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Marine Pollution Bulletin 51 (2005) 361–369
Organochlorine and heavy metal concentrations in blubberand liver tissue collected from Queensland (Australia)
dugong (Dugong dugon)
David Haynes a,*, Steve Carter b, Caroline Gaus c, Jochen Muller c, William Dennison d,1
a Great Barrier Reef Marine Park Authority, P.O. Box 1379, Townsville 4810, Australiab Queensland Health and Scientific Services, P.O. Box 594, Archerfield 4108, Australia
c National Research Centre for Environmental Toxicology, The University of Queensland, 39 Kessels Rd, Coopers Plains 4121, Australiad Marine Botany, The University of Queensland, St. Lucia 4072, Australia
Abstract
Tissue samples of liver and blubber were salvaged from fifty-three dugong (Dugong dugon) carcasses stranded along the Queens-
land coast between 1996 and 2000. Liver tissue was analysed for a range of heavy metals and blubber samples were analysed for
organochlorine compounds. Metal concentrations were similar in male and female animals and were generally highest in mature
animals. Liver concentrations of arsenic, chromium, iron, lead, manganese, mercury and nickel in a number of individual animals
were elevated in comparison to concentrations previously reported in Australian dugong. Dieldrin, DDT (and its breakdown prod-
ucts) and/or heptachlor epoxide were detected in 59% of dugong blubber samples. In general, concentrations of organochlorines
were similar to those reported in dugong 20 years earlier, and were low in comparison to concentrations recorded from marine mam-
mal tissue collected elsewhere in the world. With the exception of lead, the extent of carcass decomposition, the presence of disease
or evidence of animal starvation prior to death did not significantly affect dugong tissue concentrations of metals or organochlo-
rines. The results of the study suggest that bioaccumulation of metals and organochlorine compounds (other than dioxins) does
not represent a significant risk to Great Barrier Reef dugong populations, particularly in the context of other pressures associated
with coastal development and other anthropogenic activities.
� 2004 Elsevier Ltd. All rights reserved.
Keywords: Bioaccumulation; Dioxins; Dugongs; Great Barrier Reef; Heavy metals; Marine mammals; Organochlorines; Seagrass
1. Introduction
Southern Great Barrier Reef (Australia) dugong (Du-
gong dugon) populations are documented to have under-
gone a massive decline over the last 40 years (Marshet al., 1994, 1995, 2001). This is of particular concern
as populations of this herbivorous marine mammal are
threatened or in decline throughout much of its world-
0025-326X/$ - see front matter � 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.marpolbul.2004.10.020
* Corresponding author. Tel.: +61 7 47500700; fax: +61 7 47726093.
E-mail address: d.haynes@gbrmpa.gov.au (D. Haynes).1 Present address: University of Maryland, College Park, MD
20742, USA.
wide range (Marsh et al., 1999). Although large popula-
tions of dugong still exist, principally in Australian
waters (Preen, 1993), the species is considered to be vul-
nerable to extinction (IUCN, 1996). Definitive reasons
for the species decline are unclear, but are likely to in-clude legal and illegal hunting, boat strikes and acciden-
tal capture in fishing nets, as well as loss of seagrass
habitat and the release of pollutants following coastal
and hinterland development (Haynes et al., 1998; Marsh
et al., 1999). Recent surveys of pollutant concentrations
in Great Barrier Reef habitat have indicated that near-
shore marine sediments contain a range of organochlo-
rine pollutants including DDT and its breakdown
362 D. Haynes et al. / Marine Pollution Bulletin 51 (2005) 361–369
products as well as dieldrin and lindane and PCDD/Fs
(Muller et al., 1999; Haynes et al., 2000a; Gaus, 2002).
