Ecological risk assessments of endocrine disrupting organotin compounds using marine neogastropods in Hong Kong

As active ingredients of anti-fouling paints that are widely used on ship hulls, organotin compounds, in particular tributyltin (TBT), are well-known endocrine disruptors causing sex changes in marine organisms and widespread in coastal waters and sediments worldwide. In this study, a comprehensive ecological risk assessment (ERA) of organotins was conducted in Hong Kong waters through determining the imposex status, sex ratio and tissue burdens of these compounds in the neogastropods, Thais clavigera and Thais luteostoma collected from 29 coastal sites. We also investigated the historical trend of organotin effects on these gastropods, and performed a probabilistic ERA based on tissue burden of TBT in the animals. Our results demonstrated that imposex indices were positively correlated with the body burden of organotins in the gastropods. Across all sites, the sex ratio (female:male) decreased significantly with increasing imposex levels or tissue burden of organotins, implying that such pollutants can result in a male-biased population, potentially leading to local extinction in extreme cases. Based on the ERA, 5.4% of all populations of T. clavigera are at risk due to exposure to TBT; the risks include growth inhibition, impairment of immune functions and reduced fitness. Seriously impacted areas included Aberdeen, Repulse Bay, Butterfly Beach, Mui Wo and Ha Mei Wan. A comparison with historical data revealed that there had been some improvement in the areas with low marine traffic, and distant from the major harbour/port. This could partly be due to the restriction on the use of TBT on small vessels (<25m in length) since 1992. Nevertheless, the organotin contamination still remains severe in areas with high marine traffic or adjacent to large harbours/ports. In particular, the situation in the northeastern waters of Hong Kong has been getting worst since 1996 that is probably associated with the rapid development of the cargo container port at Yantian in China.     

Assessment of imposex and butyltin concentrations in Gemophos viverratus (Kiener, 1834), from São Vicente,Republic of Cabo Verde (Africa)

This work constitutes the first assessment of tributyltin (TBT) pollution levels in the Republic of Cabo Verde (Africa) and proposes the marine gastropod Gemophos viverratus (Kiener, 1834) as a new bioindicator of TBT pollution in the Macaronesia and west coast of Africa. Specimens were collected between August and October 2012 along a gradient of naval traffic in São Vicente Island. The results clearly indicate an increase of imposex levels (percentage of females affected with imposex, 0–100 %; vas deferens sequence index, 0–4.1; relative penis length index, 0–54.6 %) and female TBT contamination (from 5 to 37 ngSn g^?1 dry weight (dw)) from outside to inside the harbour of Porto Grande Bay and identify this area as the focus of TBT pollution in the island. The butyltin degradation index for G. viverratus tissues ranged between 1.3 and 2.2, which being above 1 suggests that a considerable part of TBT inputs to the bay may not be very recent. Sterile females were found inside the harbour with an incidence up to 21.4 %. Considering the existence of a planktonic veliger stage in the life cycle of G. viverratus, it is expected that recruitment of newborn individuals can be supplied from unaffected breeding females inside and outside the Porto Grande Bay, resulting in a reduced impact of TBT pollution on population abundance. G. viverratus is very promising to be used as a simple, inexpensive and efficient novel tool for TBT pollution biomonitoring in the Macaronesia and west coast of Africa, a region for which there is an astonishing lack of information concerning levels and ecological impacts of TBT pollution.     

Butyltins concentration levels and imposex occurrence in snails from the Sicilian coasts (Italy)

Two sampling campaigns have been carried out along the Sicilian coasts within the frame of a European project (Hic-TBT) financed by the LIFE programme. Snails and sediments have been sampled at 5 stations, characterised by very low (Ustica natural sea reserve), low (Ustica harbour), intermediate (Castellamare and Termini Imerese) and high shipping densities (Palermo). Biological and chemical analyses were carried out in order to evaluate the incidence of imposex occurring in snails, and the concentration levels of organotins in sediment and snail samples. Despite the low organotin concentration levels in sediment and snail samples, the results show that imposex is widespread around Sicily. In four locations almost all female snails were affected by imposex at advanced development stages, even in areas with a fairly low shipping density. Only in the natural sea reserve of Ustica Island imposex was relatively less severe. Finally a logarithmic correlation between TBT and imposex stages was observed.     

