Long-Term Spatio-Temporal Trends of Organotin Contaminations in the Marine Environment of Hong Kong

Sulforaphane modulates some stress parameters in TPT-exposed Cyprinus carpio in relation to liver metabolome

This study aimed to investigate the protective effect of sulforaphane (SFN) on liver injury induced by triphenyltin (TPT) in Cyprinus carpio (C. carpio). The fish (average weight of 56.9±0.4 g) were divided into 4 groups with four replicates: the control, TPT, SFN+TPT and SFN groups. Twenty fish were selected from each tank and cultured for 8 weeks. Then, serum and liver samples were collected for physiological, biochemical and metabolomic analyses. In the present study, TPT downregulated the expression of the lysozyme gene, upregulated HSP70 and Hsp90 gene expression, and decreased the activities of serum antioxidant enzymes (SOD, CAT, and GPX). However, dietary SFN alleviated oxidative stress, and prevented changes in immune genes. Metabolomic analysis revealed that TPT exposure changed key metabolites in the main phenylalanine, fatty acid and glycerophosphatide metabolic pathways, which are related to inflammation, oxidative stress and immunity and might also lead to an imbalance of liver energy and lipid metabolism. Dietary SFN promoted amino acid metabolism and increased metabolites related to immunity, anti-inflammation, antioxidation, and protein synthesis in liver of C. carpio. In summary, dietary SFN supplementation reversed TPT-induced decreases in immunity and oxidative stress and regulated amino acid metabolism, lipid metabolism, inflammation and immunity-related metabolic pathways.

Transcriptomic analysis reveals the endocrine toxicity of tributyltin and triphenyltin on the whelk Reishia clavigera and mechanisms of imposex formation

Organotin compounds (OTs) are endocrine disruptors that induce imposex in hundreds of gastropods, but little is known about their underlying molecular mechanisms. This study aimed to investigate the endocrine toxicity and molecular responses to tributyltin (TBT) and triphenyltin (TPT) exposure in the whelk Reishia clavigera, which often serves as a biomonitor for OT contamination. Over a 120-day exposure to environmentally relevant concentrations of TBT (1000 ng L-1) and TPT (500 ng L-1), we observed a significant increase in penis length in both male and female whelks. Notably, TPT exhibited a stronger potency in inducing pseudo-penis development and female sterility, even at a half dose of TBT. Bioaccumulation analysis also revealed higher persistence and accumulation of TPT in whelk tissues compared to TBT. Differential expression analysis identified a substantial number of differentially expressed genes (DEGs), with TPT exposure eliciting more DEGs than TBT. Our results demonstrated that OTs induced xenobiotic metabolism and metabolic dysregulation in the digestive gland, impaired multiple cellular functions and triggered neurotoxicity in the nervous system, and disrupted lipid homeostasis and oxidative stress in the gonads. Furthermore, imposex was possibly associated with disturbances in retinoic acid metabolism, nuclear receptor signaling, and neuropeptide activity. When compared to TBT, TPT exhibited a more pronounced endocrine-disrupting effect, attributable to its higher bioaccumulation and substantial interruption of transcriptional regulation, OT detoxification, and biosynthesis of retinoic acids in R. clavigera. Our results, therefore, highlight the importance of considering the differences in bioaccumulation and molecular toxicity between TBT and TPT in future risk assessments of these contaminants. Overall, our study provided molecular insights into the toxicity and transcriptome profiles in R. clavigera exposed to TBT and TPT, shedding light on the endocrine-disrupting effects and reproductive impairment in female gastropods.

Determination of organotin compounds in marine sediments from Arctic Svalbard and West Antarctic Fildes Peninsula

This study investigated the contamination levels of five typical organotin compounds in Arctic and Antarctic marine sediments. Organotin total concentrations ranged from not detected (ND) to 37.9 ng Sn/g dw and from ND to 34.0 ng Sn/g dw in surface sediments of Svalbard and Fildes Peninsula, respectively. Dibutyltin accounted for 11.3 %-100 % of butyltins in Arctic sediments, whilst diphenyltin was the predominant phenyltin species in both Arctic and Antarctic. However, the concentrations of tributyltin and triphenyltin were lower than low-substituted organotins in the study areas, indicating the effectiveness of international ban on the use of triorganotin-based antifouling paints. No significant difference in organotin contamination was found between Arctic and Antarctic, although the time suffered from human interference was shorter in the Antarctic. Overall, these data can provide a diagnosis of recent organotin inputs in polar regions and serve as a baseline for future study assessing their local applications.

