Comparison of the acute toxicity of tributyltin and copper to veliger larvae ofNassarius reticulatus(L.)

Responses of zebra and quagga mussels to copper and tribytiltin exposure: Bioconcentration, metabolic and cardiac biomarkers

One of the top ecological priorities is to find sensitive indicators for pollution monitoring. This study focuses on the bioconcentration and responses (condition index, survival, oxygen consumption, heart rates, and oxidative stress and neurotoxic effect biomarkers) of mussels from the Volga River basin, Dreissena polymorpha and Dreissena bugensis, to long-term exposure to toxic chemicals such as tributyltin (TBT, 25 and 100 ng/L) and copper (Cu, 100 and 1000 μg/L). We found that TBT was present in the tissues of zebra and quagga mussels in comparable amounts, whereas the bioconcentration factor of Cu varied depending on its concentration in water. Differences in responses between the two species were revealed. When exposed to high Cu concentrations or a Cu-TBT mixture, quagga mussels had a lower survival rate and a longer heart rate recovery time than zebra mussels. TBT treatment caused neurotoxicity (decreased acetylcholinesterase activity) and oxidative stress (increased levels of thiobarbituric acid reactive substances) in both species. TBT and Cu levels in mussel tissues correlated positively with the condition index, but correlated with the level of acetylcholinesterase in the mussel gills. The principal component analysis revealed three main components: the first consists of linear combinations of 14 variables reflecting TBT water pollution, TBT and Cu levels in mussel tissues, and biochemical indicators; the second includes Cu water concentration, cardiac tolerance, and mussel size; and the third combines weight, metabolic rate, and heart rates. Quagga mussels are less tolerable to contaminants than zebra mussels, so they may be used as a sensitive indicator.

The ecotoxicology of marine tributyltin (TBT) hotspots: A review

Tributyltin (TBT) was widely used as a highly efficient biocide in antifouling paints for ship and boat hulls. Eventually, TBT containing paints became globally banned when TBT was found to cause widespread contamination and non-target adverse effects in sensitive species, with induced pseudohermaphroditism in female neogastropods (imposex) being the best-known example. In this review, we address the history and the status of knowledge regarding TBT pollution and marine TBT hotspots, with a special emphasis on the Norwegian coastline. The review also presents a brief update on knowledge of TBT toxicity in various marine species and humans, highlighting the current understanding of toxicity mechanisms relevant for causing endocrine disruption in marine species. Despite observations of reduced TBT sediment concentrations in many marine sediments over the recent decades, contaminant hotspots are still prevalent worldwide. Consequently, efforts to monitor TBT levels and assessment of potential effects in sentinel species being potentially susceptible to TBT in these locations are still highly warranted.

Protective potency of ascorbic acid supplementation against cytotoxicity and DNA fragmentation induced by triphenyltin on human liver carcinoma cells

Agrochemicals are one the most significant sources of environmental pollution. Cytotoxicity and genotoxicity are the serious side effects of fungicide. In the current study, I have evaluated acute cytotoxicity and genotoxicity of triphenyltin (TPT) on human hepatic carcinoma (HepG2) cells and the ameliorating effect of ascorbic acid for 24 h. In this experiment, I have exposed HepG2 cells to ascorbic acids (50, 100, and 200 μM) simultaneously and 24 h prior triphenyltin (TPT, 400 ng/ml) exposure for 24 h to determine the protective effect of ascorbic acid by using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and NRU (neutral red uptake) assays. Oxidative stress, such as intracellular reactive oxygen species and glutathione levels, was measured in HepG2 cells. The intracellular reactive oxygen species was evaluated using fluorescent probe DCFDA (6-carboxy-2',7' dichloro-dihydrofluorescein diacetate). Apoptosis and genotoxicity effects of TPT in HepG2 cells were determined using flow cytometry and comet assay. The result of these experiments showed that the TPT compound (400 ng/ml) induced cytotoxicity, oxidative stress and apoptosis, and DNA damage in HepG2 cells.Ascorbic acid reduced cytotoxicity, oxidative stress, apoptosis, and genotoxicity induced by TPT. Thus, ascorbic acid is a potent antioxidant, and it showed a significant protective effect against toxicity induced by TPT in HepG2 cells.

Copper sulphate impact on the antioxidant defence system of the marine bivalves Cerastoderma edule and Scrobicularia plana

Anthropogenic activities, such as agriculture and industrial activities, are a main source of pollution contributing for the degradation of water quality and thus affecting the living organisms of aquatic systems. Copper is widely used at these practices being often released into the aquatic systems and may cause negative effects in its communities. This study proposes to determine the effects of copper in the antioxidant defence system of two size classes (big and small sizes) of Scrobicularia plana and Cerastoderma edule, two marine bivalve species with commercial interest. It was observed the behaviour activity of the organisms during the exposure to copper sulphate (CS) and was determined the enzymatic activities of glutathione-S-transferases (GST), glutathione reductase (GR) and glutathione peroxidase (GPx) (both selenium-dependent (SeGPx) and total (tGPx)) in the muscle tissue (foot). Lipid peroxidation (LPO) was evaluated through thiobarbituric acid reactive substances (TBARS) measurement in the foot. Changes in the behaviour and enzymatic activity were observed. Lipid peroxidation was observed at C. edule and S. plana big and small size classes, respectively, according to TBARS levels. The foot showed to be a good tissue to be used in biochemical analysis to detect the presence of toxicants.