Organotin contamination in the Atlantic Ocean off the Iberian Peninsula in relation to shipping

Imposex in female snails, a bioindicator of TBT contamination, and the presence of organotins in snails' tissue and sediments were studied at nine sites off the western Iberian Peninsula. The study was part of a European project (acronym HIC-TBT) co-financed by the EU-LIFE programme, intending to investigate and communicate the impact of organotins from ships in marine ecosystems. Snails and sediments were sampled during two cruises in May/June 1999 and in January 2000 in areas of high, intermediate and low-shipping density. Imposex was found in female snails from several sampling sites, some of which had an imposex incidence of 100%. Differences in sensitivity were found between species; hence comparison of imposex levels between locations where different species were collected was not straightforward. Total organotin concentrations in sediments (sum of butyl and phenyltin compounds) ranged from 21 to 185 ng Sn g(-1) with higher values for most sites sampled in the vicinity of shipping lanes. Organotin concentration in snails' tissue ranged from <5 to 196 ng Sn g(-1), which are similar to those found in snails from other offshore areas contaminated by TBT. Overall, these results give further support to the recent ban on the use of organotin based antifouling paints to all ship size.     

Imposex occurrence in marine whelks at a military facility in the high Arctic

Imposex was found in the Arctic whelk Buccinum finmarkianum at several marine stations off Thule Air Base, an US military facility in Northwest Greenland. This indicates a widespread contamination with the antifouling agents, tributyltin (TBT) or triphenyltin (TPhT) in the area, but such contamination was not supported by the organotin analyses in sediments, whelks and clams, which in general was below the analytical detection limit. Organotin concentrations above the detection limit were found only at one station close to a quay, where the highest frequency of imposex also occurred. This suggests that imposex in B. finmarkianum is a biomarker of TBT more sensitive than the detection limits, which the analytical chemistry could achieve in this study.     

Survey of butyltin contamination in Portuguese coastal environments

Butyltin compounds (MBT, DBT and TBT) in intertidal sediments collected in four different Portuguese coastal environments have been measured in order to evaluate the extent of contamination. The sites chosen were the Rias of Aveiro and Faro, and the Sado and Tejo estuaries. These zones were traditional areas for shellfish production in the recent past, but the effects of industrial development have caused a deterioration of the environment. Specific contaminations were derived from the harbour (commercial and/or fisheries) and shipyard activities, resulting in a release of TBT and causing the oyster populations of the above mentioned estuaries to almost disappear. Results presented in this study give a survey of TBT contamination levels found in the four areas. The paper discusses the importance of the pollution in comparison with other European coastal areas.     

Gyrineum natator: a potential indicator of imposex along the Indian coast

Imposex related studies have used neogastropods as sentinel organism. In this effort, we elucidate the potential of a mesogastropod, Gyrineum natator, for imposex monitoring on the central west coast of India. Observations were made with specimens collected from Mumbai (three stations), Ratnagiri (two stations), Goa (one station) and Mangalore (one station). The analyzed populations at all four sites were affected by imposex. The six different stages of imposex in this organism are illustrated through schematic and scanning electron micrographs. In view of the anticipated ban on TBT based antifouling paints this baseline information can serve as an indicator for environmental monitoring in this region.     

Quantification of organotin compounds and determination of imposex in populations of dogwhelks (Nucella lapillus) from Norway

Unintentional effects of the antifouling agent tributyltin (TBT) have been discovered in marine gastropods as the induction of male sex characters in females, known as imposex. The occurrence of imposex in dogwhelks (Nucella lapillus) was investigated in 41 populations sampled in 1993-1995 along the Norwegian coast. A method for quantification of organotin species using gas chromatography and atomic emission detection (GC-AED) was developed. Some degree of imposex occurred in almost all populations of dogwhelks studied, except in four from Northern Norway. The concentration of organotin compounds in the gastropods from the unaffected populations was below the detection limit (7 ng Sn/g d.w.). The concentration of TBT in dogwhelks from affected populations was in the range 48-1096 ng Sn/g d.w. A positive relation between the concentration of TBT in dogwhelks and the degree of imposex was found.     