Triphenyltin Influenced Carotenoid-Based Coloration in Coral Reef Fish, Amphiprion ocellaris, by Disrupting Carotenoid Metabolism

Triphenyltin (TPT), a kind of persistent pollutant, is prevalent in the aquatic environment and could pose a threat to coral reef fish. However, little is known about the toxicity of TPT on coral reef fish, especially regarding the representative characteristics of body coloration. Therefore, this study chose the clownfish (Amphiprion ocellaris) in order to investigate the effects of TPT exposure on its carotenoid-based body coloration under the environmentally relevant concentrations (0, 1, 10 and 100 ng/L). After TPT exposure for 60 d, the carotenoid contents were decreased and histological damage in the liver was found, shown as nuclear pyknosis and shift, lipid deposition and fibrotic tissue hyperplasia. Liver transcriptomic analysis showed that TPT exposure interfered with oxidative phosphorylation and fatty acid metabolism pathways, which related to carotenoids uptake and metabolism. Furthermore, TPT exposure led to oxidative damage in the liver, which is responsible for the changes in the antioxidant capacity of enzymes, including GSH, MDA, POD, CAT and T-SOD. TPT exposure also affected the genes (Scarb1, CD36, Stard3 and Stard5) related to carotenoid absorption and transport, as well as the genes (GstP1 and Bco2) related to carotenoid deposition and decomposition. Taken together, our results demonstrate that TPT influenced carotenoid-based coloration in coral reef fish by disrupting carotenoid metabolism, which complements the ecotoxicological effects and toxic mechanisms of TPT and provides data for the body color biology of coral reef fishes.

Organotins in fish, shrimp, and cephalopods from the Pearl River Estuary, China: Dietary exposure risk to Indo-Pacific humpback dolphin and human

Food has regularly been proven to be a key source of exposure to environmental pollutants, drawing attention to the dietary exposure risks of contaminants to mammals with significant daily food intake. Here, the levels of six organotin compounds (OTs) in 18 fish (n = 310), three cephalopods (n = 50), and one shrimp (n = 34) from the Lingdingyang (LDY) and west four region (WFR) of the Pearl River Estuary (PRE) and their dietary exposure risks to Indo-Pacific humpback dolphins and humans were first investigated. Total OT levels ranged from 3.84 to 901. 48 ng/g wet weight (ww) in 22 prey species from the LDY, and from 14.37 to 1364.64 ng/g ww in 19 species from the WFR. The LDY marine species generally accumulated higher butyltin levels but lower phentyltin levels than those in the WFR. All species have a phenyltin degradation index <1 and over 60 % of the sampled species have a butyltin degradation index <1, suggesting the PRE marine species might be exposed to the fresh discharge of OTs. A total of nine marine species exceeded the threshold levels of OT intake for adverse health effects on human juveniles by consumption, all 22 marine species posed high dietary risks to the PRE humpback dolphins. Moreover, probabilistic risk assessment using Monte Carlo simulation revealed that the probabilities of RQ values associated with WFR OT exposure higher than 1 were 18.87 % for human adults, 40.55 % for human juveniles, 100 % for both humpback dolphin adults and humpback dolphin juveniles. Our results highlighted the potentially high dietary exposure risks of OTs to marine mammals and residents in the PRE.

Current Status of Antifouling Biocides Contamination in the Seto Inland Sea, Japan

A monitoring survey of antifouling biocides was conducted in the Harima Nada Sea and Osaka Bay of the Seto Inland Sea, Japan to assess contamination by organotin (OT) compounds and alternative biocides. The concentrations of tributyltin (TBT) compounds in surface water ranged from 1.0 to 2.8 ng/L, and the detected TBT concentrations in the bottom water layer were higher than those in the surface water. The concentrations of TBT compounds in sediment samples ranged from 2.0 to 28 ng/g dry weight (dw), respectively. The concentrations of alternative biocides in the water and sediment were lower than those before the banning of TBT by the International Maritime Organization (IMO). Although triphenyltin (TPT) compounds were not detected in water samples, TPT compounds were detected in the range of < 0.1-2700 ng/g dw in sediment samples. Their concentrations in the water samples were as follows: diuron, < 1-53 ng/L; Sea-Nine 211, < 1-1.8 ng/L; Irgarol 1051, < 1-4.0 ng/L; dichlofluanid, < 1-343 ng/L; and chlorothalonil, < 1-1 ng/L, and the ranges of these alternative compounds in sediment samples were diuron, 32-488 ng/g dw; Sea-Nine 211, 47-591 ng/g dw; Irgarol, 33-128 ng/g dw; dichlofluanid, 67-8038 ng/g dw; and chlorothalonil, 31-2975 ng/g dw. Thus, the OTs and alternative biocides have still been detected in water and sediment samples from closed sea areas.

Toxic effects of triphenyltin on the development of zebrafish (Danio rerio) embryos

Triphenyltin (TPT) is known to be an environmental endocrine disruptor and has adverse effects on aquatic animals. In this study, zebrafish embryos were treated with three different concentrations (12.5, 25, 50 nmol/L) based on the LC₅₀ value at 96 h post fertilization (96 hpf), after TPT exposure. The developmental phenotype and hatchability were observed and recorded. Reactive oxygen species (ROS) levels in zebrafish were detected at 72 hpf and 96 hpf using 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) as a probe. The number of neutrophils after exposure was observed using transgenic zebrafish Tg (lyz: DsRed). RNA-seq analysis was used to compare the gene expression changes in zebrafish embryos at 96 hpf in the control group and 50 nmol/L TPT exposure group. The data revealed that TPT caused a delay in hatching of zebrafish embryos in a time- and dose-dependent manner, as well as causing pericardial edema, spinal curvature and melanin reduction. ROS levels in embryos exposed to TPT increased, and the number of neutrophils increased after TPT exposure to Tg (lyz: DsRed) in transgenic zebrafish. RNA-seq results were also analyzed, and KEGG enrichment analysis showed that significant differential genes were enriched in the PPAR signaling pathway (P < 0.05), and the PPAR signaling pathway mainly affected genes related to lipid metabolism. The RNA-seq results were verified using real-time fluorescence quantitative PCR (RT-qPCR). Oil red O and Nile red staining showed increased lipid accumulation after TPT exposure. These findings suggest that TPT affects the development of zebrafish embryos even at relatively low concentrations.