Accumulation of organochlorine pesticides and poly-
chlorinated biphenyls (PCBs) has been implicated in
reproductive, nervous system and immunological abnor-
malities observed in marine mammal populations in theNorthern Hemisphere (Reijnders, 1986; Brouwer et al.,
1989; Kuiken et al., 1994; de Swart et al., 1996; Johnston
et al., 1996). Examples include adrenocortical hyperpla-
sia and disruption of steroid metabolism in seals attrib-
uted to DDE metabolites (methylsulphones) produced
in the liver (Lund, 1994), and reduced testosterone con-
centrations in Dall�s porpoise (Phocoenidae dalli) caused
by organochlorine contamination (Subramanian et al.,1987). The consequences of accumulation of elevated
heavy metals in marine mammals is less clear (Langston,
1990; O�Shea, 1999).Most studies of environmental contaminants in mar-
ine mammals have been based on the determination of
residues of organochlorine compounds and metals in
small cetaceans and pinnipeds (O�Shea and Brownell,
1994). Little is known about the accumulation of persis-tent organic pollutants in herbivorous marine mammals
(O�Shea and Brownell, 1994), and very few data exist on
concentrations of heavy metals or organochlorines in
dugong (Heinsohn and Marsh, 1978; Miyazaki et al.,
1979; Denton et al., 1980; Denton, 1981; Vetter et al.,
2001) or the closely related manatee (Trichechus manatus
latirostris) (Forrester et al., 1975; O�Shea et al., 1984;
Ames and van Vleet, 1996). As a consequence, the con-centrations of heavy metals and organochlorine residues
in Queensland dugong and the potential risk they pose
to dugong health in tropical and subtropical Australian
waters remains essentially unknown. This study presents
contemporary data on concentrations of heavy metals
and organochlorines in dugong stranded along the
Queensland coastline between 1996 and 2000 and dis-
cusses potential risks from past exposure of Queenslanddugong to these pollutants.
2. Materials and methods
2.1. Tissue collection
Tissue samples were collected from 53 dugong car-casses stranded on Queensland beaches between Hervey
Bay and Cairns (1200km) from August 1996 to April
2000 (Fig. 1). Twenty four of the carcasses were in good
condition (fresh) at the time of sampling. Twenty-three
animals were in fair condition (decomposing, organs in-
tact), and six sampled animals were in poor condition
(advanced decomposition) at the time of sampling.
The cause of death was unable to be ascertained for26 of the stranded carcasses. Of the others, death re-
sulted from net or mooring entanglement drownings
(n = 7), a suspected underwater explosion (n = 1), star-
vation, with underlying cause unknown, (n = 10), and
pneumonia or infection following wounding (n = 9).
Twenty-eight animals were considered mature (>2.2m
in length; 14 male, 14 female) and 25 animals were
immature (<2.2m in length; 14 male, 10 female, 1 un-known). Samples of blubber and/or liver were collected
from each carcass using standard techniques (Geraci
and Lounsbury, 1993; Eros et al., 2000). Blubber tissue
was collected from the outermost layers of blubber and
muscle, just to one side of the mid-ventral line. Samples
of liver were collected from the left caudal tip of the
organ.
Samples were collected under Scientific Purposes Per-mit No. 0011221/96/SAB, Queensland Nature Conserva-
tion Act 1992. Basic anatomical data were recorded for
each carcass at the time of sampling. Collected tissue
was divided and stored frozen in acid-washed plastic
containers for metal analyses and in solvent-washed
glass containers for organochlorine analyses. Additional
tissue samples were collected for polychlorinated-p-
dibenzodioxin and dibenzofuran (PCDD/F) analysesand for PCB and natural organohalogen compound
analyses, the results of which are reported elsewhere
(Haynes et al., 1999; Vetter et al., 2001; Gaus et al.,
2001; Gaus, 2002).
3. Sample analyses: metals
Tissue metal analyses were carried out by the Re-
sources Sciences Laboratories, Department of Natural
Resources, (Brisbane). Liver samples for metals analyses
were freeze-dried and ground to a fine powder. Approx-
imately 100mg of each dried sample was microwave di-
gested for 16min in double-distilled nitric acid. The
sample was then cooled in an ice bath and the sample
solution made up to 10g with polished reverse-osmosiswater. Three grams of each solution was reserved for
mercury analysis and the remainder (7g) evaporated to
near dryness on a hotplate and a further 2ml of
HNO3 and 2ml of H2O2 was then added drop-wise to
each residue to complete tissue digestion. The digestion
solutions were washed into separate polypropylene
tubes with 1% HNO3, and made up to 20g. Inductively
coupled mass spectrometry (ICP-MS) using a Perkin-El-mer Sciex ELAN 5000 was used to determine sample
solution concentrations of all metals (aluminium, ar-
senic, cadmium, chromium, copper, iron, lead, manga-
nese, mercury, nickel, selenium and zinc).
