Effect of selenium on cadmium uptake in selected ... - Inter Research

Vol. 48: 17-28. 1988

MARINE ECOLOGY - PROGRESS SERIES Mar. Ecol. Prog. Ser.

Published September 5

Effect of selenium on cadmium uptake in selected benthic invertebrates Poul Bjerregaard Institute of Biology, Odense University, Campusvej 55, DK-5230 Odense M, Denmark

ABSTRACT. Effect of selenium on uptake of cadmium in the benthic marine invertebrates Asterias rubens, Mytilus edulis, Littorina littorea, and Arenicola marina was investigated in a series of laboratory experiments. A. rubens exposed to 200 ~ c gCd 1-' alone took up cadmium in body wall, pyloric caeca, and tube feet at initial rates of 1 to 2 pg Cd g-' dry wt d-'; steady state concentrations of 10 to 30 pg Cd g-l were reached after 1 to 2 wk. Concurrent exposure to 141 pg Se-Se03- 1-' increased cadmium uptake rates to 5 to 10 pg Cd g-' d-'; uptake proceeded linearly with time over 4 wk. Exposure to 200 pg Cd I-' did not affect uptake of selenium from 141 pg Se-Se0;- I-'. Uptake of cadmium (from 200 pg Cd I-') in tube feet and body wall was augmented by 17 vg Se-Se0;- I-', whereas higher selenite concentrations were required to augment cadmium uptake in pylonc caeca. In specimens exposed to radioactive cadmium for 2 wk, selenite concentrations at and above 75 @gS e - S e 0 3 - 1-' augmented cadmium uptake. A. rubens exhibited concentration factors (expressed on dry weight basis) for cadmium of ca 800 for ambient cadmium concentrations up to 3 pg Cd 1 - l ; between 3 and 400 pg Cd 1-', concentration factors decreased from 800 to 100. When exposed to 200 ~cgCd 1-' alone, A4. edulis took up cadmium at inltlal rates of 9.3, 36, 7.7, 6.4, 24, and 0.8 ,ug Cd g-' dry wt d-' in mantle, digestive gland, foot, adductor muscle, gills, and shell, respectively, L. littorea took up cadmium at 11 and 0.6 ,ug Cd g-' dry wt d-' in soft parts and shell, and A. marina took up c a d m ~ u mat 6.1 and 10.4 yg Cd g-' dry wt d-' in body wall and gut and 0.23 pg Cd ml-' d-l in blood Uptake proceeded linearly with time over 4 wk exposure in mantle, chgestive gland, foot, and adductor muscle of M. edulis, soft parts of L. littonna, and gut, body wall, and blood of A. marina. In the other tissues uptake rates declined after 1 to 2 wk of exposure. Exposure to an equimolar concentration (141 pg S e - S e 0 3 - I-') of selenite did not affect cadmium uptake in these 3 species. Exposure to a 5-fold concentration of selenite (703 pg SeSe0;- I-') augmented cadmium uptake in gills, mantle, and foot of M. edulis.

INTRODUCTION

Since the discovery that selenium protects rat testes against the toxic effects of cadmium (Kar et al. 1960), interactions between selenium and cadmium and mercury in mammals have been studied intensively (reviewed by Magos & Webb 1980). Although the interaction between selenium and mercury in aquatic organisms has been investigated in some detail (reviewed by Pelletier 1985), the effect of selenium on cadmium uptake and toxicity in aquatic organisms is poorly understood. Positive correlations between cadmium and selenium concentrations in black marlin Makaira indica (Mackay et al. 1975) and several species of marine birds (Norheim 1987) have been found. Selenium augments uptake of cadmium in gills a n d haemolymph of the shore crab Carcinus maenas (Bjerregaard 1982, 1985, 1988) a n d counteracts the O Inter-Research/Printed in F. R Germany

toxic effects of cadmium in the freshwater snail Lymnaea stagnalis (Puymbroeck et al. 1982). Selenium is present in unpolluted seawater in ng 1-' quantities (Measures & Burton 1980, Measures et al. 1980, Cutter & Bruland 1984, Apte et al. 1986). Selenium concentrations in fresh a n d coastal waters may b e augmented from anthropogenic sources such as drainage from irrigated a n d selenite-fertilized soils (Phillips 1987), leaching from fly-ash deposits (Ahsahnullah & Brand 1985), and discharges from refineries (Phillips 1987). Fly-ash leachates a n d effluents from refineries may contain u p to 2400 yg S e 1-' (Ahsanullah & Brand 1985) a n d 150 yg S e 1-' (Phillips 1987), which may locally augment the selenium concentration of the seawater to yg S e 1-'. It is not known if discharges of selenium compounds in coastal a n d estuarine environments affect uptake of metals by organisms living in these habitats. This study examines the effect of selenite on cad-

