Factors influencing the uptake of technetium by the brown alga Fucus serratus

Marine Pollution Bulletin

This probably explains the different behaviour of the molluscs examined in this investigation: D. trunculus and E. siliqua appear to greatly concentrate; M. galloprovincialis reflects the variability of the environment where it feeds (water); C. gallina shows a poor accumulation power, at least, with regard to the microbial enteric flora. Therefore, different species of molluscs may represent a different risk as vectors of microbial and perhaps viral diseases. Bayne, B. L., Thompson, R. J. & Widdows, J. (1976). In Marine Mussels. Their Ecology and Physiology' (B. L. Bayne, ed), pp. 121-234. Cambridge University Press, Cambridge. D.M. 27/4/78. Norme concernenti i requisiti microbiologici, biologici, chimici e fisici delle zone acquee sedi di banchi e di giacimenti naturali di molluschi eduli lamellibranchi e delle zone acquee destinate alia molluschicoltura ai fini della classificazione in

approvate, condizionate e precluse. Gazzetta Ufficiale della Repubblica ltaliana suppl, n. 125, 8/5/78, pp. 1-14. Earampamoorthy, S. & Koff, R. S. (1975). Health hazards of bivalve mollusks ingestion. Ann. Intern. Med. 83, 107-110. Hedstrom, C. & Lycke, E. (1964). An experimental study on oysters as virus carriers. Am. J. Hyg. 79, 134-142. Loosonoff, V. L. & Engle, J. B. (1947). Fisher}' Bull. Fish Wildl. Serv. U.S. 51. Mohlenberg, E & Riisgard, H. U. (1978). Efficiency of particle retention in 13 species of suspension feeding bivalves. Ophelia 17,239-246. Volterra, L. & Tosti, E. (1983). Faecal pollution and shellfish hygienic condition. Ann. [st. Sup. Sanitd 19, 317-322. Volterra, L., Piccininno, G., Palliola, E., Auticino, E A. & Gianfranceschi, M. (1984). Environmental fecal pollution and concentration power of the clam Chamelea gullina, t~lter, Air and Soil Pollut. 21,415-424. Volterra, L., Aulicino, F. A., Bonadonna, L., Mancini, L., Marilungo, S. & Pietrangeli, 13. M. (1987). Condizioni igienico sanitarie di banchi naturali di molluschi lungo la costa tirrenica. L'lg. Mod 88,770-781. Wood, P. C. (1978). Public Health aspects of shellfish from polluted waters. Int. Syrup. on biological indicators of water quality, Newcastle upon Tyne, 12-15 September, 1978.

0025-326X/90 $3.00+0.00 © 1990PergamonPressplc

MarinePolhaionBulletin,Volume21, No. 2, pp. 84-86, 1990. Printedin Great Britain.

Factors Influencing the Uptake of Technetium by the Brown Alga Fucus serratus D. VAN DER BEN*, M. COGNEAU*, V. ROBBRECHT*, G. NUYTS ~, A. BOSSUS §, C. HURTGEN§ and S. BONOTTO§ *Institut royal des Sciences naturelles de Belgique, B-1040 Bruxelles; t Laboratoire de Chimie Inorganique et NuclOaire, UniversitO Catholique de Louvain, B-1348 Louvain-la-Neuve; *Departement Biologic, Universitaire Instelling Antwerpen, B-2610 Wilrijk; ~Department of Radioprotection, C.E.N./S. C.K., B-2400 Mol, Belgium.

Various experiments on the brown alga Fucus serratus, under light, in darkness, at two different temperatures (4 and 20°C) and after heat-inactivation, suggest that the accumulation of technetium is a physiologically controlled process. This hypothesis is supported also by chromatographic analyses of algal extracts, in which the proportion of technetium bound to organic molecules was found to be higher under light than in darkness or at 4oc.

