METALS AND ORGANOCHLORINE COMPOUNDS IN THE
MUSCLE OF DU GONG FROM SULAWESI ISLANDNOBUYUKI MIYAZAKI
National Science Museum, TokyoKAZUOMI ITANO, MINORU FUKUSHIMA, SHIN-ICHIRO KAWAIThe Osaka Ciry Institute of Public Health and Environmental Sciences, OsakaAND
KATSUHISA HONDAEhime Universiry, Matsuyama

ABSTRACTThe muscle of two dugongs from Sulawesi Island were analyzed of metals
and organochlorine compounds. Total mercury in the adult female was0.005 ppm and 0.002 ppm in the immature female. The ratio of total mercury to the selenium was higher in the older individual. Metal concentrations, except for arsenic, were higher in the adult female. PCB, DDT andBHC were not detected in both dugongs. Concentrations of mercury andorganochlorine compounds in the dugong were compared with those of othermarine mammals.
INTRODUCTION

In recent years the presence of significant concentration of metals and organochlorine compounds has been reported in seals and dolphins which are high-ordercarnivores. As the dugong, Dugong dugon (Muller), are hervivorous, comparison ofmetals and organochlorine residues in the dugong with those in other marinemammals appears to throw some light on concentrations through the food chain.
On this problem very few study has been made chiefly due to difficulty of collecting
the fresh samples. Present study was undertaken to investigate the accumulationof metals and organochlorine compounds in the muscle of dugong, and to compare
the data with those of other marine mammals.
MATERIALS AND METHODS

The muscle samples analyzed here were obtained from two dugongs caught in1975 in Laikang Bay, Sulawesi Island and preserved for the Okinawa Exposition.
These animals were kept alive for about 20 days at the Exposition. The biological informations of two individuals are shown in Table 1 and age of them is citedfrom Kasuya and Nishiwaki (1978), who made age determination of dugongs basing
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MIYAZAKI, ET AL.

126

on the dentinal growth layers in the larger tusk. Samples (about 2 kilogram perindividual) were kept frozen to about -20°C after death until the analyses in 1979.
In order to protect against dryness they were glazed twice during cold storage byDr T. Kasuya. All substance data described here were expressed in wet weightbasis.
Mercury: Total mercury was determined directly by a semiautomated flamelessatomic absorption spectrophotometer (Itano et al., 1977).
1Uethylmercury: Methylmercury was analyzed by the gas chromatographic
method based on the procedure of West06 (1967).
TABLE 1.

LIST OF MATERIALSSpecimenNo.

Captured
Date

Captured
Place

Death
Date

Death
Place

Sex

Body
Length(cm)MaturityAge*

RRMOOl
RRM00225 July, '75
26 Aug. '75

Sulawesi Is.
Sulawesi Is.

20 Oct. '75
21 Oct. '75

OkinawaOkinawa

FemaleFemale254
204

AdultImmature

187* cited from Kasuya and Nishiwaki (1978).

Arsenic, selenium and other metals: Arsenic, selenium and other metals were determined using silver diethyldithiocarbamate method, a fluorometric spectrophotometer (Itano et al., 1977) and an atomic absorption spectrometer, respectively.
Organochlorine compounds: Muscle was ground with anhydrous sodium sulfate,and extracted by blending with n-hexane. The extracted fat was removed byflorisil dry column method. Then the sample was cleaned up by silicagel column
chromatography and determined by GC-ECD.
TABLE 2.

CONCENTRATIONS OF TOTAL MERCURY, METHYLMERCURY
AND SELENIUM IN THE MUSCLE OF DUGONGS

SpecimenNo.

Total mercury
ppm

Methylmercury
ppm

Seleniumppm

Total mercury

RRMOOl
RRM002

0.005
0.002

0.004
ND

0.087
0.074

0.057
0.027

Selenium

The tissue weights used for the determination of total mercury, methylmercury and selenium were
0.2 g, 10 g and 3 g, respectively.

RESULTS AND DISCUSSION

Concentrations of total mercury, methylmercury and selenium m the muscle oftwo dugongs are shown in Table 2. This Table indicates that total mercury concentrations in the adult female (RRMOOl) was 2.5 times as much as that in the immature female (RRM002). As the values of total mercury in dugongs were rather
close to 0.001 ppm of the detectable limit of this method, these data might be notadequate for a strict analysis. However, it can be definitely said that contamination by mercury in the dugong is lower than that of grey, harbour, hood and harp
seals (Sergeant and Armstrong 1973), harbour porpoise (Gaskin et al., 1972), striped
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POLLUTANTS IN DUGONG

127dolphin, spotted dolphin, short-finned pilot whale, bottlenose dolphin and finless
porpoise (Arima and Nagakura 1979). Concentration of methylmercury of theadult individual was 0.004ppm and that of the immature was lower than 0.001 ppmof the detectable limit of this method. Ratio of total mercury to selenium in twodugongs was conspicuously lower than that in the ringed seal (Kari and Kauranen1978), striped dolphin, spotted dolphin, short-finned pilot whale, bottlenose dolphin
and finless porpoise (Arima and Nagakura 1979).
Concentrations of nine metals are shown in Table 3. Metal concentration,
except for arsenic, were higher in the older individual. On the contrary arsenic
showed higher concentration in the immature individual. Denton (personal communication) also obtained the similar result on the North Queensland dugong
whose tissue concentrations of metals varied with the age.
TABLE 3.

