organochlorine and heavy metal residues in harbour seals from the wadden sea and their possible...

Netherlands Journal of Sea Research 14 ( t ) : 30-65 (1980)

O R G A N O C H L O R I N E A N D H E A V Y M E T A L R E S I D U E S IN H A R B O U R SEALS F R O M T H E

W A D D E N SEA A N D T H E I R P O S S I B L E E F F E C T S ON R E P R O D U C T I O N

by

P . J . H . R E I J N D E R S

Research Institute for ,Nature Management, P.O. Box 59, 1790 AB Den Burg, Texel, The Netherlands

C O N T E N T S

I. I n t r o d u c t i o n . . . . . . . . . . . . . . . . . . . . . . . . . . 30 I I . Ma te r i a l a n d Me t hods . . . . . . . . . . . . . . . . . . . . . 33

I I I . Resul ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 1. Mercu ry , se len ium a n d b r o m i u m . . . . . . . . . . . . . . . . 34 2. Organoch l o r i ne s . . . . . . . . . . . . . . . . . . . . . . . 36

IV. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 1. Mercu ry , se len ium a n d b r o m i u m . . . . . . . . . . . . . . . . 37

a. A c c u m u l a t i o n , tissue d i s t r ibu t ion a n d m e t a b o l i s m . . . . . . . . . 37 b. Toxicologica l impl ica t ions . . . . . . . . . . . . . . . . . 41

2. PCB's a n d D D T . . . . . . . . . . . . . . . . . . . . . . 42 a. Accumula t ion , tissue d i s t r ibu t ion a n d me tabo l i sm . . . . . . . . 42 b. Toxicological impl ica t ions . . . . . . . . . . . . . . . . 46

3. O t h e r c o m p o u n d s s tudied . . . . . . . . . . . . . . . . . . . 49 4. Rou t e s of t r a n s p o r t in the m a r i n e e n v i r o n m e n t . . . . . . . . . . 49 5. In t e r re l a t ions be t w een the o rganoch lo r ines s tudied . . . . . . . . 52 6. C o m p a r i s o n of res idue levels in seals o r ig ina t ing f rom different par t s of

the W a d d e n Sea . . . . . . . . . . . . . . . . . . . . . . . 54 a. Mercu ry , se len ium a n d b r o m i u m . . . . . . . . . . . . . . . 54 b. Organoch l o r i ne s . . . . . . . . . . . . . . . . . . . . . 55 c. O t h e r c o n t a m i n a n t s . . . . . . . . . . . . . . . . . . . . 55

V. Conclus ions . . . . . . . . . . . . . . . . . . . . . . . . . . 56 VI . S u m m a r y . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

V I I . References . . . . . . . . . . . . . . . . . . . . . . . . . . 57

I. I N T R O D U C T I O N

The harbour seal population in the Dutch Wadden Sea (Fig. 1) has decreased strongly during the last decades (REuNDERS, 1976; SUMt~RS, BONNER & VAN HAArTEN, 1978). Studying its population dynamics (REuNDERS , 1978) showed that pup production in the Dutch seal population was lower than that in the stable population of Schleswig- Holstein (cf DR~.SCHER, 1978b) and Denmark. In fact it was found that pup production rates tend to increase along the Wadden Sea coast

O R G A N O C H L O R I N E S I N H A R B O U R S E A L 31

from the Netherlands to Niedersachsen, Schleswig-Holstein and Den- mark. It was suggested that environmental factors are involved and the aim of the present study is to investigate the contribution of environmental pollution.

N o r t h Sea

Marsdie

Danish Wadden Sea

55 °

54"

530

52 °

Fig. 1. Map of the Wadden Sea with the adjacent North Sea.

It is well known that environmental contaminants such as organochlorine compounds, pesticides, PCB's and several metals accumulate in marine mammals. Extremely high levels of mercury were detected in 1967 in seals in Finland (HELMINEN, KARPPANEN & KOIVISTO, 1968), relatively high levels of organochlorines in grey seals and dol- phins from the British coast (HoLDEN & MARSD~N, 1967; ROBINSON et al., 1967). Data on heavy metals and organochlorines in harbour seals from the Dutch coast have been reported by KO~.MAN & VAN GENDEREN (1966), KOEMAN, PEETERS, SMIT, TJ IOE & DE GOEY (1972) ; KOEMAN et al. (1975) and in harbour seals from the Schleswig-Holstein coast by DRESCHER, HARMS & HUSCH~.NBETH (1977).

32 P . j .n . REIJNDERS

Recently, reproductive failure in marine mammals has been asso- ciated with high levels of organochlorines, and metals (LEBoEuF & BONN~.LL, 1971; DELONG, GILMAgTIN & SIMPSON, 1973; OLSSON, JOHNELS & VAZ, 1975; GXLMARTIN et al., 1976; HELLF., OLSSON & JENSEN, 1976a, 1976b). Experimental data on the effects of PCB's in mink support the hypothesis that PCB's have detrimental effects on the reproductive performance of seals (AuLERICH, RINGER & IWAMOTO, 1977 ; J~.NS~.N et al., 1977). These experiments showed species-specific responses to PCB and total DDT, i.e. pathological changes of the uteri found in seals did not occur in minks. Besides, KOEMA~ et al. (1973) found a strong correlation between total mercury and selenium in livers of several marine mammalian species. They concluded from their and other studies that selenium might be involved in a mechanism which protects seals against the toxic effects of mercury. In this study residue levels of several pollutants in various tissues of seals from Schleswig-Holstein, Denmark and the Netherlands are compared.

It has to be stressed that sample treatments and analytical techniques used were often different and therefore quantitative results may vary considerably. Especially when residue levels in tissues of seals origi- nating from two areas have to be tested on significant differences, results taken from literature stand a large chance to lead to unreliable conclusions. In order to avoid ambiguities in the data resulting from this study the material is collected using the same procedure, and all analyses for each of the heavy metals, organochlorines and bromium are carried out with the same technique in the same laboratory.

Acknowledgements.--First of all I want to express my sincere thanks to my collegues Dr B. Clausen (State Veterinary Laboratory, Copen- hagen) and Dr H. E. Drescher (Institute for Domestic Animal Science, Kiel) who provided me with tissues of harbour seals found dead in the Danish and Schleswig-Holstein parts of the Wadden Sea. I want to express my gratitude to Prof. Dr. J. H. Koeman for discussions on the subject of this study as an important part of my thesis (RExJNDERS, 1980), to the Department of Toxicology, Agricultural University of Wageningen, for rendering me hospitality and facilities to carry out the analyses on mercury and selenium and to Mr W. S. M. van de Ven who made me familiar with the analytical procedures. I also want to acknowledge MrJ . K. Quirijns (Central Institute for Nutrition & Food Research TNO, Zeist) and Dr A. G. Rauws (National Institute of Public Health, Bilthoven) for carrying out the analyses on organochlorines and bromium respectively. I am gratefull to Mr W. G. van Arkel (Netherlands Institute for Sea Research, Texel) for his assistance in mathematical affairs, Dr W. van Utrecht (Institute for Taxonomic

O R G A N O C H L O R I N E S IN H A R B O U R SEAL 33

Zoology, Amsterdam) who kindly carried out the age determination of the Schleswig-Holstein seals and to Mr J. Schoonheden who made the drawings.

Finally I want to thank Dr J. C. Duinker and Dr W.J . Wolff for critical reading of the manuscript.

The study was partly financed by a grant from the European Communities (Environment Research Programme contract nr. 198-77-1-ENV NL) and the TNO Committee for Research on Side- effects of Pesticides and Related Compounds.

I I . M A T E R I A L A N D M E T H O D S

The material is collected during 1975 and 1976. It consists of harbour seals found dead on the beach, 16 animals from the Schleswig-Holstein and Danish Wadden Sea and 14 from the Dutch Wadden Sea. The animals are autopsized, and brain, liver, kidney and blubber tissues are collected and deep-frozen. The age is determined by counting annual growth layers in teeth cementum, according to LAWS (1962).