Population dynamics of the rock shell Reishia clavigera associated with different degrees of organotin contamination in Hong Kong

Application of organotins in antifouling systems on ship hulls has been globally prohibited by the International Maritime Organization since September 2008. It is, therefore, anticipated that there is a recovery of imposex-affected gastropod populations worldwide. We studied the population dynamics of the rock shell Reishia clavigera in six locations around Hong Kong's coastal waters, covering different degrees of organotin contamination for 25months (2011-2013). Abundance and density of R. clavigera were higher in clean sites, while they tended to grow faster in polluted sites. Over time, we observed recruitments in clean sites while recruitments in polluted sites were limited. The results suggested that the lack of apparent recovery of the local R. clavigera populations was probably due to the prevalence of organotin contamination, especially triphenyltin, in this region. This study, therefore, calls for mitigation and long-term monitoring of organotin contamination in marine environments of Hong Kong and South China.

A chronic toxicity test for the tropical marine snail Nassarius dorsatus to assess the toxicity of copper, aluminium, gallium, and molybdenum

Chronic toxicity test methods for assessing the toxicity of contaminants to tropical marine organisms are generally lacking. A 96-h chronic growth rate toxicity test was developed for the larval stage of the tropical dogwhelk, Nassarius dorsatus. Growth rates of N. dorsatus larvae were assessed following exposures to copper (Cu), aluminium (Al), gallium (Ga), and molybdenum (Mo). Exposure to Cu at 28 °C validated the sensitivity of the test method, with 10% (EC10) and 50% (EC50) effect concentrations of 4.2 μg/L and 7.3 μg/L Cu, respectively. The EC10 and EC50 values for Al (<0.45-μm filtered fraction) at 28 °C were 115 μg/L and 185 μg/L, respectively. The toxicity of Cu and Al was also assessed at 24 °C and 31 °C, representing average year-round water temperatures for subtropical and tropical Australian coastal environments. At 24 °C, the growth rate of control larvae was reduced by 52% compared with the growth rate at 28 °C and there was an increase in sensitivity to Cu (EC50 = 4.7 μg/L) but a similar sensitivity to Al (EC50 = 180 μg/L). At 31 °C the control growth rate increased by 35% from that measured at 28 °C and there was reduced sensitivity to both Cu and Al (EC50s = 8.5 μg/L and 642 μg/L, respectively). There was minimal toxicity resulting from Ga (EC50 = 4560 μg/L) and Mo (no effect at ≤7000 μg/L Mo). Environ Toxicol Chem 2016;35:1788-1795. © 2015 SETAC.

Imprinting of metal receptors into multilayer polyelectrolyte films: fabrication and applications in marine antifouling

Polymeric films constructed using the layer-by-layer (LbL) fabrication process were employed as a platform for metal ion immobilization and applied as a marine antifouling coating. The novel Cu2+ ion imprinting process described is based on the use of metal ion templates and LbL multilayer covalent cross-linking. Custom synthesized, peptide mimicking polycations composed of histidine grafted poly(allylamine) (PAH) to bind metal ions, and methyl ester containing polyanions for convenient cross-linking were used in the fabrication process. Two methods of LbL film formation have been investigated using alternate polyelectrolyte deposition namely non-imprinted LbLA, and imprinted LbLB. Both LbL films were cross linked at mild temperature to yield covalent bridging of the layers for improved stability in a sea water environment. A comparative study of the non-imprinted LbLA films and imprinted LbLB films for Cu2+ ion binding capacity, leaching rate and stability of the films was performed. The results reveal that the imprinted films possess enhanced affinity to retain metal ions due to the preorganization of imidazole bearing histidine receptors. As a result the binding capacity of the films for Cu2+ could be improved by seven fold. Antifouling properties of the resulting materials in a marine environment have been demonstrated against the settlement of barnacle larvae, indicating that controlled release of Cu ions was achieved.

