A discussion on the results of our contaminant assay of organochlorines in blubber biopsy samples, taken from free-ranging blue whales in the St. Lawrence.


    The results of our study show a significant difference between levels of PCBs in male specimens, compared to females. Total PCBs were in the ~300 - 2600 parts per billion range, which is quite close to the limited data available from other studies of blue and related whales.

    It is interesting to note that for other species of marine mammals or whales from areas other than the Gulf of St. Lawrence, the total PCB levels in the blubber differ--this is because both the level of contaminantion in the immediate environment, and species influences how much PCB a whale will accumulate. Some studies on the beluga whales of the St. Lawrence show much greater levels of PCB accumulation than that which we found in blue whales.

    There are several reasons for the difference:

      a) Blue whales feed at a lower trophic level than do belugas. Because beluga whales feed on a higher trophic level, there is more of an oppurtunity for biomagnification. PCBs and similar contaminants preferentially accumulate in the fatty tissues of organisms. Therefore, every time you move up a level in the food chain each organism will be accumulating not just the sum of all contaminants in whatever it feeds on, but also from everything that its prey feeds on, and so on down the food-chain.

      b) St. Lawrence blue whales, unlike the belugas, do not spend all of their time in the Gulf, and so they are not always taking up contaminants to the same degree as the belugas.

      c) Variation in PCBs found in various organisms occurs, additionally, because different species metabolize chemicals differently. Also, different PCB congener levels are found because different compounds have a greater affinity to partition into an organism. This 'desire' for a contaminant to move out of water and into an organism is often described using a Kow value (the 'octanol-water partition coefficient'), which is the ratio of a chemical's solubility in octanol to a chemical's solubility in water.

    Reports in the scientific literature show that the higher-numbered PCB congeners tend to be present in greater proportions than lower-numbered ones. The results of our study are in general agreement with this (see figure below). PCB congeners assigned higher numbers are more heavily chlorinated. These PCBs are more difficult to metabolize, and so they may remain unchanged with greater frequency than the lower chlorinated congeners.

    The highly chlorinated congeners are not readily broken-down, and tend to accumulate more in an unchanged form.


    Our results show a very similar pattern of PCB contamination occurring in the blubber of blue whales in the Gulf of St. Lawrence, as other reserachers have described for other marine mammals in both the St. Lawrence and the arctic regions. The graph below represents the contribution of each PCB congener, to PCBs.

        Notice, above, that lower numbered PCB congeners occur proportionally less than those with higher numbers. A similar distribution of PCB congeners has been found in beluga whales (Delphinapterus leucas), in Dallís porpoise, and in many seals (pinnipeds). The very high, proportionally speaking, levels of congener numbers 52, 153, and 138, is a particular feature that has been noted by others in previous studies.


Pesticide analysis

      Below is a similar graph for DDT, DDD, and DDE average contribution to total DDTs. It is interesting to note that DDE levels were found to be higher in females than in males--typically, the reverse has been found to be true. It is generally thought that males will have higher DDE levels, as DDE is a metabolite of DDT. Since male's metabolism of such compounds is thought to be heightened by their elevated contaminant burden, males generally higher DDE levels are rationalized. Because, particularily, our measured DDT, DDE and DDD levels had such a high amount of variability, these findings may be somewhat suspect, and warrant further investigation.


        Summary

        The root of the differences between male and female contaminant burdens is in that female marine mammals transfer a large portion of their contaminants to their offspring. The females of some species of marine mammals have been found to rid themselves of as much as 98% of their organochlorine contaminant burden. This is largely because the milk of marine mammals is extremely high in fat--more than 50% in some, compared to about 8%, on average, in terrestrial mammals (see introduction).

        Unlike females, males lack the ability to rid themselves of their contaminant burden at any time during their life cycle. In males, therefore, the rate of PCB intake always exceeds the rate at which they are eliminated. If females do not reproduce, their contaminant intake rate also exceeds the elimination rate, and so they accumulate contaminants just like males do. In light of this, the significant sex differences shown above can be taken to suggest active reproduction.