Selenium and inorganic and organic mercury are analyzed by Atomic Absorption Spectrophotometry; mercury according to the procedure devised by MAOOS (1971) and modified by VAN DE VEN, KOEMAN & SVENSON (1979). For analysis of selenium, tissue samples are digested according to the procedure devised by WATKINSON (1966) and measured according to the method of DUNCAN & PARam~ (1974) modified by VAN DE VEN, KOEMAN & SVENSON (1979).

Organochlorines are analyzed by Gas Liquid Chromatography with electron capture detection. The sample extracts (hexane) are treated according to the clean-up procedure of HOLDEN & MARSDEN (1969). The PCB components are converted to decachlorobiphenyl (DCB) according to BERo, DIOSADY & REES (1972). This might be less accu- rate when most of the lower chlorinated components dominate in the PCB's mixture. In seals, however, the higher chlorinated components predominate (DuINKER, HILLEBRAND & NOLTING, 1979) and therefore this procedure appears to be acceptable as can also be deduced from a report of an international intercalibration programme on monitoring organochlorine and mercury residues in wildlife (HOLDEN, 1973). Organochlorines analyzed are PCB's, o,p'-DDT, p,p'-(DDT + DDE + TDE), dieldrin, aldrin, endrin, endosulfan, ~-HCH, ~-HCH, y-HCH, HCB (hexachlorobenzene), pentachlorobenzene and HEPO (heptachloroepoxide).

Bromium is analyzed by a colorimetric method according to HUNTER (1955), as modified and applied by RAuws & VAN LOOTEN (1974).

The results are divided in two age classes of seals: (a) juveniles and

34 P. J. H. REIJNDERS

subadults and (b) adults. Correlations between age and residue levels of pollutants, and between residue levels in several tissues are computed (TEKTRONIX, 1975). For both age classes the results are statistically tested for significant differences between the areas. The equali ty tests are Wilcoxon's, Student 's t-test and DE WmR'S (1960) s tandardized t-test. Since the total D D T group consists of D D T and its metabolites DDE and T D E - - e a c h of which is related to the others by metabolic processes--a mukivar ia te statistical technique (KRAMER & JENSEN, 1969) is used for DDT.

III . RESULTS

Values for mercury, selenium and b romium are expressed in ~g-g-1 on wet weight basis. The da ta on organochlorines in blubber are expressed in t~g.g -1 on extractable lipid basis whereas the residues found in kidney and liver are on wet weight basis.

1. MERCURY, SELENIUM AND BROMIUM

Concentrations of total Hg are different between the different organs (Fig. 2; Table I).

T A B L E I

Means and ranges ([zg-g -x wet weight) of total mercury (Y. Hg), methyl mercury (CHsHg), seleniur (Se) and bromlum (Br) contents in kidney, liver and brain of juvenile and subadult and of adult harbou seals from Schleswig-Holstein and Denmark and from the Netherlands [number of specimens analyzec between brackets]. For each age group, significantly higher areal values are indicated (** for 0.01 < p <

0.05; * for 0.05 < p < 0.I ; Wileoxon test, Students t-test and Weir's standardized t-test).

Schleswig-Holstein plus Denmark Netherlands

Juveniles and Adults Juveniles and Adults subadults subadults

kidney [6-8] [4] [5] [4] Y. Hg 4.3( 1.6-8.3)** 7.5(2.2-17.9) 3.3(0.7-3.2) 17.0( 5.4-28.2)* CHaHg 2.2( 0.6-4.0) 3.5(1.0-9.2) 1.7(0.3-4.7) 7'9(2.1-15.4) Se 0 . 6 ( t r a c e - - 1 . 3 ) 3.5(1.9-7.3) 1.2( 0.6-1.6)** 7.1( 2.3-10.0)* Br 18.5(12.4-28.6) 10,6(7.1-13.9) 14.9(11.4-23.9) 21.1(17.1-24.9)**

liver [6-8] [5] [5-6] [8] Y. Hg 10.2(1.1-27.3) 214 (13.6-751) 8.4(0.9-23.0) 293 (58.6-573) CHsHg 3.5( 0.5-6.6) 31,1(3.6-103) 3.3(0.5-7.6) 60.6(16.0--134) Se 2.6(trace-0,8) 112 (9.2-409) 2.8(0.7-6.5) I09 (3.9-350) Br 16.6(12.9 -20,7) 13.6(8.9-19.0) 19.3(10.0-24.0)** 20.7(13.4-34.4)**

brain [8] [3] [5] [6] ]g Hg 1.2( 0.5-1.7) 1.7(0.6-3.8) 1.4(0.4-2.1) 12.6( 4.3-17.5)** CHsHg 0.9(0.4-1.2) 0.5(0.2-1.0) 1.0(0.2-1.5) 3.2(1.0-5.2) Se 1.1 (trace-7.4) ** 1.5 (0.5-2.2) traces 5.9 (2.2-8.3) ** Br 8.3( 5.1-14.6) 10.8(4.6-14.0) 7.5(5.5-9.7) 18,3(8.6-42.8)


The tissue concentrations of total Hg increase with age (Fig. 2), most pronounced in the liver, but also in brain and kidney. An increase of the mercury content in tissue of seals with age was reported before by several authors (HzLMINEN, KARPPANEN & KOIVlSTO, 1968; HEN- RICKSSON, KARPrANZN & H~LMIN~N, 1969; KO~MAN, PrmamRs, SMIT, TJIO~ & D~ GO~Y, 1972; FR~MAN & HORN~., 1973; H~.rPL~STON & FRENCH, 1973; S~ROZANT & ARMSTRONO, 1973; KO~.MAN et al., 1975; SMITH & ARMSTRONG, 1975 ; ROBERTS, HErPL~STON & ROB~-RTS, 1976 ; DRrSCHZR, HARMS & HUSCHENBZTH, 1977). A strong correlation between mercury and selenium in both liver and brain is found (Fig. 3). The highest Se levels are found in liver (maximum 409 ~tg.g-1) and age relationships are similar to those for mercury. These data confirm those previously found by KOEMAN, PEETERS, KOUDSTAAL-HOL, TjIoz

J . I g . g ' l ~ Hg

100

x

10

nl

0 0

X

X

X

0

J.Ig.g-~=E Hg

I00¢

x

10C

o

x ,g P

x

x

x x x

x

x o

.ug.g-12EHg

10C

x

el

o o

b

I I I i I I

Age Age

0 X

X

0 OX

Age

Fig. 2. Relations between total mercury content (tzg.g -1 wet weight) and age (years) in a. liver, b. brain and c. kidney tissue ofharbour seals from the Netherlands

( × ) and from Sehleswig-Holstein and Denmark (©) .

36 P . j . H . REIJNDERS

& DE GOEY (1973) and KOEMAN et al. (1975) who demonstrated an almost perfectly linear correlation between mercury and selenium in several species of marine mammals.

Jag'g-'=E Hg

1000

10[

0 0 X

X'

x

x

x o

o xo

i i 0.1 1 1~]

X o ° o

o x

, U g . g - ~ Hg

2£

x x x

10 x

a b

s i ~

, o; ~' , ° ' ' ~oo ~o~ , 2 , ; e ~o

,ug.g -I Se Jag-9"1Se

Fig. 3. Relation between total mercury (~tg. g-Z wet weight) and selenium contents (~g.g-X wet weight) in a. liver and b. brain tissue of harbour seals from the Nether-

lands ( × ) and from Sehleswlg-Holstein and Denmark (©).

No dependency of bromium content on age could be deduced from the material available (Fig. 4).

2. ORGANOCHLORINES

PCB, E D D T (p,p '-DDT, p,p '-DDE, p,p ' -TDE), ~-HCH, ~-HCH, H E P O and dieldrin levels in blubber, liver and kidney tissues are shown in Table II). The maxima for PCB and Y, D D T are 1447 and 178 ~tg.g -z respectively. The highest levels of all contaminants are found in seals from the Dutch area. In general, levels are lower in juveniles than in adults.

Concentrations of y - H C H (lindane), endosulfan and endrin were not detectable (detection limit 0.1 ~g.g).

