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Effects of heavy metals on survival and respiration rate of tubificid worms: Part II—Effects on respiration rate
EFFECTS OF HEAVY METALS ON SURVIVAL A N D RESPIRATION RATE OF TUBIFICID WORMS: PART II--EFFECTS ON RESPIRATION RATE*
1. BRKOVId-PoPovld& M. PoPovIc ITEN-ENERGOINVEST, Department of Waste Water Treatment Research, Sarajevo, Yugoslavia
A BSTRA CT An investigation o f the relationship between the concentration o f some heavy metals (Cd, Cu, Hg, Zn, Cr and Ni) and respiration rate o f tubificid worms is described. The results showed that the direction o f the change, caused by various metals, does not have to be the same and depends upon the range o f tested concentrations. In six hour experiments cadmium, mercury and copper, at concentrations which are lethal during 24 and 48 h exposure, have a visible depressive effect on the respiration rate. Copper has a depressive effect on the respiration rate o f tubificid worms at very low concentrations; on the other hand, cadmium and mercury increase oxygen consumption at concentrations that are lower than the acute lethal range. Zinc, nickel and chromium, at concentrations which are lethal during short exposures, considerably increase the respiration rate o f tubificids above the control values. In the range o f concentrations under 48-h L C 5o the respiration rate does not differ significantly from the control.
INTRODUCTION In pollution control work, the toxicity of heavy metals is most frequently evaluated in short-term toxicity survival tests. Recently, the chronic effects of heavy metals on survival, growth and reproduction of aquatic animals has received considerable attention. The present study on respiration rates was designed to meet the urgent need for a rapid and sensitive test for the detection of sublethal effects of toxicants. Walden et al. (1970) determined the minimum safe concentrations of kraft mill effluents by measuring respiration irregularities of fish. * Part I of this paper appears in Vol. 13, No. I, pp. 65-72. 93 Environ. Pollut. (13) (1977)--© Applied Science Publishers Ltd, England, 1977 Printed in Great Britain
94
I.
BRKOVi(~-POPOVI(~,M. POPOVl(~
O'Hara (1971) suggested that change in oxygen consumption could be used as a measure of sublethal effects of copper on fish. Whitley & Sikora (1970) investigated the effect of lead, nickel and pentachlorophenate on the respiration rate of tubificid worms. They concluded that the effect of metal on the respiration process might be of a mechanical nature, i.e. reduction or interruption of respiration due to precipitation of the mucus secreted by epidermal cells. But, in sublethal concentrations of toxicants, insufficient to precipitate the mucus, reduced respiration rate might not occur.
MATERIAL AND METHODS
The investigations included the definition of the toxicity action of cadmium (3CDSO4 × 8H20), copper (CuSO4 × 5H20), mercury (HgCI2), zinc (ZnSO4 × 7H20), chromium (K2Cr2OT) and nickel (NiSO4 x 7H20 ) on the respiration rate and survival of Tubifex tubifex. The 48-h LCs0 values for the six metals tested were determined in dilution water for BOD test with phosphate buffer, as already described (Part I of this paper). In our experiments the manometric estimation of oxygen consumption at various metal concentrations not lethal for 7". tubifex in six hours of experiment were carried out using a procedure proposed by Whitley & Sikora (1970), slightly modified. In order to standardise our conditions for the survival and respiration assay we used dilution water for the BOD test with phosphate buffer instead of Kn6pp solution as proposed by Whitley & Sikora (1970). The experiments were conducted at 20°C. The results are given in microlitres of oxygen per milligramme of the wet weight of animals.
RESULTS AND DISCUSSION
The studies of the cadmium and copper effects on the respiration rate of tubificid worms have shown that the direction of the changes caused by various metals does not have to be the same and depends upon the range of the concentrations (Fig. 1). Both metals in the range of acute lethal concentrations depress the oxygen consumption of tubificid worms. Whitley & Sikora (1970) also discovered that an increase in the lead concentration brought about a general decrease in the respiration rate of tubificid worms. Our results are in agreement with O'Hara's (1971) findings on fish subjected to copper. The oxygen consumption rates of fish in copper concentrations near the 96 h LCso become stabilised (in long-term assays) at approximately 6 0 ~ of the normal rate, but there is still a significant reduction of oxygen consumption at the concentration ten times lower than the 96-h LCso.