4. Sample analyses: organochlorines
Tissue organochlorine concentrations were deter-
mined at Queensland Health and Scientific Services Lab-
NN
0 100 200 300 400
Kilometres
Q U E E N S L A N D
PAPUAN EW
GUINEA
C O R A L S E A
BRISBANE
Bundaberg
GladstoneRockhampton
Mackay
Ingham
Townsville
Cairns
Ayr
Yeppoon
Proserpine
Bowen
Innisfail
Tully
Port Douglas
LockhartRiver
Port Moresby
Hervey Bay
Nambour
Cooktown
15°S
10°S
145°E 150°E
145°E 150°E
20°S
25°S
10°S
15°S
20°S
25°S
Tropic of Capricorn (23°26.5’S)
BRA Q201 1998
17°30'S147°00'E
10°41'S145°00'E
13°00'S145°00'E
15°00'S146°00'E
21°00'S152°55'E
24°30'S154°00'E
FAR NORTHERNSECTION(Area: 85 050 sq km)
CAIRNS SECTION(Area: 35 500 sq km)
CENTRAL SECTION(Area: 75 850 sq km)
MACKAY / CAPRICORNSECTION
(Area: 143 000 sq km)
GUMOO WOOJABUDDEESECTION
(Area: 350 sq km)
Bamaga
Thursday Island
1
1
1
10
34
7
14
9
3
3
C a r c a s s r e c o v e r y s i t e a n d n u m b e r o f s a m p l e s c o l l e c t e d
Fig. 1. Dugong carcass recovery locations, Queensland, 1996–2000.
D. Haynes et al. / Marine Pollution Bulletin 51 (2005) 361–369 363
oratories (Brisbane). Between 2 and 5g of blubber sam-ple for organochlorine analyses were extracted by mac-
erating the sample in 100ml of acetone in a blender.
The samples were then centrifuged and the supernatant
transferred into separating funnels. This was repeated
twice and the extracts were combined. A 100ml aliquot
of dichloromethane (DCM) and 5ml of saturated NaCl
aqueous solution were added to the supernatant. Fol-
lowing phase separation, the non-polar fraction wasconcentrated, and then passed through a gel-permeation
column (GPC, Envirogel, Waters) using DCM as themobile phase. Following the GPC step, the extract was
taken up in hexane and transferred to a column packed
with 10g of 5% deactivated Florisil. This was eluted with
150ml of 6% diethylether (DEE) in hexane and 100ml of
10% acetone in hexane. The volumes of the individual
fractions were then reduced to 1ml. The samples were
then analysed for HCB (Limit of detection (LOD)
0.1lgkg�1), lindane (LOD 0.2lgkg�1), heptachlor(LOD 0.2lgkg�1), heptachlor epoxide (LOD
Table 2
Recoveries (%) of organochlorine compounds in spiked samples
Compound c7–c13 c17–c19 c23–c26 c27–c52 c53–c98
HCB 64 18 35 71 88
Lindane 89 41 61 98 123
Heptachlor 91 32 56 72 134
364 D. Haynes et al. / Marine Pollution Bulletin 51 (2005) 361–369
0.2lgkg�1), aldrin (LOD 0.2lgkg�1), dieldrin (LOD
0.2lgkg�1), DDT (LOD 0.2lgkg�1), DDE (LOD
0.1lgkg�1) and DDD (LOD 0.2lgkg�1) on a gas chro-
matograph employing an electron capture detector
(GC-ECD). The total lipid content of each sample was
determined gravimetrically.
Heptachlor epoxide 96 na 62 93 110Dieldrin 101 34 48 102 106
Aldrin 84 22 31 87 112
DDT (pp) 115 52 80 98 112
DDE (pp) 102 44 67 98 132
DDD (pp) 104 46 78 93 108
PCBs na na na 84 na
na: not available.
5. Quality assurance and statistical analysis
Certified Standard Reference Material (National Re-
search Council, Canada; DORM-2; dogfish muscle), re-
agent blanks and sample duplicates were analysed
concurrently with dugong tissue to validate the metalanalyses methods used (Table 1). Reagent blanks and
spiked recovery samples for organochlorine compounds
were analysed concurrently with dugong tissue samples.
Average recoveries of spikes ranged from 18% to 115%
(Table 2). No organochlorines were detected in reagent
blanks.
