Figure 1: Relatlonship between total Hg concentratlon in muscle and ageo! harbour porpoises PIJI'>I.';(>(/oa plJl'>I.':l.'>eO.1 trom the North sea andKattegat areas.

Figure 2: Ptrcentage of Methyl mercury (~MeHg) in muscle, liver andkldney ot eommon dolphins ,D"Jp1l/.Dus d,pJp1Jis strandtd on the FrenchAtlantle coast, as a tunctlon ot total mercury contaminatlon ijJ.g1 g dryweight).

•

•

I•I •••

2 3 4 5 6 7 6 9 10age

120emuscle. ~M Oliver. ~ akldney, ~ k

100 P

60It!

~ 60~'1i

~ 40 •,20 L

~..&0... • 0 0 0 0 0 00

0 100 200 300 400 500 600 700lIllal Hg

e25

22.5

.... 20~ 17.5........

10 h... 15a.. 12.5

i 10.. 7.5! 5" 2.5

00

CR. Joiris *, L. HolsbHk *, I. Jansegers **, JM. Bouquegneau **,U. Siebert*and M. Bossicart *

CM.19921N:6 - Ref.EMarine Mammals Committee

Do older cetaceans die from merc1UY contamination1

- l.3b..,raA,IYfi,rEa,t<Jxkl.,k>gy. ErN (lnip~rsityoIlJru$$t?/s (VlmJPJ~i.tJ1aao ~ B-Jt150lJru$$t?Js., Bt9Jgium.

" S~rpk(l 01o..WOI,Jogy,. ll.DiJ'ersity I,flJeg~ Bt91gium.

In the frame of an interdisciplinary study of seabirds and marinemammals tound dead (stranded and bycaught) ineluding veterinarian(anato-pathology, microbiology, parasitology) and ecotoxicologica1 aspects,we determined the eoneentraion ot stable pollutants - organochlorinepestlcides, PCBs, heavy metals - in eetaeeans eollected in the North sea, theKattegat and the Preneh Attantlc coast. Tbe sampling eoneerned differentt.lssues (musele, liver, kldney and blubber) from 30 eommon dolphinsDeJp1JiJ:tus Mlphis., 17 harbour porpoises PIJ~J18 pIJI?t.~O~ 7 bottle-nosedolphins Tursiops truocatlJs.. 2 striped dolphins st4o~Da l-~ruJM1J1u.. 1sperm whale PbySlPtiJrD1aa~p1Ja1us., as well as 6 Norwegian minke wbales1JaJa~ol'Pt4ra acuAv(JStrata.

Tbe study ot mercury concentratlons showed an important increase oftotal Hg With age (when age data are not yet avallable, the differenee inconcentratlon between juveniles and adults 15 highly significant)(fig. 1);organie (methyl) Hg was increasing as well, but at a much lower rate. As aconsequenee, the ratlo MeHg to LHg O.e. IMeHg) was strongly decreasingWith increasing LHg level, and thus With age (fig. 2), providing aconfirmatlon of the existenee ot a slow mineralization process in smallcetaeeans (Koeman ,pt aJ.., 1973; !hibaud and Duguy, 1973; capelli ~t aJ..•1989; Joir15 ~t aJ., 1991, 1992).

!his resulted, for older adults, in very high coneentratlons of inorganic Hgin the liver and 4 tlmes higher liver to muscle and liver to kldney ratlos foradults than tor juveniles. In the cast ot the harbour porpoise, the level otdetoxiticatlon was also det.ermined: about 501 of the inorganie Hg in theliver ot the adults were not bound to metallotbioneins nor to selenium. andwere thus potentlally tome.

PCB levels were relatlvely high, as expected, and indicatlons werecollected, retlecting the possible existence ot problems ot high Cdconcentrations, whUe tlle other heavy metals did not seem to retlect theexlstence of any harmtull ettect (table 1).

fi,jris ~t aJ 1

Table 1: Synopsis of the data on heavy metals and organochlorlnes levels In harbour porpoisesP!la:ven~ plJaxJen~ from the North Sea lind Kllttegllt arBllS (\.lg / g riw); melln (std dev); n 2 21.

