The ubiquitous native periphyton was used to entrap Cu and Cd from paddy fields. Results showed that Cu- and Cd-hydrate species such as CuOH(+), Cu2(OH)2(2+), CdOH(+), and Cu3(OH)4(2+) decreased with time in the presence of periphyton. When the initial concentrations of Cu and Cd were 10mg/L, the heavy metal content in the periphyton fluctuated from 145.20mg/kg to 342.42 mg/kg for Cu and from 101.75 mg/kg to 236.29 mg/kg for Cd after 2h exposure. The concentration of Cd in periphytic cells varied from 42.93 mg/kg to 174 mg/kg after 2h. The dominant periphyton microorganism species shifted from photoautotrophs to heterotrophs during the exposure of periphyton to Cu and Cd co-contamination. Although Cu and Cd could inhibit periphyton photosynthesis and carbon utilization, the periphyton was able to adapt to the test conditions. Cu and Cd accumulation in rice markedly decreased in the presence of periphyton while the number of rice seeds germinating was higher in the periphyton treatments. These results suggest that the inclusion of native periphyton in paddy fields provides a promising buffer to minimize the effects of Cu and Cd pollution on rice growth and food safety.

Lesions of Copper Toxicosis in Captive Marine Invertebrates With Comparisons to Normal Histology

Despite increasing concern for coral reef ecosystem health within the last decade, there is scant literature concerning the histopathology of diseases affecting the major constituents of coral reef ecosystems, particularly marine invertebrates. This study describes histologic findings in 6 species of marine invertebrates (California sea hare [ Aplysia californica], purple sea urchin [ Strongylocentrotus purpuratus], sunburst anemone [ Anthopleura sola], knobby star [ Pisaster giganteus], bat star [ Asterina miniata], and brittle star [ Ophiopteris papillosa]) with spontaneous copper toxicosis, 4 purple sea urchins with experimentally induced copper toxicosis, and 1 unexposed control of each species listed. The primary lesions in the California sea hare with copper toxicosis were branchial and nephridial necrosis. Affected echinoderms shared several histologic lesions, including epidermal necrosis and ulceration and increased numbers of coelomocytes within the water-vascular system. The sunburst anemone with copper toxicosis had necrosis of both epidermis and gastrodermis, as well as expulsion of zooxanthellae from the gastrodermis. In addition to the lesions attributed to copper toxicosis, our results describe normal microscopic features of these animals that may be useful for histopathologic assessment of marine invertebrates.

Salinity changes impact of hazardous chemicals in Enchytraeus albidus

Supralittoral ecosystems are among the most challenging environments for soil organisms, particularly when salinity fluctuations are involved, frequently combined with the presence of contaminants as a result of intense anthropogenic activities. Knowledge of how salinity influences the effect of contaminants in supralittoral species is crucial for determining the safety factors required when extrapolating results from optimal laboratory conditions to these natural ecosystems. The present study therefore evaluated the effects of 2 metals (copper and cadmium) and 2 organic compounds (carbendazim and 4-nonylphenol) in the absence or presence of 15‰ NaCl in the potworm Enchytraeus albidus, a model organism for ecotoxicology studies commonly found in supralittoral ecosystems, The potworms had a higher reproduction in saline soil than in control soil. Moreover, the effects of copper and carbendazim on reproduction were smaller than when they were tested in nonsaline soil. Potworms exposed to nonsaline soils also had significantly higher tissue concentrations of metals, which partly explains the effects on reproduction. The influence of salinity on effects of 4-nonylphenol was, however, less clear; effects on survival decreased in saline soil, but effects on reproduction were highest in saline soil. The latter slightly correlated with tissue concentrations of the chemical. The present study provides the first evidence that soil salinity has a significant influence on the impact of contaminants evaluated with the enchytraeid reproduction test.