Three-way analysis of variance (ANOVA; a = 0.05)
was used to compare dugong liver metal concentrationsand animal maturity (juvenile or adult), gender and
health status (healthy, unhealthy or unknown condition)
using animal body condition (good, fair, poor) as an
analysis covariate (Borrell and Aguilar, 1990). Un-
healthy animals were those that showed evidence of star-
vation or disease at autopsy. Data were plotted and
visually assessed for gross deviations from normality
and, where necessary, transformed (log10) prior to anal-yses. Where metal concentrations were less than detec-
tion limits, values were assigned at half the detection
limit. Two-way ANOVA (a = 0.05) was used to investi-
gate the relationship between detectable blubber orga-
nochlorine concentrations (DDE and dieldrin) and
animal maturity and health status (healthy, unhealthy,
unknown) using animal body condition (good, fair,
poor) as an analysis covariate (Borrell and Aguilar,
Table 1
Average recoveries (%) of Standard Reference Material (DORM 2, Dogfish
Metal Average recovery,
samples 1996
Average recovery,
samples 1997
Average re
samples 19
Al 88 83 91
As 106 87 88
Cd 100 100 100
Cr 87 80 96
Cu 98 101 88
Fe na 91 105
Pb 109 115 123
Mn 93 86 100
Hg 97 95 96
Ni 91 81 99
Se 109 86 81
Zn 95 86 96
na: not available.
1990). Statistical analyses were performed using the
SYSTAT V7.0 statistical package (Wilkinson, 1996).
6. Results
6.1. Metals
Thirty-eight liver tissue samples were collected from
stranded dugong carcasses and analysed for metal con-
centrations between 1996 and 2000. Detectable concen-
trations of all metals analysed were present in dugong
liver, although not all dugongs had detectable concen-
trations of all metals (Table 3). Average concentrations
of all metals were similar to those reported in dugong
previously, although elevated concentrations of one ormore of arsenic, chromium, iron, mercury, manganese,
nickel and/or lead were present in individual animals
collected from the wet tropics region (Cairns to Towns-
ville), the central Queensland coast (the Whitsundays)
and/or Hervey Bay (southern Queensland coast). The
generally higher concentrations of metals present in du-
gong stranded in the vicinity of Hervey Bay may have, in
part, been sourced from the urban environment of Mor-
muscle, National Research Council, Canada)
covery,
98
Average recovery,
samples 1999
Average recovery,
samples 2000
86 75
77 92
105 110
88 84
107 90
108 99
94 na
99 84
94 104
84 73
91 95
104 86
Table 3
Summary statistics, dugong liver metal concentrations (all concentra-
tions, mgkg�1 wet weight)
Mature animals (n = 18) Minimum Maximum Mean SD
Length (cm) 213 320 263 31
% Tissue wet weight 69 80 75 4
Al <5 157
As 0.45 7.7 3.0 1.9
Cd <0.005 32.5
Cr 0.2 18 2.7 4.0
Cu 9.5 303 101 89
Fe 1660 172,300 35,776 48,321
Hg 0.05 1.11 0.3 0.29
Pb <0.08 3.08
Mn <1 35
Ni <0.16 14
Se <0.02 3.6
Zn 458 5375 2658 1400
Immature animals (n = 20)
Length (cm) 110 205 154 26
% Tissue wet weight 69 85 77 3
Al <5 264
As 0.04 5.3 2.1 1.6
Cd <0.005 3.0
Cr <0.2 10.2
Cu 6.8 259 83 74
Fe 537 12,127 4114 3328
Hg 0.04 0.28 0.09 0.06
Pb <0.08 0.85
Mn <1 33
Ni <0.3 7.4
Se <0.02 2.9
Zn 46 1601 695 400
D. Haynes et al. / Marine Pollution Bulletin 51 (2005) 361–369 365
eton Bay (Brisbane, southern Queensland; Fig. 1) as ani-
mals have been observed to migrate between the two re-
gions to feed. No significant differences between male
and female animals in liver metal concentrations were
detectable (Table 4). Concentrations of aluminium, cad-
mium, iron, lead, mercury and zinc were significantly
higher in the liver of mature animals (Table 4). In con-trast, liver tissue concentrations of manganese were sig-
nificantly higher in immature animals (Table 4). The
general trend of increasing average metal concentrations
with animal maturity in these samples is in accordance
with metal accumulation patterns present in other mar-
ine mammals (Aguilar et al., 1998; O�Shea, 1999; O�Shea
Table 4
Summary (p values) of three-way ANOVAs of dugong liver metal concentra
body condition as an analysis covariate (all metal concentrations dry wt. an
Al As Cd Cr Cu
Maturity 0.05 0.054 <0.001 0.789 0.886
Health 0.068 0.938 0.634 0.060 0.138
Gender 0.927 0.815 0.995 0.303 0.542
Maturity · health 0.758 0.447 0.205 0.280 0.697
Maturity · gender 0.565 0.992 0.256 0.054 0.513
Health · gender 0.558 0.185 0.345 0.769 0.345
Maturity · health · gender 0.728 0.845 0.443 0.362 0.551
Condition index 0.481 0.967 0.493 0.695 0.407
et al., 1999). Animal health at the time of death (as
determined at autopsy) was not significantly related to
tissue metal concentrations. Tissue lead concentrations
were significantly higher in carcasses in later stages
of carcass decomposition at the time of liver sampling
(Table 4).