The results of the statistical tests on possible significant differences in residue levels between (a) German and Danish and (b) Dutch seals are presented in Tables I and II. The residue levels of total mercury in kidney and selenium in the brain of the juvenile and subadult group are significantly higher in the Schleswig-Holstein and Danish seals whereas selenium in kidney and bromium in liver are significantly higher in the Dutch seals. In the adult group, both total mercury and selenium levels are significantly higher in brain and liver and bromium

O R G A N O C H L O R I N E S I N H A R B O U K S E A L 37

in kidney and liver of Dutch seals. Dieldrin concentrations are low ( < 0.1 to 0.9 ~g.g-Z). In the juvenile and subadult group, dieldrin levels in blubber are significantly higher in Dutch seals. In the adult group significantly higher levels of DDT, TDE, dieldrin, ~-HCH and PCB's are found in blubber of the Dutch seals.

.ug,g- IBr

40

35

30

25

2C o

lS o x

IC

5

0

.ug.| " B r

4(

35

3( o

2- = x

2C

15

10

5

01

J

X

0 0

,'o ;o

0 X X

0

Age

a

3~

.ug.g- IBr i

40'

35

3O

2S

2O

15

10

5

0

x

x

o o

x

x x

b o

;o 2'o ~'0 Age

x x

o o

o o

c

,'0 2; 30 Age

Fig. 4. Relations between bromium content (~g. g-Z wet weight) and age (years) in a. liver, b. brain and c. kidney tissue of harbour seals from the Netherlands ( × ) and

from Schleswig-Holstein and Denmark (©).

IV. DISCUSSION

1 . M E K C U R Y ~ S E L E N I U M A N D B R O M I U M

a . A C C U M U L A T I O N ~ T I S S U E D I S T R I B U T I O N A N D M E T A B O L I S M

Figs 2, 3 and 4 show that considerable amounts of mercury, selenium and bromium are present in organs of just born and a few days old

38 P.j.H. REIJNDERS

T A B L E I I

Means and ranges of PCB, 3" DDT, DDT, DDE, TDE, ~-HCH, ~-HCH, HEPO and dieldrin contenl in blubber (~g,g- t fat weight) and in kidney and liver (~g.g-1 wet weight) of juvenile and subadu and of adult harbour seals from Schleswig-Holstein and Denmark and from the Netherlands [number c specimens analyzed, between brackets]; n.d. means not detectable; + means except one, all measur~ ments below detection limit. For the blubber values of each age group, significantly higher areal valu~ are indicated (*** forp < 0.01 ; ** for 0.01 < p ~ 0,05; * for 0,05 < p .~ 0.t ; Wilcoxon test, Student

t-test and Weir's standardized t-test).

Sehleswig-Holstein plus Denmark Netherlands

Juveniles and Adults Juveniles and Adults subadults subadults

kidney [8] [4-5] [5] [4] %fat 2.9 (2.5 -5.2) 3.5 ( 1.7 -7.5) 2.7 (2.1 -3.3) 4.9 ( 1.8 -6.5) PCB 1.8 (0.3 -7.2) 3.7 (0.26-13.0) 1.5 (0.2 -5.8) 27.4 ( 3.3 -72.3) Ig DDT 0.2 (0.01-0.9) 0.2 (0.02-0.6) 0.4 (n.d.-1.6) 0.9 ( 0.2 -2.1) DDT 0.02(n.d.-0.1) +(n.d. -0.1) 0.02(n.d.-0,8) 0.03(n.d. -0.1) DDE 0.2 (0.01-0.6) 0.2 (0.02-0,5) 0.3 (0.02-1.2) 0.6 (0.14--1.5) TDE 0.03(n.d.-0.2) 0.05(n.d. -0.1) 0.08(n.d.-0.3) 0.2 (0.02-0.6) ~-HCH + (n.d.-0.01) n.d. + (n.d.-0.01) + (n.d. -0.01) ~-HCH n.d. n.d. n.d. n.d. HEPO + (n.d.-0.02) + (n.d. -0.01) + (n.d.-0.05) 0,02 (n.d. -0.04) dieldrin n.d. n.d. 0.01 (n.d.-0.03) 0.02(n.d. -0.03)

liver [0] [4-5] [1] [4] %fat 7.3 ( 2.1 -17.8) 4.8 6.8 ( 3.9 -9.9) PCB 4.4 ( 0.7 -9.4) 1.7 31.5 (22.4 -46.3) Y. DDT 0.4 (0.03-1.0) 0.1 2.1 ( 0.9 -4.7) DDT n.d. n.d. n.d. DDE 0.2 (0.02-0.6) 0.1 1.6 ( 0.8 -3.3) TDE 0.2 (0.01-0.5) 0.03 0.5 ( 0.1 -1.3) =-HCH n.d. n.d. 0,02(0.01-0,03) ~-HCH n.d. n.d. n.d. HEPO 0.02(n.d. -0.04) n.d. 0.1 (0.04-0.2) dieldrin n.d. 0.02 0.02(n.d. -0,03)

blubber [8] [6] [5q5] [8] PCB 113.8 (23 -340) 76.4 (40.5 -123) 134,0 (5.0 -680) 701 ( 87 -1447) **" Z DDT 16.9 (4.0 -47.1) 8.5 ( 3.7 -15.2) 29.8 (3.3-127) 47.3 ( 6.6 -178) DDT 5.5 (1.3 -13.0) 2.0 ( 0.7 -6.1) 9.0 (0.9 -36) 11.7 ( 1.0 -64)** DDE 10.8 (2.6 -30.0) 5.0 ( 2 .4-8.8) 16.1 (1.2 -83) 26.6 ( 3.8 -72) TDE 0.6 (0.1 -2.1) 0.7 ( 0.2 -3.0) 1.8 (0.2 -8. t) 9.0 ( 0.3 -42)* ~-HCH 0.5 (0.2 -1.4) 0.2 ( 0.1 -0.3) 0,3 (n.d.-0.6) 0.4 (n.d. -0.7)** ~-HCH 0.3 (n.d.-1.4) n.d. + (n.d.-0.3) + (n,d. -0.1) HEPO 0.4 (0.I -1.4) 0.2 (0.1 -0.4) 1.0 (n.d.-3.5) 1.0 ( 0.2 -3.1) dieldrin +(n.d . -0 .2 ) n.d. 0.5 (n.d.-0.9)*** 0;4 (n.d. -0.4)***

seals. T h u s , t r a n s p o r t o f these c h e m i c a l s across the p l a c e n t a results in a c c u m u l a t i o n in t h e e m b r y o d u r i n g the ges ta t ion per iod~ M e r c u r y levels a r e h ighes t in l iver , b r a i n a n d k i d n e y tissue o f 5 to 8 yea r s old


animals. HEPPLESTON & FRENCH (1973) concluded that levels in brain tissue reached a maximum at the age of 12 to 18 months, though concentrations in liver continued to increase with age. This is not confirmed by other studies including the present one (Fig. 2) that show a definite positive correlation between levels in the liver and in the brain (Fig. 5).

Bra in

100

x

6

x o x o o o ~k

o x

o o o

x i

i oi, , ;o ~oo' ~o'oo Liver

Fig. 5. Relation of total mercury content (ptg. g-Z wet weight) between brain and liver tissues ofharbour seals from the Netherlands ( x ) and from Schleswig-Holstein

and Denmark ((D).

Most of the mercury in seal tissues is recovered in the inorganic form (Figs 6 and 7). This is remarkable as in fish (the principal food of the seal) most of the mercury is generally present as methylmercury (WEsTSO & RVDALV, 1971 ; BEROLUI~rD et al., 1971 ; KOEMAN, P~.ETERS, SMIT, TJtOE & DE GOEY, 1972; KOEMA~ et al., 1975; RISSANEN & MtETTINEN, 1972). This implies that most of the methylmercury taken up by seals is converted into inorganic mercury, though to a different extent in the various age-classes (Fig. 7).

JONES et al. (1976) analyzed methylmercury in blood samples from pups caught shortly after birth, normally fed or fasted for 2 or 3 days. The residue level in the fasted pups was twice as high as that observed in normally fed pups. They concluded that methylmercury is tram- ported through the placental barrier, and is already present at a level of 0.5 to 1.2 [zg. g-1 at birth, but that only small amounts were passed from mother to pup in milk. KtM, CHU & BARRON (1974) confirmed this observation in fur seal pups and it was also reported in humans (WALLACE et al., 1971). This conflicts with the observations of FRSEMAN & I-IoRNE (1973) that in harp seal pups the stomach content (milk) contained about 70.5% methylmercury.