Tissuemuscle liver kidneymelln stdd!v melln stdd!v melln stdd!v

r PCBs 7.41 8./8 2.98 2.64ODE 0.02 004 0 0

!Hg 5.6 6 71.66 /44.9 8.96 8.3/MeHg 6.04 3.39 5.87 3.69 3.84~ MeHg 79.3 44.5 60Zn 70.\ 37./ 140.7 78.4 92.8 /8.6Pb 0.9 /.55 1.13 2./8 0.97 /./7Cd 0.23 022 0.31 024 1.81 2. 75Fe 1105 596 2026 1/62 1061 362Cr 0.32 03/ 0.29 025 0.42 0.25Cu 6.63 3.2 45.56 73.96 15.5 4.74Tl 1.55 6. 7/ 0 0 0 0.0/

Pinnipeds and cetaceans present the exceptional phenomenon that theirhealth status, more espectally their reproduction potential, could be actually!ffected by pollution in nature, like it was the case for raptors in the sixties.It is generally recognized that the main tllreat is due to high PCBsconcentrations. These effects of PCBs could be at the origin of viral massmortalities of marine mammals, by repressing their immunologica1 defensemechanisms, or on the contrary be a consequence of physiologca1 stress, suchas viral infection or starvation. In tJle frame of both interpretations, PCBsmight anyway hinder the recovery of populations after the occurence ofmass mortallties.

In the frame of a broader study of stable pollutants, ho~ver, it appearsthat one should take into account the levels of other residues as ~Il. In ourresults, this seems to be the case for Hg and, possibly, for Cd.

Mercury contamination of small cetaceans and its evolution in time couldbe interpreted as foUows: they are contaminated by methyl mercury, themain form of mercury in their food. Most of the mercury is present as MeHgin juveniles where it is accumulating in lipids. Later on, it is than sloWlymineralized and remobilized (or first remobilized, as it seems to be the casefor two dolphins from the Tyrrhenian sea (Carlini and Fabbri, 1969), andthen mineratized), and is accumulatlng as inorganic Hg in the liver, where itreaches very high levels. A detailed study of the speciation of this inorganicHg is necessary, in order to detect which proportion is detoxified bymeta11othioneins or selenium, or remains potential1y tonc. So that it does notseem excluded that not only PCBs, but also inorganic Hg might influence thehealth status of older animals.

References.Andre, J., A. Boudou, F. Ribeyre and M. Bernhard. 1991. Comparative study of

mercury accumulation in dolphins i:rt.mel13 t':t?eruJe..wb4) from FrenchAtlantic and Mediterranean coasts. Sä. Tt,t31.EtJJ"irt'I1... 104: 191-209.

Alzieu, C. et R. Duguy. 1979. Teneurs en composes organochlores chez lescetaces et pinnipedes frequentant les cotes fran~ses. (~~t?/t'. At~t~.

107-120.capelli, R., R. oe PeUegrini, V. Mingani and R. Pogg!. 1989. Prellminary results

on the prestnce of inorganic, organic mercury and selenium in do1phinsm~.n~1Ja t':l.~.ruJAwlu) from the Ugurian sea. Eurt?p. .Res. Ctft.!tt':tfMS., 3:19-21.

Carlini, R. and F. Fabbri. 1989. Mercury, methylmercury and se1enium inItalian stranded odontocetes. EUrt'p. Hes. Ct9t3t'WU1~ 3: 25-28.

Joiris, CR., L. Ho1sbeek, ]M. Bouquegneau and M. Bossicart. 1991. Mercurycontamination of the harbour porpoise PlJt't':t?e03 plJt't':t~J1" and othercetaceans from the North Sea and tht Kattegat. Wate:. AU, & Siw A'>J1ut...56: 283-293-

JolriS, CR., L. Ho1sbeek, U. SIebett, JM. Bouquegneau, M. Bossicart, R. Duguyand M. Simmonds. 1992. Heavy metals and organochlorines in commondo1phins ~lplJi.lJus d~1plJjs stranded on the French Atlantic coasl Eurt?p.

.Res. Cet~w~ 6. In press.Koeman, JR., W.SM. Peeters, CRM. Koudstaal-Hol, P.S. Tfioe and lJM. de

Goeij. 1973- NatlJrtf" 245: 365.Law, RJ., BR. Jones, JR. Baker, S. Ktnnedy, R. MUne and RJ. Morris. 1992. Trac.

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Thibaud, Y. and R. Duguy. 1973. Teneur en mercure chtz les cetac&s des cot.esde Franc•. lCES' CM 1973/ N:2. 6 ps.

Wagemann, R. and D.G.C. Mutr. 1964. Concentrations of heavy metals andorganochlorines in marine mammals of northern wat&rs: overview andevaluation. C.1O. T~:;hJ1. Hep. Fjsh Aquat. .~~.. 1279: 97 pps.