The eel A. anguilla offers several properties of a useful bioindicator such as its worldwide distribution, abundance, size, long life span and euryhalinity. This last ...
Wat. Sci. Tech.
Vol.
19,
Rio, pp.
1229-1232, 1987.
0273-1223/87 $0·00 + ·50 1987 IAWPRC
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THE EEL (ANGUILLA ANGUILLA L.) AS A BIOINDICATOR OF METAL POLLUTION: FACTORS LIMITING ITS USE C. Amiard-Triquet*, 1. C. Amiard*, A. C. Andersen*, P. Elie** and C. Metayer* *
Universite de Nantes, Centre de Dosage des Elements Traces, 1 rue
Gaston Veil, 44035 Nantes Cedex, France * * CEMAGREF,
Division A. L.A. Gazinet, 33160 Cestas Principal, France
Several bioindicators have been proposed to monitor the distribution of aquatic contaminants such as mosses in freshwater environments (Wehr et a!., 1983 ; Mouvet et al., 1984), algae, gastropods and filter-feeding molluscs in marine environments (N .A.S., 1980 ; Bryan et a!., 1985). The eel A. anguilla offers several properties of a useful bioindicator such as its worldwide distribution, abundance, size, long life span and euryhalinity. This last characteristic which is more marked than in all other bioindicators allows the comparison of the contamination levels of marine and estuarine areas as well as river basins, according to their degree and pattern of industrialization. On the other hand, the eel is an important species from the point of view of fisheries resources. The general stress tolerance of the eel is well known .(Itazawa, 1971). However, the larval stages are generally more susceptible than adults (Fontaine, 1972), and elvers live in coastal and estuarine areas which are particularly at risk since they are among the most heavily polluted. Moreover, it is important to determine if the tolerance is accompanied by a high bioaccumulation which should constitute a threat to consumer health. NATURAL FACTORS INFLUENCING THE METAL LEVELS IN THE EEL Season of sampling The biological characteristics of elvers varied according to the time of sampling. In pigmen tary stages VB and VIAO (described by Elie et a!., 1982) of the elvers collected from the Loire estuary which were the only stages observed in all samples - the mean individual dry weight decreased from 92.5 to 67.5 mg from early February to late March. However, the period of sampling had generally little influence on both metal body burdens (Fig. 1) and concentrations. Developmental stages The elvers collected from the Gironde, the Loire and the Vilaine estuaries have been at tributed to the pigmentary stages VB to VIA3' For the all four metals and the all three estuaries, the pig mentary stage had little influence on the metal bioaccumulation (Fig. 1) . The only noticeable observation was the increase of lead in the elvers of the Loire estuary when they began to ingest food (pigmentary stage VIA3) (Lecomte-Finiger, 1983). When young and yellow eels were taken into account, the logarithm of the whole body burden in each specimen increased linearly with respect to the logarithm of its weight (Fig. 2). The regres sion coefficients varied from one metal to another, indicating different behaviours of the four studied metals during the growth of A. angUilla.
1229
1230
C. AMIARD-TRIQUET
et al. B
February
Loire estuary , early late Loire estuary Loire estuary , late
-+-
February March March March
Vtlaine estuary , late Gironde estuary, late
A
_
-
x
Lead
_
ng
-
-e-
100
---e---
.. ...... .. ......
Cadmium
ng 50
50
-9�' "" '�"'
,-:.:....JI . � e-_ ...
.,. , .. •... . .. .. . . ... ' ---:; 2,>-.....
10
10
>
1
C
_
o
Copper
_
Zinc
ng
ng
5
5000 "
./
\
,
..
\../�,
lIA0, rOO
B
Y
AD
.
.
-- --..... __ •
A,
A2
::..:::� . ........ .... . . .. . ... ...... � .� .. ,
It
.�.. . ...;t�.:-...... ..
+
100
-
?--'--
A3,
1lI Pigmentary
.
. ....
1 B
1l s tages
Ao
A,
A2
A3.
JZI
Fig. 1 - Metal bioaccumulation in elvers sampled from three estuaries and exhibiting various pigmentary stages.
The elvers caught in the brackish area of the Loire estuary, were acclimatized to various salinities (10, 20, 25 % ) for one week. Then they were exposed for 96 hours to a large range of concen trations of Cd, Cu or Zn in those different artificial saline waters. At the end of the experiment, the animals of each control or contaminated group were pooled for metal analysis (according to the method of Boiteau and Metayer, 1978 ; adapted by Amiard-Triquet et al., 1980). As shown in Fig. 3, the salinity had little or no short-term effect upon the accumulation of the all three metals in elvers.
1231
The eel
Leng t h
of
exposure: 4d
-.:t'""}
- ....... - ...... - - :;..:..=:.t .----:- � --Zn +-- -.._._._._.-:._._.-._._.
6
Zn
"
3
J
1
f
'i
i
Cu'
,
'&
J
11�------�2�--�3�---4��5 Log
of
body
Fig. 2 - Fate of dry weight and metal body burden over the life span.
waight
rng/I 10-'
concentration
° 10
in
10'
water
Fig. 3 - Relations between Cd, Cu and Zn concentrations in elvers and in waters of different salinities.