There is general support for the hypothesis that in older seals mercury demethylation takes place in liver and kidney (e.g. T!LL~NDER, MZETTINEN & KOIVISTO, 1972; RONALD et al., 1977).

,Ug.g-~CI.~Hg

100(

t ~

X O e o

x

X X

X X XOOO

oXo

.ug.g"Cl'~ Hg

6

5

3

2 ×

I O° 2

ox 1

' '0 ' 'o ' 1 1 100 10 0 ~; pcJ.g "~:~ Hg

.ug,g-~CHzHg

r i i 6 8 10

×

x x x

b

i i ,2 1, 1'~ 1'~ .ug.g' l~ Hg

o

c

¢9

° s 1~ ,'~ 2'0 2's 3'0 pQ.g'~Hg

Fig. 6. Relations of methylmercury (CHsHg) and total mercury content (~tg.g -z wet weight) in a. liver, b. brain and c. kidney tissue in harbour seals from the

Netherlands ( × ) and from Schleswig-Holstein and Denmark (©) .

In the present material, the ratio of organic to inorganic mercury found in the liver of older seals is more or less stable and fluctuated around 20%. This agrees with results found in other seat species (KoEMAN, PE~.TERS, SKIT, TJIOE & DE GO~.Y, 1972; KOEMAN et al., 1973; FgE~.MAN & HORNE, 1973; G~KIN et al., 1973; SERO~.ANT & AR~STRONO, 1973; HOLDEN, 1975; ROBERTS, HEPPLESTON & ROBERTS, 1976) and sea lions (ANAs, 1974). Also in livers of seals from brackish and fresh waters only 10% of the total mercury, consisted of methylmercury (KARx & KAURA~EN, 1978). Tentative efforts to identify the mechanism of the demethylation process did not yield definite results and it is as yet not clarified whether the process is of enzymatical, bacteriological or chemical nature (VAN DE VEN, KOEMAN & SWNSON, 1979).

ORGANOCHLORINE8 IN HARBOUR SEAL 41

b. TOXICOLOGICAL IMPLICATIONS

The possible effects of mercury on several organisms were reported in a large number of studies (a.o. BXDSTRUP, 1964; BERGLUND et ah, 1971; O.E.C.D., 1974). These reports will not be discussed here. The conclusion is that it is not possible to indicate to what extent the environ-

°IoCH

60

SC

30

20

10

H ~ H g o

x x x

x o

Ii

i i i

Age

"I,CH3HgI:~ Hg

10C

8(

k

+IO o

2O

o ~ ;0 ,'s

o

x A

b

i

A g t

Fig. 7. Relations (curves hand drawn) between percentage methylmercury of total mercury (% CHaHg/Y. Hg) and age (years) in a. liver and b. brain tissue of harbour seals from the Netherlands (×) and from Schleswig-Holstein and Den-

mark (©).

mental contamination with mercury contributes to intoxication of seals. KOEMAN, PEETERS, SMIT, TJIOE & DE GOEY (1972) and KOEMAN et al. (1975) found in a large number of seals and other marine mammals from widely distributed parts of the world an equimolecular relationship for the concentrations of mercury and selenium in both liver and brain and they postulated possible mutual protection mechanisms of both elements. This was partly based on experiments presented by PAi~IZEK, BENE~, O~kDALOVk, BABICK~, BENE~ & PYI'HA (1969) and PAi~fzEx et al. (197 I) and other workers who demonstrated that selenium compounds can protect animals against toxic effects of mercury compounds. A molecular Hg :Se ratio of I. 16 was established in livers of seals from fresh and brackish waters in Finland (KARI & KAURANEN, 1978). However, it is still unclear whether selenium really is involved in the demethylation process or the binding of mercury (ROBERTS, HEPPLESTON & ROBERTS~ 1976). Experiments with rats showed that small amounts of selenium compounds administered during pregnancy or lactation decreased the passage of mercury from the maternal organism into the offspring (PAklZEI¢, BABICK~?, O.~kDA- LOVA, KALOUSKOVk & PAVLIK, 1969). The same effect was shown for

4 2 P . j . H . R E I J N D E R S

selenium at the administration of mercuric compounds (PAi~ZEK et al., 1971).

MARTIN et al. (1976) reported a mercury-selenium-bromine imbalance in premature parturient California sea lions. They found atomic ratios Hg : Se : Br of about 1 : 1 : 1 in livers of normal parturient mothers. In premature parturient mothers the H g : S e hepatic ratios were also near unity in contrast to Br concentrations that were always severely depressed.

No relation with age is found for the bromium content in tissues (Fig. 4) and therefore no detoxifying effect of bromium can be deduced from the data obtained during this study.

A general conclusion with respect to mercury as an intoxicant of seals can not be given. The simultaneous presence of selenium makes it difficult to assess the ecological risks for the harbour seals on basis of the data available.

2 . P C B ~ S A N D ~ D D T

a . A C C U M U L A T I O N ~ T I S S U E D I S T R I B U T I O N A N D M E T A B O L I S M

Most organochlorine compounds, because of their lipophilic nature, tend to accumulate in lipid tissues. Like in other studies the highest concentrations are found in blubber tissue of the seals~ Considerable amounts already occur in young seals (Figs 8 and 11). As for mercury, these contaminants are taken up by the foetus during gestation. In this

~9"~'PCB

200¢ x ×

1000

t ~ x x X

x

o lO0 -.. ......... °~o----x---

o

pg,g~'~DOT

20C ×

10C

o ×

2

l0 '~ . . . . . . . . . . . . . ~ o -- - -Z - - - %

o xX o O

a b

Age Age

Fig. 8. Relationships between a, PCB, b. total DDT (btg. g-1 fat weight) and age (years) in blubber tissue of harbour seals from the Netherlands (×) and from

Sehleswig'Holstein and Denmark (©) (curves handdrawn).

ORGANOCHLORINES IN HARBOUR SEAL 43

study two still-born pups are found to contain already 5 and 29 ~g. g-1 PCB respectively in blubber. Transplacental transfer of organochlorine residues is suggested for a large number of mammals (HAYES, 1966; HUNTER & ROBINSON, 1967; ROBINSON & ROBERTS, 1967; ACKER & SCHULTE, 1970; CLARK & LAMONT, 1976; ORBERO, 1977) and especially in seals (FRANK, RONALD & BRAUN, 1973; GASKIN et al., 1973; JoNEs et al., 1976; ADDISON & BRODm, 1977). After approxi- mately 4 years a plateau is reached but at a different level for Schleswig- Holstein and Denmark as for The Netherlands. As seals in both areas consume the same kind of fish (flatfish mainly), these different residue levels must originate from different levels of contaminants in their diets. This fits well with the results of ROBINSON & ROBERTS (1967), HUNTER • ROBINSON (1967), HAYES & CURLEY (1968) and HUNTER, ROBINSON & ROBERTS (1969) who studied pharmacodynamics of several organochlorines and found residues levels resulting from an equilibrium between rate of intake and rate of excretion. These plateau levels may increase when the concentrations in the environment continue to increase. Though HOLDEN (1972), HEPPLmTON (1973), OLSSON, JOHNELS & VAZ (1975), DRESCHER, HARMS ~; HUSGHENBETH, (1977) and H~.~s , DRESCHER & HUSCHENBETH (1977) found no clear relations between levels of organochlorines in blubber and age or sex, FRANK, RONAt.D & BRAUN (1973), ADDISON, KERR, DALE & SERO~-ANT (1973), ADDISON & SMITH (1974) and HELLE, OLSSON &JENsEN (1976a) did find positive correlations of organochlorine levels with age. This was more pronounced in males than in females. Some authors (GAsraN, HOLDRINET & FRANK, 1971; GASKIN et al., 1973; ADDISON, KERR, DALE & SERO~ANT, 1973; ADDISON & SMITH, 1974) suggested that females will loose residues through parturition and lactation when fat is mobi- lized, as it explains the variation in organochlorine residue levels with sex.