7. Organochlorines
Fifty-two blubber samples collected from stranded
dugong between 1996 and 2000 were analysed for orga-
nochlorine concentrations. The concentration of one or
more organochlorine compounds of interest (dieldrin,heptachlor epoxide, DDT, DDD and/or DDE) exceeded
the limit of detection in 30 samples (i.e. 59% of those
analysed). Detectable concentrations of dieldrin, DDT
and DDE ranged from 0.4 to 9.2lgkg�1 wet weight
(1–43lgkg�1 lipid weight), 0.5–59lgkg�1 wet weight
(2.8–66lgkg�1 lipid weight) and 0.3–15.0lgkg�1 wet
weight (0.9–52lgkg�1 lipid weight), respectively. One
blubber sample contained detectable concentrations ofheptachlor epoxide (0.2lgkg�1 wet weight; 0.26lgkg�1
lipid weight) and one blubber sample contained detect-
able concentrations of DDD (6lgkg�1 wet weight;
6.73lgkg�1 lipid weight). Lindane (detection limit
0.1lgkg�1), heptachlor (detection limit 1.0lgkg�1), al-
drin (detection limit 0.2lgkg�1) and HCB (detection
limit 0.1lgkg�1) were not detected in any of the sam-
pled tissues in this study.Average detectable concentrations of DDE expressed
on a lipid weight basis in blubber decreased with increas-
ing age in both male and female animals (Fig. 2)
although these differences were not statistically signifi-
cant (Table 5). Average detectable lipid weight concen-
trations of dieldrin in blubber increased with
increasing maturity in female animals and decreased
with maturity in male animals (Fig. 2), although again,these differences were not statistically significant. Ani-
mal health at the time of death (as determined at au-
topsy) or stage of carcass decomposition at the time of
liver sampling had no significant effect on tissue organo-
chlorine concentration (Table 5).
tions between animals of different age, gender and health status using
d log10 transformed prior to analyses)
Fe Pb Mn Hg Ni Se Zn
<0.001 0.010 0.002 0.007 0.664 0.152 <0.001
0.319 0.159 0.721 0.138 0.120 0.816 0.771
0.993 0.701 0.824 0.758 0.835 0.327 0.521
0.093 0.754 0.094 0.001 0.336 0.627 0.246
0.375 0.762 0.762 0.031 0.188 0.251 0.213
0.002 0.002 0.557 0.538 0.483 0.507 0.696
0.146 0.077 0.187 0.468 0.260 0.305 0.567
0.102 0.028 0.762 0.239 0.470 0.158 0.955
Fig. 2. Variability in detectable dugong blubber DDE and dieldrin concentrations (error bars = 1 SEM).