Mar Ecol. Prog. Ser. 48: 17-28, 1988

18

rnium uptake in sea stars Asterias rubens, mussels Mytilus edulis, periwinkles Littonna littorea, and lugworms Arenicola manna.

MATERIALS AND METHODS Experimental animals. Sea stars Asterias rubens and periwinkles Littorina Littorea were obtained from Lillebalt, Denmark. For Expt 2, sea stars were caught in seines, while those used in the remaining experiments were collected from the shore. Sea stars used in December were collected in October and kept in flowing seawater tanks at the Marine Biological Station, Bggebjerggzrd, until they were brought to the laboratory. Lugworms Arenicola marina and mussels Mytilus edulis were collected in Denmark at Bregnor, NE Funen, and Kertinge Nor, E Funen, respectively. Exposure procedures. Arirnals were acclimated in the laboratory for 1 to 5 d prior to experiment and then

exposed to cadmium as CdC12 and selenium as Na2Se03. Details of exposure conditions in each experiment are g v e n in Tables 1 and 2. Cadmium and (in some of the experiments) selinite concentrations in the aquaria were monitored, and unless otherwise stated concentrations varied by less than 1 0 O/O between water changes. The water in the exposure aquaria was aerated and no sediment was placed in the aquaria. The animals were not fed during the experiments. Store Bielt seawater with background cadmium and selenite concentrations of ca 25 ng Cd 1-' (Magnusson & Rasmussen 1982) and less than 1 0 ng Se-Se03- 1-' (Bjerregaard 1982) was used in the experiments. Selenium analysis. Selenium concentrations in the tissues were determined by gas chromatography with a modified version of the technique described by Shirnoishi (1976). The 5-nitropiaselenol produced (Shimoishi 1976) was extracted into toluene and 2 111 samples were manually injected into a Hewlett Packard 5 8 3 0 A Gas Chromatograph equipped with an

Table 1. Summary of experimental conditions in which animals were exposed to 200 pg Cd I-' and various selenite concentrations Organism Experiment no.

yg Se-Se0;added 1-'

Asterias rubens Expt l

0 141

Asterias rubens Expt 2

0 2.2 4.4 8.8 17.6 35 70 141 281 562 1124 2248 4496

Initial no. of animals

Days of sampling and no. of animals (n) sampled

25 25

5, 10, 14, 18, 28 (5) 21 ( 4 ) 21 (3) 21 (2) 21 (4) 21 (41 21 (0) 21 ( 2 ) 21 (51 21 (5) 21 (0) 21 (0) 21 (0) 21 (0) 7 (5). 17 (5) 28 (6)

Astenas rubens Expt 3

141a 141

16 16

Mytilus edulis Expt 7

0 141 703

21 21 21

littorina tittorea Expt 8

0 141

Arenicola marina Expt 9

0 141

Type a n d volume of aquaria

22-23 15.5

20-50 13 J u n 1986

8 l polystyrene aquaria

21-23 15.5

20-50 30 Jul 1986

30 l glass aquaria

20-50 16 Dec 1986

7 (51, 14 (81 28 (8)


4.7-5.7C 2 Jun 1985

40 40

7, 14, 21, 27 (10)

8 l polystyrene aquariab

20 20

5, 12. 19, 26 (5)


Equipped with a mesh to prevent the periwinkles from l e a v ~ n gthe water phase Dry wt (mg) of soft parts

("c)

Size of animals (g wet wt) Date

60 l glass aquaria

" No cadmium added

' Shell length (cm)

Salinity (S %o) Temperature

10-18 10 Oct 1985

Bjerregaard: Effect of selenium on cadmium uptake

Table 2. Astenas rubens. Summary of experimental conditions in Expts 4, 5, and 6. Each of the expermental groups initially consisted of 7 small sea stars (1 to 9 g wet wt) placed in 8 1 polystyrene aquaria containing ca 600 000 dpm lo9Cd.Water was not changed during the 14 d exposure period, and '09Cd In the water was determined on Days 0, 7 and 14. Total radioactivity after exposure in the 5 to 7 sea stars from each aquarium is given. Temperature was 15.5 "C and sallnity was 20.5 %D Experiment no. Date

