Integrated biomarker assessment of the effects of tailing discharges from an iron ore mine using blue mussels (Mytilus spp.)

Evaluation of the long-term effects of formaldehyde on the physiology of the Mediterranean mussel, Mytilusgalloprovincialis

Formalin baths are the most widely used treatment for ectoparasitic fish diseases. Nonetheless, their use in fish cages has been blamed for a number of problems. Although a considerable amount of literature has been produced on the short-term toxic effects of formaldehyde, there is virtually no data on the long-term side effects of the compound on non-target organisms. Therefore, the purpose of this research was to assess the long-term formaldehyde toxicity in Mediterranean mussel, Mytilus galloprovincialis, a common sentinel species that inhabits the area surrounding cage farms. Mussels were kept in a laboratory microenvironment at 20 ± 1 °C for 21 days and exposed to two different formaldehyde concentrations during experimentation: a low dose (L; 40 ppb) based on formaldehyde field measurements in the vicinity of Mediterranean cages, and a high dose (H; 400 ppb) generated by a factor of 10 of the previous dose. A multi-biomarker approach that included antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD), lipid peroxidation (MDA), lysosomal stability (NRRT), genotoxicity tests, condition index (CI), and stress on stress (SoS), was used to evaluate the toxicity of formaldehyde on mussels. The results of the selected tests indicate that formaldehyde does not cause chronic toxicity in mussels subjected to commonly measured concentrations in the aquatic environment following formalin bath treatments. Despite being defined as reversible, the stress brought by the high dose used seems to reduce the antioxidant activity of the tested organism. The significance of this research lies in its contribution to understanding the wider ecological effects of formaldehyde exposure. Moreover, the results highlight the need for further research on other non-target marine organisms to fully understand the cumulative effects of formaldehyde on marine ecosystems.

The long-lived deep-sea bivalve Acesta excavata is sensitive to the dual stressors of sediment and warming

Human influence in the deep-sea is increasing as mining and drilling operations expand, and waters warm because of climate change. Here, we investigate how the long-lived deep-sea bivalve, Acesta excavata responds to sediment pollution and/or acute elevated temperatures. A. excavata were exposed to suspended sediment, acute warming, and a combination of the two treatments for 40 days. We measured O2 consumption, NH4+ release, Total Organic Carbon (TOC), and lysosomal membrane stability (LMS). We found suspended sediment and warming interacted to decrease O:N ratios, while sediment as a single stressor increased the release of TOC and warming increased NH4+ release in A. excavata. Warming also increased levels of LMS. We found A. excavata used protein catabolism to meet elevated energetic demands indicating a low tolerance to stress. A. excavata has limited capacity for physiological responses to the stressors of warming and sediment which may lead to decreased fitness of A. excavata.

Ecotoxicity of tire wear particles to antioxidant enzyme system and metabolic functional activity of river biofilms: The strengthening role after incubation-aging in migrating water phases

Tire wear particles (TWPs) are commonly studied for their exudation toxicity, yet a critical knowledge gap exists regarding the source nature and migration of these particulate pollutants, hindering comprehensive environmental risk assessments. This study explores the pristine properties of three typical TWPs (rolling friction (R-TWPs), sliding friction (S-TWPs), and cryogenically milled tire treads (C-TWPs)) and their aging characteristics after incubation in runoff (primary aging) and sewage (further aging). Our investigation aims to unveil the intrinsic mechanisms of TWPs ecotoxicity towards freshwater biofilms. Results reveal that the generation modes significantly impact pristine physicochemical properties, including surface structure, particle size, and EPFR abundance. These factors, in turn, influence acute ecotoxicity, as evidenced by cell mortality, antioxidant enzyme activity responses, and metabolic changes in freshwater biofilms. The ecological toxicity ranking of pristine exposure groups is S-TWPs, R-TWPs, and C-TWPs, attributed to variations in surface properties and particle size. Following incubation and aging, especially in sewage, differences in physicochemical properties among TWPs types diminish. Alarmingly, ecotoxicity intensifies and becomes consistent across TWPs types, driven by the screening of small particles during water incubation aging and the formation of EPFRs on TWPs surfaces stimulated by photosensitive organic matter or groups. This study underscores the aquatic ecological risks associated with TWP surface properties, highlighting the significant influence of environmental aging conditions on these risks.

An integrated biological effects assessment of the discharge water into the Sunndalsfjord from an aluminium smelter

An integrated biological effects study using field transplanted mussels was applied to determine the potential biological effects of an effluent discharge from an aluminium smelter into a Norwegian fjord. Chemical body burden and biological effects were measured in mussels positioned downstream (1, 2, 5, 10 and 20 km) from the aluminium smelters discharge for a period of 6 weeks. A suite of biomarkers, from whole organism to subcellular responses were measured. Chemical concentrations in mussel tissues were low; however, a change in the PAC (polyaromatic compound) profile from high to low pyrogenic influence provided evidence of exposure to the smelter's effluent. Overall, the biological responses observed where greater in the mussels positioned closest to the smelter (1-5 km). Lowest chemical accumulation and biomarker responses were observed in mussels positioned 10 km from the smelter and were considered as the reference field population. Mussels located furthest from the smelter (20 km) exhibited significant biomarker responses and suggested a different contaminant source within the fjord. The integrated biological response index (IBR) was applied and reflected the expected level of exposure to the smelters discharge, with highest IBR calculated in mussels positioned closest to the discharge (1-5 km). Principal component analysis (PCA) also differentiated among mussel groups, with the most impacted located closest to the smelter. Not one chemical factor could explain the biological responses observed in mussels, but the presence of PAH16, PAH41 and metals Mn, Ni and Cr were the main contributors measured to the higher stress seen in the mussels from the 1 and 5 km groups.

