Environmental Pollution 116 (2002) 265–271 www.elsevier.com/locate/envpol Accumulation and tissue distribution of mercury and selenium in striped dolphins (Stenella coeruleoalba) from the Mediterranean Sea (southern Italy) N. Cardellicchio *, A. Decataldo, A. Di Leo, A. Misino CNR — Istituto Sperimentale Talassografico, via Roma 3, I-74100 Taranto, Italy Received 13 October 2000; accepted 6 March 2001 Abstract Tissues and organs from Stenella coeruleoalba stranded along the Apulian coasts (southern Italy) during the period April–July 1991 were analyzed for their mercury and selenium content. Analysis showed considerable variations in the mercury concentration in the examined organs and tissues. The highest concentrations of mercury were found in the liver (from 2.27 to 374.50 mggÀ1 wet wt.). After the liver, lung, kidney, muscle and brain were the most contaminated, while the lowest mercury contamination was found in the melon. As mercury, the liver also showed the highest selenium levels. Liver samples were also analyzed for their methyl mercury contents. The role of selenium in detoxification process of methyl mercury has been discussed. Mercury concentrations related to geographic variations and pollution of the marine environment have been examined. The possible implications between mercury accumulation and dolphin death have also been discussed. # 2001 Elsevier Science Ltd. All rights reserved. Keywords: Mercury; Selenium; Mediterranean; Dolphin; Accumulation 1. Introduction monitoring researches on stranded animals both in the anatomo-pathological and in chemico-toxicological The study of mercury accumulation in dolphins is field have been carried out (Andre´ et al., 1991; Leonzio particularly interesting from the ecotoxicological point et al., 1992; Augier et al., 1993b; Cardellicchio, 1995; of view because of the position of these organisms at the Monaci et al., 1998; Capelli et al., 2000; Cardellicchio et end of the trophic networks. Due to its persistence and al., 2000; Frodello et al., 2000). The correlations between high mobility in the marine ecosystem, mercury shows a contaminant accumulation and observed pathologies are high level of biomagnification in the upper levels of the actually a very important topic of researches. food chain. The dolphins of the Mediterranean have In this paper, a study on mercury and selenium dis- much higher levels of mercury and selenium than those tribution and accumulation in tissues and organs of 10 of the Pacific and Atlantic (Andre´ et al., 1991; Augier et specimens of Stenella coeruleoalba stranded along the al., 1993a). For mercury, this can be explained by the Apulian coasts (south-eastern Italy) during the period presence of cinnabar deposits in the Mediterranean Sea: April–July 1991 is presented. As mercury in muscles of the use of mercury in industrial activities may also con- cetaceans is found as methyl mercury (Itano et al., 1984 tribute to increase mercury levels in the marine envir- a, b) and then detoxified by demethylation in the liver onment (Bacci, 1989; Andre´ et al., 1991). and stored in this organ as mercury selenide (Koeman et Dolphins stranded along the coasts are nowadays a al., 1973; Martoja and Berry, 1980; Nigro, 1994), liver noteworthy source of information about physiology and samples have been analyzed for both mercury and biology of these organisms: for this reason, various methyl mercury contents. The role of selenium in the detoxification process of methyl mercury has been dis- * Corresponding author. Tel.: +39-99-4542-208; fax: +39-99- cussed. Finally mercury and selenium levels have been 4542-215. compared with those found in striped dolphins from E-mail address: [email protected] (N. Cardellicchio). other marine areas. 0269-7491/01/$ - see front matter # 2001 Elsevier Science Ltd. All rights reserved. PII: S0269-7491(01)00127-0 266 N. Cardellicchio et al. / Environmental Pollution 116 (2002) 265–271 2. Materials and methods Baker) H2SO4-HNO3 mixture (1:1) for 4 h at 160 C. Mercury concentrations were determined by cold Fig. 1 shows the coastal area where the cetaceans were vapour atomic absorption spectrophotometry using a found. Table 1 reports the main morphological char- Perkin Elmer mod. 1100 B spectrophotometer. acteristics of 10 specimens analyzed, together with the After acid digestion of the homogenized liver with 10 date and the location of stranding. Classification of the ml of Ultrex-grade (J.T. Baker) HNO3 (4 h at 160 C), individuals in three classes (calves, young, adults) was selenium was determined by graphite furnace atomic based on the