From data on organochlorine residues in maternal blubber, milk and pup blubber obtained by JoNEs et al. (1976) and ADDISON ~; BRODIE (1977) it can be concluded that mothers with high levels of organochlorines did not necessarily have pups with relatively high levels. They gave no explanation for this but an explanation may be that the information was obtained from environments with different residues concentrations. Obviously at high residue levels parturition and lactation may only have a slight temporary effect on the contaminants burden.

ANAS (1974) and HARMS, DRESCHER ~2 HUSCHENBETH (1977) stated that high values of contaminants are probably correlated with feeding behaviour. That is in agreement with the results of this study when different feeding behaviour leads to differences in the uptake of contaminants via the food available.

44 P. J. H, REIJNDERS

The mean levels of PCB and total DDT (Table II) for juvenile (0 to 1 year) and sub-adult (1 to 3 year) seals of Schleswig-Holstein and Denmark are higher than those in adult seals (4 years and more). Fig. 8 shows high levels for young seals, less high levels for subadults and levels for adults that do not exceed that of juveniles. The same was observed by JoNEs et al. (1976),

juv.+subad adults

10fl .'/o 100 -°/°

8~

2O

0 0 ~ DDE DOT TQE

8O

2O I o

OOE ~DT "FDE

Fig. 9. Percentages of DDT, DDE and TDE in total DDT content (means and ranges) in juvenile and subadult and in adult harbour seals from the Netherlands

( × ) and from Sehleswig-Holstein and Denmark (©).

Apparently the balance between uptake and excretion becomes negative for some period and changes later on. The difference between the German and Dutch seals in PCB and total DDT content may be explained by a lower uptake of these contaminants by young seals through their diet in the German WaddeD Sea area than in the Dutch area. This effect may be reinforced by the increase in lipid content of the blubber tissue in maturing pups before a certain ratio is established.

The composition of the DDT group in blubber of seals from both areas (Fig. 9) shows DDE to be the main compound, followed by DDT and a relatively small amount of TDE. The values lie in a range mostly found in a seal blubber (JoHNELS, 1970; ADDISON, KERR, DALE & SEROEANT, 1973; ADDISON & BRODIE, 1977; DRESCHER, HARMS & HUSCHENBETH, 1977; OLSSON, 1977). HEATH et al. (1970) and MET- CALF (1971) gave evidence that DDE is less toxic than DDT and suggested that the high DDE percentages may indicate a protective mechanism. But OLSSON (1977) supposed that DDE is the main metabolite because of its higher persistence compared to the others.

It is stated before that the highest concentrations of organochlorines are found in the blubber. For PCB and total DDT they are closely followed by those in the kidney (Fig. 10).

Several authors (KOEMAN & VAN GENDEREN, 1966; HOLDEN & MARSDEN, 1967; GASKIN, HOLDRINET • FRANK, 1971; HOLDEN, 1975; ALZIEU ~; DUGUY, 1978; DUINKER, HILLEBRAND ~Z NOLTING, 1979) reported considerable amounts also in kidney, liver, heart, muscle,


spleen and brain of seals and porpoises, although kidney and liver ranked next to blubber. FRANK, RONALD & BaAUN (1973) suggested a blood-brain barrier in harbour seals because in brain tissue total D D T and PCB residue levels on extractable fat basis were much lower than

JJg.g't kidney

2 0 0 0

1 0 0 0

100 0 0 0 0 x 0

X X 0

x o

x

x

ug.g-lkidney

100

O ~ X

0 x o

O X

X

X 0

0 0

, I , 1'o ,~ ,ooo' 2ooo' , ,'o ,~o ,~oo ug.g.lbtubber }jg.g.1 bt ubber

Fig. 10. Relations ofa. PCB and b. total DDT contents (izg .g-Z fat weight) between kidney and blubber tissue of harbour seals from the Netherlands ( × ) and from Sehleswig-Holstein and Denmark (O). Regression equation for PCB:y = 0.41x +

1.6 (r = 0.94); for D D T : y = 0.78x -- 21.3 (r = 0.94).

those in blubber and liver. Whether this is correct or not, the differences in PCB and D D T concentrations in brain and blubber are also influenced by the fact that brain tissue consists to a large proportion of phospholipids, and PCB's and D D T are less soluble in phospholipids

,ug-s-I~ HCH

1.2

tC

0.m

0.E x

0.4

x

0 . 2 ~ x

x

I 0 5

x x a

o

o o o

o

,'0 ,'s ;0 2'~ ;0 A g e

. u g . g - ' HEPO

10

x x

~ o

X

X

o o

o o

x

o b

x

AOe

Fig. 11. Relations ofa. ~-HCH and b. HEPO (~g. g-X fat weight) and age (years) in blubber tissue of harbour seals from the Netherlands ( × ) and from Schleswig-Hol-

stein and Denmark (O).

46 P.J.H. REIJNDERS

t h a n in b l u b b e r . I n t h e s a m e w a y i t is a lso poss ib l e t h a t l i p i d s in s e ve ra l o t h e r o r g a n s d i f fe r i n c o m p o s i t i o n .

b. T O X I C O L O G I C A L IMPLICA T IO N S

In in vitro experiments, organochlorine compounds were found to cause reproductive failure in fish (COPE, 1963; BURDICK et al., 1964), birds (PEAr,~LL, 1967, 1970; STICKEL, 1973) and mammals (BARNARD & GAERTNER, 1963; KORSCHGEN & MURPHY, 1967; GILBERT, 1969; AULERICH et al., 1971).

Chlorinated hydrocarbons as DDT and PCB's affect the steroid hormone balance, i,e. induce microsomal enzyme activity in the liver (PARvINI, 1971; VILL~NEUVE, GRANT & PHILLIPS, 1972) resulting in virtually accelerated destruction of normal body steroids as androgens and estrogens (KUPFER, 1967; PEAKALL, 1967; BITMAN & CECXL, 1970; LINCER & P~AKALL, 1973; PLATONOW & FUNN~LL, t972; PLATONOW, LIPTRAP & G~ISSINGER, 1972; VOS, 1972).

The mechanisms by which reproductive processes are affected, vary considerably, and therefore only information on mammals with a reproductive physiology similar to that of seals will be considered. Experimental and epidemiological effects of PCB's and DDT on reproduction reported for marine mammals and mink are compared in Table III.

In California sea lions, increased abortion was reported by LEBo~uF & BONN~LL (1971). DELONG, GILMARTIN & SIMPSON (1973) found

TABLE In

Results reported in literature on reproduction under influence of PCB's and DDT: effect demonstrated ( + ), not demonstrated ( - - ) or not considered (?). Epidemiologi-

cal data on marine mammals and experimental data on mink.

Reference Species Effects PCB's D D T

Cal. sea lion idem idem ringed seal ringed, grey and harbour seal mink

LEBoEuF & BONNEL, 1971 DELoNo et al., 1973 GILMARTIN et al., 1976 HELLE etal., 1976a HELLE et al., 1976b

AUL~mCH et al., 1973

AULERICH ~; RINGER, 1977 idem JENSEN et al., 1977 idem

premature pupping ? + idem + + idem -~- + low reproduction + + stenosis and occlusions in uteri + -- mating occurred; less whelps born per female + -- idem + -- mating and implantation occurred; less whelps born per female + --

O R G A N O C H L O R I N E S I N H A I ~ B O U R S E A L 47

significantly higher amounts of DDT and PCB compounds in aborting females than in normally breeding females. Independent studies on high PCB and DDT levels in seals from Swedish waters, did OLSSON, JOHNELS & VAZ (1975) also postulate effects on reproduction in these seals. A low reproductive rate reported for the ringed seal in the north- ern Bothnian Bay (HELLE, 1975) did start research by HELLE, OLSSON & JENSEN (1976a) in which significantly higher levels of PCB and total DDT were found in non-pregnant females than in pregnant females. In comparing these results with those on the California sea lions, they postulate that PCB's were the responsible agent. Later on they (HELLE, OLSSON & JENSEN, 1976b) discovered that the uterine horns of about 40% of a sample of Baltic ringed seals were closed by stenosis and occlusions. These pathological changes appeared to be positively correlated with PCB, not with DDT, levels. However, it is felt that their test was not complete, as they did not test the non-pregnant females with stenosis and occlusions versus the non-pregnant ones with normal uteri. After carrying out the same test as they used (Student's t-test) it appeared that in the non-pregnant group high levels of PCB and total DDT were not linked to the occurrence of these pathological changes. Unfortunately, the number of specimens in the non-pregnant group of females with normal uteri was rather small compared to the other (8:29). This will have influenced the standard errors, but it is also possible that within the non-pregnant group conditions are apt to lead to pathological changes. Anyhow, the conclusions of HELLE, OLSSON & JENSEN (1976b) about pathological changes caused exclusively by PCB's should be considered with reserve.