Polystyrene microplastics increase Pb bioaccumulation and health damage in the Chinese mitten crab Eriocheir sinensis

Microplastics may be potential vectors for environmental contaminants such as heavy metals in the aquatic ecosystem due to their highly hydrophobic surfaces and fugacity property. To investigate the combined effects of microplastics with Pb, we exposed juvenile Chinese mitten crabs Eriocheir sinensis to different Pb concentrations (0, 5 and 50 μg/L) combined with microplastics (0 and 400 μg/L) for 21 days to determine the Pb bioaccumulation, oxidative stress, lipid anabolism, and histopathology of hepatopancreas. In general, the results showed that compared to single Pb exposure, the combination of MPs and Pb significantly increased the bioaccumulation of Pb, activities/content of antioxidant biomarkers and lipid metabolism enzymes, and liver injury parameters in crabs, indicating MPs are potential vector of heavy metals and co-exposure exerts more severe effects on crabs. This study provides the insights into the oxidative defense and preliminary lipid anabolism of economic crustaceans in response to combined stress of Pb and MPs.

Interactive effects of ocean acidification, ocean warming, and diurnal temperature cycling on antioxidant responses and energy budgets in two sea urchins Strongylocentrotus intermedius and Tripneustes gratilla from different latitudes

To accurately predict the fitness of marine ectotherms under the climate change scenarios, interactive effects from multiple environmental stressors should be considered, such as ocean acidification (OA), ocean warming (OW) and diurnal temperature cycling (DTC). In this work, we evaluated and compared the antioxidant capacity and metabolism homeostasis of two sea urchins, viz. the temperate species Strongylocentrotus intermedius and the tropical species Tripneustes gratilla, in response to oceanic conditions under a climate change scenario. The two species were treated separately/jointly by acidic (pH 7.6), thermal (ambient temperature + 3 °C), and temperature fluctuating (5 °C fluctuations daily) seawater for 28 days. The activities of antioxidant enzymes (catalase and superoxide dismutase) and the cellular energy allocation in the urchins' gonads were assessed subsequently. Results showed that exposure to OA, OW, and DTC all induced antioxidant responses associated with metabolism imbalance in both S. intermedius and T. gratilla. The physiological adjustments and energy strategies towards exposure of OA, OW, and DTC are species specific, perhaps owing to the different thermal acclimation of species from two latitudes. Moreover, decrease of cellular energy allocation were detected in both species under combined OA, OW, and DTC conditions, indicating unsustainable bioenergetic states. The decrease of cellular energy allocation is weaker in T. gratilla than in S. intermedius, implying higher acclimation capacity to maintain the energy homeostasis in tropical urchins. These results suggest that climate change might affect the population replenishment of the two sea urchins species, especially for the temperate species.

Ammonia in the presence of nano titanium dioxide (nano-TiO2) induces greater oxidative damage in the gill and liver of female zebrafish

Water pollution caused by a highly hazardous chemical ammonia and a widespread application nanomaterials-nano titanium dioxide (n-TiO₂) in nature water has attracted extensive concern of the world. However, the potential joint effects of the two factors are unknown. Aim to investigate the potential interactive effects of ammonia and n-TiO₂ and the behind mechanisms, adult female zebrafish (Danio rerio) were co-exposed for 8 weeks by total ammonia nitrogen (TAN; 0, 3, 30 mg/L) and n-TiO₂ (0, 0.1, 1 mg/L) in different combination conditions based on a full-factorial design. The analysis of absorption kinetics confirmed that n-TiO₂ could absorb free ammonia (NH₃) in aqueous solution and the loss rate of free NH₃ increased with the rise of n-TiO₂ concentration. Consistent with this, free NH₃ concentrations in the gill and liver were higher in the presence of n-TiO₂ compared to TAN exposure alone. The increases of MDA and PC concentrations in the gill and liver of fish indicated that TAN and n-TiO₂ alone or in combination caused oxidative stress. Simultaneously, the activity and transcription of antioxidant enzymes (T-SOD, CuZn-SOD, Mn-SOD, CAT, GPx and GST) as well as antioxidant GSH contents were extensively inhibited by TAN and n-TiO₂ via Nrf2-Keap1 signaling. The significant interactive effects of TAN and n-TiO₂ were detected on levels of GSH, GST and gstr1 mRNA in the gill, and on levels of GSH, T-SOD, Mn-SOD, CAT levels as well as gpx1a and keap1 mRNAs in the liver, implying synergistic toxic risk of TAN and n-TiO₂. The more severe histopathological alterations and higher IBR analysis in co-treatment groups further proved that the existence of n-TiO₂ excavated ammonia-induced toxicity in the gill and liver, especially in liver. In conclusion, ammonia and n-TiO₂ have a synergistic toxic risk of fish health because ammonia and n-TiO₂ cause oxidative-antioxidative imbalance by inducing ROS overproduction.