Making sense of nickel accumulation and sub-lethal toxic effects in saline waters: Fate and effects of nickel in the green crab, Carcinus maenas

In freshwater, invertebrates nickel (Ni) is considered an ionoregulatory toxicant, but its mechanism of toxicity in marine settings, and how this varies with salinity, is poorly understood. This study investigated Ni accumulation and physiological mechanisms of sub-lethal Ni toxicity in the euryhaline green crab Carcinus maenas. Male crabs were exposed to 8.2μg/L (the US EPA chronic criterion concentration for salt waters) of waterborne Ni (radiolabelled with (63)Ni) at three different salinities, 20%, 60% and 100% SW for 24h. Whole body Ni accumulation in 20% SW was 3-5 fold greater than in 60% or 100% SW, and >80% of accumulated Ni was in the carapace at all salinities. Ni also accumulated in posterior gill 8, which showed a higher accumulation in 20% SW than in other salinities, a pattern also seen at higher exposure concentrations of Ni (500 and 3000μg/L). Gill perfusion experiments revealed that Ni was taken up by both anterior and posterior gills, but in 20% SW the posterior gill 8, which performs ionoregulatory functions, accumulated more Ni than the anterior gill 5, which primarily has a respiratory function. The sub-lethal consequences of Ni exposure were investigated by placing crabs in Ni concentrations of 8.2, 500, and 3000μg/L at 20, 60 or 100% SW for 24h. In 20% SW, haemolymph Ca levels were significantly decreased by exposure to Ni concentrations of 8.2μg/L or higher, whereas Na concentrations were depressed only at 3000μg/L. Na(+)/K(+)-ATPase activity was inhibited at both 500 and 3000μg/L in gill 8, but only in 20% SW. Haemolymph K, Mg, and osmolality were unaffected throughout, though all varied with salinity in the expected fashion. These data suggest that Ni impacts ionoregulatory function in the green crab, in a gill- and salinity-dependent manner.

Salinity and dissolved organic carbon both affect copper toxicity in mussel larvae: Copper speciation or competition cannot explain everything

Predicting copper (Cu) toxicity in marine and estuarine environments is challenging because of the influence of anions on Cu speciation, competition between Cu(2+) and other cations at the biotic ligand and the effect of salinity on the physiology of the organism. In the present study the combined effect of salinity and dissolved organic carbon (DOC) on Cu toxicity to larvae of Mytilus galloprovincialis was assessed. Two statistical models were developed and used to elucidate the relationship between Cu toxicity, salinity, and DOC. All models based on dissolved Cu indicate a decrease in Cu toxicity with increasing DOC concentrations, which can partly be explained by complexation of Cu(2+) ions with DOC. These models also indicate an increase in Cu toxicity (modeled with dissolved Cu or Cu(2+) activity) with increasing salinity, suggesting a salinity-induced alteration in the physiology of the mussel larvae. When based on Cu body burdens, neither of the models indicates an effect of salinity or DOC. This shows that the Cu body burden is a more constant predictor of Cu toxicity, regardless of the water chemistry influencing Cu speciation or competition and possible physiological alterations or changes in Cu speciation or competition.

Impacts of multiple stressors during the establishment of fouling assemblages

Limited knowledge of the mechanisms through which multiple stressors affect communities and ecosystems limits capacity to predict their effects. Less clear is how stressors impact early colonization of newly available habitats due to scarcity of studies. The present study tested whether copper and freshwater input affect colonization of hard substrata independently or interactively and assessed differences in community respiration and total biomass among early stage assemblages which developed under different regimes of copper and freshwater input. While copper influenced effectively the colonization of individual species, freshwater effect was weak or null. Apart from a significant effect on total community composition, the interactive effect between stressors was weak and mainly driven by antagonistic interactions between copper and water flow. Total biomass and respiration of the community studied were not affected by stressors. These findings contradict the expectation that changes in community structure are likely to cause changes in functioning.