Expt 4 1 Jul1987

Expt 5 1 Aug 1987

Exposure (PS 1-7 Cd

Se-Se0;-

0 0 0.0125 0.0125 0.025 0.025 0.05 0.05 0.1 0.1 0.2 0.2 0.4 0.4 0.8 0.8 1.6 1.6 3.2 3.2 6.3 6.3 12.5 12.5 25 25 50 50 100 100 200 200 400 400

0 14 1 0 141 0 141 0 14 1 0 14 1 0 141 0 14 1 0 141 0 141 0 14 1 0 14 1 0 141 0 141 0 141 0 141 0 141 0 141

b b b b b b

b

b b b

Expt 6 22 Sep 1987

b

b b b b

b

" Mean

2 SD of wet weight.

0 0.25 0.50 1 2 4 8 16 32 64 0 25 50 75 100 125 150 200

[ logCd] (dpm ml- l ) Day 0 7 14

Weight" and no. (n)of animals sampled

lo9Cdin animals (dpm)

Loss from water accounted for by uptake in animals (% of '09 Cd)

(6) (5) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (7) (6) (7)

168405 270 370 136310 340 695 180 945 377 485 139 195 376210 108 820 397 585 114 150 395 595 145 400 444 870 166 360 445 640 119850 429455 154 975 425 111 81 120 281 440 49 765 466 060 66 430 153 900 65 220 220 710 43 315 151 795 34 520 94 650 31 010 91 570

105 84 57 97 90 107 73 100 72 92 51 110 83 105 87 111 79 93 75 95 51 62 52 108 69 62 51 92 50 100 62 50 55 50

63 65 76 66 71 70 76 71 79 74 74 74 71 75 78 73 75 78 79 75 75 73 74 74 74 74 79 76 78 76 79 78 78 80

60 37 64 33 59 34 65 33 68 36 62 46 64 28 65 33 71 25 67 28 70 23 70 42 71 52 75 60 73 67 79 69 75 72

48 25 46 22 46 26 52 24 60 20 46 29 62 22 54 23 56 20 53 19 55 16 62 20 62 43 63 46 67 57 72 54 71 57

2.5 ? 1.6 2.4 1.8 3.4 1.7 3.6 3.0 3.1 +- 1.1 2.9+ 1.7 3.3 f 2.0 3.4 f 2.0 3.9 t 2.2 2.8 f 1.5 2.7 t 1.6 3.1 t 1.2 3.1 t 2.2 2.3 t 1.4 3.0 t 1.9 2.4 1.0 2.5 1.3 2.4 1.7 3.1 2 1.6 2.3 f 1.1 3.2 2.2 3.0 1.1 2.7 1.2 3.1 f 1.3 2.7 f 0.9 3.2 f 1.9 2.8 t 1.7 2.7 f 1.3 3.2 f 1.9 2.9 f 2.0 2.4 t 1.2 3.5 2.1 3.5 f 2.0 3.7 f 2.1

74 78 76 74 78 78 77 72 78 75

50 55 52 56 54 56 52 55 49 53

35 37 37 41 43 39 34 40 33 37

5.4 2.4 5.8 2.3 5.7 3.2 4.9 2.3 4.2 f 2.2 5.3 f 1.6 5.9 f 2.4 5.0 1.9 5.5 f 1.5 5.2 f 2.0

(7) (7) (7) (7) (7) (7) (7) (7) (7) (7)

189 725 184 859 168 155 142290 164 815 164 695 190 870 186 220 225 705 213 670

61 56 54 54 59 53 56 73 63 70

65 64 69 67 69 65 69 63

55 61 50 56 54 47 32 15

49 53 44 47 42 30 21 16'

3.4 f 1.8 2.9 f 1.3 3 . 2 5 1.1 3.6 2 0.8 4.0 1.3 3.4 f 1.4 3.0 t 1.8 2.4 5 0.8

(7) (7) (7) (5) (6) (7) (7) (5)

94 905 100610 155 290 147 890 220 185 196 220 325 615 285 920

91 125 72 92 101 70 85 76

No stable cadmium added.