Evaluation of Ammonia Nitrogen Exposure in Immune Defenses Present on Spleen and Head-Kidney of Wuchang Bream (Megalobrama amblycephala)

Ammonia is one of the most important environmental factors in aquatic ecosystems. However, there are limited studies on the effects of chronic or long-term ammonia stress and its potential molecular mechanism in fish. This study aimed to investigate the immune response and molecular mechanisms in the spleen and head-kidney of fish following chronic ammonia exposure. Megalobrama amblycephala (9.98 ± 0.48 g) were exposed to different concentrations of total ammonia nitrogen (0-30 mg/L) for 30 days. Ammonia exposure caused significant increases in cortisol levels and decreases in lysozyme and complement 3/4 concentrations in the serum, indicating inhibitory effects of ammonia stress on innate immune responses. Ammonia exposure also induced concentration-dependent increases in ammonia concentrations in tissue, pathological damage and indexes of spleen and head-kidney. Additionally, the contents of immunoglobulin M (IgM), interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α) as well as mRNA levels of toll-like receptors (TLRs)/Myeloid differentiation factor 88 (MyD88)-independent signaling molecules in the spleen and head-kidney were significantly downregulated after ammonia exposure. Our findings suggested that chronic ammonia exposure caused the suppression of innate and adaptive immune responses through downregulating TLR/MyD88-independent signaling. Adverse influences of chronic ammonia stress were more severe in the spleen than in the head-kidney.

New insights into submarine tailing disposal for a reduced environmental footprint: Lessons learnt from Norwegian fjords

Submarine tailing disposal (STD) in fjords from land-based mines is common practice in Norway and takes place in other regions worldwide. We synthesize the results of a multidisciplinary programme on environmental impacts of STDs in Norwegian fjords, providing new knowledge that can be applied to assess and mitigate impact of tailing disposal globally, both for submarine and deep-sea activities. Detailed geological seafloor mapping provided data on natural sedimentation to monitor depositional processes on the seafloor. Modelling and analytical techniques were used to assess the behaviour of tailing particles and process-chemicals in the environment, providing novel tools for monitoring. Toxicity tests showed biological impacts on test species due to particulate and chemical exposure. Hypersedimentation mesocosm and field experiments showed a varying response on the benthos, allowing to determine the transition zone in the STD impact area. Recolonisation studies indicate that full community recovery and normalisation of metal leakage rates may take several decades due to bioturbation and slow burial of sulfidic tailings. The results are synthesised to provide guidelines for the development of best available techniques for STDs.

Oxidative stress induced by nanoplastics in the liver of juvenile large yellow croaker Larimichthys crocea

There are many toxicological studies on microplastics, but little is known about the effect of nanoplastics (NPs). Here, we evaluated the oxidative stress responses induced by NPs (10, 10⁴ and 10⁶ particles/l) in juvenile Larimichthys crocea during 14-d NPs exposure followed by a 7-d recovery. After exposure, the activities of antioxidant enzymes (SOD, CAT, GPx) and MDA levels increased in the liver of fish at the highest NPs concentration. SOD and CAT activities remained elevated above the baseline after recovery under high-concentration NPs but returned to the baseline in two other NP treatments. Although lipid peroxidation in liver was reversible, juvenile fish in NPs treatments exhibited a lower survival rate than the control during both exposure and recovery. Furthermore, IBR value and PCA analysis showed the potential adverse effects of NPs. Considering that NPs can reduce the survival of fish juveniles, impacts of NPs on fishery productivity should be considered.

Integrated biomarker response in Mytilus chilensis exposed to untreated urban discharges along the coast of Ushuaia Bay (Beagle Channel, Argentina)

The short-term effects of coastal untreated effluents from Ushuaia Bay, Beagle Channel, on the biochemical and physiological biomarkers of Mytilus chilensis were assessed. An integrated biomarker response (IBR) index was calculated as a helpful tool to represent the general stress of the experimental organisms. Cultured mussels were exposed during 96 h to three coastal sites impacted by sewage effluents. At the beginning (T₀) and every 24 h, mussels were subsampled from each site and different biochemical and physiological biomarkers were determined. There was no mortality registered in the experiments during the 96 h. However, biochemical and physiological biomarkers presented significant variations. Lipid peroxidation mean levels in mussels decreased in mantle and increased in digestive gland with respect to T₀ in almost all cases. Acetylcholinesterase activity was inhibited in all sites, reaching a maximal decrease of 35% with respect to T₀. Catalase remained stable and glutathione-S-transferase was activated. Oxygen consumption and ammonia excretion rates increased in organisms from two sites and, consequently, O:N ratio decreased, denoting a symptom of stress. IBR values showed the existence of different stress levels between exposed and unexposed mussels. These results exhibited an alteration of the general metabolism of mussels exposed for a short period of time to untreated coastal wastewater, suggesting the use of these organisms as early indicators of changes in the environmental quality of coastal waters of Ushuaia Bay.

Combined metabolomics and histological analysis of the tissues from cuttlefish Sepia pharaonis exposed to inking stress

Inking is part of a defensive stress response in cephalopods (cuttlefish, squid, and octopus). Some individual cuttlefish (Sepia pharaonis) die after continued stress and inking; however, the physiological effects of cephalopods in response to stress and inking remain unknown. The present study investigated the metabolic profile and discussed the physiological roles of S. pharaonis tissues in response to continuous inking using the ¹H NMR spectroscopy coupled with multivariate data analysis. A total of 50 metabolites, including amino acids, organic osmolytes, nucleotides, energy storage compounds, and obvious tissue-specific metabolites induced by inking stress, were identified in S. pharaonis tissues. Exposure to inking stress had different effects on the levels of the studied metabolites, for example, the levels of isoleucine, trimethylamine-N-oxide, and betaine increased, but those of arginine and ATP decreased in the liver; inosine and lactate were accumulated whereas glutamate and choline were depleted in the gill; the levels of lactate and isoleucine were elevated but those of arginine and glycogen were depleted in the muscle tissue. Furthermore, the corresponding metabolic pathways of the characteristic metabolites indicated major changes in the functions of these metabolites. Histological changes in the studied tissues revealed liver lobule damage immediately after inking, with the presence of disordered epithelial cells and partial cell necrosis in the gill. Our results demonstrated that a combination of metabolomics and histological analyses could provide molecular-level insights for elucidating the defense response of cuttlefish against predators.