95
EFFECTS OF METALS IN TUBIFICID WORMS: PART 11
,::f
t,oo
[]
24. h LC 50
[]
4.8 h LC 50
CcZ
[]
24. h L c 5o
[]
4.8 h LC 50
Cu
0,90 t~ 0,90
o . 0,80
t~
/
0,70
0,60 4 Cb
l
10-~
l
I0 -s
I
10-2
J
I
10-t
Concentration
of
I
I0 "s
10 -2
metals
(rag/l)
~/"
~0-'
tO °
Fig. I. T h e plitre oxygen c o n s u m e d by Tubificidae exposed to various concentrations of c a d m i u m a n d copper ( : m e a n oxygen c o n s u m p t i o n o f the control; . . . . : 95 ~ confidence limits o f the m e a n ; L C s 0 s indicated on the d i a g r a m are defined in dilution water for the B O D test with p h o s p h a t e buffer).
While copper, at significantly lower concentrations than 48-h LCso, reduces oxygen consumption, cadmium has a stimulating effect on the oxygen consumption at concentrations out of the acute lethal range. With further reduction of the cadmium concentration the oxygen consumption approaches the control value (0.00091 mgCd/litre). These results indicate that the effect of cadmium on the respiratory mechanism of tubificid worms is not immediate and is different from that of copper. The'results of the investigation of the influence of mercury and zinc upon oxygen consumption of T. tubifex are shown in Fig. 2. The results of the investigations prove that mercury has a depressive effect upon the respiration rate of T. tubifex at the concentrations equal to, or higher than, 24-h and 48-h LCso. In the concentrations lower than these, mercury increases oxygen consumption (Fig. 2). Dorn (1974) also reached similar conclusions and found that mercury at concentrations under 0.01 mg/litre increased oxygen consumption in the bivalve mollusc Congeria. Our data indicate that in the tested range of concentrations zinc does not reduce the quantity of the oxygen consumption during the six hours of the experiment.
96
i. BRKOVI(~-POPOVI(~,M. POPOVIC
ZD
"~ 1,00
]
24 h LC 50
[]
4 8 h LC 50
~ 0,90 ~.. o,80
~ o,7o o
c 0,e0 Q
0,50 10-3
I0 -~
lO-p
I0 °
Concen'~ration
10-~
of
roe~-als
I
lO-'
iI
lO °
----i I0'
(rng/L)
Fig. 2. The/tlitre oxygen consumed by tubificid worms exposed to various concentrations of mercury and zinc. See Fig. i for explanation. Even at high concentrations, which would be lethal during the shorter exposure (24-h LCso), the oxygen consumption is somewhat higher than the control values. At the lowest concentration of zinc tested (0.091 mg/litre) the oxygen consumption approaches the values of consumption of the control organisms. The investigation of the effects of chromium and nickel on the respiration rate of T. t u b i f e x showed that the direction of the change for both metals is the same (Fig. 3). In the concentration range under 24-h and 48-h LCso, the respiration rates do not differ significantly from the control. In the high concentrations lethal during the 48-h exposure, the oxygen consumption is considerably above the control values during the 6-h respiration assay. According to Jones (1964), the rates of opercular movement and of oxygen consumption of fish exposed to heavy metals are above the control values at the beginning of the experiment. During the longer period of exposure, despite the animal's effort to maintain its oxygen supply, the oxygen consumption falls, returns to normal and becomes sub-normal. When the oxygen consumption rate is at 20 ~o of the normal, the fish dies.
97
EFFECTS OF METALS IN TUBIFICID WORMS" PART 11
]
24 h LC 50
I~
24 h LC 50
[]
Lc 50
Cr
[]
Ni
~e h LC so
Z k \ \
o,9o
\ \ \
.
),
~-~o,80
-
\ 3
c
O,TG
g o,so
i"
0
10 -2
I0 -t
tO °
10 ~
Concenfrctfion
Fig. 3.
I 0 -! of
rnefals
10 °
70 ~
lO 2
(rag~l)
The #litre oxygen consumed by tubificid worms exposed to various concentrations of chromium and nickel. See Fig. 1 for explanation.
Whitley & Sikora (1970), studying the effect of three toxic substances on the respiration rate of tubificids, found that the respiration function was affected very little by nickel, inhibited by lead and stimulated by pentachlorophenate. Our data on the effects of nickel and chromium on the respiration rate oftubificids apparently are not in accordance with Whitley & Sikora's (1970) data. But, considering the data on the effects of heavy metals on the respiration rate of fish (Jones, 1964), those of Whitley & Sikora (1970) cited, and the data from our experiments, one could state that, in general, the interpretation of the results of the respiration bioassay is difficult unless the parameters of the survival tests are defined under the same conditions (abiotic and biotic factors) at least at the short exposure.
