Environ. Sci. Technol. 2002, 36, 4224-4228
Organotin Pollution in Deep-Sea Fish from the Northwestern Mediterranean VERONICA BORGHI AND CINTA PORTE* Environmental Chemistry Department, IIQAB-CSIC C/Jordi Girona, 18, 08034 Barcelona, Spain
Aquatic pollution resulting from extensive usage of organotin compounds has been of great concern due to their deleterious effects in nontarget organisms. However, organotin contamination in deep-sea ecosystems has been rarely studied. The present work attempted to determine butyltin and phenyltin compounds in deep-sea fish collected between 1000 and 1800 m depth in the NW Mediterranean. The concentration of tributyltin (TBT) and its degradation products, mono- (MBT) and dibutyltin (DBT), as well as triphenyltin (TPT), and mono- and diphenyltin (MPT, DPT) was determined in different tissues (liver, gills, digestive tube, and muscle) of several fish species. Total butyltin residues were up to 175 ng/g wet wt, and they were comparable to levels found in coastal fish collected along the Catalan coast. In contrast, deep-sea fish contained much higher levels of phenyltins (up to 1700 ng/g wet wt), and particularly TPT (up to 1430 ng/g wet wt), than previously reported concentrations in shallowwater organisms. The obtained results confirm the longrange transport of organotin compounds to the deep-sea environment, and the subsequent exposure of fish inhabiting nonpoint source areas. The use of TPT in agriculture or as an antifouling agent, its transport to the deep-sea environment associated to particulate matter, and its nonbiodegradable nature in the food chain may account for the high residue levels detected in deep-sea organisms.
Introduction Deep-sea regions (depth > 1000 m) are poorly studied areas, that encompass about 75% of the biosphere, and are characterized by the absence of light, elevated pressures, and low temperatures. Research has demonstrated the occurrence of organochlorinated compounds, polycyclic aromatic hydrocarbons (PAHs), and heavy metals in deepsea sediments and their uptake and bioaccumulation by deep-sea organisms (1-3). A similar feature could be expected for organotin compounds due to their widely use, relatively high affinity for particulate matter, which makes sediments a major reservoir for these pollutants, and elevated half-life in deep-sea anoxic sediments (4). However, despite available monitoring data for coastal and shallow environments (58), few works have addressed the contamination of deep-sea areas (9) and the uptake of those compounds by inhabiting organisms (10). Organotin compounds are used worldwide not only as biocides in antifouling paints but also as preserving agents for wood and timber, fungicides in agricultural activities, * Corresponding author phone: 34 93 4006175; fax: 34 93 2045904; e-mail:
[email protected]. 4224
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ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 36, NO. 20, 2002
FIGURE 1. Map of the NW Mediterranean showing the locations of the sampling sites (grey area). Collections carried out at 42°35′N 4°07′E, 42°28′N 4°06′E, 41°14′N, 1°58′E. heat and UV stabilizers of PVC, and as catalyst in the production of polyurethane foams (11). The application of trialkyltin compounds as biocides, fungicides, and alguicides results in direct release into the water, with the consequent uptake and accumulation in aquatic fauna. Earlier studies have demonstrated that tributyl- and triphenyltin compounds exert chronic toxic effects on susceptible mollusks at water concentrations of a few nanograms per liter (12). Their acute toxicity to fish embryonic and early life stages lies in the range of 7-10 µg/L (11). Concern over the ecotoxicological impacts of TBT lead in the early 1990s to restrict its application to large vessels (>25 m long) in most developed countries. However, up to date, there is no regulation on the use of triphenyltin (TPT), neither in antifouling paints nor in agriculture. The area of study, the NW Mediterranean, has suffered a great touristic development in the past decades, with a consequent increase in the number of marinas, considerable commercial ship traffic, and an augment of the TBT input into the marine environment in some areas (13). Nowadays, TBT contamination is certainly not limited to harbors and marinas but extends along the coast (5, 6), including protected areas in Corsica (14) and organisms collected in the open sea, e.g. tuna fish and marine mammals (15, 16). Hence, the present study attempted to determine residue levels of organotin compounds in five species of deep-sea fish (Mora moro, Lepidion lepidion, Coryphaenoides guentheri, Alepocephalus rostratus, and Bathypterois mediterraneus) from the Gulf of LionssNW Mediterraneanscollected at a depth between 1000-1800 m, with the aim of elucidating the status of contamination of the deep-sea environment by using fish as sentinel organisms. Chemical analysis were carried out in several fish organs: gills, digestive tube, liver, and muscle, which play a key role in the uptake, distribution, detoxification, and storage of pollutants.
