Dyer, K. R. (1973). Estuaries: A Physical Introduction. John Wiley, Chichester.

FAO (1975). Manual of Methods in Aquatic Environment Research Part L Methods of Detection, Measurement and Monitoring of Water Poilu- tion, FAO, Rome. 212-219.

Franson, M. A. (1976). Standard Methods for the Examination of Water and Wastewater. American Public Health Association, Washington.

HMSO (1964). Effects of Polluting Discharges on the Thames Estuary. Water Pollution Research Technical Paper No. 11. Her Majesty's Stationary Office, London.

Johnson, D. L. & Pilson, E. Q. (1972). Spectrophotometric determina- tion of arscnitc, arsenate and phosphate in natural waters. Anal Chem. Acta. 55, 289-299.

Marine Pollution Bulletin

Narvekar, P. V., Zingde, M. D. & Kamat Dalai, V. N. (1983). Behaviour of boron calcium and magnesium in a polluted estuary. Estuar. Coast. Shelf&'i. 16, 9-16.

Zingdc, M. D., Sarma, R. V. & Desai, B. N. (1979). Pollution in river Par and its abatement. Ind. J. Mar. Sci. 8,266-278.

Zingde, M. D., Narvekar, P. V., Sarma, R. V. & Desai, B. N. (1980a). Water quality of the river Damanganga. Ind. J. Mar. Sci. 9, 94-99.

Zingde, M. D., Sabnis, M. M., Mandalia, A. V. & Desai, B. N. (1980b). Effects of industrial waste disposal on the water quality of the river Kolak. Mahasagar Bull. Nat. Inst. Ocean. 13, 99-110.

Zingde, M. D., Chander, S. & Desai, B. N. (1981). Base-line Water qual- ity of the river Narmada (Gujarat). Ind. J. Mar. Sci. 10, 161-164.

Marine Pollution Bulletin, Volume 17, NO. 6, pp. 274-276,1986. Printed in Great Britain.

Metals in Sediments off Trinidad, West Indies The island of Trinidad lies just off the South American continent (61-61½~ long., I~ 'N lat.) close to the mouth of the Orinoco river (Fig. 1). Recently its Government embarked on an industrialization programme geared to utilize effectively the island's reserves of natural gas. Since pollution problems frequently follow industrialiTa- tion (Whaffe & Van den Brock, 1977; Forstner, 1980; Grosjean, 1983), it was decided to monitor the metals Fe, Mn, Cr, Ni, Cu, Pb and Cd in the vicinity of the proposed industrial estate. Monitoring was conducted over a 3-year period at twelve stations indicated on the map (Fig. 1).

Sediment samples were collected by a 15.2 cm X 15.2 cm Petite Ponar (Wildco, Michigan, U.S.A.) grab. Two grabs of top sediment were taken at each station and about I kg of a composite from the mixed sediment was kept frozen in polythene bags until required for analysis. Sediments were dried at 60"C for 24 h and duplicate samples from each sediment were digested with concen- trated nitric acid in PTFE digestion bombs (R.A. Scientific, London, England) for 2 h at 100"(2. The diluted digests were then filtered through Whatman 541 filter paper. The metals were then determined by atomic absorption spectrophotometry using a Pye Unicam SP9 spectrophotometer with automatic background correction.

Precision of Chemical Analyses. The precision of the metal analyses was determined by the relative standard deviations for replicate determina- tions on a typical sediment. The data are presented in Table 1.

The metal levels in the sediments showed a depen- dence on dredging/reclamation activities and current movement.

The dredging/reclamation activities occurred within the period June 1980-August 1981 of the sampling interval which extended from December 1979 to December 1982. During the dredging period, the mobilization and redeposition of compounds of the

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3 7 3_~1 Numbered tronsect stations / ~ ~ t~ . . . . . . t,~ Flu'. ~-n-inime

. . . . undercurrents 9.5 9 I

Rectaimea areas

GuLf /

I

i ! I

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1.7

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\

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~--~ Mangrove swamps "

km [ ] Industrial areas 0 I I , I [ ~ Navigational channels

Fig. 1 Map of area sampled.

