Mercury content in different size classes of important edible species of the northern Tyrrhenian sea

Marine PollutionBulletin The author would like to thank Julian Priddle for his advice on the writing of this paper, the crew and officers of the RRS John Biscoe and the OBP team for their assistance at sea. Clarke, A. & Law, R. (1981). Aliphatic and aromatic hydrocarbons in benthic hydrocarbons from two sites in Antarctica. Mar. Pollut. Bull. 12, 10-14. Cripps, G. C. (1990). Hydrocarbons in the seawater and pelagic organisms of the Southern Ocean. Polar Biol. 10,393-402. Heywood, R. B. (1985). Environmental conditions in the Antarctic Peninsula area of the Southern Ocean during the Anglo-German Joint Biological Expedition, February 1982. Meeresforschung 30, 220-239. Minitab, Inc. (1987). MINITAB, Data Analysis Software, Release 6.2-Standard version copyrightC State College, PA, USA. Patterson, S. L. & Sievers, H. A. (1980). The Weddell-Scotia Confluence. J. Phys. Oceanogr. 10, 1584-1610. Platt, H. M. & Mackie, P. R. (1980). Distribution and fate of aliphatic and aromatic hydrocarbons in Antarctic fauna and environment. Helgoldnder Meeresunters. 33,236-245. Reinhardt, S. B. & Van Vleet, E. S. (1986). Hydrocarbons of Antarctic midwater organisms. Polar Biol. 6, 47-51.

Marine I'ollution Bulh,tin. Volume24, No. 2, pp. 114 116. 1992. Printedin Great Bri'~ain.

0025-326X/92 S5.00+0.00 © 1992PergamonPressplc

Mercury Content in Different Size Classes of Important Edible Species of the Northern Tyrrhenian Sea C. BARGHIGIANI* and S. DE RANIERI? *Istituto di Biofisica, CNR, Via S. Lorenzo 26, 56100Pisa, Italy ? Centro Interuniversitario di Biologia Marina, P. le Mascagni, 57100 Livorno, Italy

Mercury contamination of the northern Tyrrhenian sea due to the geological anomaly of Mt. Amiata (Tuscany, Italy) has long been known. Nearly 20 years ago Renzoni et al. (1973) found that the metal concentrations in marine sediments from the area between the gulf of Follonica and the promontory of Argentario (Fig. 1) was particularly high and, although the mercury content of the water was low (Bharghigiani et al., 1981), many marine organisms were also found to be heavily contaminated (Bernhard and Renzoni, 1981). Among these, several flatfish species displayed high mercury concentrations (Barghigiani et al., 1986a,b; PeUegrini & Barghigiani, 1989), as well as many other fish, molluscs, and crustaceans eaten by man (UNEP/FAO/WHO, 1987). The aim of this paper is to see through which marine species and length classes, of the area reported in Fig. 1, mercury mostly enters the human food chain. For this purpose an evaluation was made of the marine edible species most important commercially and in terms of abundance, together with the yearly production and distribution among different size ranges. Then the mercury concentrations of the length classes of the chosen species were determined. The research was carried out during three consecutive years (1985, 1986, 1987) in the framework of a program on the evaluation of demersal resources from 0 to 700 m 114