A new role for carbonic anhydrase 2 in the response of fish to copper and osmotic stress: implications for multi-stressor studies

The majority of ecotoxicological studies are performed under stable and optimal conditions, whereas in reality the complexity of the natural environment faces organisms with multiple stressors of different type and origin, which can activate pathways of response often difficult to interpret. In particular, aquatic organisms living in estuarine zones already impacted by metal contamination can be exposed to more severe salinity variations under a forecasted scenario of global change. In this context, the present study aimed to investigate the effect of copper exposure on the response of fish to osmotic stress by mimicking in laboratory conditions the salinity changes occurring in natural estuaries. We hypothesized that copper-exposed individuals are more sensitive to osmotic stresses, as copper affects their osmoregulatory system by acting on a number of osmotic effector proteins, among which the isoform two of the enzyme carbonic anhydrase (CA2) was identified as a novel factor linking the physiological responses to both copper and osmotic stress. To test this hypothesis, two in vivo studies were performed using the euryhaline fish sheepshead minnow (Cyprinodon variegatus) as test species and applying different rates of salinity transition as a controlled way of dosing osmotic stress. Measured endpoints included plasma ions concentrations and gene expression of CA2 and the α1a-subunit of the enzyme Na+/K+ ATPase. Results showed that plasma ions concentrations changed after the salinity transition, but notably the magnitude of change was greater in the copper-exposed groups, suggesting a sensitizing effect of copper on the responses to osmotic stress. Gene expression results demonstrated that CA2 is affected by copper at the transcriptional level and that this enzyme might play a role in the observed combined effects of copper and osmotic stress on ion homeostasis.

Waste biomass adsorbents for copper removal from industrial wastewater--a review

Copper (Cu(2+)) containing wastewaters are extensively released from different industries and its excessive entry into food chains results in serious health impairments, carcinogenicity and mutagenesis in various living systems. An array of technologies is in use to remediate Cu(2+) from wastewaters. Adsorption is the most attractive option due to the availability of cost effective, sustainable and eco-friendly bioadsorbents. The current review is dedicated to presenting state of the art knowledge on various bioadsorbents and physico-chemical conditions used to remediate Cu(2+) from waste streams. The advantages and constraints of various adsorbents were also discussed. The literature revealed the maximum Cu adsorption capacities of various bioadsorbents in the order of algae>agricultural and forest>fungal>bacterial>activated carbon>yeast. However, based on the average Cu adsorption capacity, the arrangement can be: activated carbon>algal>bacterial>agriculture and forest-derived>fungal>yeast biomass. The data of Cu removal using these bioadsorbents were found best fit both Freundlich and Langmuir models. Agriculture and forest derived bioadsorbents have greater potential for Cu removal because of higher uptake, cheaper nature, bulk availability and mono to multilayer adsorption behavior. Higher costs at the biomass transformation stage and decreasing efficiency with desorption cycles are the major constraints to implement this technology.

The combined effect of dissolved organic carbon and salinity on the bioaccumulation of copper in marine mussel larvae

Larvae of Mytilus spp. are among the most Cu sensitive marine species. In this study we assessed the combined effect of salinity and dissolved organic carbon (DOC) on Cu accumulation on mussel larvae. Larvae were exposed for 48 h to three Cu concentrations in each of nine salinity/DOC treatments. Synchrotron radiation X-ray fluorescence was used to determine the Cu concentration in 36 individual larvae with a spatial resolution of 10 × 10 μm. Cu body burden concentrations varied between 1.1 and 27.6 μg/g DW larvae across all treatments and Cu was homogeneously distributed at this spatial resolution level. Our results indicate decreasing Cu accumulation with increasing DOC concentrations which can be explained by an increase in Cu complexation. In contrast, salinity had a nonlinear effect on Cu. This cannot be explained by copper speciation or competition processes and suggests a salinity-induced alteration in physiology.