Material and Methods Sample Collection. Fish samples were collected by trawling in April 1996 from the Gulf of Lions (NW Mediterranean) at a depth ranging between 1000 and 1800 m (Figure 1, Table 1). Once on board, fish organs were immediately dissected, wrapped in clean aluminum foil, and stored at -20 °C. Samples were preserved for up to 6 months before their analysis. 10.1021/es025725c CCC: $22.00
2002 American Chemical Society Published on Web 09/12/2002
TABLE 1. Sample Depth and Biological Data of Collected Specimens organisms
common name
depth (m)
weight (g)
length (cm)
CFa (g/cm3)
M. moro L. lepidion C. guentheri A. rostratus B. mediterraneus
Common mora Mediterranean codling Gu¨ nther’s grenadier Risso’s smooth-head Spiderfish
1008-1146 1161-1615 1008-1153 1146-1593 1548-1816
556 ( 46 57.3 ( 4.9 26.9 ( 2.5 168 ( 37 15.0 ( 2.2
41.2 ( 1.4 22.6 ( 0.6 22.0 ( 0.7 28.3 ( 1.8 14.9 ( 0.5
0.79 ( 0.02 0.52 ( 0.02 0.27 ( 0.01 0.72 ( 0.06 0.44 ( 0.04
a
CF ) condition factor calculated as [weight/ (length)3] × 100. Values are mean ( SEM (n ) 6).
Organotin Analysis. The analysis were based on those described by Morcillo et al. (5). Briefly, frozen samples were thawed, and the organs of two individuals were pooled and cut into small pieces. Afterward samples (1-2 g wet wt) were digested with 20% tetramethylammonium hydroxide for 2 h at 60 °C. After the digestion step, pH was adjusted to 5.0 with 2.0 M sodium acetate-acetic buffer, and the following reagents added to the buffered solution subsequently: 4 mL of freshly made 2% sodium tetraethylborate as the ethylation agent, 10 mL of n-hexane, and 50-100 ng of tetrabutyltin and tripentyltin as internal standard. The sample was shaken for 45 min, the hexane layer was collected, and the aqueous phase was extracted again twice with n-hexane. The combined organic phase was reduced to approximately 1 mL, passed through a 5% water deactivated alumina column (5 g), and eluted with 10 mL of n-hexane to remove lipids. The final extract was injected into a gas chromatograph coupled with a flame photometric detector (GC-FPD). A fused silica capillary column (30 m length × 0.25 mm; DB-17) was used for GC separation. The operating conditions were as follows: injector and detector temperature 280 °C, column temperature programmed from 60 to 280 °C at a rate of 10 °C/min, 10 min at 280 °C. The carrier gas was hydrogen (50 cm/s). Organotin compounds were identified by assigning peaks in samples to the corresponding peaks of external standard. Peak areas of individual organotin compounds were used for the quantification, and results were corrected for the recovery of the internal standard (92-104%). The limits of quantificationsdetermined as 3 times baseline noiseswere 1.0 ng/g wet wt as Sn for butyltins and triphenyltin metabolites and 1.4 ng/g for triphenyltin. Procedural blanks were processed with every set of samples, and they were all free from organotin contamination or other interferences. The accuracy of the analytical method was checked using a certified reference biological material (NIES-11), being the recovery of TBT of 71% ( 3 (n > 10). Concentrations were normalized to Sn for comparative purposes. Selected samples were analyzed for confirmatory identifications by computerized gas chromatography-mass spectrometry (GC-MS). The instrument was a Fisons 800GC interfaced to a Fisons MD 800 MS. Helium was the carrier gas at 30 cm/s. The GC oven temperature was programmed as above. The ion source, injector, and transfer-line temperatures were set at 200, 270, and 290 °C, respectively. All injections were in the splitless-mode with the split vent closed for 30 s. The mass spectrometer was operated in the electron ionization mode, and the mass range was scanned from 50 to 600 u at 0.5 s/scan.