Adult exposure to the synthetic hormone 17α-ethynylestradiol affects offspring of the gastropods Nassarius burchardi and Nassarius jonasii

The aim of this study was to determine whether adult exposure to endocrine disrupting compounds affects offspring using trans-generational testing. Adult estuarine dwelling gastropods Nassarius burchardi and Nassarius jonasii were exposed to the synthetic estrogen 17α-ethynylestradiol (EE2) to determine the effects on the development and survival of their offspring. Adults were maintained in synthetic seawater controls and EE2 treatments (0.005, 0.05, 0.5, 50µg/L) over a sixteen week period. Egg capsules were collected from the adults following four, ten and sixteen weeks of adult exposure and transferred to different EE2 exposure scenarios. Treatment concentrations were selected to represent changes in EE2 exposure that could occur over different periods in an organism's lifecycle. Egg capsules laid by adults were therefore transferred to control or EE2 treatments (0.005, 0.05, 0.5, 5, 50, 500µg/L) to develop until hatching. The percentage of egg capsules with unviable eggs and abnormalities, number of days for hatching to occur and hatching success were measured. The veliger larvae that hatched from egg capsules following two, eight and fourteen weeks of adult exposure to EE2 and controls were used in 96h acute toxicity tests with controls and EE2 treatments at concentrations of 0.5, 5, 50, 500, 1250, 2500, 4000µg/L. Exposure of adult N. burchardi and N. jonasii to EE2 affected the percentage of egg capsules with unviable eggs, the development and hatching success of embryos and survival of veligers. These toxicity tests produced a complex set of results with different responses in developing eggs and veliger larvae to the adult EE2 treatments and length of adult exposure. This study demonstrates the importance of trans-generational testing and adult exposure scenarios in toxicity investigations.

Inhibition of larval swimming activity of the coral (Platygyra acuta) by interactive thermal and chemical stresses

This study examined the interactive effects of copper and elevated temperature and subsequent depuration on Platygyra acuta coral larvae. Larval mortality and motility were significantly affected by copper alone (70% and 100% inhibition respectively). Their respective lethal/inhibitory concentration (LC50/IC50) were 10-130% and 86-193% higher than those reported for other larvae. Temperature (ambient, 27°C and elevated, 30°C) alone and the combination of temperature and copper did not significantly affect both endpoints. This study provides the first quantitative data on depuration effect on resumption of larval motility after copper exposure, although no sign of larval recovery was observed. These findings suggest that the effects of copper pollution outweigh the thermal tolerance of coral larvae. High LC50 and IC50 recorded may be unique for corals from marginal reefs like Hong Kong which have already been exposed to high levels of copper pollution.

Effect of tributyltin (TBT) in the metabolic activity of TBT-resistant and sensitive estuarine bacteria

The effect of tributyltin (TBT) on growth and metabolic activity of three estuarine bacteria with different TBT resistance profiles was investigated in an organic-rich culture medium (TSB) and in phosphate buffered saline (PBS) buffer. Exposure to TBT was assessed by determining its effect on growth (OD(600 nm) measurement), bacterial productivity (leucine incorporation), viability (CFU counts), aggregation and cell size (from Live/Dead analysis), ATP and NADH concentrations. TBT exposure resulted in decrease of bacterial density, cell size, and metabolic activity. In addition, cell aggregates were observed in the TBT-treated cultures. TBT strongly affected bacterial cell metabolism and seemed to exert an effect on its equilibrium, interfering with cell activity. Also, TBT toxicity was lower when cells were grown in TSB than in PBS, suggesting that a nutrient-rich growth medium can protect cells from TBT toxicity. This study contributes to our understanding of the TBT-resistant cell behavior reflected in its physiology and metabolic activity. This information is of utmost importance for further studies of TBT bioremediation.

Environmental levels, toxicity and human exposure to tributyltin (TBT)-contaminated marine environment. a review. b_antizar@hotmail.com

Tributyltin (TBT) is a toxic chemical used for various industrial purposes such as slime control in paper mills, disinfection of circulating industrial cooling waters, antifouling agents, and the preservation of wood. Due to its widespread use as an antifouling agent in boat paints, TBT is a common contaminant of marine and freshwater ecosystems exceeding acute and chronic toxicity levels. TBT is the most significant pesticide in marine and freshwaters in Europe and consequently its environmental level, fate, toxicity and human exposure are of current concern. Thus, the European Union has decided to specifically include TBT compounds in its list of priority compounds in water in order to control its fate in natural systems, due to their toxic, persistent, bioaccumulative and endocrine disruptive characteristics. Additionally, the International Maritime Organization has called for a global treaty that bans the application of TBT-based paints starting 1 of January 2003, and total prohibition by 1 of January 2008. This paper reviews the state of the science regarding TBT, with special attention paid to the environmental levels, toxicity, and human exposure. TBT compounds have been detected in a number of environmental samples. In humans, organotin compounds have been detected in blood and in the liver. As for other persistent organic pollutants, dietary intake is most probably the main route of exposure to TBT compounds for the general population. However, data concerning TBT levels in foodstuffs are scarce. It is concluded that investigations on experimental toxicity, dietary intake, potential human health effects and development of new sustainable technologies to remove TBT compounds are clearly necessary.