The brown alga Fucus serratus and other Fucales (F. spiralis, F. vesiculosus and Ascophyllum nodosum) are considered good bioindicators of radioactive contamination by technetium (Jeanmaire et al., 1981; Aarkrog et al., 1986, 1989; Holm et al., 1986a,b; Patti et al., 1986; Bonotto et al., 1988; Hurtgen et al., 1988). However, little information exist on the main factors which 84

affect the uptake of this important radionuclide by marine macroalgae (Topcuo~lu & Fowler, 1984). This paper, which is an extension of previous work (Bonotto et at., 1988), reports experimental results on the effect of various physical factors (light and darkness, temperature and heat inactivation) on the uptake and metabolism of 95mTcin the species E serratus. Materials and M e t h o d s

The brown alga Fucus serratus (Fucales) was collected in the southern part of The Netherlands, cleaned from contaminants and kept in aerated seawater (in plast]c aquaria), with 10pg ml -l chloramphenieol added to avoid bacterial development. The collected plants were more than 1 yr old, as judged from the figures published by Knight & Parke (1950). Cut vegetative apical fragments, 1-2 cm long, were supplied with 95mTc-potassium pertechnetate (37, 55.5, or 59.2 Bq ml-~), under different experimental condi-

Volume 21/Number 2/February 199(I

tions (light (about 400 lux); darkness; 4 and 20°C, under light). In addition, the uptake of 95mTcwas investigated in apical fragments heat-inactivated (2 min in sea water at 50*C) according to the procedure of Topcuo~lu & Fowler (1984). 95mTC, a gamma-emitter which decays to stable 95Mo with a half-life of 61.2 days, was produced in the cyclotron of Louvain-laNeuve (Belgium), by irradiating a Mo-source. The radioactivity, present in apical fragments (in vivo measurements), in algal extracts or in chromatographic fractions, was measured in a Packard Auto-Gamma spectrometer. Autoradiography was done as previously reported (Bonotto et aL, 1988). Column chromatography of 95mTc-labelled extracts (post-mitochondrial supernatants) of Fucus serratus was done according to the procedure reported in a previous paper (Bonotto et aL, 1986), except that Sephacryl S-200 superfine was used as packing gel.

i

A

B

C Results and Discussion Autoradiographic investigations on excised fragments (vegetative apical fragments of Fucus and vegetative lateral branches of Ascophyllum) have shown that the cutting edges had not fixed more technetium than the other regions (Fig. 1). This finding allowed further non-destructive measurements of 95mTcuptake by living algal fragments, maintained under various experimental conditions, since the wound did not increase the fixation of technetium. Experiments with vegetative apical fragments of Fucus serratus have shown that the uptake of 9 5 m T C w a s higher in light than in darkness (Fig. 2). Moreover, heatinactivation resulted in its almost complete inhibition (99% or more) (Fig. 2, black line). In addition, in algae kept at 4°C, an important reduction (up to 70%) of 95mTc fixation was observed in short-term (few hours) experiments (Fig. 3). After several days, this reduction progressively decreased, probably as a consequence of an adaptation of the algae to a lower temperature; Fucus serratus and other related brown algae grow preferentially in relatively cold waters. By chromatographic analysis of labelled extracts, it was possible to show that the percentage of technetium bound to organic molecules (peak 1 in Fig. 4) was higher under light (76%) than in darkness (48%) or at low (4°C) temperature (36%). Concommitantly, unbound technetium increased from 24% (light) to 52% (darkness) and 64% (4°C). These results clearly show that the proportion of technetium entering the metabolic pathways is highest under light conditions. The results reported here deserve some comment. The fact that light and temperature significantly increased the accumulation of technetium in Fucus serrams supports the hypothesis that this process is under physiological control. Similarly, the almost complete loss of the capability of fixing technetium by heatinactivated algae suggests the presence of an active metabolic mechanism. Our results are in good agreement with those previously reported by Topcuo~lu & Fowler (1984) on the brown algae Cystoseira compressa and Sargassum vulgare.

A Fig. 1 Autoradiographs of excised lateral branches of Ascophyllum nodosum (A) and of apical fragments of Fucus ~esiculosus (B) and of E serrams (C), supplied with 95mTcKO4 (37 Bq ml -~) during 24 h under light. The cutting edges (arrowheads) do not show an increased darkening, a fact which excludes a preferential entrance of technetium through the wound. Scale = 2 cm.