Tributyltin contamination around an oil terminal in Sullom Voe (Shetland)

This report provides clear evidence of tributyltin (TBT) contamination of coastal waters close to an oil terminal handling large tankers. Dogwhelk populations from Sullom Voe, Shetland, have been examined for the development by females of certain male sexual characteristics (e.g. a penis and vas deferens). This condition, termed imposex, is a response to exposure to tributylin compounds, and can be quantified by use of the relative penis size index (RPSI). Dogwhelk populations throughout Sullom Voe were strongly affected by TBT (RPSI 34 to 81%), and up to 90% of the females in the oil terminal area were sterile. Queen scallops collected in the Voe contained enhanced concentrations of tin in adductor muscle and gonad tissue (0.02 to 0.23 mg kg(-1) wet weight), but it is considered unlikely that their growth and development is adversely affected. Tin was rarely detected in scallops, queens, or dogwhelks outside the Voe, although the development of a vas deferens in many of the female dogwhelks indicated a degree of contamination of the open waters of Yell Sound. TBT was detectable (2 ng litre(-1) as tin) in only two sea water samples taken from the terminal area.     

Oxygen levels versus chemical pollutants: do they have similar influence on macrofaunal assemblages? A case study in a harbour with two opposing entrances

Generally, harbours are polluted zones characterised by low values of hydrodynamism and oxygen in the water column and high concentrations of pollutants in sediments. The harbour of Ceuta, North Africa, has an unusual structure; it is located between two bays connected by a channel, which increases the water movement and exchange in the harbour, maintaining moderate oxygen levels in the water-sediment interface. Nevertheless, high concentration of organic matter, nutrients and heavy metals were measured in sediments from this harbour. Under these unusual conditions (high levels of pollution but total saturation of oxygen in the water column) we studied the responses of soft-bottom macrobenthic communities using uni and multivariate analyses. The number of species was similar inside and outside the harbour but the species composition differed between internal and external stations; oxygen levels seem to control the "quantity" of species whereas pollutants control the "quality" of them.     

Imposex and tributyltin contamination as a consequence of the establishment of a marina, and increasing yachting activities at Phuket Island, Thailand

The objective was to investigate how tributyltin (TBT) contamination resulting from the establishment of a new marina and increasing yachting activities at Phuket Island, Thailand affects the area. A minimum of 30 specimen of the mangrove dwelling muricid Chicoreus capucinus were collected at five stations 2 months before and 5, 9, 18 and 33 months after Yacht Haven Marina was constructed. Imposex measured as RPLI and VDSI were significantly correlated to duration of time after construction and distance from the marina. All females developed imposex close to the marina after 18 months, whereas no significant increase occurred at stations more than 2 km from the marina. To evaluate the range of effects of the increasing yachting activities the muricid Thais distinguenda was used as an indicator of imposex at two popular mooring sites for yachts at Phi Phi and Raja Island in Phangna Bay, Thailand. The incidence of imposex was 100% at stations close to the mooring sites. A significant correlation existed between the distance from the sites and the incidence of imposex. The increasing incidence of imposex suggest that TBT contamination is worsening, against global trends, because regulations prohibiting the use of TBT-based paints, do not exist in Thailand.     