Assessing the ecotoxicity of combined exposure to triphenyltin and norfloxacin at environmental levels: A case study of immunotoxicity and metabolic regulation in carp (Cyprinus carpio)

This paper evaluates the coexistence risks of triphenyltin (TPT) and norfloxacin (NOR) to aquatic organisms in the aquatic environment. Carp (Cyprinus carpio) was used as the test organism, the control and exposure groups (1 μg/L TPT), 1 mg/L (NOR), 1 μg/LTPT+1 mg/LNOR (TPT_NOR)) were set up according to the environmental concentration in the severely polluted area for 42 days. The single/combined toxic effects of TPT and NOR on aquatic organisms were evaluated by analyzing carp brain transcriptome sequencing, gut microbiota structure, and detection of biochemical indicators and RT-qPCR. Our results show that TPT and NOR induce lipid metabolism disorder in carp brain tissue, affecting the metabolism of cytochrome P450 to exogenous substances, and NOR also induces immunosuppression in carp. Long-term exposure to TPT combined with NOR amplifies the monotoxicity of TPT or NOR on lipid metabolism and immunosuppression in carp, induces immune dysfunction in brain tissue and changes in gut microbiota structure. However, TPT_NOR has no obvious neurotoxicity on the brain, but it can inhibit the level of intestinal MDA. This highlights that co-exposure of TPT and NOR amplifies metabolic disorders and immunosuppressive functions in carp.

Organotin contamination in seafood from the Yucatán Peninsula, Mexico: Is there a potential risk for the health of consumers?

Since seafood is considered an important source of organotin compounds (OTCs), the present study assessed the potential risk to human health of ingesting butyltins (BTs) and phenyltins (PhTs) along with this type of food. Seafood samples were collected at five fishing sites in the Yucatán Peninsula (Mexico) during February and March 2018. In general, organotins were detected in all samples, suggesting a widespread occurrence of these compounds in the investigated region. The average concentration of total organotins in the muscle of demersal fish (Lutjanus synagris, Lutjanus campechanus, Calamus pennatula, Haemulon plumierii, Rhomboplites aurorubens), pelagic fish (Euthynnus alletteratus, and Opisthonema oglinum), gastropods (Melongena bispinosa and Strombus pugilis), oyster (Crassostrea virginica) and shrimp (Penaeus duorarum) was 146.7 ± 76.2, 93.1 ± 92.6, 61.0 ± 53.0, 76.7 ± 2.6, and 28.8 ± 2.7 ng Sn g-1 dry weight, respectively. Overall, MPhT among PhTs was the dominant compound in fish, while TBT among BTs was the dominant compound in shellfish. Regarding the toxic OTCs, TBT followed by DBT were the predominant compounds in all seafood species, while TPhT was below the quantification limit in most samples. The estimated daily intake values were lower than the tolerable daily intake (TDI) for the sum of organotins established by the European Food Safety Authority (EFSA). Furthermore, the hazard quotients (HQ) and hazard indices (HI) values were all lower than 1, suggesting that daily exposure to these levels of organotins is unlikely to cause any harm to the human health of seafood consumers at the Yucatán Peninsula. Thus, consumers may not be at risk through the inclusion of these investigated seafood species in their normal diet. However, due to the increasing coastal urbanization, maritime activities, and the likely illegal use of tin-based paints in Mexico, additional monitoring is needed to assess organotin levels in other regions along the Mexican coastal zone and using other seafood species.

Organotins Remain a Serious Threat to the Indo-Pacific Humpback Dolphins in the Pearl River Estuary

Marine mammals often accumulate high levels of environmental contaminants, even those that are globally regulated regarding usage, raising concerns about their health status. Here, we conducted the first investigation of tissue distribution, spatiotemporal trends, and potential risks of six organotin compounds (OTs) in Indo-Pacific humpback dolphins (n = 101) from the northern South China Sea during 2003-2021. We detected the highest level of hepatic triphenyltin in these humpback dolphins compared with the results reported in cetaceans globally, and the liver accumulated the highest OT concentrations than other analyzed tissues. Despite the downward trend of butyltins in humpback dolphins after the global ban on the use of OTs as antifouling paints, levels of phenyltins have continued to increase over the past 20 years, suggesting that the other applications of phenyltins in South China remain prevalent. In vitro and in vivo analyses revealed that tissue-relevant doses of OTs could induce agonistic effects on the dolphin peroxisome proliferator-activated receptor γ as a master regulator of lipid homeostasis and altered the dolphin fatty acid profiles. Our results highlight the lipid-disrupting effects of current OT exposure in humpback dolphins and emphasize the need for further efforts to eliminate OT contamination in South China.