depth (De Ranieri et al., 1988). The samplings were made in two annual trawl surveys (spring and summer). In eachy survey 30 hauls were made with nets commonly used by local fishermen, lasting 1 h each and distributed in the area according to a randomized stratified design (Grosslein & Laurence, 1982). First, the evaluation of the species most important both commercially and for their abundance in the study area was made using an 'importance index' reported in De Ranieri et aL (1988) and the percentage distribution of the various species with respect to the total catch of 1985. The most relevant species from this point of view proved to be the following: Merluccius merluccius (hake), Eledone cirrhosa (a small octopus-like cephalopod), Trisopterus rninutus capelanus (poor cod), and Nephrops norvegicus (Norway lobster). Over 30% of the total commercial species collected in 1985 was in fact represented by these four species. In particular, E. cirrhosa comprised 10.1% of the total catch, M. merluccius 12.3%, T. m. capelanus 8.6%, and N. norvegicus 1.4%. Several length classes were chosen for each species as reported in Table 1. Of each species, samples of muscle tissue were analysed for Hg. The number of samples analysed was as follows: M. merluccius, 1-2 samples of each class, n = 25; E. cirrhosa, 4-5 samples of each class, n = 3 3 ; T. m. capelanus, 2-3 of each class, n = 2 0 ; N. norvegicus, 2 of each class, n = 26. Mercury measurements were performed by flameless atomic absorption spectrometry with a Coleman MAS 50 Perkin-Elmer after digestion with concentrated HNO3 in a pressurized decomposition system at 120°C for 6 h. The analytical procedures were tested using Certified Reference Materials DORM-1 (dogfish muscle: 0.789_+0.074 ~tg g-i Hg) of the National Research Council of Canada), Table 1 reports the amounts of the single length classes collected in 1985 together with the theoretical landed and mercury concentrations. The theoretical landed was estimated on the basis of the percentage distribution of the species resulting from the experimental catches and of the commercial landed at Porto Santo Stefano. Although the maximum mercury limit accepted by the European Economic Community for edible parts of marine organisms is 0.7 gg g-~ fresh wt, a limit decided upon on the basis of considerations regarding human health, our results indicate that many specimens had higher Hg concentrations. In particular, as concerns hake, the organisms had an average content higher than this limit from the 10th to the 17th length class. According to our theoretical calculations, 26.3 t of hake is landed per year. All classes of Eledone, except for the 1st, exceeded the EC limit, while only the last four of poor cod and the last six of Norway lobster had higher values. Of these four species, 117.7 t with a mercury content higher than 0.7 ppm fresh wt is theoretically landed each year. On the basis of the percentage distribution of length classes and the total landed, the percentage Hg amount of each class that reaches the fish market yearly and enters the human diet was calculated (Fig. 2). For hake, the organisms of 12-16, 56-60, and 68-72 cm length

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Hg in the different length classes. The weight (kg) of each class collected in 1985 is reported together with the theoretical landed fish (kg), and the average Hg concentration (ppm fresh wt) of each class. M. merluccius

Class no. ! 2 3 4 5 6 7 8 9 10 11 12 13

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T. m. capelanus

Total length cm

Weight kg

Theoretical landed kg

4-07.9 8-11.9 12-15.9 16-19.9 20-23.9 24-27.9 28-31.9 32-35.9 36-39.9 40-43.9 44-47.9 48-51.9 52-55.9 56-59.9 60-63.9 64-67.9 68-71.9

0.967 54.936 122,363 51.981 33.584 28.445 19.557 9.511 10.110 4.353 4.368 5.334 7.633 9.814 2.346 4.172 6.644

32 374.4 72 107.6 30 632.0 19 790.8 16 762.4 II 524.8 5892.9 5957.7 2565.2 2574.0 3143.3 4498.1 5783.3 1382.5 2458.5 3915.3

Hg p p m fresh wt 0.13 0.21 0.27 0.34 0.40 0.46 0.53 0.61 0.72 0.93 1.27 1.62 2.03 2.43 2.81 3.21

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Class no. 1

2 3 4 5 6 7

Mantle length cm

Weight kg

Theoretical landed kg

Hg ppm fresh wt

0-1.9 2-3.9 4-5.9 6-7.9 8-9.9 10-11.9 12-13.9

0.005 3.379 33.661 43.655 60.647 21.181 2.985

0.3 1991.2 19 836.0 25 725.5 35 738.7 12 481.8 1759.0

0.78 0.81 0.87 1.10 1.36 1.64

Weight kg

Theoretical landed kg

Hg ppm fresh wt

10 10-11.9 12-13.9 14-15.9 16-17.9 18-19.9 20-21.9 22-23.9

15.743 18.566 26.669 24.928 15.546 4.331 4.218 0.795

9277.39 10 940.79 15 715.93 14 689.74 9160.95 2552.04 2485.51 468.66

0.22 0.31 0.47 0.72 0,98 1,19 1.46

Carap. length mm

Weight kg

Theoretical landed kg

Hg p p m fresh wt

14-17 18-21 22-25 26-29 30-33 34-37 38-41 42-45 46-49 50-53 54-57 58-61 62-65

0.199 0.394 1.908 5.144 10.278 10.066 9.214 4.742 2.515 0.671 0.844 0.463 0.182

116.8 231.3 1120.1 3019.7 6033.5 5909.0 5408.9 2783.7 1476.4 393.9 495.5 271.8 106.8