METAL CONCENTRATIONS IN THE MUSCLE OF DUGONGS IN PPM

Specimen
No.

FeMn

Zn

CuPbNiCoCdAs

RRMOOl
RRM00232.0
18.0

0.094
0.031

29.5
14.8

0.97
0.74

0.25
0.20

1.25
0.55

0.043
0.040

0.120
0.031

0.015
0.050

The tissue weights used for the determination of arsenic and the other elements were 20 g and 10 g,
respectively.

Fat contents in the muscle of the adult female and the immature were 0.084%
and 0.065%, respectively. These were remarkably lower than those of harbour
seal, ranging 0.45 to 5.80% (Gaskin et al., 1973). Since the organochlorine compounds are expected to be most concentrated in the fat of animal tissues, fat wasextracted from a large amount of muscle (240 g) for the analyses. However,PCB, DDT and BHC were not detected. The detectable limits of PCB, a-BHC,,8-BHC, r-BHC, p, P'-DDE, p, P'-DDD and p, P'-DDT were 0.001, 0.0005, 0.001,0.001, 0.0001, 0.001 and 0.001 ppm, respectively. The concentration of organochlorine compounds in the dugong might be extremely lower than in harbour
seal (Gaskin et al., 1973). Heinsohn and Brich (1972) reported that stomach contents of dugongs were almost exclusively sea grasses and no animal matter wasfound. Marine mammals accumulate various pollutants from their environment
mostly through food unlike fihes which concentrate pollutants through both foodand water. Therefore it is concluded that the difference in contamination by
mercury and organochlorine compounds between dugongs and other marine carnivorous mammals is mainly due to the difference of their food.
ACKNOWLEDGMENTS

The present specimens were collected by Dr T. Kasuya of Ocean Research Institute of Tokyo University through the cooperation of the Okinawa Aquarium ofthe Okinawa Ocean Exposition and Professor M. Nishiwaki of University of theRyukyus. Professors M. Nishiwaki and T. Fujiyama of University of Ryukyus,and Professor R. Tatsukawa of Ehime University are acknowledged for their kind
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128

MIYAZAKI, ET AL.

help through this work. Our sincere thanks are due to Dr T. Kasuya for his kindreading and criticizing the draft. We also thank to Dr G. Denton of James Cook
University for his permission to refer the abstract from his major paper which has
been submitted to Marine Biology for publication.
REFERENCESARIMA, S. and K. NAGAKURA, 1979. Mercury and selenium content of Odontoceti. Bul~. Japan Soc. Sci.
Fish. 45 (5): 623--626.
GASKIN, D. E., K. lsHIDA and R. FRANK, 1972. Mercury in harbour porpoises (Phocoena phocoena) from theBay of Fundy Region. J. Fish. Res. Board Can., 29: 1644-1646.
GASKIN, D. E., R. FRANK, M. NoLDRINET, K. lsHIDA, C.J. WALTON and M. SMITH, 1973. Mercury, DDTand PCB in harbour seals (Plwca vitulina) from the Bay of Fundy and Gulf of Maine. J. Fish. Res. BoardCan., 30: 471-475.
HEINSOH, G. E. and W.R. BRicH, 1972. Foods and feeding habits of the dugong Dugong dugon (Erxleben),in northern Queensland, Australia. 1Vfammalia, 36 : 414-422.
lTANO, K., K. SASAKI, K. OKAMURA and R. TATSUKAWA, 1977. Selenium and mercury in marine organisms(1). Distribution of selenium and mercury in the tissues of marine fish. J. Food Hyg. Soc. Japan, 18:547-552.
KARI, T. and P. KAURANEN, 1978. Mercury and selenium contents of seals from fresh and brackish waterin Finland. Bull. Environ. Contam. Toxicol., 76: 273-280.
KAsUYA, T. and M. NrsmWAKr, 1978. On the age characteristics and anatomy of the tusk of Dugong dugon.
Sci. Rep. Whales Res. Inst., 30: 301-311.
SERGEANT, D. E. and F. A. ARMSTRONG, 1973. Mercury in seals from Eastern Canada. J. Fish. Res. Board
Can., 30: 843-846.
WESTOO, G., 1967. Determination of methylmercury compounds in foodstuffs. Acta Chem. Scand., 21:
1790-1800.

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