Pollutants from shipping - new environmental challenges in the subarctic and the Arctic Ocean

Maritime activities in the subarctic and Arctic Ocean are predicted to substantially increase in the future due to climate change and declining sea ice cover. Inevitably, the consequences will be seen in impacts on marine ecosystems in this region at many different levels, such as increased pollution load due to antifouling biocides, polycyclic aromatic hydrocarbons, metals and pharmaceuticals. Here we discuss the current situation and evaluate the effect of increased shipping on the environmental status of subarctic and Arctic waters, in relation to elevated loads of both legacy and emerging pollutants in the region. It is of high importance to evaluate the current levels of selected pollutants, which will most likely rise in near future. Furthermore, it is important to improve our understanding of the effects of these pollutants on marine organisms at high latitudes, as the pollutants may behave differently in cold environments compared to organisms at lower latitudes, due to dissimilar physiological responses and adaptations of the cold-water organisms. Integrative studies are needed to better understand the impact of pollutants on the marine fauna while monitoring programmes and research should be continued, with an increased capacity for emerging pollutants of concern.

Tissue distribution of triphenyltin compounds in marine teleost fishes

Continuous release of the highly toxic triphenyltin compounds (TPT) from antifouling paints and fungicides has caused serious pollution to urbanized coastal marine environments worldwide since the 1960s. Using gas-chromatography mass-spectrometry (GC-MS), this study investigated the distribution profile of TPT in 15 types of tissues of four marine teleost fish species collected from Hong Kong waters. Concentrations of TPT in various tissues had a significant positive correlation with protein contents in the tissues (r = 0.346, p < 0.001) and, to a lesser extent with lipid contents (r = 0.169, p =  0.020). Highest concentrations of TPT were consistently found in liver, ranging from 1074.9 to 3443.7 ng/g wet weight; whereas fish scales always contained the least concentration of TPT in all species, ranging from 10.4 to 48.5 ng/g wet weight. Through mass balance models and regression analyses, muscle tissues were found to contribute most to the total TPT body burden, and the average TPT concentration of both dorsal and ventral muscles was identified as the best predictor for estimating TPT burden in the entire fish. Hence, further investigations of bioaccumulation and biomagnification of TPT in fishes should adopt this modelling approach in estimating its total body burden in individual fish.

Toxicity evaluation of triphenyltin in zebrafish larvae by embryonic malformation, retinal development, and GH/IGF axis

The adverse influences of triphenyltin (TPT) on the aquatic system have been of great concern due to their widespread use and ubiquity in water environment, although it has been prohibited as antifouling coatings. In the present study, we investigated the developmental toxicity of TPT on zebrafish embryos by exposure to different concentrations (0, 1, 10, and 100 ng/l) from 2-h post-fertilization (hpf). Some parameters of developmental abnormalities (hatching, survival, body length, and malformation) were recorded, as well as the expression of several genes involved in the retinal development and growth hormone/insulin-like growth factor (GH/IGF) axis. Our results showed that TPT exposure induced developmental toxicity, including growth inhibition, malformation, and the dysregulation of gene expression levels related to the retinal development and GH/IGF axis. Thus, our data indicated that environmental exposure of TPT could induce developmental toxicity in zebrafish embryos, and those parameters could extend our understanding of the adverse effects of TPT on aquatic organisms.

Occurrence, ecological and human health risks of phenyltin compounds in the marine environment of Hong Kong

Triphenyltin (TPT) has been known as one of the most toxic compounds being released into the marine environment by anthropogenic means. This study assessed the contamination statuses of TPT and its two major degradants, i.e., monophenyltin and diphenyltin, in seawater, sediment and biota samples from marine environments of Hong Kong, a highly urbanized and densely populated city, and evaluated their ecological and human health risks. The results showed that the Hong Kong's marine environments were heavily contaminated with these chemicals, especially for TPT. Concentration ranges of TPT in seawater, sediment and biota samples were 3.8-11.7 ng/L, 71.8-91.7 ng/g d.w., and 9.6-1079.9 ng/g w.w., respectively. As reflected by high hazard quotients (1.7-5.3 for seawaters; 46.1-59.0 for sediments), TPT exhibited high ecological and human health risks. Our results are essential for the future management and control of anthropogenic TPT use in antifouling paints and as biocides in agriculture.