It is obvious that the toxic substances in the acute lethal range of concentrations might cause an inhibition of the respiratory processes of tubificid worms (results of Whitley & Sikora for lead, our data for copper, cadmium and mercury). On the other hand, zinc, chromium and nickel at the same range of concentrations cause an increase in oxygen consumption during the six hours of the experiment.
98
L BRKOVI(~-POPOVI(~, M. POPOVI(~
The direction and significance o f the deviation o f the respiratory rate from the normal, under the influence o f concentrations o f metals which are not lethal (mercury, c a d m i u m a n d copper), c a n n o t be clear without d a t a on the effect o f the c o n c e n t r a t i o n s mentioned on life span, growth a n d other biotic characteristics o f the species tested. O u r results indicate that the alteration o f the respiration rate used as an isolated p a r a m e t e r has limited significance in the a p p r e c i a t i o n o f sublethal concentrations. But, when used in c o m b i n a t i o n with other results o f toxicity effects, it is a valid p a r a m e t e r , even if the c o m p e n s a t o r y and t e m p o r a r y reactions are in question.
ACKNOWLEDGEMENTS
W e wish to thank Professor D r Hrvoje Ivekovic for his helpful suggestions a n d great s u p p o r t during our investigation and also The Republic Association for the Scientific W o r k o f SR B. and H. which financed this study.
REFERENCES
DORN, P. (1974). The effects of mercuric chloride upon respiration in Congeria leucophaeta. Bull. Environ. Contain. & Toxicol., 12, 86--91. JONES, J. R. E. (1964). Fish and river pollution. London, Butterworths. O'HARA, J. 0971). Alterations in oxygen consumption by bluegills exposed to sublethal treatment with copper. Water Res., 5, 321-7. WALDEN, C. C., HOWARD,T. E. 8~. FROUD, G. C. (1970). A quantitative assay of the minimum concentrations of kraft mill effluents which affect fish respiration. Water Res., 4, 61-8. WmTLEV, L. S. & SmORA, R. A. (1970). The effects of three common pollutants on the respiration rate of Tubificid worms. J. Wat. Pollut. Control Fed., 42, R57-R66.
1. BRKOVId-PoPovld& M. PoPovIc ITEN-ENERGOINVEST, Department of Waste Water Treatment Research, Sarajevo, Yugoslavia
A BSTRA CT An investigation o f the relationship between the concentration o f some heavy metals (Cd, Cu, Hg, Zn, Cr and Ni) and respiration rate o f tubificid worms is described. The results showed that the direction o f the change, caused by various metals, does not have to be the same and depends upon the range o f tested concentrations. In six hour experiments cadmium, mercury and copper, at concentrations which are lethal during 24 and 48 h exposure, have a visible depressive effect on the respiration rate. Copper has a depressive effect on the respiration rate o f tubificid worms at very low concentrations; on the other hand, cadmium and mercury increase oxygen consumption at concentrations that are lower than the acute lethal range. Zinc, nickel and chromium, at concentrations which are lethal during short exposures, considerably increase the respiration rate o f tubificids above the control values. In the range o f concentrations under 48-h L C 5o the respiration rate does not differ significantly from the control.
INTRODUCTION In pollution control work, the toxicity of heavy metals is most frequently evaluated in short-term toxicity survival tests. Recently, the chronic effects of heavy metals on survival, growth and reproduction of aquatic animals has received considerable attention. The present study on respiration rates was designed to meet the urgent need for a rapid and sensitive test for the detection of sublethal effects of toxicants. Walden et al. (1970) determined the minimum safe concentrations of kraft mill effluents by measuring respiration irregularities of fish. * Part I of this paper appears in Vol. 13, No. I, pp. 65-72. 93 Environ. Pollut. (13) (1977)--© Applied Science Publishers Ltd, England, 1977 Printed in Great Britain
94
I.
BRKOVi(~-POPOVI(~,M. POPOVl(~
O'Hara (1971) suggested that change in oxygen consumption could be used as a measure of sublethal effects of copper on fish. Whitley & Sikora (1970) investigated the effect of lead, nickel and pentachlorophenate on the respiration rate of tubificid worms. They concluded that the effect of metal on the respiration process might be of a mechanical nature, i.e. reduction or interruption of respiration due to precipitation of the mucus secreted by epidermal cells. But, in sublethal concentrations of toxicants, insufficient to precipitate the mucus, reduced respiration rate might not occur.