With respect to the capacity ofseals for specific metabolization of PCB (J~SON et al., 1975), it is not clear whether PCB's or PCB-metabolites are responsible.

Comparing the residue levels of PCB and total DDT, found in killed animals, total DDT levels in Baltic seals are about tenfold those in German seals whereas PCB levels in German seals are about the same or higher than those in Baltic seals. Moreover during the last 5 years out of all adult females autopsized (at least 15) not a single female harbour seal in the German Wadden Sea area was found to show pathological changes in the uterine tract as reported for the Baltic ringed seal (DRzsCHEg, personal communication). This difference is not caused by a species specific reaction on biocides, as in Sweden the noted phenomena have been detected also in harbour and grey seals (Table III) . Therefore, it has to be assumed that either DDT should be held responsible for the pathological changes in seal uteri or---only beyond a certain threshold level of total DDT---eventually PCB or some of its metabolites.

48 P.j.H. REIJNDERS

However, not DDT but PCB's had a pronounced effect on the reproductive capacity of a fish-eating mammal by delayed implantation, as was clearly shown by experiments of AULERICIt & RINGER (1977) and JENSEN et al. (1977). The latter authors set 3 groups of mink on diets with different amounts of PCB's and showed that the frequencies of mated or pregnant bitches and the number of implantation sites per pregnant bitch did not differ significantly, but that the frequency of delivering bitches and the number of whelps born per bitch were significantly smaller. It is clear from their report that pregnancy was interrupted by PCB at an early stage of gestation. Their results lead to a closer view on the phenomenon of delayed implantation and the possible part PCB's may play in this part of the reproduction cycle, controlled by steroid hormones.

Delayed implantation appears to be widespread in pinrtipeds. Al- though the precise cause is still unknown, HARRISON (1969) states that undoubtedly there is a hormonal factor because when the suppression of progesteron production is terminated, the increased availability of progesteron stimulates the uterine mucosa. Considering the earlier discussion about destruction of body steroids by PCB (page 46), it is obvious that this phase in the reproductive cycle of the female harbour seal is a very critical one. Accelerated lipid mobilization induced by factors as starvation, pregnancy and lactation leads to an increased transport of biocides but also in absence of such conditions transport of biocides will occur. The adipose tissue is not an inert depot locking up chlorinated hydrocarbons beyond the period of pregnancy and lactation. It is believed that mobilization during periods of starvation and lactation is not that important as was obviously assumed by several authors (2~LDDISON, KERR, DALE • SERGEANT, 1973; ADDISON & SMITH, 1974; ADDISON & BRODIE, 1977; HOLDEN, 1978; DUINKER & HILLE- BRAND, 1979b).

Some data have been reported on the composition of fatty acids in blubber of seals but little is known of the dynamics (JANGAARD & KE, 1968; ACKMAN, EPSTEIN & EATON, 1971; ACKMAN, EATON & CREatE, 1977).

In adipose tissue, because of the function of fatty acids as initial substratum for the biosynthesis of steroids (PRosSER, 1973; NEWSHOLME & START, 1974; BEENAKKERS, 1978), probably at least two lipid metabolizing compartments seem to exist, one in constant exchange with the plasma pool and with a high turnover, the other with a slow turnover as became evident from half-life times (DOLE, I961; STEIN & STEIN, 1962).

As a result of these processes organochlorines are presumably per- manently released and a continuing interference of organochlorines with the steroid hormone balance may take place.

O R G A N O G H L O R I N E S I N H A R B O U R S E A L 49

Contrary to other phases in the reproductive cycle where feed-back mechanisms have due time to reestablish adequate concentrations, this might not be possible around the time of implantation. As in short time adequate concentrations of circulating hormones (progesteron) have to be available to bring the uterus in the right condition, the impact of high PCB levels may especially be severe at the end of the implantation delay period. This hypothesis is supported by the experiments in mink OfJENsEN et al. (1977).

Besides the presumable direct effects of PCB on the reproductive system it should not be neglected that PCB's are known to have a strong immunosuppressive capacity. Experiments with fish (HANSEN et al., 1971), birds (FRIEND & TRAINER, 1970) and mammals (Vos et al., 1970; Vos & VAN DRIEL-(~ROOTENHUIS, 1972; Vos & DE Roy, 1972; Vos, 1977) showed an increased susceptibility to diseases. GILMARTIN et al. (1976) gave evidence for an interrelation between environmental contaminants and disease agents. DRESCHER (1978a) reported skin lesions in the harbour seals of the Wadden Sea and suggested that one of the important factors involved is disturbance of the pups during the first weeks of life, resulting in inflammation of the umbilical region. Considering the rather high residues of PCB's already present in a few weeks old seal pups it is reasonable to assume that reduced immunity makes them more vulnerable to infection after mechanical injury.

3. O T H E R C O M P O U N D S S T U D I E D

For ~-HCH and ~-HCH, hepo and dieldrin residue levels no relation with age is found in blubber of seals from both parts of the Wadden Sea (Table II). The values are of the same order as found in other recent studies (CLAUSEN & BERG, 1975; DRESCHER, HARMS & Hu- SCHENBETH, 1977; DUINKER, HILLEBRAND ~ NOLTING, 1979).

Chlorinated dibenzofurans are impurities in manufactured PCB's. These extremely toxic chemicals are till now not detected in marine organisms (Vos et al., 1970; ZIT~¢O, 1972; BowLs et al., 1973).

4. R O U T E S OF T R A N S P O R T IN T H E M A R I N E E N V I R O N M E N T

Presence of organochlorines and metals have been reported in marine food chains--including man--from the Arctic, Subarctic and Ant- arctic (TATTON & RUZICKA, 1967; ADDISON & SMITH, 1974; Bow~s & JONKEL, 1974; CHARLEEOIS, 1978) as well as from industrialized areas (HoLDEN 8£ MARSDEN, 1967; RISEBROUGH, REICHE, PEAKALL, HERMAN ~; KIRVEN, 1968; JENSEN et al., 1969; ACKEFORS, LOFROTH • ROS~N, 1970; NUORTEVA, 1971 ;JoNm, JONES & STEWART, 1972; WILLIAMS &

50 P.J.H. REIJNDERS

W~ss, 1973; FRANK, RONALD & BRAUN, 1973; ANAS, 1974; ANDERSEN & NEELAr,.a~TAN, 1974; ICES, 1974; BUrILER, Cc~'¢s & MATE, 1975; WRIOHT, 1976; KOEMAN & STASS~.-WOLTHUIS, 1978).

Although aerial transport of metals and organochlorines occurs, even over long distances (ABBOT et al., 1966; RISEBROUG~I, HUGGET, GRn~rIN & GOLDBERO, 1968; TARRANT & TATTON, 1968; GOLDBERO, 1970; S6DERGREN, 1972; YOUNG, MCDERMOTT & H~.mEN, 1976) the main source of pollution in the Wadden Sea is by riverine discharge. Ap- proximately 10% of the water and 50% of the suspended matter supplied by the highly polluted Rhine river to the North Sea enters the Dutch Wadden Sea (DuINKER, 1974). Several authors I DE GROOT, DE GOEY & ZEGERS, 1971; WEICHART, 1973; DUINKER, VAN ECK & NOL- TINt, 1974; MOLLER & F6RSTNER, 1974; DUINKER & NOLTING, 1976; POEm, SNOEK & HUIZENGA, 1978; DUINKER & HILLEBRAND, 1979a) reported on the transport of heavy metals and organochlorines along this route.