        Finally, in conclusion, the table below lists each of the major contaminant groups we tested for, the average (and range of values) concentrations in both males and females, the sample size (ie. the number of animals in each test group), and a P value from a statistical test performed to determine if the differences between the sexes were significant (the non-parametric Mann-Whitney test)--if an NS is specified, the test showed no significant difference, where otherwise there was a significant difference found.

 Compound

(ng/g lipid)

Male

(n = 7)

 Female

(n = 12) 

 

P

å PCB

1635.7 (538.2-2613.3)

887.9 (306.4-1552.3)

0.05

å DDT

7522.7(2470.9-23025.3)

1930.1(329.8-6024.3)

<0.01

å HCH 

88.2 (57.3-122.1)

68.7 (30.7-114.4)

NS

å ChlordaneÜ

611.3 (216.5-1164.6)

134.1 (25.8-317.3)

<.001

Mirex

8.7 (3.5-14.5)

6.4 (2.0-12.2)

NS

HCB

528.7 (51.3-1686.3)

91.5 (36.3-170.8)

0.02

Aldrin

0.4 (0.0-1.2)

0.0 (no values)

NS

Endrin

10.9 (0.0-23.2)

1.7 (0.0-9.9)

NS

Heptachlor

0.6 (0.0-2.8)

0.1 (0.0-1.4)

NS

Heptachlor Epoxide

360.2 (107.6-1144.8)

157.4 (22.0-601.1)

0.03

            Üsum of trans-, and cis-chlordane, trans-, and cis- nonachlor

            NS = not significant, P > 0.05

    For furthur information on contaminant accumulation differences between male and female marine mammals, read:

      Aguilar, A., and A. Borrell. 1988. "Age and Sex-related Changes in Organochlorine Compound Levels in Fin Whales (Balaenoptera physalus) from the Eastern North Atlantic." Marine Environmental Research, vol. 25: pp. 195-211.

      Borrell, A., A. Aguilar, S. Corsolini, and S. Focardi. 1996. "Evaluation of Toxicity and Sex- related Variation of PCB Levels in Mediterranean Striped Dolphins Affected by an Epizootic." Chemosphere, vol. 32: pp. 2359-2369.

      Stern, G. A., D. C. G. Muir, M. D. Segstro, R. Dietz, and M. P. Heide-Jorgensen. 1994. "PCBs and Other Organochlorine Contaminants in White Whales (Delphinapterus leucas) from West Greenland: Variations With Age and Sex." Bioscience, vol. 39: pp. 245-259.

Site map: click on an elliptical region to learn more!


RAW DATA for each whale (by sample number)

ID

1565

1566

1567

1568

1569

1570

1571

2528

2529

2530

SAMPLE WT/g

0.629

0.767

0.643

0.693

0.239

0.559

0.567

0.460

0.482

0.438

LIPID WT/g

0.460

0.224

0.420

0.129

0.108

0.287

0.217

0.210

0.269

0.293

COLLECTION DATE Oct. 10/92 Oct. 3/92 Oct. 3/92 Oct. 3/92 Jun.16/93 Jun.25/93 not available Oct. 4/95 Oct. 4/95 Oct. 4/95

SEX

m

m

m

f

unknown

f

m

f

m

f

BODY SITE: SIDE

L

L

L

unknown

unknown

R

unknown

L

L

L

BODY SITE: LENGTH

P

P

M

M

unknown

P

M

M

M

M

PCB 18

5.832

6.041

4.296

nd nd

9.603

13.141

nd nd

2.604

PCB 31 nd

4.444

4.158

nd nd nd

7.700

nd nd nd
PCB 52

103.517

230.011

52.846

98.406

70.362

129.651

410.849

79.663

292.566

103.035

PCB 49

12.467

19.358

9.624

14.598

9.591

33.470

30.021

13.248

16.857

13.867

10.939

1.048

6.731

7.642

2.034

3.629

1.022

TOTAL PCBs

839.348

1828.626

538.179

1321.698

568.495

1175.305

2613.330

881.321

2478.368

936.353

a BHC

54.591

64.897

54.059

36.640

6.632

21.576

64.871

61.043

59.335

50.427

b BHC

16.533

34.731

14.331

11.518

21.736

13.612

41.159

16.463

21.556

15.524

g BHC

12.807

13.390

12.984

19.165

4.479

7.503

14.587

9.414

12.126

8.532

d BHC

1.011

2.330

1.517

3.042

1.737

1.513

1.526

nd nd nd
TOTAL BHC

84.942

115.349

82.890

70.365

34.584

44.203

122.143

86.921

93.017

74.483

HCB

51.328

1100.238

334.609

62.008

120.006

83.725

1686.313

122.405

215.029

137.689

HEPTACHLOR nd

1.371

nd

1.367

1.429

nd

2.792

nd nd nd
HEPTACHLOR EPOX.