TABLE 1

Precision for Metal Determinations as Measured by Relative Standard Deviation

(n-5)

Metal Average relative standard deviation

Fe 25432.00 ± 1.2% Cu 13.13± 1.8% Cr 14.30 ± 7.0% Mn 386.60 :l: 1.8% Ni 16.56 ± 5.1% Pb 26.07 + 1.8% Cd 0.38 ± 4.0%

Average values in ppm

V o l u m e 17/Number 6/June 1986

TABLE 2

Metal levels in sediments from stations in the vicinity of the dredged area

Station Dec. 79 Apr. 80 Jul. 80 Oct. 80 Jan. 81 Mar. 81 Jul. 81 Dec. 81 May 82 Dec. 82

Fe (rag g-' dry wt.) 4.1 -- -- 1.08 14.19 20.31 20.72 12.00 15.23 21.89 17.82 4.4 -- -- 16.64 20.84 28.85 27.86 15.48 24.29 26.96 28.21 5.1 -- 23.32 18.03 21.43 28.36 28.36 18.41 26.49 25.76 29.10 5.5 -- 27.33 18.25 24.25 29.45 29.79 - - 21.81 25.86 28.18 6.1 25.43 21.35 18.04 20.40 20.90 18.73 22.29 22.64 22.11 28.38 6.4 24.06 20.58 19.05 23.59 27.87 23,12 26.49 19.54 22.11 24.12 Mn (ppm dry wt.) 4.1 -- -- 220 214 240 201 120 186 241 198 4.4 -- -- 188 320 300 290 421 280 347 358 5.1 -- 357 346 253 330 261 273 304 315 332 5.5 -- 366 358 360 360 289 387 266 334 313 6.1 377 326 275 247 178 201 228 237 211 324 6.4 326 311 366 366 342 225 278 328 271 288 Cr (ppm dry wt.) 4.1 -- -- 7.90 12.44 7.28 11.21 6.27 3.08 8.94 7.79 4.4 -- -- 10.63 18.88 12.67 21.86 7.62 8.95 12.95 16.87 5.1 -- 12.41 19.23 34.19 20.20 21.61 8.19 7.92 14.28 17.23 5.5 -- 15.45 22.60 26.62 19.75 30.64 14.30 7.90 13.62 18.89 6.1 12.01 13.65 27.35 39.89 22.07 15.14 8.43 18.72 29.35 30.82 6.4 11.23 15.08 21.42 28.41 18.94 42.82 3.92 7.25 12.66 14.00 Ni (ppm dry wt.) 4.1 -- -- 10.20 8.35 6.12 8.90 6.51 5.70 10.16 6.66 4.4 -- -- 14.22 15.04 10.45 18.49 7.64 17.03 14.16 14.64 5.1 -- 8.12 19.15 22.65 19.56 15.99 10.82 20.13 16.35 16.36 5.5 -- 15.27 20.22 23.33 20.92 24.77 16.56 14.83 14.34 14.23 6.1 14.59 15.91 26.86 32.28 18.58 13.82 13.36 16.56 20.14 19.42 6.4 12.88 12.57 18.02 23.17 17.62 19.92 11.66 10.40 13.21 9.91 Pb (ppm dry wt.) 4.1 -- -- 10.04 8.93 11.66 12.37 8.14 2.35 7.32 4.29 4.4 -- -- 12.88 15.96 17.01 23.42 14.90 11.69 13.34 12.18 5.1 -- 18.45 29.18 22.63 22.59 25.39 16.16 12.20 14.47 16.36 5.5 -- 23.13 23.51 26.24 24.09 27.37 26.14 12.52 13.62 11.32 6.1 13.62 23.61 27.52 30.49 22.23 13.57 6.68 12.84 12.83 15.10 6.4 11.56 17.06 27.22 26.52 22.52 19.58 13.32 11.24 10.28 8.72 Cd (ppm dry wt.) 4.1 -- -- N.D. 0.94 0.09 N.D. 0.08 0.88 0.28 0.40 4.4 -- -- 0.20 0.14 0.05 0.12 0.31 N.D. N.D. N.D. 5.1 -- 0.34 N.D. 1.96 0.45 0.27 0.10 N.D. N.D. N.D. 5.5 -- 0.38 0.51 0.86 0.35 4.45 0.38 N.D. N.D. N.D. 6.1 0.43 0.83 N.D. 4.87 0.05 0.20 N.D. 0.27 0.50 N.D. 6.4 0.57 0.45 N.D. 0.20 0.29 4.90 N.D. N.D. 0.24 0.65 Cu (ppm dry wt.) 4.1 -- -- 2.35 3.34 4.98 5.35 2.47 1.88 7.82 4.35 4.4 -- -- 9.32 8.69 6.74 12.89 3.82 14.50 12.17 13.82 5.1 -- 13.88 16.81 19.59 16.50 15.86 9.02 15.30 15.65 17.75 5.5 -- 17.49 23.46 18.67 17.41 16.02 13.13 12.29 12.65 15.37 6.1 20.01 18.40 67.90 65.84 43.39 9.03 15.63 32.71 49.27 40.01 6.4 15.03 13.52 17.13 19.47 17.35 11.99 13.32 10.87 14.24 12.17

-- Samples not taken

metals monitored were assumed responsible for the relatively large increases and/or variatiom (Table 2) in these metal levels especially in the vicinity of the dredged areas. After the dredging, there was a general tendency for the levels of the respective metals to approach similar values.