Occurrence and trophic magnification profile of triphenyltin compounds in marine mammals and their corresponding food webs

The occurrence of triphenyltin (TPT) compounds, a highly toxic antifouling biocide, has been documented in marine environments and organisms all over the world. While some studies showed that marine mammals can be used as sentinel organisms to evaluate the pollution status of emerging contaminants in the environment because of their long lifespans and high trophic levels, information regarding the contamination status of TPT in marine mammal species has been limited over the past decade. More importantly, the primary bioaccumulation pathway of TPT in these long-lived apex predators and the corresponding marine food web is still uncertain. Therefore, this study aimed to evaluate the contamination statuses of TPT in two marine mammal species, namely the finless porpoise and the Indo-Pacific humpback dolphin, and assess the trophic magnification potential of TPT along the food webs of these two species, using stable isotope analysis, and chemical analysis with gas chromatography-mass spectrometry. The results showed that TPT is the predominant residue in majority of the analyzed individuals of two marine mammals, with concentrations ranging from 426.2 to 3476.6 ng/g wet weight in their muscle tissues. Our results also demonstrated an exponential increase in the concentration of TPT along the marine food web, indicating that trophic magnification occurs in the respective food webs of the two marine mammals. The range of trophic magnification factors of TPT in the food webs of finless porpoise and Indo-Pacific humpback dolphin was 2.51-3.47 and 2.45-3.39, respectively. These results suggest that high trophic organisms may be more vulnerable to the exposure of TPT-contaminated environments due to the high trophic magnification potential, and thus ecological risk of these compounds ought to be assessed with the consideration of their bioaccumulation potentials in these marine mammals.

Long-term triphenyltin exposure disrupts adrenal function in adult male rats

Triphenyltin is an organotin, which is widely used as a fungicide in agriculture. Here, we reported the effects of triphenyltin on adrenal function in adult male rats. Adult male Sprague Dawley rats were daily gavaged with triphenyltin (0, 0.5, 1, and 2 mg/kg body weight) from postnatal day 56-86. Triphenyltin significantly decreased serum corticosterone levels at 1 and 2 mg/kg without affecting serum levels of aldosterone and adrenocorticotropic hormone. Triphenyltin increased thickness of zona glomerulosa without affecting that of zona fasciculata. Triphenyltin did not affect cell number in zona fasciculata and zona glomerulosa. Triphenyltin down-regulated the expression of Scarb1, Star, Cyp11a1, Hsd3b1, Cyp21, Cyp11b1, and Hsd11b1 at 1 and/or 2 mg/kg while it up-regulated the expression of At1, Nr4a2, and Hsd11b2 at 2 mg/kg. Triphenyltin activated the phosphorylation of AMPKα while suppressed the phosphorylation of AKT1 and SIRT1/PGC-1α in rat adrenals in vivo and H295R cells in vitro. In vitro, triphenyltin also induced ROS production in H295R cells at 100 nM, a concentration at which no apoptosis was induced. In conclusion, triphenyltin disrupts glucocorticoid synthesis in rat adrenal cortex via several mechanisms: 1) lowering AKT1 phosphorylation and SIRT1/PGC-1α levels; 2) activating AMPKα; and 3) possibly inducing ROS production.

Effects of low concentrations of triphenyltin on neurobehavior and the thyroid endocrine system in zebrafish

In the present study, to evaluate neurobehavioral toxicity and the thyroid-disrupting effects of environmental levels of triphenyltin (TPT), the zebrafish larvae were exposed to 1, 10 and 100 ng/l TPT. In the neurobehavioral assay, increased levels of dopamine and serotonin, decreased content of nitric oxide, inhibited activities of acetylcholinesterase and monoamine oxidase were observed in the whole body of zebrafish larvae after TPT treatment, as well as the serious abnormal non-reproductive behavior. Moreover, the whole-body the T4 levels were markedly decreased significantly, whereas T3 levels were not significantly changed under TPT stress. In addition, TPT exposure significantly changed the expression levels of genes related to thyroid system, including corticotropin-releasing hormone gene crh, thyroid-stimulating hormone gene tshβ, thyroglobulin gene tg, sodium/iodide symporter gene nis, thyroid hormone nuclear receptor trα, isoform trβ, types I deiodinase gene dio1and types II deiodinase gene dio2. The regulated responsiveness of thyroid hormone and related genes expression levels suggested that TPT could induce the thyroid disrupting effects in zebrafish larvae. Therefore, our results provide new aspects of TPT as an endocrine disrupting chemical.

Triphenyltin exposure alters the antioxidant system, energy metabolism and the expression of genes related to physiological stress in zebrafish (Danio rerio)

The adverse influences of triphenyltin (TPT) on aquatic system have been of great concern due to their widespread use and ubiquity in water environment. Here, zebrafish larvae (7 days after hatching) were exposed to TPT for 14 days to study its toxicity on the antioxidant system, energy metabolism and the expression of genes related to physiological stress. Results shows that the oxidative stress was generated in fish larvae exposed to TPT with higher concentrations (10 and/or 100 ng/l), and the energy metabolic parameters (RNA/DNA ratio, Na + -K + -ATPase) were significantly inhibited in fish exposed to 100 ng/l TPT. Additional, the expression levels of genes related to physiological stress were up-regulated in a dose-dependent manner, including heat shock protein70 (hsp70) and metallothionein (mt). Moreover, the PERK-eIF2α pathway was found as the main branch activated by TPT exposure in fish larvae. Thus, TPT-induced antioxidant responses, energy metabolism disorder and physiological stress in fish larvae were reflected by the parameters measured, which could provide some useful information for full understanding the exact mechanisms of TPT toxicity.