566.886

306.678

144.769

601.079

783.736

148.423

1144.769

68.033

118.520

76.771

ALDRIN

0.439

1.162

nd nd nd nd

0.932

nd nd nd
DIELDRIN

0.681

1.397

1.257

1.960

5.929

0.547

1.532

282.924

523.149

289.823

ENDRIN

19.896

23.245

8.150

6.823

20.689

9.902

15.129

nd

9.900

nd
DDE

2701.680

8001.211

2372.976

4115.194

62388.230

5541.435

17210.389

798.279

1848.556

522.425

DDD

17.468

11.140

5.549

3.712

6.991

5.022

9.053

187.500

735.755

138.720

DDT

1417.184

2856.904

1507.039

383.581

2920.735

477.863

5805.858

249.248

1327.524

171.580

TOTAL DDT

4136.332

10869.255

3885.565

4502.487

65315.956

6024.320

23025.300

1235.027

3911.835

832.726

MIREX

3.692

10.943

3.512

10.753

6.898

11.188

10.503

4.976

14.524

4.662

a-CHLORDANE

39.544

52.194

34.275

24.011

40.086

33.258

58.484

30.457

51.041

27.686

g-CHLORDANE

8.626

12.524

4.595

3.701

8.486

5.058

10.557

nd nd nd
T-NONACHLOR

145.227

275.647

92.365

104.586

224.632

122.775

228.427

131.071

98.063

58.331

C-NONACHLOR

304.632

773.760

236.668

184.956

383.077

112.537

867.092

14.929

327.836

22.751

TOTAL CHLORDANE

498.029

1114.126

367.903

317.253

656.281

273.628

1164.560

176.457

476.941

108.768

ENDRIN ALDEHYDE

223.793

1258.329

169.056

707.136

331.130

171.362

1636.967

nd nd nd
METHOXYCHLOR

51.662

119.096

47.700

33.306

61.859

29.848

106.546

nd nd nd

ID

2531

2532

2533

2534

2535

2536

2537

2538

2539

2540

SAMPLE WT/g

0.495

0.515

0.513

0.244

0.428

0.362

0.437

0.363

0.434

0.485

LIPID WT/g

0.102

0.294

0.579

0.081

0.230

0.152

0.261

0.207

0.251

0.220

COLLECTION DATE Sep.25/95 Oct. 4/95 Oct.10/95 Oct. 5/95 Oct.11/95 Oct.10/95 Oct. 4/95 Oct. 4/95 Oct. 5/95 Oct.10/95