As discussed before, different levels of contaminants in tissues of equally old seals have to originate mainly from differences in contamination of their food. Biomagnification during transport from prey to predator does increase the levels of these substances considerably.

A higher position in the food chain is not indissolubly related to higher concentrations in the organisms (JERNEL6V & LANN, 1971; KNAUER & MARTIN, 1972; OLSSON, 1976, 1977) as abiotic factors play a part as well (ROBINSON et al., 1967; OLSSON, 1977; CEMBER, CURTIS & BLAYLOCK, 1978). However, residues of organochlorines and heavy metals tend to be greater in marine organisms of higher trophic levels as is demonstrated for total mercury, PCB and total DDT by data available on biota from the Dutch, German and Danish Wadden Sea area. The analyses shown in Fig. 12 were carried out during several years by several institutes and mostly by different techniques. There- fore, values are given as ranges and not as means and standard de- viations. Even these rough data indicate a more pronounced increase with trophic levels for PCB and total DDT than for total mercury. Obvious differences for PCB and total DDT occur in fishes from the Schleswig-Holstein Wadden Sea and from the Dutch Wadden Sea whereas such differences are absent for total mercury. This results in similar differences for PCB and total DDT residue levels in seals from both the areas (Section 6b).

OLSSON, JOHNELS & VAZ (1975) found an accumulation ratio of 7 to 9 for PCB and a ratio of 10 to 12 for total DDT in Baltic seals. Also HOLDEN & MARSDEN (1967), JENSEN et al. (1969) and FRANK, RONALD & BRAUN (1973) found a tenfold increase of PCB and Z DDT from fish to seals.


The accumulation ratios from fish to seal (in extractable fat) found for PCB and for total D D T in Schleswig-Holstein and Denmark are about 10 and 4 respectively, and in the Netherlands about 30 and 50 respectively. The data for fishes in the areas are too limited, however, to prove that the differences in accumulation ratios are statistically significant; they have to be considered just as an indication. For total

Water -~ Sediment - ~ Plankton -~ Shrimps -.~ Molluscs Fishes Birds Seals

~Hg

t ~ l H z z . . . . . . . . .

I I i I i

10 -1 100 l 0 102 10 3 10 ~ "Ug'g'l ~DDT

Phytoptankton -[~ ~ r~]~l Macro zoobenthos--~ i i

Birds ~ ~ e - ~ Seats ~ b . ~ c

i i i i i i t 10-6 10 -/. 10-2 1010 10 2. 10 I/. 10-6 10-4 10-2 tO~0 102 10/,

ug.g -~ JJg-g-~

a I

Fig. 12. Prevailing ranges ofa. total Hg, b. PCB and c. total DDT contents in biota of different trophic levels in marine food chains (t~g. g - t wet weight ; except that for fishes, birds and seals PCB and DDT values are expressed in ~tg. g-Z fat weight) for Schleswig-Holstein and Denmark (hatched) and for the Netherlands (blank). References for total Hg: I. FONDS (1971), 2. DE GOEY, Z E G ~ & DS GROOT (1971) ; DE GROOT, DE GOEY & ZEOERS (1971), 3. GADOW & SCH.~FER (1974); MULLER & F6t~STNER (1974); D6RJES, GAVOW & SC~O, FER (1976), 4. KO~.~N et al. (1971), 5. KOE~N et al. (1971); QuI~JNS, RXJNAARS & W Vos (1975), 6. GONTHER, Oos- TINOA & BURC~HART (1972); HAAR (1974); Q mRUNS , RIJNAARS & VE Vos (1975), 7. KOEMAN et al. (1971); nE WOLF (1975), 8. I)E WOLF (1975); KARBE, SCHNmR & NXEDERO~,SS (1978), 9. KOEMAN et al. (1975) ; (~UIRIJNS, RIJNAAI~ & DE Vos (1975), I0. GONTHER, OOSTXNGA & BURCKHART (1972); I-IAR~S (1975), 11. KOEMAN et al. (1971), 12. VAVK, LOHS~ & ZUNK (1979), 13. KOEUAN, P~ET~m, S~T, TJXOE & nE GoEY (1972) ; present study, 14. SCH~D, STANmNDA & KRAFT (1976) ; DRESCHER, HARMS & HUSCHENBETH (1977) ; present study. References for PCB and total DDT: 1. DUZNKER (1974, 1976), 2. STAVLER & ZmnARTH (1975), 3. DUIN~:ER (1974), 4. TEN BEROE & HmLEnRAND (1974), 5. TEN BEROE & I-IZLLESRAND (1974); O UIRIJNS, RUNA~.S & DE VOS (1975), 6. SCHAEFER et al. (1976), 7. TEN B~.RO~. & HmLEnRAND (1974); QUIRUNS, RIJNAARS & DE gos (1975), 8. HUSCHENBETH (1973); SCHAEFER et al. (1976), 9. KOEMAN, BOTHOF, I~. VRmS, VAN VEt.ZEN-BL~LD & VOS (1972), 10. FtOOE, HOERSCHEta~tANN & POLZHOFER (1976), 11. KOE~N, PESTERS, Sma', TjmE & vE GoEY (1972); present study, 12. DI~SSCHER, HARMS & HUSCHENE~Tn (1977);

present study.


mercury content in seal liver and total fish, accumulation ratios of at least 100 can be deduced from data given by HEPPLESTON & FRENCH (1973) and ROBERTS, HEPPLESTON & ROBERTS (1976). In the Schles- wig-Holstein and Danish seals this ratio is about 1000 and in Dutch seals 1500.

5. INTERRELATIONS BETWEEN THE ORGANOCHLORINESSTUDIED

There is a positive relation between PCB and D D T residues (~zg'g -1) as shown by Fig. 13a (the regression equation for blubber is: PCB = 12.5 ~ D D T -- 36.3; r = 0.81). Also HOLDEN (1972) found a similar relationship but considered it to be coincidental. As his results, those of DRESCHER, HARMS & HUSCHENBETH (1977), DUINKER, HILLEBRAND

NOLTING (1979) and this study are, however, all in a close range this cannot be coincidence. Ratios of PCB and total D D T found in other areas are different and show total D D T values to exceed PCB

u g g '~ :EOOT

1000

I00

x x

o

o

o

%

× ~ g ' g - ~ ° C H C H

x 10

x

a

I o.l

' 'o ~o . . . . I I I 10002000 I I0 Jagg'~PC8

,ug g " H E P O

10

x x

O

X x X O

O O X X O a~ x

b

x o

I I I 100 1 0 0 0 2 0 0 0

~ g . g - ' P C B

0 X

X O X X ~ X

o o

c

0 oc= o

i i i j 10 100 1 0 0 0 2 0 0 0

;~g g ' ~ P C B

Fig. 13. Relations between total DDT, a-HCH, HEPO and PCB contents (Izg. g-X fat weight) in blubber tissue of harbour seals from the Netherlands (× ) and from

Schleswig-Holstein and Denmark (O).


values (up to a factor 10) as in Baltic and East-Canadian seals (JOHN- ELS, 1970; F ~ K , RONALD & Bm~U1% 1973; ADDiSOn, KERR, DALE & Sm~OEA~T, 1973) and in California sea lions (DELoNo, GInMARTm & SiMPSOn, 1973) found a mean ratio of total DDT to PCB in blubber tissue of 6.6. Considering the geographical distribution of both organochlorines, PCB has disperse sources and reaches highest levels in areas with high industrialization, e.g. the Wadden Sea and the Baltic, whereas levels are low in e.g. Arctic regions. DDT was generally used in agriculture, especially in forested areas, and pollution is through surface runoff ( ¢ NICHOLSON, 1967; EDWARDS, 1970; ZITKO ~: CHOI, 1971; SANDERMAN, 1974).