The recovery of populations of dogwhelks suffering from imposex in the Firth of Forth 1987-1997/98

The impact of tributyltin (TBT) contamination on dogwhelk (Nucella lapillus) populations was assessed at 33 sites in the Firth of Forth, UK, during spring 1997 and summer 1998. The sex ratio of the animals; the ratio of juveniles to adults; the degree of imposex, as determined by the relative penis size index (RPSI); and the total tin concentration in a sample of dogwhelk tissue were used as measurements of TBT impact on dogwhelk populations. These data were compared with data from a similar survey carried out at the same sites in the Firth of Forth in 1987 (Bailey, S.K., Davies, I.M., 1988. Tributyltin contamination in the Firth of Forth (1975-1987). Science of the Total Environment 76, 185-192.) before restrictions were introduced on the use of TBT. The results demonstrate a general recovery in dogwhelk populations from the impact of TBT at the majority of the sites studied, although at six of the sites, the RPSI value remains high enough to suggest breeding problems in the population. It is suggested that large vessels are responsible for localised cases of imposex within the Firth of Forth.     

Tributyltin distribution in the coastal environment of Peninsular Malaysia

The occurrence of tributyltin (TBT) is reported in the coastal waters of a few selected sites in Peninsular Malaysia. Water, bivalves and sediment samples collected were analysed specifically for TBT using sensitive analytical methods which involved a solvent extraction procedure with appropriate clean-up followed by graphite furnace atomic absorption spectrometric measurements. The levels of TBT in the seawater in unexposed areas were found in the range from <3.4 to 20 ng litre(-1) as compared to coastal areas with high boat and ship activities where TBT levels in seawater were generally above 30 ng litre(-1), with the highest level found at 281.8 ng litre(-1). TBT levels in the tissues of random cockle and soft-shell clam samples from local markets were found in the range from <0.5 to 3.7 ng g(-1) wet weight. The levels of TBT found in green mussel samples both from the market (23.5 ng g(-1) wet weight) and those from a mussel farm (14.2 ng g(-1) wet weight) indicate slight accumulation of TBT. In sediments, TBT levels were found ranging from <0.7 ng g(-1) dry weight in unexposed coastal sites to as high as 216.5 ng g(-1) dry weight for a site within a port area.     

Effects of triphenyltin chloride and five other organotin compounds on the development of imposex in the rock shell, Thais clavigera

The imposex promotion activities of six organotin compounds--tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT), diphenyltin (DPT) and monophenyltin (MPT)--were examined by injection experiments with the rock shell, Thais clavigera (Prosobranchia; Muricidae). TPT and TBT had strong effects on the development of imposex in the rock shell (p<0.001). The other organotin compounds (DBT, MBT, DPT and MPT) had no or less effects on the development of imposex in T. clavigera. The difference between the effects of TPT and TBT was statistically insignificant (p>0.01). The effects of these compounds are estimated, from the relationships between TBT or TPT concentration in tissue and mean penis length of females after injections, to be approximately the same.     

Organotin concentrations in three intertidal neogastropods from the coastal waters of Taiwan

This study was aimed to determine organotin concentrations in the muricids Thais clavigera, Thais tuberosa and Morula granulata on an island wide scale and to find an adequate bioindicator species for long-term monitoring purpose. Samples were collected from the coast of Taiwan and vicinity islands with organotin analysis by graphite furnace atomic absorption spectrophotometry. Because triphenyltin (TPT) could not be discriminated from tributyltin (TBT) by the extraction method, organotins were measured as TBT + TPT and total hexane extractable organotins. Severity of imposex in the muricid population samples expressed as relative penis size (RPS) indices were calculated and compared to determine a suitable bioindicator species. In T. clavigera, T. tuberosa and M. granulata, TBT + TPT were 17-157, 1-44 and 117-1343 ng Sn g(-1) dry wt, respectively. And total organotins varied in the range of 181 to 1125, 23 to 44 and 229 to 1402 ng Sn g(-1) dry wt, respectively. A positive correlation was found between TBT + TPT and total organotins in M. granulata (TBT + TPT = Total organotins x 1.01-110.79; R2=0.97; p<0.001). At the site of Dapaisha, total organotins in M. granulata was 10 times higher than in T. tuberosa (i.e. 242 versus 23 ng Sn g(-1) dry wt). No signs of imposex were found in T. tuberosa (a single site in two subsequent years) and in M. granulata (seven collection sites). The degree of imposex (RPS) of T. clavigera varied from 0.2 to 38.1%. The RPS indices from fishing harbors were not higher than from rocky shores and oyster culture sites. No correlation was found between RPS indices and concentrations of TBT + TPT or total organotins. M. granulata seemed to be insensitive to organotin pollution although organotins were also detected. Our results indicate that organotin pollution is wide spread in coastal waters of Taiwan and pollutants at least include butyltins and phenyltins. As a bioindicator species, T. clavigera is more appropriate than T. tuberosa and M. granulata to monitor organotin contamination.     