MATERIAL AND METHODS
The investigations included the definition of the toxicity action of cadmium (3CDSO4 × 8H20), copper (CuSO4 × 5H20), mercury (HgCI2), zinc (ZnSO4 × 7H20), chromium (K2Cr2OT) and nickel (NiSO4 x 7H20 ) on the respiration rate and survival of Tubifex tubifex. The 48-h LCs0 values for the six metals tested were determined in dilution water for BOD test with phosphate buffer, as already described (Part I of this paper). In our experiments the manometric estimation of oxygen consumption at various metal concentrations not lethal for 7". tubifex in six hours of experiment were carried out using a procedure proposed by Whitley & Sikora (1970), slightly modified. In order to standardise our conditions for the survival and respiration assay we used dilution water for the BOD test with phosphate buffer instead of Kn6pp solution as proposed by Whitley & Sikora (1970). The experiments were conducted at 20°C. The results are given in microlitres of oxygen per milligramme of the wet weight of animals.
RESULTS AND DISCUSSION
The studies of the cadmium and copper effects on the respiration rate of tubificid worms have shown that the direction of the changes caused by various metals does not have to be the same and depends upon the range of the concentrations (Fig. 1). Both metals in the range of acute lethal concentrations depress the oxygen consumption of tubificid worms. Whitley & Sikora (1970) also discovered that an increase in the lead concentration brought about a general decrease in the respiration rate of tubificid worms. Our results are in agreement with O'Hara's (1971) findings on fish subjected to copper. The oxygen consumption rates of fish in copper concentrations near the 96 h LCso become stabilised (in long-term assays) at approximately 6 0 ~ of the normal rate, but there is still a significant reduction of oxygen consumption at the concentration ten times lower than the 96-h LCso.
95
EFFECTS OF METALS IN TUBIFICID WORMS: PART 11
,::f
t,oo
[]
24. h LC 50
[]
4.8 h LC 50
CcZ
[]
24. h L c 5o
[]
4.8 h LC 50
Cu
0,90 t~ 0,90
o . 0,80
t~
/
0,70
0,60 4 Cb
l
10-~
l
I0 -s
I
10-2
J
I
10-t
Concentration
of
I
I0 "s
10 -2
metals
(rag/l)
~/"
~0-'
tO °
Fig. I. T h e plitre oxygen c o n s u m e d by Tubificidae exposed to various concentrations of c a d m i u m a n d copper ( : m e a n oxygen c o n s u m p t i o n o f the control; . . . . : 95 ~ confidence limits o f the m e a n ; L C s 0 s indicated on the d i a g r a m are defined in dilution water for the B O D test with p h o s p h a t e buffer).
While copper, at significantly lower concentrations than 48-h LCso, reduces oxygen consumption, cadmium has a stimulating effect on the oxygen consumption at concentrations out of the acute lethal range. With further reduction of the cadmium concentration the oxygen consumption approaches the control value (0.00091 mgCd/litre). These results indicate that the effect of cadmium on the respiratory mechanism of tubificid worms is not immediate and is different from that of copper. The'results of the investigation of the influence of mercury and zinc upon oxygen consumption of T. tubifex are shown in Fig. 2. The results of the investigations prove that mercury has a depressive effect upon the respiration rate of T. tubifex at the concentrations equal to, or higher than, 24-h and 48-h LCso. In the concentrations lower than these, mercury increases oxygen consumption (Fig. 2). Dorn (1974) also reached similar conclusions and found that mercury at concentrations under 0.01 mg/litre increased oxygen consumption in the bivalve mollusc Congeria. Our data indicate that in the tested range of concentrations zinc does not reduce the quantity of the oxygen consumption during the six hours of the experiment.