Results and Discussion Biological Data of Samples. Main characteristics of the analyzed fish are given in Table 1. Individuals were adults and samples homogeneous (fish size and weight). The condition factor (CF) was calculated as a general measure of the nutritional status (17). The highest CFs (0.72-0.79) were recorded for A. rostratus and M. moro, which indicates a better nutritional state of these organisms. The lowest CF (0.27) was detected in C. guentheri, a species adapted to live at greater depths, with maximum abundance at 1600-2200 m (18).
Species Differences. Organotin levels differed greatly among species (Table 2). The highest butyltin and phenyltin residues were recorded in the liver of M. moro (174 and 1668 ng/g wet wt as Sn, respectively) followed by L. lepidion (43 and 260 ng/g wet wt as Sn), both species from the moridae family. The lowest residues were detected in A. rostratus (5 ng of butyltins/g wet wt in the liver). The uptake of butyl- and phenyltin compounds through the gills was particularly high in M. moro and L. lepidion (Table 2). Both organisms are large demersal species that swim actively in the upper slope (1000-1400 m), and this might lead to a relatively high and similar uptake of pollutants through the gills. Interestingly, Michel and Averty (9) reported a TBT contamination peak of 0.04 ng/L as ion (0.02 ng/L as Sn) at 1200 m in deep-waters from the area, that progressively reduced down to 2500 m depth. In contrast, butyl- and phenyltin residues were close to or below detection limit in the gills of the other three species examined. The reduced motility of these species, particularly B. mediterraneus and C. guentheri, and the fact that they are well adapted to live at greater depths, with a maximum abundance at 16002200 m (18), would probably account for the very low or undetectable uptake of organotin compounds through the gills. The organotin compound uptake through the diet was high in M. moro, followed by L. lepidion and B. mediterraneus, while organotin residues were below detection limit in digestive tube of A. rostratus and C. guentheri (Table 2). The results are again indicative of different habitats and patterns of exposure. In general terms, those organisms that feed actively, either on small fish, crustaceans, and cephalopods (M. moro) or on copepods and small decapods (L. lepidon) (19), exhibited high organotin residues in digestive tube. In contrast, those with a very specialized diet, such as A. rostratus, a large fish which feeds predominantly on gelatinous macroplankton, had residues below detection limit. B. mediterraneus, a sedentary fish, well adapted to the oligotrophic deep environment, which feeds on zooplankton carried by the marine currents (20), showed relatively higher uptake of organotin compounds through the diet than through the water. Although there is increasing information on the composition and variability of the diets of deep-sea fish (18-20), no data on organotin concentrations on their prey species are available. Rough estimates on the food chain magnification of organotin compounds in M. moro and L. lepidon can be obtained by dividing the concentration in the whole body and the concentration in their digestive tube. This putative biomagnification factor (BMF) ranges for TBT from 0.02 in M. moro to 0.04 in L. lepidion, whereas for TPT goes from 0.27 in M. moro to 0.93 L. lepidion. These values are in the lower range of those described previously in fish (9, 20), and they clearly indicate the biodegradable nature of TBT in comparison with TPT in the food chain. Patterns of Occurrence. Both butyl- and phenyltin compounds were recorded in muscle (