Butyltin residues in blue mussels (Mytilus edulis) and arkshells (Scapharca broughtonii) collected from Korean coastal waters

Butyltin compounds (BTs) including tributyltin (TBT) and its degradation products, di- (DBT) and mono-butyltin (MBT), were determined in bivalves such as blue mussels (Mytilus edulis) and arkshells (Scapharca broughtonii) collected from Korean coastal waters. BTs were detected in all the blue mussels and arkshells analyzed. The concentrations of total butyltin (sigmaBTs: MBT + DBT + TBT) in blue mussels and arkshells ranged from 49 to 2500 ng/g and 29 to 87 ng/g wet weight, respectively. Higher concentrations of BTs were found in blue mussels collected from Okpo and Kohyonsong Bays and Jangsengpo Harbor where large shipyards and harbors are located with dry-dock facilities. This suggested that maritime activities nearby the harbors play a major role as the source of BTs. Concentrations of TBT in mussels collected from Korea were one of the highest values reported, suggesting ongoing TBT contamination in Korea. Among BTs, TBT was the predominant compound both in blue mussels and arkshells collected from almost all the sampling locations, indicating the fresh input of TBT in Korean coastal waters. Smaller mussels tended to accumulate BTs at higher concentrations than larger ones, which may be due to higher filtration rate of small mussels and/or contact with surface microlayer in intertidal zones.     

Temporal fluctuations of tributyltin in the bivalve Venerupis decussata at five stations in southwest Spain

Filter feeding clams, Venerupis decussata, were sampled every 4 months for 8 years at five locations on the southwest Spain coast and analysed for organotins. All the stations showed a significant sinusoidally shaped seasonal evolution pattern for tributyltin (TBT) superimposed upon a linear decreasing tendency. The amplitude and frequency of fluctuations differed among stations and were correlated to the harbour activities. Fluctuations were greatest at stations with the greatest TBT presence. The long-term trend of TBT in clams indicated half-life values of about 7-14 years. During 1993, water and sediment samples were also collected at monthly intervals and analysed. Correlations between TBT bivalve contents and water concentrations were higher than those found between biota and sediments.     

Butyltins in water, biofilm, animals and sediments of the west coast of India

Biofilm, fish, oyster, mussel, clam, surface seawater, suspended particulate matter (SPM), and sediment samples were collected from marine and/or estuarine waters of the west coast of India. These samples were analysed for butyltin derivatives such as dibutyltin (DBT) and tributyltin (TBT). The concentrations DBT plus TBT varied between 2.4 and 8.3, 163 and 363 ng/l, 5 and 2853 ng/g dry wt in the SPM, seawater and sediment samples, respectively, of the Marmugao harbour. The values of DBT plus TBT ranged between 0.60 and 29, 123 and 242 ng/l and 1.4 and 65 ng/g dry wt in SPM, water and sediment samples, respectively, collected from the Mandovi estuary. In the Dona Paula Bay the DBT plus TBT varied from 10 to 89 ng/l in surface seawater, and TBT from 10 to 513 ng/g in biofilm samples. For the coastal sediment samples the concentration of DBT plus TBT ranged between 36 and 133 ng/g dry wt of sediment. For the animal samples the DBT plus TBT ranged between 58 and 825 ng/g dry wt of the tissue. Mussel tissues contained the highest amount of DBT plus TBT (825 ng/g dry wt tissue), whereas highest TBT concentration was recorded in the oyster (732 ng/g dry wt). TBT was generally the most abundant butyltin compound in most of the samples suggesting fresh inputs and/or less degradation of TBT. A wide range of the observed butyltin concentrations suggests the presence of localized areas of contamination. Leaching of tributyltin-containing antifouling paints from the ocean going ships, fishing and recreational boats, barges, and the inputs of TBT from the Goa shipyard and dry dock facility situated in the harbour are the probable sources of the DBT and TBT in the samples of the west coast of India. Higher levels of TBT were observed in biofilm relative to that in the surrounding seawater. When fed on TBT contaminated biofilm of the diatom Navicula subinflata, butyltin concentrations in the clam Paphia malabarica increased over the period of feeding suggesting the importance of biofilm in the transfer of butyltins to higher group of organisms.     