Table 5
Summary (p values) of two-way ANOVA of dugong blubber DDE and
dieldrin concentrations (all concentrations, lgkg�1 lipid weight and
data Log10 transformed prior to analysis)
DDE df Mean square F-ratio p
Maturity 1 0.078 0.215 0.646
Health 2 0.386 1.061 0.356
Maturity · health 2 0.297 0.815 0.450
Body condition 1 0.306 0.841 0.365
Error 41 0.364
Dieldrin
Maturity 1 0.012 0.031 0.861
Health 2 0.616 1.561 0.222
Maturity · health 2 0.015 0.039 0.962
Body condition 1 1.209 3.061 0.088
Error 41
366 D. Haynes et al. / Marine Pollution Bulletin 51 (2005) 361–369
Detectable DDE concentrations varied between sam-
pling regions with highest average concentrations pres-
ent in dugong blubber collected from mature animals
stranded at northern sampling sites between Inghamand the Whitsundays (central Great Barrier Reef coast)
CairnsCardwell
Ingham
TownsvilleBowen
WhitsundaysMackay
Gladstone
Mon Repos
Hervey Bay
Sampling region
0
10
20
30
40
50
60
DD
E (u
g kg
lipi
d w
t)
Fig. 3. Detectable DDE and dieldrin concentrations in Queensland du
and in animals collected from a sampling site further
south at Hervey Bay (Fig. 3). Highest detectable dieldrin
concentrations were present in animals stranded at sam-
pling sites at Cardwell, the Whitsundays and at Hervey
Bay (Fig. 3).
8. Discussion
Concern about the conservation and protection of
marine mammals inevitably extends to considerationof the impact of contaminants (O�Shea et al., 1999).
Dugongs are coastal residents and it is these waters that
tend to receive highest concentrations of metals and or-
ganic pollutants from riverine inflows and direct emis-
sions, as well as the highest rates of atmospheric
pollutant deposition due to their proximity to land-
based sources (Wania et al., 1998). In Queensland, ele-
vated concentrations of a number of heavy metalsderived from igneous parent material are also present
in coastal Queensland sediments (Moss and Costanzo,
1998). Pesticides such as dieldrin and DDT are still
widely distributed in Queensland agricultural soils (Cav-
CairnsCardwell
Ingham
TownsvilleBowen
WhitsundaysMackay
Gladstone
Mon Repos
Hervey Bay
Sampling region
0
10
20
30
40
50
Die
ldrin
(ug
kg li
pid
wt)
gong blubber by carcass salvage location (error bars = 1 SEM).
Table 6
Comparison of metal concentrations in Australian dugong liver tissue (all metal concentrations, mgkg�1 dry weight)
Location Northern Australia
Dugonga (Denton et al.,
1980; Denton and
Breck, 1981)
McArthur River
Dugong
(Marsh, 1989)
McArthur River
Dugong (Parry and
Munksgaard, 1992, 1993)
Torres Strait Dugongc
(Dight and Gladstone,
1993; Gladstone, 1996)
Torres Strait
Dugong
(Haynes and
Kwan, 2001)
Queensland
Coast Dugong
(this study)
Date 1974–1978 1984 1992–1993 1991–1993 1997–1999 1996–2000
Sample size 43 2 3 3 36 38
Al <4 <5–264
As 0.2–0.8 0.9–1.9 0.26–2 0.04–7.7
Cd <0.1–58.8 16.4–36.6 10–15 23–46 0.44–54 <0.005–32
Cr <0.5 <0.1–2.9 <0.2–18
Cu 9.1–608 22–107 8.6–28 105–1760 823–1795 7–303
Fe 778–82,363 25,879–69,377 462–34,137 540–172,300
Hg 0.24b <0.02–0.03 0.1–0.19 <0.005–0.22 0.04–1.11
Mn 1.3–9.2 4.0–9.9 <0.6–7.0 <1–35
Ni <0.3 <0.16–1.32 <3–14
Pb <0.3 0.17–0.42 0.24–0.48 <0.04 <0.1–3.1
Se 5.2–7.6 0.40–4.2 <0.02–3.6
Zn 219–4183 1378–1928 1002–1448 470–3430 260–1166 46–5375
a Dugongs sampled in Townsville (n = 14), Torres Strait (n = 1), Cairns (n = 1) and Mornington Island (n = 27).b Originally reported as wet wt. (conversion factor = 4.17).c Originally reported as wet wt. (conversion factor = 4.76).