RELATIONSHIPS BETWEEN METAL LEVELS IN WATER AND IN ELVERS In brackish water, short-term exposures to external concentrations as high as 2 and 20 Ilg/1 respectively, did not disturb the level of these metals in the organisms (Fig. 3). In similar experimental conditions, exposure to Cd induced an enhancement of Cd concentrations in elvers. On the other hand, elvers caught in the upper part of the Loire estuary were reared in freshwater and exposed for one month to a low and a high concentration of each metal. The results of metal analysis (performed in individual samples) are listed in Table I 1) for Cd, its level in the body increased with the external concentration and no equilibrium level was reached within 4 weeks ; 2) for Cu, the experimental exposure induced an increase of uptake in the elver but an apparent equilibrium level was reached after only 2 weeks; 3) for Zn, the elvers exposed to the lowest assayed overload maintained their Zn concentration at a steady level. The slight increase observed after 4 weeks of exposure was not significant (F test of Snedecor). For higher experimental inputs, a significant increase of Zn levels in organisms occured even for the shortest period of contamination. However, the highest Zn concentration in elvers (74 mg/kg dry wt) did not double the normal one. The only significant interaction observed in elvers between the three metals was a temporary synergy exerted by Cd on the bioaccumulation of CU (Table n.
:
CONCLUSIONS As shown previously for different species (Bryan, 1984) elvers are able to regulate their whole body level of Cu and Zn at least partly. Consequently, they are not useful bioindicators for these essential metals. On the contrary, the internal Cd concentrations seem to reflect its environmental level. It will be necessary to establish precisely the mathematical relation between these two parameters in the case of chronic contamination. In the Loire estuary, the young stages exhibit the highest Cd concen trations and it will be necessary to verify if this is a general pattern. On the contrary, Pb bioaccumulation is very limited in elvers prior to the pigmentary stage VIA3 but the ability of older specimens to concentrate this metal must be investigated.
1232
C. AMIARD-TRIQVET
et al.
Table I - Metal bioaccumulation in elvers experimentally contaminated in freshwater
Metal conc. added to water (mgfl)
Length of exposure (weeks)
Number of individual samples
Concentrations in the elvers: mean (S.D.) in mg/kg dry matter Cd
Cu
Zn
2 3 4
6 7 7
0.38 (0.05) 0.40 (0.07) 0.34 (0.05)
2.84 (0.35) 2.16 (0.15) 2.09 (0.10)
40.5 (1.7) 39.2 (1.0) 46.0 (1.2)
2 4
3 8
1.44 (0.24) 3.00 (0.27)
16.07 (8.07) 2.76 (0.19)
39.2 (1.2) 43.3 (1.9)
2 3
3 3
9.23 (0.89) 19.46 (6.89)
4.88 (1.67) 2.54 (0.23)
36.7 (1.5) 43.3 (1.2)
2 4
3 12
0.32 (0.06) 0.45 (0.06)
8.43 (0.54) 8.75 (0.66)
43.9 (3.3) 42.1 (1.2)
0.3
2 3
3 4
0.36 (0.07) 0.35 (0.04)
12.35 (2.76) 13.08 (0.51)
42.8 (3.5) 37.7 (1.5)
Zn 0.1
2 4
3 10
0.31 (0.05) 0.41 (0.06)
3.10 (0.40) 2.60 (0.19)
37.6 (0.8) 50.7 (2.4)
1
2 3
3 7
0.40 (0.05) 0.38 (0.03)
2.33 (0.16) 2.14 (0.23)
53.1 (3.1) 65.4 (0.7)
5
2
3
0.42 (0.09)
6.37 (1.57)
74.0 (9.9)
controls
Cd 0.06 2.5
Cu 0.05
REFERENCES
AMIARD-TRIQUET C., METAYER C., AMIARD J.C. (1980). Etude du transfert de Cd, Pb, Cu et Zn dans les chaines trophiques ntlritiques et estuariennes. n. Accumulation biologique chez les poissons planc tonophages. Water Res. 14, 1327-1332. BOITEAU H.L., METAYER C. (1978). Microdosage du plomb, du cadmium, du zinc et de l'etain dans les milieux biologiques par spectrometrie d'absorption atomique apres mineralisation et extraction. Analusis 6, 350-358. BRYAN G.W. (1984). Pollution due to heavy metals and their compounds. In : Marine Ecology. � (3), O. Kinne, ed., John Wiley & Sons Ltd, 1289-1431. BRYAN G.W., LANGSTON W.J., HUMMERSTONE L.G., BURT G.R. (1985). A guide to the assessment of heavy-metal contamination in estuaries using biological indicators. Mar. BioI. Ass. U.K. Occasional Publ. 4, 92 pp. ELIE P., LECOMTE-FINIGER R., CANTRELLE I., CHARLON N. (1982). Definitions des limites des different stades pigmentaires durant la phase civelle d'Anguilla anguilla (Poisson TeIeosteen Anguilliforme). Vie Milieu 3 2, 149-157. FONTAINE M. (1972). Vaction des polluants sur la vie marine. Du choix de criteres experimentaux. In: Marine Pollution and Sea Life. Ruivo M. ed., Fishing News LTD, 194-203. ITAZAWA Y. (1971). Characteristics of respiration of fish considered from the arteriovenous difference of oxygen content. Bull. Jap. Soc. Sci. Fish 36, 571-577. LECOMTE-FINIGER R. (1983). Regime alimentaire des civelles et anguillettes (Anguilla anguilla) dans trois etangs saumatres du Roussillon. Bull. Ecol. 14, 297-306. MOUVET C., KIRCHMANN R., LAMBINON J. (1984}.The use of aquatic Bryophytes for the determination of freshwater radioactive contamination : general concepts and detailed results from the river Meuse. In : Environmental transfer to man of radionuclides released from nuclear installations. C.E.E. ed., Luxembourg, 155-173. N.A.S. (1980). The International Mussel Watch. National Academy of Sciences ed., Washington, D.C., 248 pp. WEHR J.D., EMPAIN A., MOUVET C., SAY J.P., WHITTON B.A. (1983). Methods for processing aquatic mosses used as monitors of heavy metals. Water Res. 11, 985-992.