Organotins and imposex in the rock shell, Thais clavigera, from oyster mariculture areas in Taiwan

The amounts of organotin compounds such as butyltins [sigma BTs: tributyl- (TBT), dibutyl- (DBT), monobutyl- (MBT)] and phenyltins [sigma PhTs: triphenyl- (TPhT), diphenyl- (DPhT) and monophenyl- (MPhT)] in rock shells, Thais clavigera, from the northern (Shiangsan), central (Lukang) and southern (Chiku) Taiwan oyster mariculture areas varied with season and location. High values of sigma BTs (mainly TBT) and low values of sigma PhTs (mainly TPhT) were found during winter (January 1999) at Shiangsan, while high amounts of sigma PhTs (mainly TPhT) and low sigma BTs (mainly TBT) were found during summer (August 1998) at Lukang. The snails were also affected by imposex. Imposex at Shiangsan, Lukang and Chiku increased from 67.1, 59.3 and 36.7% in summer to 100, 100 and 80% in winter, respectively. Relative penis size indices similar trend at Chiku site. No male displayed rock shells were found at Shiangsan and Lukang in winter. Linear correlations between pseudopenis length versus TBT (r = 0.7655, P < 0.001), DBT (r = 0.4253, P < 0.05), MBT (r = 0.5865, P < 0.01) and TPhT (r = -0.6160, P < 0.01) were obtained significant. Among 200 samples, significant positive correlations between length (pseudopenis/shell) ratio of female versus TBT (r = 0.6944, P < 0.005) and sigma BTs (r = 0.6413, r < 0.01) were also observed. The weak correlations between length (pseudopenis/shell) ratio of female versus DBT (r = 0.3085) and MBT (r = 0.4240, P < 0.1) and TPhT (-0.4917, P < 0.05; negative correlation) could indicate that DBT, MBT and TPhT have little or no effect on the development of imposex in rock shells.     

Bivalve mollusks in metal pollution studies: From bioaccumulation to biomonitoring

Contemporary environmental challenges have emphasized the need to critically assess the use of bivalve mollusks in chemical monitoring (identification and quantification of pollutants) and biomonitoring (estimation of environmental quality). Many authors, however, have considered these approaches within a single context, i.e., as a means of chemical (e.g. metal) monitoring. Bivalves are able to accumulate substantial amounts of metals from ambient water, but evidence for the drastic effects of accumulated metals (e.g. as a TBT-induced shell deformation and imposex) on the health of bivalves has not been documented. Metal bioaccumulation is a key tool in biomonitoring; bioavailability, bioaccumulation, and toxicity of various metals in relation to bivalves are described in some detail including the development of biodynamic metal bioaccumulation model. Measuring metal in the whole-body or the tissue of bivalves themselves does not accurately represent true contamination levels in the environment; these data are critical for our understanding of contaminant trends at sampling sites. Only rarely has metal bioaccumulation been considered in combination with data on metal concentrations in parts of the ecosystem, observation of biomarkers and environmental parameters. Sclerochemistry is in its infancy and cannot be reliably used to provide insights into the pollution history recorded in shells. Alteration processes and mineral crystallization on the inner shell surface are presented here as a perspective tool for environmental studies.