C

+ + +

+ + + + + +

+

+ + + + +

+

This group analysed after 9 d

20

Mar. Ecol. Prog. Ser. 48: 17-28, 1988

electron capture detector and a 2000 mm X 2 mm glass column packed with 10 % SE-30 and acid-washed dimethyldichlorosilan-treated chromosorb W 100/120. Oven temperature was 200°C. The selenium concentration in an NBS oyster standard with a certified selenium concentration of 2.1 k 0.5 big Se g-' was found to be 2.05 and 2.17 pg Se g-' in duplicate measurements. Determinations of selenium concentrations in 6 replicate samples of pyloric caeca from selenite exposed sea stars resulted in a standard deviation of 4.2 %. Selenite concentrations in the seawater were determined with a Perkin-Elmer MHS-20 hydride generating system. Cadmium analysis. Tissue samples were freeze dried, weighed and dissolved in 2 to 3 m1 concentrated nitric acid at 120°C to obtain a clear yellow solution. The samples were evaporated almost to dryness, then 200 p1 30 % H z 0 2 was cautiously added. Thereafter the samples were evaporated to dryness and redissolved in 10.0m1 0.2 % nitric acid. The cadmium concentration in the solution resulting from this procedure was determined on a Perkin-Elmer 2380 atomic absorption spectrophotometer. Air-acetylene flame and deuterium background correction were used. An NBS oyster standard with a certified cadmium concentration of 3.5 k 0.4 pg Cd g-' dry wt was found to contain 3.1 and 3.2 pg Cd g-' dry wt (duplicate determinations). Radioactivity measurements. Radioactive cadmium ('09Cd) was obtained from New England Nuclear and radioactivity was measured with a Searle Mark 111 Liquid Scintillation Counter. Tissue samples were dissolved in Lumasolve prior to determination of '09Cd content. Radioactivity is given as disintegrations per minute (dpm). Statistical treatment of data. Two-tailed student's ttests and regression analysis were used in statistical evaluation of the data (Sokal & Rohlf 1969). Experiments. The 4 experimental species were exposed to 200 pg Cd 1-' (1.78 alone and 200 yg Cd 1-' plus a n equimolar selenite concentration (141 pg SeI-') for ca 1 mo (Expts 1, 7, 8 and 9; Table 1).An Se0:additional group of mussels was exposed to 200 (*g Cd 1-' and a 5-fold molar selenite concentrat~on(Expt 7 ; Table 1). Marked effects of selenite on cadmium uptake were noted in Asterias rubens, and additional experiments (Expts 2 to 6) were carried out with this species. In Expt 2, the effect of varying selenite concentrations on cadmium uptake (from 200 pg Cd 1-') was assessed and in Expt 3 it was investigated whether cadmium affected selenium uptake (Table 1). In Expt 4 the effect of selenite on cadmium uptake was investigated at cadmium concentrations ranging from background levels to 400 big Cd I-' and in Expts 5 and 6 the effects of different selenite concentrations on uptake of '09Cd

from background concentrations were investigated (Table 2). Background levels of cadmium and selenium in A. rubens were determined.

RESULTS Experiment l Background levels of selenium and cadmium in Asterias mbens from L i l l e b ~ l tare shown in Table 3. Sea stars exposed to 200 pg Cd 1-' took up cadmium in tube feet and pyloric caeca at a rate of ca 1.2 pg Cd g-' dry wt d-' during the first 10 d, when steady state Table 3. Asterias rubens. Background selenium and cadmium concentrations ( W g-' dry wt SD) in 4 0 to 50 g sea stars from I-lllebaelt

*

I

I Pyloric caeca

Body waU

Tube feet

l

concentrations of 10 to 12 yg Cd g-' were reached (Fig. l a ) . Uptake in the body wall proceeded at a slightly higher rate and a steady state concentration of 20 to was reached after 2 wk (Fig. l a ) . 25 pg Cd Sea stars exposed to 200 pg Cd + 141 yg Se-Se031-' took up cadmium in body wall and pyloric caeca at a rate of 5 CL^ Cd g-' d-' and in tube feet at a rate of 10 ~ t g Cd g-' d-' (Fig. l b ) . Uptake proceeded linearly over 4 wk, and no trend toward a steady state level was observed. Differences between cadmium concentrations in selenite and non-selenite exposed groups were statistically significant (p