A Commentary on the Use of Bivalve Mollusks in Monitoring Metal Pollution Levels

The objective of this commentary is to promote the use of bivalves as biomonitors, which is a part of the continual efforts of the International Mussel Watch. This commentary is an additional discussion on "Bivalve mollusks in metal pollution studies: From bioaccumulation to biomonitoring" by Zuykov et al., published in Chemosphere 93, 201-208. The present discussion can serve as a platform for further insights to provide new thoughts and novel ideas on how to make better use of bivalves in biomonitoring studies. The certainty of better and more extensive applications of mollusks in environmental monitoring in the future is almost confirmed but more studies are urgently needed. With all the reported studies using bivalves as biomonitors of heavy metal pollution, the effectiveness of using Mussel Watch is beyond any reasonable doubts. The challenge is the development of more accurate methodologies for of heavy metal data interpretation, and the precision of the biomonitoring studies using bivalves as biomonitors, whether in coastal or freshwater ecosystems. Lastly, inclusion of human health risk assessment of heavy metals in commercial bivalves would make the research papers of high public interest.

From sinks to sources: The role of Fe oxyhydroxide transformations on phosphorus dynamics in estuarine soils

The availability of phosphorus (P) in estuarine ecosystems is ultimately controlled by the nature of interactions between dissolved P and the soil components (e.g., soil minerals), especially iron (Fe) oxyhydroxides. P retention on Fe oxyhydroxides and its subsequent availability depends on mineral crystallinity and susceptibility to dissolution. However, in estuarine soils, geochemical conditions (e.g., redox oscillation and high soil organic matter content) may alter the fate of P and decrease the environmental quality of estuarine waters. The large input of Fe-rich tailings into the Rio Doce Estuary in Brazil in 2015 after a rupture of a Fe ore tailings dam (i.e., "Mariana mine disaster") offers a unique framework to evaluate the Fe oxyhydroxides role in P availability in estuarine soils, their potential effects on the cycling of P and eutrophication. We observed a significant correlation between Fe minerals and the P content in the estuary soils, suggesting that P enrichment was promoted by the deposited Fe-rich tailings. Adsorption isotherm curves indicated that mine tailings had a strong affinity for P due to presence of crystalline Fe oxyhydroxides in the tailings. Significant losses of Fe (62%) and P (56%) from the estuarine soil was observed two years after the initial impact and in response to redox conditions oscillations. Additionally, the content of high crystallinity Fe oxyhydroxides decreased significantly, whereas that of low crystallinity Fe oxyhydroxides showed an increase over time. These changes were associated with the dissimilatory Fe reduction, which led an increase in the concentrations of readily available P (2015: 2.30 ± 0.41 mg kg^-1; 2017: 3.83 ± 1.82 mg kg^-1; p < 0.001) in the studied soils. Moreover, in 2017, the dissolved P content exceeded the recommended environmental safety limits by five times. Our results indicate that Fe oxyhydroxides are a continuous source of dissolved P for the ecosystem, and Fe-rich tailings deposited in the estuarine ecosystem may be linked to a potential eutrophication.

1H NMR-based metabolomic analysis of cuttlefish, Sepia pharaonis (Ehrenberg, 1831) exposed to hypoxia stresses and post-anoxia recovery

Oxygen deficiency (hypoxia and anoxia) is an emerging concern in estuarine and coastal ecosystems worldwide. Previous studies on Mollusca Cephalopoda have focused on the effects of hypoxia stress on physiological performance and survival, but there are few reports on the molecular mechanism, and the application of metabolomics in cephalopods remains unknown. In this study, a ¹H nuclear magnetic resonance (NMR) based metabolomics approach was applied to investigate the metabolites profiles of Sepia pharaonis (Ehrenberg, 1831) during hypoxia and post-anoxia recovery. The results revealed that obvious tissue-specific metabolic responses were induced by hypoxia stresses. Hypoxia exposure influenced the levels of many metabolites (e.g. BCAAs, lactate, and betaine strongly accumulated in the hepatic tissue while arginine and ATP significantly reduced; lactate and adenosine significantly increased in gills whereas arginine and choline significantly decreased; GABA, taurine and adenosine levels increased in brain but a significant depletion of N-Acetylaspartate and glycogen was found), disturbed energy and amino acid metabolism, and broke the balance of neurotransmitters and osmoregulators. Notably, almost all metabolites returned to pre-exposure levels after acute hypoxia recovery. However, we noted a pronounced depletion of the amino acid pool (arginine, glutamine, and alanine) in hepatic and gills after recovery, as well as organic osmolytes fluctuations (choline, betaine, and taurine). This work highlights the potential of metabolomics methods to elucidate the response of cuttlefish to hypoxia stress, as well as to provide knowledge on metabolic changes in cephalopods under the influences of environmental stress.