The similarity in DDT to PCB ratios (Fig. 13a) in seal blubber from the different parts of the Wadden Sea suggests identical sources by which the seals got contaminated. That the Rhine is the main source is supported by ICES data (1974) showing that both organochlorine pesticide residues and PCB's in fish and shellfish are higher in the Southern Bight than in the German Bight of the North Sea. Also KOEMAN (1971) and QpmUNS, RIJNAARs & DE Vos (1975) reported on decreasing levels of chlorinated hydrocarbons going from the Rhine

y g - g - ' c x HCH pg.g.t H EPO

10 10

X x

a

% ~x

o

x o

o o o oo x

x o

;o

x x

o o o

b o o ox~o

0.1 ~ oo

' ' 0'00 ' '0 ' ' 1 100 1 1 1 100 1000 .ug.G"=E DDT ,gg.g'qE D DT

)Jg .g° '¢x HCH

10

o

x x x o

o ~ x ® o x

c ~ x S " o x ~

x

i Oa.1 1

.gg.g-IHEPO

Fig. 14. Relationships between =-HCH, HEPO and total DOT contents (sg.g-Z fat weight) in blubber tissue of harbour seals from the Netherlands ( × ) and from

Sch]eswig-HoLstein and Denmark (©).

54 P . j . H . R E I J N D E R S

estuary along the coast to the eastern part of the Dutch Wadden Sea. The strongest support is given by DUINKER & HILLEBRAND (1979b) who carried out organochlorine analyses of sea water during a survey over the total length of the Wadden Sea, from the Rhine estuary to Esbjerg. They stated that the contributions of the German and Danish rivers to the PCB and DDT pollution in the Wadden Sea is negligible compared to that of the river Rhine.

PEAKALL • LINCER (1970 ) , MOILANEN & CROSBY (1973) and M A U G H

(1973) reported on a mechanism by which D D T is converted into PCB's under influence of uv-light. They did n o t get much support so far (ZEPP et al., 1977) but this would complicate the discussion on DDT-PCB ratios.

For the other organochlorines studied similar interrelations between residue levels in seal blubber exist (Figs 13 and 14). Because PCB and total D D T concentrations are considerably higher in the Dutch seals than in those from Schleswig-Holstein and Denmark, which is not the case in the other contaminants, the data of both areas are not pooled in calculating regression equations (Table IV). The best correlations for PCB versus other organochlorines are found in t h e German and Danish material. For total D D T versus H E P O and versus ~-HCH there is no difference between areas.

T A B L E I V

Correlat ion coefficients of lineair relationships between residues in blubber of Schleswlg-Holstein and Denmark (n = 14) and of Dutch seals (n = 19).

Compounds Correlation coefficient correlated

Schleswig-Holstein and Denmark The Netherlands

PCB -Y, DDT 0.96 0.77 PCB -u-HCH 0.90 0.67 PCB -HEPO 0.94 0.61 Y, DDT--tz-HCH 0.84 0.84 Y.. DDT-HEPO 0.95 0.94 u-HCH-HEPO 0.92 0.82

6. C O M P A R I S O N OF R E S I D U E L E V E L S IN SEALS O R I G I N A T I N G FROM D I F F E R E N T P A R T S OF T H E W A D D E N SEA

a. MERCURY~ S E L E N I U M AND B R O M I U M

Significantly higher total mercury and selenium levels (Table I) in juveniles and subadults from German and Danish than in Dutch seals reverse into significantly lower levels in the adult group. The com-


bining values of mercury and selenium (in brain and kidney tissues) is not unexpected because of the mentioned (page 35) equimolecular Hg-Se relationship. For possible effects of both contaminants the adult group of both populations has to be considered. But the levels of total mercury in kidney and brain of the Dutch adults are still far below the levels where RONALD et al. (1977) did not yet find any clinical signs of neurological, renal or hepatic dysfunction.

Greatest amounts of mercury and selenium are accumulated in the liver tissue and there is no significant difference in residue levels of Schleswig-Holstein plus Danish seals on one hand and Dutch seals on the other. In view of the results it is assumed that mercury and selenium are not the cause of the decreased reproduction in the Dutch population.

Suppression of bromium residue levels as expected for the Dutch seals (page 42) is not confirmed; on the contrary they are significantly higher in the Dutch seals than in Schleswig-Holstein and Danish ones, as are the PCB residue levels.

b. OROANOCHLORINES

The highest amounts of organochlorines are accumulated in blubber tissue. PCB levels in blubber of adult seals from the Dutch Wadden Sea are significantly higher than in those from the Schleswig-Holstein and Danish area (Table II). The same holds for DDT, TDE, dieldrin and ~-HCH. For the DDE metabolite, as the most prevalent member of the DDT group, and for total DDT no significant differences are found. The presence of DDT (Table II) implies that in both areas DDT uptake happened rather recently.

The observed rather low amounts of dieldrin and ~-HCH in the blubber tissue of adult Dutch seals are of the same order of magnitude as DRESCHER, HARMS & HUSCHENBETH (1977) found in a stable population with normal reproduction, and therefore seem of less importance when compared to the PCB contamination burden.

C. O T H E R C O N T A M I N A N T S

No analyses are obtained during this study for other contaminants. Comparing available data on cadmium, arsenic and lead from literature shows no differences between levels found in tissues of seals from Schleswig-Holstein and Denmark and from the Netherlands (KoEMAN, PEETERS, SMIT, TJIOE & DE GOEY, 1972; DRESCHER, HARMS & Hu- SCHENBETH, 1977; VAN H~FTEN, personal communication; DUINm~R, HILLEBm~ND & NOLTINO, 1979).

56 P.j .H. REIJNDERS

V. C O N C L U S I O N S

Considering the residue levels found in seal tissues, it is concluded that the tenfold higher PCB values in blubber of Dutch seals than in Schles- wig-Holstein and Danish seals, a highly significant difference, is the most important result of this study.

The conclusion can be drawn that the observed decrease in the reproductive success of the decreased Dutch seal population correlates strongly with an elevated concentration of PCB's in the tissues. As the available epidemiological and experimental data indicate that PCB's interfere with mammalian reproduction, the hypothesis is put forward that the low reproduction in the Dutch seal population is caused by high PCB levels. It should be recognised, however, that the symptoms observed are not similar to the symptoms observed with reproductive failure found elsewhere (e.g. in the Bothnian Gulf).

Within the limits of the information available it is assumed that either implantation does not occur or is shortly followed by resorption or abortion.

V I . S U M M A R Y

As the harbour seal population in the Dutch Wadden Sea decreased significantly and its pup production is too low compared to the more stable population in Schleswig-Holstein, Germany, it is tried to correlate this with an assumed inverse trend of contaminants residue levels in seal tissues.

Dead stranded animals are collected in both areas and blubber, liver, brain and kidney are analyzed for PCB, o,p'-DDT, p,p'-(DDT q- DDE ÷ TDE), dieldrin, aldrin, endrin, endosulfan, ~-HCH, ~-HCH, y-HCH, HCB, Q CB (pentachlorobenzene), HEPO, total mercury and methyl mercury, selenium and bromium.

High levels of all contaminants except bromium occurred together in the seals. An equimolecular relationship is found for mercury and selenium but not for bromium. A clear cut correlation is also demonstrated for PCB and total DDT in blubber and kidney. The main metabolite present in the DDT family is DDE.

Deposition of contaminants is generally lower in juvenile seals reaching a certain plateau level in older ones. The highest ratios of methyl mercury to total mercury are found in juveniles.

The residue levels already present in stillborn pups,indicate transplacental transport of all organochlorines and metals analyzed.

Differences in residue levels between Schleswig-HOlstein and Den- mark on one hand and the Netherlands on the other revealed higher


values for the latter, especially PCB levels in Du tch adul t seals are a tenfold higher.

Increase o f PCB and total D D T residue levels with age is present in Du tch seals bu t absent in the Schleswig-Holstein and Danish specimens.

The conclusion is d r a w n tha t the observed decrease in the reproductive success o f the Du tch seal popula t ion correlates strongly with the high concentra t ions of PCB's in the tissues. The informat ion indicative for the abili ty of these c o m p o u n d s to interfere with m a m m a l i a n re- p roduc t ion leads to the hypothesis tha t PCB's will be responsible for the low rate of reproduc t ion in the D u t c h seal popula t ion.

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organochlorine and heavy metal residues in harbour seals from the wadden sea and their possible...

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