Influences of Salinity and Organic Compounds on Embryo Development in Three Medaka Oryzias Congeners with Habitats Ranging from Freshwater to Marine

To clarify whether Oryzias congeners, including freshwater, brackish water, and marine medaka, would be useful models for evaluating environmental chemical effects in various aquatic ecosystems, we examined the influence of salinity on their embryo development. We also compared the toxicity values of the organotin compounds triphenyltin and tributyltin, which remain pollutants of marine and freshwater ecosystems, between Oryzias latipes (freshwater), Oryzias melastigma (brackish water), and Oryzias javanicus (saltwater). Hatching and survival rates of O. latipes were significantly decreased at a salinity of 34, whereas O. melastigma and O. javanicus were adaptable to various salinities from freshwater to seawater. The lowest observed effect concentrations of organotin compounds for survival and embryo development were the similar in the three species. The similarity of the species' responses to organotin compounds indicated that Oryzias congeners are useful for ecological risk assessment of chemicals in a range of aquatic ecosystems, from freshwater to marine.

The effect of polystyrene plastics on the toxicity of triphenyltin to the marine diatom Skeletonema costatum-influence of plastic particle size

The effect of polystyrene (PS) particles on the toxicity of triphenyltin (TPT) to the marine diatom Skeletonema costatum was investigated. The 0.1-μm PS particles attached to the cell walls of S. costatum but did not cause adverse effects on the growth of the diatom. The adsorption of TPT to PS particles was negligible in seawater systems, but the presence of 0.1-μm PS significantly reduced the bioavailable concentrations of TPT in f/2-Si medium, indicating a potential three-way interaction between TPT, PS particles, and components of f/2-Si medium. The adsorption of TPT to PS of smaller size (i.e., 0.1 μm) was stronger than that of PS of larger size (i.e., 5 μm), which was probably attributed to larger surface areas of smaller PS particles. The presence of PS could reduce the toxicity of TPT. IC₅₀ values of TPT increased from 0.56 to 0.85 and 0.71 μg/L at the presence of 20 mg/L 0.1-μm PS and 5-μm PS, respectively. The overall results of this study profiled the combined toxic effects of PS and TPT on marine phytoplankton species and highlighted the difference in adsorption of organic pollutants by microplastics in different ambient mediums.

Concentration of Organotin and Booster Biocides in Sediments of Seagrass Area from Sungai Pulai Estuary, South of Johor, Malaysia

Antifouling compounds are widely used in paints applied on ship hulls to prevent attachment of fouling organisms. However, a certain amount of these chemicals could leach from the painted surface, enter seawater, and pose deleterious effects on various marine biotas. The present study aimed to determine the concentration of organotin (OT) compounds and booster biocides in sediments collected from the seagrass area of Sungai Pulai estuary, Malaysia. The sediment samples were collected from three points on the seagrass bed, brought back to the laboratory, extracted using standard extraction procedure, and the analytes were analysed using gas chromatography-mass spectrometry (GC-MS) method. The results showed that tributyltin (TBT) concentrations in sediments were within the range of 8.1 ± 0.4 to 10.6 ± 0.5 µg/kg, whereas the values of triphenyltin (TPT) were between 17.1 ± 0.9 and 19.4 ± 1.0 µg/kg. The range of concentration of booster biocides, namely diuron, dichlofluanid chlorothalonil, Irgarol 1051, M1, and Sea-Nine 211, were from <0.1 to 22.9 ± 1.1, 48.7 ± 2.4 to 800 ± 40, <0.1 to 6.2 ± 0.3, <0.1 to 1.4 ± 0.1, 44 ± 2.2 to 877 ± 44, and 9.1 ± 0.5 to 170 ± 8.5 µg/kg, respectively. The concentration of organotin was much lower than the previous study conducted in southern Johor. Meanwhile, the increased concentration of booster biocides proves the use of these compounds as antifouling paints in shipping systems nowadays.

Organotin contamination in commercial and wild oysters from China: Increasing occurrence of triphenyltin

Organotin contamination in marine environment has been a public concern for many years due to its adverse impacts on biota and human health. This study investigated levels, distribution and health risks of six organotin compounds: tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT) and monophenyltin (MPhT) in commercial and wild oysters in China. The total organotin in commercial oysters ranged from 251 to 1949 ng Sn g^-1 dw (dry weight) >. Two endocrine disruptors TBT and TPhT were detected in these samples with the highest level of 68.1 ± 20.1 ng Sn g^-1 dw and 747 ± 7.3 ng Sn g^-1 dw, respectively. For wild oysters, the concentrations of total organotins varied from 33.3 to 2671 ng Sn g^-1 dw. Butyltins were dominated by TBT with the mean level of 26.1 ± 30.0 ng Sn·g^-1 dw and showed no significant spatial variation between the southern and northern coastal zones (p > 0.05). However, compared with the north, phenyltin levels especially TPhT were much higher in the south coastline (246-1484 ng Sn·g^-1 dw) due to the wider use of TPhT-based biocides in local mariculture and agriculture. Health risk assessment indicated that a daily exposure of TPhT-contaminated oysters (including commercial and wild ones) may pose adverse threats to human particularly children as the risk quotients (RQ) were higher than 1. Organotin contamination (e.g., TPhT) still occurs in the South China's coastal zones after the TBT ban, which deserves future research and effective measures to protect the marine ecosystem and human health.