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Time(h) Fig. 3 Uptake of USmTc(37 Bq ml-t) by vegetative apical fragments of Fucus serrams kept respectively at 4 and 20°C under light conditions.

Column chromatographic analyses of extracts from Fucus serratus, labelled under different conditions, add

new experimental support in favour of a metabolically controlled process. It should be noted, however, that in 85

Marine Pollution Bulletin

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might be adsorbed to organic materials, which would be denatured or lost during heat-inactivation. Experiments are in progress to check this possibility. Finally, investigations on the influence of other factors (salinity, age, biological cycle) are planned or are already in progress.

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Fig. 4 Chromatographic analysis of extracts (post-mitochondrial supernatants) of Fucus serratus supplied with 9S~'Tc (55.5 Bq) under light (1), in darkness (B) and at 4"C (C) during about ten days.

all samples 30-40% of the total technetium taken up by Fucus serratus could not be extracted by the buffer used in our method. Probably, part of technetium is so firmly bound that it resists conventional non-destructive extraction procedures. Our findings do not exclude that in living Fucus serratus (as well as in other brown algae) technetium

86

This work was supported in part by Contract CEC nr B16-0049-B. We thank Mrs Eliane Bonnijns and Mrs Katia Bouckaert for drawing the graphs. Aarkrog, A., Dahlgaard, H., Hallstadius, L., Holm, E., Mattsson, S. & Rioseco, J. (1986). Time trend of 99Tc in seaweed from Greenland waters. In Technetium in the Environment (G. Desmet, & C. Myttenaere, Eds.), pp. 69-78. Elsevier, London & New York. Aarkrog, A., Botter-Jensen, L., Qing Jiang, C., Dahlgaard, H., Hansen, H., Holm, E., Lauridsen, B., Nielsen, S. P. & Sagaard-Haensen, J. (1989). Environmental radioactivity in Denmark in 1987. Riso-R563, pp. 1-141. Riso National Laboratory, Roskilde. Bonotto, S., Kirchmann, R., van Baelen, J., Hurtgen, C., Cogneau, M., van der Ben, D., Verthr, C. & Bouquegneau, J.-M. (1986). Behaviour of technetium in marine algae. In Speciation of Fission and Activation Products in the Environment (R. A. Bullman & J. R. Copper, Eds.), pp. 382-390. Elsevier, London & New York. Bonotto, S., Robbrecht, V., Nuyts, G., Cogneau, M. & van der Ben, D. (1988). Uptake of technetium by marine algae. Autoradiographic localization. Mar. Pollut. Bull. 19, 61-65. Holm, E., Rioseco, J., Aarkrog, A., Dahlgaard, H., Hallstadius, L., Bjurmann, B. & Hedvall, R. (1986a). Technetium-99 in algae from temperate and arctic waters of the North Atlantic. In Technetium in the Environment (G. Desmet & C. Myttenaere, Eds.), pp. 53-59. Elsevier, London & New York. Holm, E., Rioseco, J. & Mattsson, S. (1986b). Technetium-99 in the Baltic Sea. In Technetium in the Environment (G. Desmet & C. Myttenaere, Eds.), pp. 61-68. Elsevier, London & New York. Jeanmaire, L., Masson, M., Patti, E, Germain, P. & Cappellini, L. (1981). Technetium-99 content in some marine organisms collected near La Hague, France. Mar. Pollut. Bull. 12, 29-32. Knight, M. & Parke, M. (1950). A biological study of Fucus vesiculosus L. and E serratusL. J. Mar. Biol. Ass. U.K. 29,439-514. Patti, E, Masson, M., Vergnaud, G. & Jeanmaire, L. (1986). Activit~s du techn&ium-99 mesur6es dans les eaux rrsiduaires, reau de mer et deux bioindicateurs (Littoral de la Manche, 1983). In Technetium in the Environment (G. Desmet & C. Myttenaere, Eds.), pp. 37-51. Elsevier, London & New York. Topcuo~lu, S. & Fowler, S. W. (1984). Factors affecting the biokinetics of technetium (95mTc) in marine macroalgae. Mar. Env. Res. 12, 25-43.