Ecotoxicology and environmental safety toxicity of pyrethroid cypermethrin on the freshwater snail Chilina parchappii: Lethal and sublethal effects

The aim of the present work was to study the effect of the pyrethroid cypermethrin (CYP) on the non-target freshwater snail Chilina parchappi. Initially, the sensitivity of adult snails to CYP was evaluated via the 96-h LC₅₀ test. Then, snails were exposed to subtethal CYP concentrations (0.1 and 10 mg/l) for 1, 4 and 10 days and the digestive glands were dissected for biomarkers analyses. Enzymatic activity of catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), as well as total glutathione reduced (GSH) levels, were determined. Histological analyses of morphology, intracellular accumulation of lipofucsins and neutral lipids accumulation in the digestive gland were also evaluated. As compared to other molluscs, C. parchappi showed high resistance to CYP exposure evidenced by the 96-h LC₅₀ value (44.59 mg/l). Snails exposed to sublethal CYP concentrations showed a statistically significant increase (p < 0.01) in GST (79-116%) and GPx (45-190%) activities with respect to controls. However, CAT activity showed a tendency to decrease with CYP treatment but was not statistically significantly different compared to control. Only high CYP concentration caused a statistically significant increase (p < 0.01) in GSH content (95-196%). There was evidence of structural changes in the digestive gland of snails exposed to CYP, showing a dose-dependent response. In exposed snails, some of the main symptoms included a reduction in the thickness of the epithelium, vacuolisation of the digestive cells and an increase in the number of excretory cells. Accumulation of lipofuscins (933-1006%) and neutral lipids (403%) were statistically significantly higher (p < 0.05) in snails exposed to CYP compared to control. This study showed that C. parchappii is quite tolerant to CYP exposure and that at sublethal concentrations, GSH metabolism could play a protective role against the pesticide harm in snails. Therefore, it would be interesting to study the response of this organism to other environmental stressors to assess its potential use in monitoring programs.

Lability of toxic elements in Submarine Tailings Disposal: The relationship between metal fractionation and metal uptake by sandworms (Alitta virens)

Mine tailings from the iron ore mine Sydvaranger Gruve have been deposited in Bøkfjorden, Northern Norway, for >40 years. This study investigates the environmental impacts of submarine tailings disposal one year after the cessation of the mine by combining analyses of total metal concentrations (nitric acid digestion) and metal fractionation patterns (sequential extraction procedure) of sediments with the metal uptake (bioassays) by sandworms (Alitta virens) exposed to Bøkfjorden sediment. The analyses focused on metals (As, Cd, Cr, Cu, Fe, Ni, Pb, Zn) in sediment cores retrieved from a horizontal transect of the fjord. High concentrations of the target metal iron was found in the fjord (>13,000 mg/kg). According to Norwegian sediment quality guidelines (SQG), cadmium (2.55 mg/kg) and lead (174 mg/kg) were the only metals to exceed good sediment quality at the source area of mine tailings discharge. Despite general low total metal concentrations, labile (summarized exchangeable, acid soluble, reducible fractions) and potentially labile (summarized labile and oxidisable fractions) pools of mine tailings-related metals of cadmium (10-82%), copper (25-88%) and lead (10-67%) were detected while iron were characterized as inert (residual fraction: 89-97%). Despite spatial trends in total metal concentrations presumed to originate from mine tailings (Cd, Cu, Fe, Pb), there were no correlations between total and labile fractions. This can be explained by the high concentrations of iron, which under oxidised forms are suggested to inhibit a high lability of other metals. The metal uptake of sandworms was generally high compared to similar studies and exceeded moderate contamination classes for all metals compared to Norwegian standard values. Both labile metal fractions (cadmium, copper and iron) and total metal concentrations (copper, iron) showed positive correlations (r > 0.6) with metal uptake. Thus, both the total and labile metal fractions can pose an environmental risk.

Multiple-biomarker approach in the assessment of the health status of a novel sentinel mussel Brachidontes rodriguezii in a harbor area

The objective of this study is to analyze whether a combination of biomarkers at different levels of biological complexity could be used to assess the health status of a population of Brachidontes rodriguezii associated to a harbor area in Mar del Plata, Argentina. A battery of biomarkers of general stress was measured in mussels collected from impacted and non-impacted areas. This included: condition index; shell analysis; histopathological alterations; atrophy and integrity of the digestive gland tissue; changes in cell type composition of the digestive gland, and glycogen accumulation. The studied biomarkers were integrated into the Integrative Biological Response (IBR/n) index. Overall, the IBR/n indicated a higher level of stress in mussels located in the harbor area. Thus, this biomarker index is a sensitive analytical tool that could be used to classify the ecotoxicological risk in coastal sites.

Numerical calculations of environmental impacts for deep sea mining activities

With the expected dramatic increase of mineral resources consumption, deep sea mining (DSM) was proposed as a method supplying the running of world economy by cooperating with or compensating for the terrestrial mining industry. However, its industrialization process is hindered by various reasons including the technological feasibility, economic profitability, and the DSM environmental impacts. The objective of this paper is to calculate the DSM environmental impacts based on a DSM environmental impact framework, which was selected through a systematic literature review in earlier work. The numerical calculations focus on the initial DSM disturbances and plume source, species disturbance, sediment plume and tailings. More importantly, the interconnection between the sediment plume and the species disturbances is also analysed particularly in this paper. The research quantifies the environmental impacts into a systematic framework, which could be helpful to assess the comprehensive environmental performances of a DSM activity and to promote the DSM industrialization process in the future.