In utero exposure to triphenyltin disrupts rat fetal testis development

Triphenyltin is an organotin that is widely used as an anti-fouling agent and may have endocrine-disrupting effects. The objective of the current study was to investigate effects of triphenyltin on the development of rat fetal testis. Female pregnant Sprague Dawley dams were gavaged daily with triphenyltin (0, 0.5, 1, and 2 mg/kg body weight/day) from gestational day 12 to day 21. Triphenyltin dose-dependently decreased serum testosterone levels (0.971 ± 0.072 and 0.972 ± 0.231 ng/ml at 1 and 2 mg/kg, respectively) from control level (2.099 ± 0.351 ng/ml). Triphenyltin at 1 and 2 mg/kg doses also induced fetal Leydig cell aggregation, decreased fetal Leydig cell size and cytoplasmic size. Triphenyltin decreased the expression levels of Lhcgr, Scarb1, Star, Cyp11a1, Cyp17a1, Insl3, Fshr, Pdgfa, and Sox9 by 0.5 mg/kg dose and above. However, triphenyltin did not affect Leydig and Sertoli cell numbers. In conclusion, the current study indicated that in utero exposure of triphenyltin disrupted fetal Leydig and Sertoli cell development.

Bioaccumulation of organic pollutants in Indo-Pacific humpback dolphin: A review on current knowledge and future prospects

Indo-Pacific humpback dolphin (Sousa chinensis) are chronically exposed to organic pollutants since they inhabit shallow coastal waters that are often impacted by anthropogenic activities. The aim of this review was to evaluate existing knowledge on the occurrence of organic pollutants in Indo-Pacific humpback dolphins, identify knowledge gaps, and offer recommendations for future research directions. We discussed the trends in the bioaccumulation of organic pollutants in Indo-Pacific humpback dolphins focusing on sources, physicochemical properties, and usage patterns. Furthermore, we examined factors that influence bioaccumulation such as gender, age, dietary intake and tissue-specific distribution. Studies on bioaccumulation in Indo-Pacific humpback dolphin remain scarce, despite high concentrations above 13,000 ng/g lw we previously detected for PFOS, ∑PBDE and chlorinated paraffins. The maximum concentration of organochlorines detected was 157,000 ng/g wt. Furthermore, variations in bioaccumulation were shown to be caused by factors such as usage patterns and physicochemical properties of the pollutant. However, restrictions in sampling inhibit investigations on exposure pathway and toxicity of organic pollutants in Indo-Pacific humpback dolphin. We proposed the use of biopsy sampling, predictive bioaccumulation and toxicity modeling, and monitoring other emerging contaminants such as microplastics and pharmaceuticals for future health risk assessment on this critically endangered marine mammal species.

Long-term laboratory culture causes contrasting shifts in tolerance to two marine pollutants in copepods of the genus Tigriopus

Organismal chemical tolerance is often used to assess ecological risk and monitor water quality, yet tolerance can differ between field- and lab-raised organisms. In this study, we examined how tolerance to copper (Cu) and tributyltin oxide (TBTO) in two species of marine copepods, Tigriopus japonicus and T. californicus, changed across generations under benign laboratory culture (in the absence of pre-exposure to chemicals). Both copepod species exhibited similar chemical-specific changes in tolerance, with laboratory maintenance resulting in increased Cu tolerance and decreased TBTO tolerance. To assess potential factors underlying these patterns, chemical tolerance was measured in conjunction with candidate environmental variables (temperature, UV radiation, diet type, and starvation). The largest chemical-specific effect was found for starvation, which decreased TBTO tolerance but had no effect on Cu tolerance. Understanding how chemical-specific tolerance can change in the laboratory will be critical in strengthening bioassays and their applications for environmental protection and chemical management.

Tributyltin: Advancing the Science on Assessing Endocrine Disruption with an Unconventional Endocrine-Disrupting Compound

Tributyltin (TBT) has been recognized as an endocrine disrupting chemical (EDC) for several decades. However, only in the last decade, was its primary endocrine mechanism of action (MeOA) elucidated-interactions with the nuclear retinoid-X receptor (RXR), peroxisome proliferator-activated receptor γ (PPARγ), and their heterodimers. This molecular initiating event (MIE) alters a range of reproductive, developmental, and metabolic pathways at the organism level. It is noteworthy that a variety of MeOAs have been proposed over the years for the observed endocrine-type effects of TBT; however, convincing data for the MIE was provided only recently and now several researchers have confirmed and refined the information on this MeOA. One of the most important lessons learned from years of research on TBT concerns apparent species sensitivity. Several aspects such as the rates of uptake and elimination, chemical potency, and metabolic capacity are all important for identifying the most sensitive species for a given chemical, including EDCs. For TBT, much of this was discovered by trial and error, hence important relationships and important sensitive taxa were not identified until several decades after its introduction to the environment. As recognized for many years, TBT-induced responses are known to occur at very low concentrations for molluscs, a fact that has more recently also been observed in fish species. This review explores the MeOA and effects of TBT in different species (aquatic molluscs and other invertebrates, fish, amphibians, birds, and mammals) according to the OECD Conceptual Framework for Endocrine Disruptor Testing and Assessment (CFEDTA). The information gathered on biological effects that are relevant for populations of aquatic animals was used to construct Species Sensitivity Distributions (SSDs) based on No Observed Effect Concentrations (NOECs) and Lowest Observed Effect Concentrations (LOECs). Fish appear at the lower end of these distributions, showing that they are as sensitive as molluscs, and for some species, even more sensitive. Concentrations in the range of 1 ng/L for water exposure (10 ng/g for whole-body burden) have been shown to elicit endocrine-type responses, whereas mortality occurs at water concentrations ten times higher. Current screening and assessment methodologies as compiled in the OECD CFEDTA are able to identify TBT as a potent endocrine disruptor with a high environmental risk for the original use pattern. If those approaches had been available when TBT was introduced to the market, it is likely that its use would have been regulated sooner, thus avoiding the detrimental effects on marine gastropod populations and communities as documented over several decades.