Copper, zinc, and cadmium body concentrations in Hexaplex trunculus collected from the Tunisian coast

Copper, Zn, and Cd were analyzed in the soft tissues of the edible gastropod Hexaplex trunculus collected from seven localities along the Tunisian coast. The body concentration of these metals was significantly different depending on the gender and site. Copper and Zn varied, respectively, from 47.70 to 343.64 μg/g dry weight (dw) and 149.46 to 530.44 μg/g dw, being higher in males. Cadmium varied from 0.22 to 18.95 μg/g dw and was always higher in females. Overall, the highest concentrations of the three metals were all recorded in Gabès fishing harbor. Comparison of metal concentrations with the European standards compiled by the Food and Agriculture Organization showed that values exceeded standards in several localities. Imposex had been previously recorded in H. trunculus along the Tunisian coast; however, it does not seem to be related with Cu, Zn, and Cd pollution because the body concentration of these metals is not correlated with imposex degree. Nevertheless, interactive effects resulting from the combination of different pollutants and other stressors cannot be disregarded.

Immunomodulating effects of environmentally realistic copper concentrations in Mytilus edulis adapted to naturally low salinities

The monitoring of organisms' health conditions by the assessment of their immunocompetence may serve as an important criterion for the achievement of the Good Environmental Status (GES) as defined in the Marine Strategy Framework Directive (EU). In this context, the complex role of natural environmental stressors, e.g. salinity, and interfering or superimposing effects of anthropogenic chemicals, should be carefully considered, especially in scenarios of low to moderate contamination. Organisms from the Baltic Sea have adapted to the ambient salinity regime, however energetically costly osmoregulating processes may have an impact on the capability to respond to additional stress such as contamination. The assessment of multiple stressors, encompassing natural and anthropogenic factors, influencing an organisms' health was the main aim of the present study. Immune responses of Mytilus edulis, collected and kept at natural salinities of 12‰ (LS) and 20‰ (MS), respectively, were compared after short-term exposure (1, 7 and 13 days) to low copper concentrations (5, 9 and 16 μg/L Cu). A significant interaction of salinity and copper exposure was observed in copper accumulation. LS mussels accumulated markedly more copper than MS mussels. No combined effects were detected in cellular responses. Bacterial clearance was mostly achieved by phagocytosis, as revealed by a strong positive correlation between bacterial counts and phagocytic activity, which was particularly pronounced in LS mussels. MS mussels, on the other hand, seemingly accomplished bacterial clearance by employing additional humoral factors (16 μg/L Cu). The greatest separating factor in the PCA biplot between LS and MS mussels was the proportion of granulocytes and hyalinocytes while functional parameters (phagocytic activity and bacterial clearance) were hardly affected by salinity, but rather by copper exposure. In conclusion, immune responses of the blue mussel may be suitable and sensitive biomarkers for the assessment of ecosystem health in brackish waters (10-20‰S).

Challenges for the development of a biotic ligand model predicting copper toxicity in estuaries and seas

An effort is ongoing to develop a biotic ligand model (BLM) that predicts copper (Cu) toxicity in estuarine and marine environments. At present, the BLM accounts for the effects of water chemistry on Cu speciation, but it does not consider the influence of water chemistry on the physiology of the organisms. We discuss how chemistry affects Cu toxicity not only by controlling its speciation, but also by affecting the osmoregulatory physiology of the organism, which varies according to salinity. In an attempt to understand the mechanisms of Cu toxicity and predict its impacts, we explore the hypothesis that the common factor linking the main toxic effects of Cu is the enzyme carbonic anhydrase (CA), because it is a Cu target with multiple functions and salinity-dependent expression and activity. According to this hypothesis, the site of action of Cu in marine fish may be not only the gill, but also the intestine, because in this tissue CA plays an important role in ion transport and water adsorption. Therefore, the BLM of Cu toxicity to marine fish should also consider the intestine as a biotic ligand. Finally, we underline the need to incorporate the osmotic gradient into the BLM calculations to account for the influence of physiology on Cu toxicity.