The responses of Oncorhynchus mykiss coping with BDE-47 stress via PXR-mediated detoxification and Nrf2-mediated antioxidation system

The low brominated polybrominated diphenyl ether (PBDE) 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is ubiquitous in the marine environment. To elucidate the stress response and possible mechanisms underlying BDE-47, the rainbow trout fish Oncorhynchus mykiss were selected and orally fed bait with BDE-47 concentrations of 50 ng/g and 500 ng/g. BDE-47 was found to be mainly accumulated in head kidney and caused lipid peroxidation after prolonged exposure. We studied the detoxification system genes pregnane X receptor (PXR) and downstream genes (cytochrome 3 A, CYP3 A; glutathione S-transferase, GST) and their corresponding enzyme activity and found that the above indicators in the treatment groups increased first and then decreased with time, while the 500 ng/g group showed more significant changes. Further, the antioxidant system gene expression levels of the NF-E2-related factor 2 (Nrf2) and downstream genes (superoxide dismutase, SOD; catalase, CAT) were found significantly up-regulated with concentration and time. The change in the enzyme activity of SOD and CAT showed the same tendency as that of indicators of detoxifying system. The results showed that BDE-47 can accumulated in head kidney and caused activate and fast increase of genes and enzymes of detoxification and antioxidant system in the short-term and then damage the response systems in longer times. After Pearson correlation analysis, the Integrated Biomarker Response (IBR) Index was established with malondialdehyde (MDA) content; PXR, Nrf2, SOD, and CAT gene expression; and CYP3 A, GST, and CAT enzymatic activity, which were significantly related to BDE-47 bioaccumulation (P < 0.5). The IBR value can indicate the ecotoxicological responses of the head kidney to different BDE-47 concentrations exposure, but the high activity of the antioxidant system might obscure the damage of the detoxification system.

An integrative biological effects assessment of a mine discharge into a Norwegian fjord using field transplanted mussels

The blue mussel (Mytilus sp.) has been used to assess the potential biological effects of the discharge effluent from the Omya Hustadmarmor mine, which releases its tailings into the Frænfjord near Molde, Norway. Chemical body burden and a suite of biological effects markers were measured in mussels positioned for 8 weeks at known distances from the discharge outlet. The biomarkers used included: condition index (CI); stress on stress (SoS); micronuclei formation (MN); acetylcholine esterase (AChE) inhibition, lipid peroxidation (LPO) and Neutral lipid (NL) accumulation. Methyl triethanol ammonium (MTA), a chemical marker for the esterquat based flotation chemical (FLOT2015), known to be used at the mine, was detected in mussels positioned 1500 m and 2000 m downstream from the discharge outlet. Overall the biological responses indicated an increased level of stress in mussels located closest to the discharge outlet. The same biomarkers (MN, SoS, NL) were responsible for the integrated biological response (IBR/n) of the two closest stations and indicates a response to a common point source. The integrated biological response index (IBR/n) reflected the expected level of exposure to the mine effluent, with the highest IBR/n calculated in mussels positioned closest to the discharge. Principal component analysis (PCA) also showed a clear separation between the mussel groups, with the most stressed mussels located closest to the mine tailing outlet. Although not one chemical factor could explain the increased stress on the mussels, highest metal (As, Co, Ni, Cd, Zn, Ag, Cu, Fe) and MTA concentrations were detected in the mussel group located closest to the mine discharge.

Salinity mediates the toxic effect of nano-TiO2 on the juvenile olive flounder Paralichthys olivaceus

Increased production of engineered nanoparticles has raised extensive concern about the potential toxic effects on marine organisms living in estuarine and coastal environments. Meanwhile, salinity is one of the key environmental factors that may influence the physiological activities in flatfish species inhabiting in those waters due to fluctuations caused by freshwater input or rainfall. In this study, we investigated the oxidative stress and histopathological alteration of the juvenile Paralichthys olivaceus exposed to nano-TiO₂ (1 and 10 mg L^-1) under salinities of 10 and 30 psu for 4 days. In the gills, Na⁺-K⁺-ATPase activity significantly deceased after 4 days 10 psu exposure without nano-TiO₂ compared with 1 day of acclimating the salinity from the normal salinity (30 psu) to 10 psu. Under this coastal salinity, low concentration (1 mg L^-1) of nano-TiO₂ exerted significant impacts. In the liver, the activities of superoxide dismutase, catalase, the levels of lipid peroxide and malondialdehyde increased with nano-TiO₂ exposed under 30 psu. Such increase indicated an oxidative stress response. The result of the integrated biomarker responses showed that P. olivaceus can be adversely affected by high salinity and high concentration of nano-TiO₂ for a short-term (4 days) exposure. The histological analysis revealed the accompanying severe damages for the gill filaments. Principal component analysis further showed that the oxidative stress was associated with the nano-TiO₂ effect at normal salinity. These findings indicated that nano-TiO₂ and normal salinity exert synergistic effects on juvenile P. olivaceus, and low salinity plays a protective role in its physiological state upon short-term exposure to nano-TiO₂. The mechanism of salinity mediating the toxic effects of NPs on estuarine fish should be further considered.