morphological data of body length, since it absorption spectrophotometry (GF-AAS) using a Per- was not possible to obtain teeth for aging. The rela- kin Elmer 3030 Z spectrophotometer. tionship between the age and total length of dolphins The validity of analytical methods was confirmed with was discussed by Miyazaki, (1977), Miyazaki et al., certified Standard Reference Materials (DOLT-2: dog- (1981), and Andre´ et al., (1990, 1991). According to the fish liver) obtained from the National Research Council authors, there is a considerable growth in dolphins dur- of Canada. Results of quality controls are reported in ing the first 4–5 years, and the total length of the indi- Table 2 and show a good agreement with certified data. viduals at that age corresponds to more than 80% of the Methyl mercury (HgMet) was determined by high average size measured after 20 years. Males and females pressure liquid cromathography coupled with cold reach sexual maturity at a length of 190–210 cm and vapour atomic absorption spectrophotometry (HPLC- 187–206 cm, respectively (Calzada et al., 1996, 1997). In CV-AAS) after an acid hydrolysis step at room tem- the Mediterranean Stenella coeruleoalba is usually 10% perature (RT) proposed by Palmisano et al. (1993). H2O shorter than the specimens from the Pacific (Andre´ et (5.5 ml), 1 g of NaCl and 1.5 ml of concentrated HCl al., 1991): therefore, it is not possible to obtain a general were added to 1 g (wet wt.) of homogenized liver. The equation between age and length for all species of dol- sample was sonicated for 30 min and centrifuged at phins from different marine areas. In this work, indivi- 5500Âg for 10 min. An aliquot of the supernatant was duals with lengths of approximately 120 cm were filtered through a 0.45-mm membrane, diluted as neces- considered as calves; the male specimen n. 4, whose sary with mobile phase (40 mmol cysteine in 0.1 mol/l body length was 168 cm, was considered as young; acetic acid at pH 2.9) and analyzed by HPLC-CV-AAS. females longer than 183 cm and males longer than 190 With this method a fraction of inorganic mercury cm were considered as adults. Organ and tissue samples (liver, brain, kidney, lung, Table 1 muscle, blubber, and melon) were collected during Main characteristics of striped dolphins (Stenella coeruleoalba) analy- autopsy. After collection, samples were transferred to zeda PTFE-containers and frozen at À20C. Before the ana- lysis, samples were homogenized in a teflon Ultra-Turrax Specimen Sex Length Age Location of Date of (cm) stranding sampling T25 homogenizer (Janke & Kunkel, Staufen, Germany). For total mercury determination, samples were digested 1 M 195 A La Specchiolla 18 June 1991 under pressure with a 10 ml of a Ultrex-grade (J.T. 2 M 111 C Minervino 20 June 1991 3 M 208 A Gallipoli 29 June 1991 4 M 168 Y Porto Cesareo 18 July 1991 5 F 137 C Castrignano 21 June 1991 6 F 208 A Gallipoli 6 July 1991 7 F 195 A S. Caterina- Nardo` 20 July 1991 8 F 183 A S. Giovanni- Ugento 24 July 1991 9 F 190 A Chiatona 10 April 1991 10 F 208 A Castellaneta 25 April 1991 a C, calf; Y, young; A, adult. Table 2 Precision and accuracy of analytical methods obtained using a certified dogfish liver (DOLT-2)a Metals DOLT-2 Certified Foundb Total mercury 1.99 Æ 0.10 1.85 Æ 0.20 HgMet (as Hg) 0.693 Æ 0.053 0.750 Æ 0.100 Selenium 6.06 Æ 0.49 6.27 Æ 0.75 Fig. 1. Coastal area in the Mediterranean Sea where dolphins (Ste- a The concentrations are given in mggÀ1 dry weight. nella coeruleoalba) were found. b Number of replicates is five. N. Cardellicchio et al. / Environmental Pollution 116 (2002) 265–271 267 Table 3 Table 4 Average concentrations (mg/g wet wt.), standard deviation (in par- Mercury and selenium compounds in the liver of striped dolphins (mg entheses) and range of mercury and selenium in Stenella coeruleoalba gÀ1 wet wt.) Tissue Hg Se Specimensa Hg HgMet %HgMet HgPro Hg* Se Se/Hg* Liver 170.76 (138.90) 2.27–374.50 63.18 (50.52) 1.90–141.00 10 374.50 6.80 1.82 8.7 359.00 141.00 1.00 Muscle 8.61 (9.31) 0.44–28.00 4.43 (3.39) 0.92–11.00 7 351.86 10.00 2.84 23 318.86 127.00 1.01 Kidney 8.99 (6.84) 1.49–23.78 7.68 (3.06) 3.21–12.92 3 263.00 8.00 3.04 5.5 249.50 92.10 0.94 Brain 8.04 (8.11) 0.22–26.26 5.84 (3.63) 1.63–12.74 6 242.00 7.00 2.89 9.6 225.40 81.00 0.91 Blubber 0.78 (0.87) 0.04–2.40 2.61 (2.18) 0.14–6.07 9 183.06 7.90 4.32 15.7 159.46 71.10 1.13 Melon 0.22 (0.23) 0.05–0.70 N.D.a 1 168.00 4.60 2.74 6.8 156.60 72.30 1.17 Lung 14.52 (12.40) 0.41–36.16 5.47 (3.04) 2.29–11.13 8 107.35 6.30 5.87 8.8 92.25 39.00 1.07 4 12.33 1.60 12.98 1.1 9.63 4.50 1.19 a N.D., no detectable.