SEX

f

f

f

f

f

f

f

f

m

m

BODY SITE: SIDE

L

L

L

unknown

R

unknown

R

R

R

R

BODY SITE: LENGTH

M

A

M

M

A

M

M

P

M

M

PCB 18 nd

2.743

1.192

nd

5.387

nd

2.387

3.512

3.531

4.975

PCB 31 nd nd nd nd nd nd nd nd nd nd
PCB 52

69.474

34.543

24.805

163.431

133.839

53.952

107.900

53.670

149.643

229.745

PCB 49 nd

7.710

3.648

19.859

13.931

3.676

8.307

9.795

10.657

26.883

PCB 44

12.668

10.598

6.130

23.143

20.409

12.858

10.837

12.814

14.530

29.158

PCB 99

34.843

17.983

13.882

81.485

73.883

25.559

50.943

28.594

74.878

115.803

PCB 87

13.020

11.118

6.094

28.815

25.801

10.825

11.309

14.995

18.214

37.704

PCB 110

59.256

62.320

29.197

111.593

43.649

24.881

23.079

32.714

34.398

57.704

PCB 118

70.049

39.367

25.986

156.156

138.748

51.702

84.963

58.144

134.215

252.141

PCB 149

79.509

47.368

34.970

195.423

155.481

54.251

91.817

71.467

139.900

232.677

PCB 151 nd nd nd nd nd nd nd nd nd nd
PCB 153

107.862

71.566

49.882

252.852

238.917

80.776

131.669

123.047

199.561

331.441

PCB 156

1.687

1.082

0.624

3.468

4.197

7.079

1.497

1.258

2.686

6.443

PCB 138

108.098

68.441

48.082

248.749

231.964

88.249

126.486

118.469

190.973

334.474

PCB 180

51.171

40.728

31.170

137.953

156.258

42.138

68.264

89.208

95.518

177.651

PCB 170

19.896

15.199

11.934

52.932

61.574

16.385

26.232

34.684

35.369

69.166

PCB 199

16.480

14.955

11.425

49.647

56.230

10.605

19.516

35.318

26.853

66.570

PCB 195

1.514

1.038

1.093

4.677

nd

1.374

nd

3.646

2.612

5.236

PCB 194

8.654

6.493

5.624

22.121

29.755

6.318

9.494

19.164

10.274

26.036

PCB 209 nd

1.468

0.624

nd

4.203

nd nd

2.000

nd

4.391

TOTAL PCBs

654.179

454.721

306.359

1552.304

1394.225

490.626

774.702

712.501

1143.813

2008.198

a BHC

72.951

42.616

21.188

75.864

42.265

35.704

24.077

37.188

37.498

40.541

b BHC

23.555

11.111

4.826

30.361

6.028

16.200

14.824

23.938

9.265

13.130

g BHC

9.647

5.469

4.732

8.160

9.139

9.092

7.912

9.807

10.518

8.255

d BHC nd nd nd nd nd nd nd

2.411

nd nd
TOTAL BHC

106.153

59.196

30.747

114.386

57.433

60.996

46.812

73.344

57.281

61.926

HCB

98.269

55.712

36.260

170.806

115.918

73.709

83.644

57.843

110.607

202.713

HEPTACHLOR nd nd nd nd nd nd nd nd nd nd
HEPTACHLOR EPOX.

63.696

37.507

22.016

93.296

69.317

585.704

50.402

72.290

107.590

132.405

ALDRIN nd nd nd nd nd nd nd nd nd nd
DIELDRIN

193.490

104.235

65.642

330.926

273.170

162.000

246.498

150.435

433.163

511.568

ENDRIN nd

0.571

0.380

1.667

nd

1.164

nd nd nd nd
DDE

347.951

247.865

215.723

2476.413

1312.306

429.169

1461.241

441.537

1092.574

2422.537

DDD

127.431

64.588

50.651

374.815

242.600

132.368

222.851

147.908

329.478

709.145

DDT

158.147

63.490

63.430

563.753

581.561

196.467

519.023

125.372

1048.833

1228.232

TOTAL DDT

633.529

375.944

329.805

3414.981

2136.467

758.005

2203.115

714.817

2470.884

4359.914

MIREX

3.966

3.773

2.696

8.775

12.167

2.014

4.211

8.070

5.857

11.799

a-CHLORDANE

33.108

17.497

10.064

32.383

33.713

22.895

17.130

37.444

37.693

36.405

g-CHLORDANE nd nd nd nd nd nd nd nd nd nd
T-NONACHLOR

31.686

20.959

8.242

26.222

46.091

17.309

32.000

10.744

93.582

105.414

C-NONACHLOR

19.422

12.837

7.468

31.049

99.743

19.178

121.778

24.478

85.243

299.182

TOTAL CHLORDANE

84.216

51.293

25.774

89.654

179.548

59.382

170.908

72.667

216.518

441.000

ENDRIN ALDEHYDE nd nd nd nd nd nd nd nd nd nd
METHOXYCHLOR nd nd nd nd nd nd nd nd nd nd

ERS | Biology | Env. Modelling | Trent home
Copyright 1997, ERS Department, Trent University. All rights reserved.
by Geoff Wild and
Jason de Koning