Integrated toxicity evaluation of metals in sediments of Jiaozhou Bay (China): Based on biomarkers responses in clam Ruditapes philippinarum exposed to sediment extracts

To evaluate the integrated toxicity of metals in sediments of Jiaozhou Bay, we exposed clam (Ruditapes philippinarum) to sediments extracts obtained using of sediment extraction with deionised water adjusted to pH 4 which simulated the weak acidity in the digestive juice of clams and tested the selected biomarkers responses in clams for exposure over 15 days. At the same time, the contents of metals in sediments were assessed with method of the mean sediment quality guideline quotient (SQG-Q). The integrated biomarker response version 2 (IBR_v2) was used to assess the integrated toxicity induced by metals in sediment extracts based on biomarkers response in clams: the results demonstrated that site S7 located in the mouth of Nanxin'an River show higher IBR_v2 values compared to the other sites. The IBR_v2 values exhibited the good consistency with SQG-Q values.

Weathering impacts the uptake of polyethylene microparticles from toothpaste in Mediterranean mussels (M. galloprovincialis)

Mediterranean mussels (Mytilus galloprovincialis) were exposed over 21 days to polyethylene (PE) particles (0.01 mg ml^-1; 50-570 μm) isolated from toothpaste. PE was deployed in the Outer Oslofjord (Norway) for 21 days, before exposing the mussels to both virgin (PE-V) and weathered PE (PE-W) particles. The mussels ingested both types of particles, but significantly more weathered particles were ingested than virgin (p = .0317), based on PE dosed by weight (mg ml^-1) but not when considering particle number (PE-V: 1.18 ± 0.16 particles ml^-1; PE-W 1.86 ± 0.66 particles ml^-1;). PE particle ingestion resulted in structural changes to the gills and digestive gland, as well as necrosis in other tissues such as the mantle. No differences were found regarding the degree of tissue alteration between PE-virgin and PE-weathered exposures. This current study illustrates the importance of using weathered particles in microplastic exposure studies to reflect the behaviour of plastic particles after entering the marine environment. The observed tissue alterations demonstrate the potential adverse effects to mussels exposed to microplastic particles.

Effects of endosulfan, thiamethoxam, and indoxacarb in combination with atrazine on multi-biomarkers in Gammarus kischineffensis

Studies addressing the toxicity of pesticides towards non-target organisms focus on the median lethal concentration and biochemical response of individual pesticides. However, when determining environmental risks, it is important to test the combined effects of pesticides, such as insecticides and herbicides, which are frequently used together in agricultural areas. Here we aimed to investigate the toxic effects of the combined use of the herbicide atrazine and the insecticides, endosulfan, indoxacarb, and thiamethoxam on Gammarus kischineffensis. To do this, we tested the activities of oxidative stress, detoxification, and neurotoxicity biomarkers. Compared to atrazine alone, we detected higher glutathione-S-transferase, catalase and superoxide dismutase activities (oxidative stress biomarkers) when atrazine was combined with either endosulfan or indoxacarb. However, higher IBR values were determined in organisms where pesticide mixtures were used according to individual use. Based on these results, mixtures of atrazine and other pesticides may cause synergistic effects and may be evidence of increased toxicity and oxidative stress.

Blue mussels (Mytilus edulis spp.) as sentinel organisms in coastal pollution monitoring: A review

The blue mussel (Mytilus spp.) is widely used as a bioindicator for monitoring of coastal water pollution (mussel watch programs). Herein we provide a review of this study field with emphasis on: the suitability of Mytilus spp. as environmental sentinels; uptake and bioaccumulation patterns of key pollutant classes; the use of Mytilus spp. in mussel watch programs; recent trends in Norwegian mussel monitoring; environmental quality standards and background concentrations of key contaminants; pollutant effect biomarkers; confounding factors; particulate contaminants (microplastics, engineered nanomaterials); climate change; harmonization of monitoring procedures; and the use of deployed mussels (transplant caging) in pollution monitoring. Lastly, the overall state of the art of blue mussel pollution monitoring is discussed and some important issues for future research and development are highlighted.

Effects of TiO2 nanoparticles at predicted environmental relevant concentration on the marine scallop Chlamys farreri: An integrated biomarker approach

Manufactured nanoparticles (NPs) have caused extensive concern about their toxic effects on the marine environment. However, the chronic toxicity of NPs at predicted environmental relevant concentration on the marine organisms is poorly understood. In this study, we investigated the oxidative stress, neurotoxicity and histopathological effects of TiO₂ NPs at predicted environmental relevant concentration (1mg/L) to marine scallop Chlamys farreri. The results showed that TiO₂ NPs caused obviously oxidative damage on the scallops as evidenced by the significantly elevated superoxide dismutase (SOD), catalase (CAT) activities and malondialdehyde (MDA) contents. The increased acetylcholine esterase (AChE) activities reflected neurotoxicity of TiO₂ NPs. The histopathological analysis revealed alterations in the gill and digestive gland, such as dysplastic and necrosis. Additionally, integrated biomarker response (IBR) values indicated that TiO₂ NPs can cause strong toxic effects on the scallop. These results suggested that predicted environmental relevant TiO₂ NPs can cause adverse effects on scallops and IBR analysis can be used as an effective approach for risk assessment of NPs on the marine organisms.