96
i. BRKOVI(~-POPOVI(~,M. POPOVIC
ZD
"~ 1,00
]
24 h LC 50
[]
4 8 h LC 50
~ 0,90 ~.. o,80
~ o,7o o
c 0,e0 Q
0,50 10-3
I0 -~
lO-p
I0 °
Concen'~ration
10-~
of
roe~-als
I
lO-'
iI
lO °
----i I0'
(rng/L)
Fig. 2. The/tlitre oxygen consumed by tubificid worms exposed to various concentrations of mercury and zinc. See Fig. i for explanation. Even at high concentrations, which would be lethal during the shorter exposure (24-h LCso), the oxygen consumption is somewhat higher than the control values. At the lowest concentration of zinc tested (0.091 mg/litre) the oxygen consumption approaches the values of consumption of the control organisms. The investigation of the effects of chromium and nickel on the respiration rate of T. t u b i f e x showed that the direction of the change for both metals is the same (Fig. 3). In the concentration range under 24-h and 48-h LCso, the respiration rates do not differ significantly from the control. In the high concentrations lethal during the 48-h exposure, the oxygen consumption is considerably above the control values during the 6-h respiration assay. According to Jones (1964), the rates of opercular movement and of oxygen consumption of fish exposed to heavy metals are above the control values at the beginning of the experiment. During the longer period of exposure, despite the animal's effort to maintain its oxygen supply, the oxygen consumption falls, returns to normal and becomes sub-normal. When the oxygen consumption rate is at 20 ~o of the normal, the fish dies.
97
EFFECTS OF METALS IN TUBIFICID WORMS" PART 11
]
24 h LC 50
I~
24 h LC 50
[]
Lc 50
Cr
[]
Ni
~e h LC so
Z k \ \
o,9o
\ \ \
.
),
~-~o,80
-
\ 3
c
O,TG
g o,so
i"
0
10 -2
I0 -t
tO °
10 ~
Concenfrctfion
Fig. 3.
I 0 -! of
rnefals
10 °
70 ~
lO 2
(rag~l)
The #litre oxygen consumed by tubificid worms exposed to various concentrations of chromium and nickel. See Fig. 1 for explanation.
Whitley & Sikora (1970), studying the effect of three toxic substances on the respiration rate of tubificids, found that the respiration function was affected very little by nickel, inhibited by lead and stimulated by pentachlorophenate. Our data on the effects of nickel and chromium on the respiration rate oftubificids apparently are not in accordance with Whitley & Sikora's (1970) data. But, considering the data on the effects of heavy metals on the respiration rate of fish (Jones, 1964), those of Whitley & Sikora (1970) cited, and the data from our experiments, one could state that, in general, the interpretation of the results of the respiration bioassay is difficult unless the parameters of the survival tests are defined under the same conditions (abiotic and biotic factors) at least at the short exposure.
It is obvious that the toxic substances in the acute lethal range of concentrations might cause an inhibition of the respiratory processes of tubificid worms (results of Whitley & Sikora for lead, our data for copper, cadmium and mercury). On the other hand, zinc, chromium and nickel at the same range of concentrations cause an increase in oxygen consumption during the six hours of the experiment.
98
L BRKOVI(~-POPOVI(~, M. POPOVI(~
The direction and significance o f the deviation o f the respiratory rate from the normal, under the influence o f concentrations o f metals which are not lethal (mercury, c a d m i u m a n d copper), c a n n o t be clear without d a t a on the effect o f the c o n c e n t r a t i o n s mentioned on life span, growth a n d other biotic characteristics o f the species tested. O u r results indicate that the alteration o f the respiration rate used as an isolated p a r a m e t e r has limited significance in the a p p r e c i a t i o n o f sublethal concentrations. But, when used in c o m b i n a t i o n with other results o f toxicity effects, it is a valid p a r a m e t e r , even if the c o m p e n s a t o r y and t e m p o r a r y reactions are in question.
ACKNOWLEDGEMENTS
W e wish to thank Professor D r Hrvoje Ivekovic for his helpful suggestions a n d great s u p p o r t during our investigation and also The Republic Association for the Scientific W o r k o f SR B. and H. which financed this study.
REFERENCES
DORN, P. (1974). The effects of mercuric chloride upon respiration in Congeria leucophaeta. Bull. Environ. Contain. & Toxicol., 12, 86--91. JONES, J. R. E. (1964). Fish and river pollution. London, Butterworths. O'HARA, J. 0971). Alterations in oxygen consumption by bluegills exposed to sublethal treatment with copper. Water Res., 5, 321-7. WALDEN, C. C., HOWARD,T. E. 8~. FROUD, G. C. (1970). A quantitative assay of the minimum concentrations of kraft mill effluents which affect fish respiration. Water Res., 4, 61-8. WmTLEV, L. S. & SmORA, R. A. (1970). The effects of three common pollutants on the respiration rate of Tubificid worms. J. Wat. Pollut. Control Fed., 42, R57-R66.