D. Haynes et al. / Marine Pollution Bulletin 51 (2005) 361–369 367
anagh et al., 1999; Muller et al., 2000) and this is re-
flected in their occurrence in nearshore subtidal sedi-
ments along the Queensland wet-tropics coastline
(Haynes et al., 2000a).A number of pollutants were detected in dugong
stranded along the Queensland coast between 1996
and 2000. Concentrations of metals in dugong liver were
generally similar to, or lower than those reported previ-
ously in dugong collected from different regions along
the northern Australian coast and in Torres Strait
(Table 6). Concentrations of dieldrin and DDT and its
metabolite DDE were present in relatively low concen-trations in dugong blubber in this study. Dieldrin con-
centrations were similar to those reported in the liver
of dugong collected from the same region more than
20 years earlier (0.32–1.02lgkg�1 wet weight) (Hein-
sohn and Marsh, 1978).
Dieldrin concentrations were also low compared with
those in marine mammals from elsewhere, including
both baleen and toothed whales (typically <100lgkg�1
and 70–3600lgkg�1 wet weight, respectively) (O�Sheaand Brownell, 1994; Jarman et al., 1996; Law et al.,
1997; Holsbeek et al., 1999). Total DDT concentrations
in dugong blubber were one to three orders of magni-
tude lower than those typically found in other marine
mammals (<5–100gkg�1), including seals (Tanabe et
al., 1994; Oehme et al., 1996; Aguilar et al., 1998), belu-
ga whales (Muir et al., 1996); dolphins (Kannan et al.,1993; Vetter et al., 2001) and baleen whales (de Kock
et al., 1994; O�Shea and Brownell, 1994; Guitart et al.,
1996). Concentrations of RDDT in dugong blubber
were also two orders of magnitude lower than levels de-
tected in liver of Florida manatee (Ames and van Vleet,
1996).
Gender and age patterns of accumulation of detect-
able DDE and dieldrin concentrations (expressed on a
lipid weight basis) in dugong did not follow the general
trend of increased concentrations in mature males com-pared with immature males and a decline in concentra-
tions in females with maturity associated with
maternal contaminant transfer (Aguilar et al., 1998;
O�Shea et al., 1999; O�Shea, 1999). The reason for this
is presently unknown, and may simply be a consequence
of the generally low concentrations of these contami-
nants in the Great Barrier Reef environment. However,
persistent contaminants are generally incorporated intothe body of marine mammals through food intake (Agu-
ilar et al., 1998), and dugong feed by uprooting entire
seagrass plants from the benthos (Spain and Heinsohn,
1973; Preen, 1995). As a consequence, variations in
dugong body burdens of organochlorine residues (and
heavy metal concentrations) could also be related to
variation in sediment and seagrass pollutant concentra-
tions, as well as the reproductive history and age of maleand female animals.
Toxicity of accumulated metals in marine mammals
is related to cellular enzyme inactivation. However, with
the exception of mercury, no experimental or field col-
lected data has yet demonstrated a toxic impact of accu-
mulated metals in marine mammals (Johnston et al.,
1996; O�Shea, 1999). Although cause of death was not
established conclusively for a majority of the Queens-land dugong carcasses, metal concentrations were typi-
cally low compared with concentrations present in
healthy animals killed during traditional hunting
(Haynes and Kwan, 2001). It is therefore unlikely that
heavy metal accumulation and toxicity played a signifi-
cant part in Queensland dugong strandings and/or
368 D. Haynes et al. / Marine Pollution Bulletin 51 (2005) 361–369
deaths. Accumulation of dieldrin and DDT in marine
mammals has demonstrated reproductive and endocrine
disruptive effects (Fossi et al., 1999). However, the con-
centrations of these pollutants accumulated by Queens-
land dugong are relatively low compared to those
accumulated in marine mammals elsewhere. It is there-fore also unlikely that these compounds, with the possi-
ble exception of dioxins (Haynes et al., 1999; Gaus,
2002; Gaus et al., 2001) present a significant risk to local
dugong populations. A greater, indirect risk to Queens-
land dugong populations is likely to be presented by the
impact of herbicide residues on their nearshore seagrass
food resource (Haynes et al., 2000b).
Acknowledgements
Grahame Byron, Andrew Griffith, Neil Hicks, Craig
Purdon, David Savage and Mike Short (Queensland
Parks and Wildlife Service), Kirstin Dobbs and Cherie
Recchia (Great Barrier Reef Marine Park Authority)
and Tony Preen (James Cook University) are thankedfor assistance with tissue collection. Metal analyses were
coordinated by Glenn Barry (Queensland Department
of Natural Resources and Mines).
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