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.

Distinguishing globally-driven changes from regional- and local-scale impacts: The case for long-term and broad-scale studies of recovery from pollution

Marine ecosystems are subject to anthropogenic change at global, regional and local scales. Global drivers interact with regional- and local-scale impacts of both a chronic and acute nature. Natural fluctuations and those driven by climate change need to be understood to diagnose local- and regional-scale impacts, and to inform assessments of recovery. Three case studies are used to illustrate the need for long-term studies: (i) separation of the influence of fishing pressure from climate change on bottom fish in the English Channel; (ii) recovery of rocky shore assemblages from the Torrey Canyon oil spill in the southwest of England; (iii) interaction of climate change and chronic Tributyltin pollution affecting recovery of rocky shore populations following the Torrey Canyon oil spill. We emphasize that "baselines" or "reference states" are better viewed as envelopes that are dependent on the time window of observation. Recommendations are made for adaptive management in a rapidly changing world.

Effects of triphenyltin on reproduction in Japanese medaka (Oryzias latipes) across two generations

Triphenyltin (TPT) is an organotin compound used in marine anti-fouling coatings to prevent the attachment and growth of marine organisms, and it has negative effects on aquatic organisms. TPT is still detected at low concentrations, although its use has been prohibited at least in the European Community and is restricted in Japan as well. Studies using Japanese medaka (Oryzias latipes) indicate that TPT has the potential to inhibit reproduction. Although TPT is detected in many aquatic ecosystems, the multi-generational impact of TPT remains unknown. We investigated the two-generational effects of TPT on Japanese medaka and examined the relationships of several such effects between the F0 and F1 generations. Suppression of fecundity was observed in both generations, and fertility and growth were inhibited in the F1 generation. Moreover, delayed hatching and lower hatchability were observed in F1 embryos. Importantly, the value of the lowest observed effect concentration (LOEC) for these influences in F1 was lower than that in F0: that is, the LOEC values of fecundity and mortality were 3.2μg/L in the F0 generation and 1.0μg/L in the F1 generation. Fertility was not affected by TPT in F0, whereas it was significantly suppressed in the 1.0μg/L-exposure group of the F1 generation. Our results provide the first evidence of the effects of TPT on reproduction in a teleost fish across two generations, highlighting the concern that TPT could affect reproduction and mortality at decreasing concentrations in temporally overlapping generations.

De novo transcriptome assembly of the marine gastropod Reishia clavigera for supporting toxic mechanism studies

The intertidal whelk Reishia clavigera is commonly used as a biomonitor of chemical contamination in the marine environment along Western Pacific region, and as a model for mechanistic studies of organotin-mediated imposex development. However, limited genomic resources of R. clavigera have restricted its role for the investigation of molecular mechanisms of such endocrine disruptions. This study, therefore, aimed to establish tissue-specific transcriptomes of the digestive gland, gonad, head ganglia, penis and the remaining body part of the male and female R. clavigera. By combining the results, a global transcriptome was obtained. A total of 578,134,720 high-quality filtered reads were obtained using Illumina sequencing. The R. clavigera transcriptome comprised of 38,466 transcripts and 32,798 unigenes with predicted open reading frames. The average length of transcripts was 1,709bp with N50 of 2,236bp. Based on sequence similarity searches against public databases, 28,657 transcripts and 24,403 unigenes had at least one BLAST hit. There were 17,530 transcripts and 14,897 unigenes annotated with at least one Gene Ontology (GO) term. Moreover, 5,776 transcripts and 5,137 unigenes were associated with 333 Kyoto Encyclopaedia of Genes and Genomes (KEGG) pathways. The numbers of unigenes were similar among the five target tissues and between sexes, but tissue-specific expression profiles were revealed by multivariate analyses. Based on the functional annotation, putative steroid hormone-associated unigenes were identified. In particular, we highlighted the presence of steroid hormone receptor homologues that could be the targets for mechanistic studies of the organotin-mediated imposex development in marine gastropods. This newly generated transcriptome assembly of R. clavigera provides a valuable molecular resource for ecotoxicological and environmental genomic studies.