Characterisation of fine-grained tailings from a marble processing plant and their acute effects on the copepod Calanus finmarchicus

Submarine tailing disposal (STD) of mining waste is practiced as an alternative to land fill disposal in several countries. Knowledge regarding the environmental implications of STD on fjord and other marine ecosystems, including the pelagic environment, is scarce. In this study, we characterised the particle shape, size and metal content of the fine-grained fraction of tailings (FGT) from a Norwegian marble processing plant and investigated their acute toxicity and impact on feeding rate in adult Calanus finmarchicus. Initial tailing dispersions with a concentration of 1 mg mL^-1 contained approximately 72 million particles, with 62% of particles between 0.6 and 1 μm in size. After a sedimentation time of 1 h, 69% of the particles between 0.6 and 5 μm remained dispersed, decreasing to 22% after 6 h. When subjected to low energy turbulence in exposure experiments, the formation of fragile agglomerates was observed. The FGT contained Al, Mn, Fe and Ni, with no detectable dissolution occurring during the 48 h exposure period. Acute exposure (up to 5 g L^-1) to FGT caused no mortality in C. finmarchicus. Similarly, feeding rates determined during a 40 h depuration period, were not significantly impacted. However, surface attachment and uptake of FGT into the digestive tract of the copepods was observed. This indicates that, whilst marble FGT are not acutely toxic to copepods, chronic effects such as impacts on organism's energy budgets could occur, highlighting the need for further research on potential sublethal effects in organisms exposed to fine inorganic particles.

Antioxidant enzyme activities as biomarkers of fluvial biofilm to ZnO NPs ecotoxicity and the Integrated Biomarker Responses (IBR) assessment

The presence of ZnO nanoparticles (ZnO NPs) in natural waters has raised concerns about their environmental impacts, but the potential influences of ZnO NPs on fluvial biofilm have not been reported. In this study, the utility of antioxidant enzyme activities (AEA) as biomarkers of fluvial biofilm to ZnO NPs toxicity and a method that combines AEA into an index of "Integrated Biomarker Responses (IBR)" were studied. Compared with the absence of ZnO NPs, scanning electron microscopy (SEM) images revealed that a large amount of ZnO NPs were adsorbed onto biofilm and these NPs exerted adverse effects on the viability of bacteria in biofilm. The production of reactive oxygen species (ROS) with high concentrations (30 and 100mg/L) of ZnO NPs exposure reached to 184% and 244% of the control, while no cell leakage and membrane damage were observed. After exposure to ZnO NPs for 0.25 and 3 days, the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR), glutathione peroxidase (GSH-Px) were significantly increased, respectively. At the end of exposure period (21 days), the AEA with the presence of 1mg/L ZnO NPs exposure were comparable to the control, while most of those in high concentrations of ZnO NPs were decreased. The results of IBR showed that the biofilm can adapt to 1mg/L ZnO NPs exposure, while be seriously damaged by 30 and 100mg/L ZnO NPs after 3 and 0.25 days. IBR can be used as an appropriate evaluation system of the toxicity effects of ZnO NPs on fluvial biofim.

Seasonal and annual variations in physiological and biochemical responses from transplanted marine bioindicator species Mytilus spp. during a long term field exposure experiment

In a pilot field study the long term response of transplanted bioindicator organisms Mytilus spp. was analyzed on the basis of physiological indices and biochemical measurements related to the energy budget. Three different time series with deployment times of eight to twelve months were compared according to seasonality and repeatability of the responses. Test organisms were incubated at a coastal station in the anthropogenically impacted estuary of the river Elbe and at a North Sea station located in vicinity to the Island of Helgoland in the German Bight. The stations differ in their hydrological as well as chemical characteristics. They can be discriminated by statistical factor analysis based on the measured biochemical parameter. Levels of all energy budget biomarker varied between seasons; however, the degree of variation of the specific response was differently expressed. The mussels deployed at Helgoland showed a reproducible high Condition Index in each sampling series and an oscillating Gonadosomatic Index representing the reproduction cycle. The lowest available energy was recorded in mussels at the estuarine sampling station compared to the off-shore station. This may be caused by the energetically costly maintenance of osmotic balance and consequently result in a lower amount of energy available for defense again chemical stress, growth and reproduction.

Biomonitoring of a polluted coastal area (Bay of Muggia, Northern Adriatic Sea): A five-year study using transplanted mussels

The subcellular effects of pollution were evaluated using two lysosomal biomarkers in mussels, Mytilus galloprovincialis, deployed periodically over a period of 5 years in a harbour area in the Bay of Muggia (Gulf of Trieste, North Adriatic Sea) that is strongly influenced by anthropogenic activities. Mussels were collected from a clean marine farm and analysed (sample T0). A sub-sample was transplanted to the harbour site (sample M) and analysed after about 12 weeks. An additional sub-sample was relocated within the farm as a control and was also tested at the end of the 12-week period (sample T1). The transplantation procedures were repeated twice yearly for 5 consecutive years, starting in 2009. Two well-established lysosomal biomarkers, i.e. lysosomal membrane stability and lipofuscin accumulation, were evaluated in hepatopancreas cells. The body condition index and mortality rate were also assessed. Moreover, various pollutants were determined in both mussel flesh, for a better comprehension of the biological response, and sediments, for a general characterization of the study area. As a whole, the applied biomarkers were found to be appropriate for determining the responses of mussels to environmental pollutant loads over time. Variations in lysosomal membrane stability and lipofuscin content were mostly related to total PAHs and metals respectively. Our results confirm the usefulness of active biomonitoring in evaluating pollution trends in marine coastal areas and in particular the value of lysosomal biomarkers as a rapid screening tool for highlighting pollutant effects at least at organism level.