0.18 0,22 0,28 0,31 0.45 0,59 0.69 0.96 1.20 1.49 1.75 2.12 2.53

N. norregicus Class no. 1

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Total length cm

2 3 4 5 6 7 8 9 10 11 12 13

115

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Fig. 2 Percentage Hg content of the different classes with respect to the total catch. (3rd, 14th, a n d 17th classes) were those which c o n t r i b u t e d most. E . c i r r h o s a c o n t r i b u t e d most with 8 - 1 0 c m s p e c i m e n s (5th class). P o o r cod c o n t r i b u t e d m a i n l y with s p e c i m e n s from 14 to 18 c m length (4th a n d 5th class), a n d the c o n t r i b u t i o n of N o r w a y lobster was mostly m a d e b y o r g a n i s m s with a c a r a p a c e length range of 3 4 - 4 5 m m (6th, 7th, a n d 8th classes), with a p e a k for the 7th class ( 3 8 - 4 1 mm). It m u s t be p o i n t e d out that Italian law does n o t p r o v i d e for the E C limit for the four studied species. This situation could entail seriQus health p r o b l e m s for p e o p l e such as the families of local fishermen.

116

I n d e e d , the average H g c o n c e n t r a t i o n of classes with a m e t a l c o n t e n t exceeding the E C limit proves to b e 1.50±0.68 p p m fresh wt. A s a c o n s e q u e n c e , cons u m p t i o n of 2 0 0 g per week of these w o u l d result in a n intake of 3 0 0 gg of Hg, which is the m a x i m u m tolerable weekly a m o u n t of t h e metal for a n individual weighing 70 kg, according to the W H O .

Barghigiani, C., Ferrara, R., Seritti, A., Petrosino, A., Masoni, A. & Morelli, E. (1981). Determination of reactive, total and particulate mercury in the coastal water of Tuscany (Italy)by atomic fluorescence spectrometry. Proc. V~s Journe~ Etud. Pollut. C.LE.S.M. 1980, Cagliari, pp. 127-130. Barghigiani, C., Pellegrini, D., D'Ulivo, A. & De Ranieri, S. (1991). Mercury assessment and its relation to selenium levels in edible species of the Northern Tyrrhenian Sea. Mar. Pollut. Bull. 22, 406409. Barghigiani, C., PeUegrini,D., Gioffra, D., De Ranieri, S. & Bargagli, R. (1986a). Preliminary results on the mercury content of Citharus linguatula (L.) in the northern Tyrrhenian Sea. Mar. Pollut. Bull. 17, 424-427. Barghigiani, C., Pellegrini, D., Gioffr6, D. & De Ranieri, S. (1986b). Presenza di mercurio in pesci piatti del Mar Tirreno del Nard. Nova Thalassia 8,555-556. Bernhard, M. & Renzoni,A. (1977). Mercury concentration in Mediterranean marine organisms and their environment: natural or anthropogenic origin. Thalassia Jugosl. 13, 265-300. De Ranieri, S., Belcari, R, Biagi, F., Mori, M. & Pellegrini, D. (1988). Valutazione delle risorse demersali tra l'Isola d'Elba e l'Isola di Giannutri: primi risultati delle campagne 1985. In Atti seminari per la pesca e l'acquacultura. Ministero Marina Mercantile and C.N.R. Eds. Roma 1986, Vol, 3, 1167-1196. EEC (1984). Objectif de qualit6 rejets industriels. Conseil des Ministres, G. V. No. L 74/49, March 17, 1984. Grosslein, M. & Laurence, A. (1982). Bottom trawl surveys design, operation and analysis.FAO. CECAF/ECAF series 81/22. Pellegrini, D. & Barghigiani,C. (1988). Feeding behavior and mercury content in Solea vulgaris and Lepidorhombus boscii of the Northern Tyrrhenian Sea. Mar. Pollut. Bull, 20,443-447. Renzoni, A., Bacci, E. & Faleiai,L. (1973). Mercuryconcentration in the water, sediments and fauna of an area of the Tyrrhenian coast. Rev. Int. Ocean Med. 31, 17-45. UNEP/FAO/WHO (1987). Assessment of the state of pollution of the Mediterranean sea by mercury and mercury compounds. MAP Tech. Rep. Series No. 18 WHO (1980). Report on consultation to re-examinethe WHO environmental health criteria for mercury. Geneva, April 21-25,198(/.