The undercurrents in the area (Fig. 1) apparently caused the translocation of some of the loose dredged sediment because metal levels from stations in or close to the paths of these currents showed similar variation patterns (Figs. 2, 3). However, in some instances the maxima and minima for the stations close to the areas of origin of the currents are out of phase with those further along the paths of the currents (Fig. 4). This appears to be due to the time required for the translocation to occur.

The highest metal levels were obtained from sediment samples in the vicinity of an area with already

30

20

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I I I I I I I 0~:.' ~ Jut. Oct. Jon. Mot JuL.

L II I [ 19--79 1900 I~I

Sampling times

I I I~lay Dec

J 1902

Fig. 2 Variation o f Fe levels at stations 1.1 and 1.7.

275

Mar ine Pollution Bullet in

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Fig. 3 Variation of Cr levels at stations 4.4, 5.5 and 9.5.

30

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SampLing times

Fig. 4 Variat ion of Fe levels at stations 3.7 and 6.1.

established industries. The sediments in this area were classified as mud by grain size analysis while the areas further removed from the industrial site were mainly sandy. Thus, the enhanced levels could have been possibly due to the proximity of the industrial site and/ or the nature of the sediment.

Departmem of Chemistry University of The West Indies. St Augustine, Trinidad W.L

L. HALL I. CHANG- YEN

Forsmer , U. (1980). In Chemistry and Biogeochemistry of Estuaries (E. Olansson and I. Cato, eds.), pp. 307-348. W'fley-Iriterseienee, New York.

Grosjean, D. (198 3). Distr ibut ion of a tmospher ic ni trogenous pollutants at a Los Angeles Smog Receptor Site. Env. Sci. Techno£ 17, 13-19.

Wharfe , J. & Van den Broek, W. (1977). Heavy metals in macroinverte- brates and fish f rom the lower Medway Estuary, Kent. Mar. Pollut. Bull 8, 31-34 .

Marine Pollution Bulletin, Volume 17, No. 6, pp. 276-278, 1986. Printed ia Great Britain.

Bio-magnification of Total Mercury in Bahia Blanca Estuary Shark

Bahia Blanca Bay (southeast Buenos Aires Province, between 38"45' and 39*40' S and 61"45' arid 62"30' W (Fig. 1)) has an area of approx. 1300 km 2. It receives several creeks and canals (Pucci et aL, 1979) and important urban and industrial centres lie along its northern coast (Bahia Blanca, Puma Alta, Ing. White and Gral. Cerri) as well as several harbours 0rig. White, Galvan, Rosales, Belgrano). All of this, plus its estuary- type dynamics, makes it an adequate environment for developing pollution-related research.

In 1983 and 1984, monthly sampling of'gatuzo shark' Mustelus schmitti was carried out at seven pre- determined stations (Fig. 1) by commercial fishing vessels. All sizes and both sexes were considered.

For each specimen caught total length, weight and sex were recorded, and a muscle sample of the dorsal post- cephalic area was taken. Samples were kept at -20°C until they processed in the laboratory.

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Total mercury was determined by t imeless atomic absorption spectrophotometry after wet digestion (Mot , no et al., 1984).

From the results (Table 1) for total mercury content and total length, a regression analysis was carried out, with correlation coefficients of approximately 0.9 in all cases. Confidence intervals at 95% were also estimated for mean values of mercury concentration for each size (Fig. 2). The functional relationships are indicated in Table 2.

The total mercury baseline of Mustelus schmitti was 0.85 +0.42 ppm wet weight. No previous measurements exist for this species within the ecosystem, but compara- tive date for other elasmobranchs are shown in Table 3.

Our data show a marked positive correlation between mercury contents and the size of the specimen (Fig. 2), as is common in large marine predators (Forrester et al., 1972; Menasveta & Siriyong, 1977; Caputi et al., 1979; Barber & Whaling, 1983, etc.).

Mustelus schmitti of Bahia Blanca bay is one of the upper links in the food chain of the ecosystem. It feeds on Crustacea (prawns, shrimps, etc), shellfish (squid, etc) and fish (anchovy, Sciaenidae, etc); mercury con- centrations in these specimens (Table 4) were always