Acute toxiciq of some heaa~y mehas to the shrimp Penaegs ms~odon ,

K. 0. Joseph, K. K. WsRnmi, B. I?. Gupta md M. Murdidha Central Iilsbtute of Braclashwater Aquaculture, 75, Sznthome High Road, R A. Puram, Chennan - 600 028, Ind~a

Static b~oassay tests for acute tonc~ty of five heay metals to the slinmp Penaeus monodon in braclnshwater med~urn (salinity 15 i 1 O ppt) were conducted The 90 h LC,o values of metals such as Cr, Zn, Cu, Cd and Hg were found to be 4 20,150,120,O IS and 0 03 ppm respecbvely for shrlmp of slze group 33-46 rnm Using the safe concentrabon factor of O 01, the allowable safe concelltrahon for Cr, Zn, Cu, Cd and Mg were O 042,O Ol5,O 012,O 0015 and 0 0003 ppm reapecbvely In order to asses the contamnabon ol heavy metals, water samples were collected from inflow, pond and discharge of shnmp farm In P u d ~ p A l areaof AndhraPradesli and Tuhcorir, areaof TmlNadu Exapt mercury t!c: concentrabon of other heavy metals were klow detechon level of the Instrument used Based on the LC,, values md derlved safe concentrahons, Tuhconn ~nflow seawater appeared to be safe at present levels of Mercury a.t 0 0003 ppm Key Words [Heavy metals, Acute torclaly, Penacus monoclora

Introduction The llicreaslng Imparment of coastal water

quality resulting from the discharge of doXeselc, agr~cultural and lndustnal wastes m coastal waters has affected the aquaculture profitabhty in certain areas (Feder~co et al). 1998), of which heavy metal pollution a recent Interest The addit~on of these metals through number of lndustr~al waste waters i~iclud~ng those from the textiles, leather tannmg, electropiatlng etc Into water bodies poses serious problems of m poss~ble entry Into the food cham (Khas~m and Nand Kumar, 1989) The mpact of heavy metal yollubon to coastal and estuarine areas could be substantld because of the vxiety of inputs and t h s can cause physiological defects to the aquatlc species (Callaway el al, 1998) Toxicological studies of the pollutants upon aquatlc orgmsms are very Importarit from the

evduation and abatement of pollut~on by prmhg rehable estmates of safe concentration from whlcin water qual~ty cnterla can be der~ved (Asnulah, 1981) Utllsabon of acute tox~city stuhes for rsesslng water quality can be employed by examnlng Werent Me stages of lnlportant aguatlc spec16 (NASBAE, 1973) Such bastc toxic~ty mformatm, pxtlcularly, on larvae IS necessary because, larvae are usually more sensluv? than adults aid the surv~val of larvae forms becomes questronable at concentrabon su~table to adult f o r n ~ (Conner, 1972) Hence, tile present study has been under taken to de te rme the acute effect of five heavy metals to the luveniles of Penaeus monodon (sue group 33-46 mm) m braciushwater mehum A study has ~ l s o been conducted to assess the heavy metals ln the coastal 1 aters m Andhra Pradesh and Tam11 Nadu

Materids and Methods view polnt of env~ronrnentai consequences Acute tox~cig stud~es offer substantial help in detectm, Chemicals and glass wares : E Merck

chemrcais (CuSO,, 5H,O, ZnSO,, 7H20, CdSO,, WgCJ, e-ma1 c~ba@tn nlcin

AQUACULT ~ o l . 3 (2) Acute toxicity of some heavy metals to the shrimp 144

m d K,Cr,O, were used. Metals stock solutions were by acidifyirlg with nitric acid. The determination cf and serial dilutio~~s of stock solutions were heavy metals was carried out by Atomic absorption

made with brackistiwater of 15 + 1.0ppt salinity to get spectrophometry (APM, 1989). Mercurywas analysed the desired concentrations for experiments. by cold vapour atomic technique 011 MS.

Rearing of animals : The test animals, I? Results and Discnssisse momdon of size group 33-46 mm were acclimatized b laboratory conditions in brackishwater (salinity 15k1.00 ppt) system for one week prior to the experiment and during acclimatization, they were fed with boiled egg pieces to avoid cannibalism. Feeding by natural plankton and other food was suspended N o days before the experiments.

Experimentation : Static bioassay test were conducted Following the standard method (MHW, 1989). The shrimps were exposed to metal concentrations for 96 h. Duplicates were run for each metal. Ten shnmps were used in each tank containing 75 1 brackishwater with a separate set of controls. Observations for nlortalitywere made every8 h intervah upto 96 h of experimentation. The criteria employed to find out mortality was absence of any movement when pored gently with a glas r d . 96 h LC, values were calculated using the method of Probit analysis (lieish and Oshida, 1987). The physico-chemical

The 96 h LC5,, values, 9 5 fiducial limits, LC,,, LC,,. slope function and 95% confidence lirnils obtained in probit method are give11 in Table 1. Percent mortality for different exposure times was plotted against the nletd concentrations to get the response curve (Fig. 1). The 96 h LC,, values of Hg, Cd, Cu, Zn and Cr for shrimr, of size group 33-46 mm were found - - to be 0.03,O. 15, 1.20, 1.50, 4.20 ppm respectively

Toxicity of the metals were compared using toxici? curves obtained by plotting changes in LC,, values with respect to different exposure times (Fig. 2). The rank order of toxicity of metals for Penaetes monodon juveniles was found to be Hg>Cd>Cu>Zn>Cr. The toxicity curve for mercury is steeper which indicates that mercury is the most pollutant followed by cadmium for shrimp R monodo~z as evidenced from the present study and previous reports for other aqut ic organisms (Selvakumar et a!, 1996;- Conner, 1972). Toxiciq

Table B : Acute toxicity of five heavy metals ofP nzmolk,n. .

cl~aracteristics of water during the experimentation curves for Cu, 2% and Cs indicate &at chromium is were water temperature 28 k 2OC, pH 8.5 5 0.2, ieasatoxic for &rimp6! nzmhn. dissolved oxygen 7.0 i 0.2 ppm, salinity 15 I ppt The LC, values showed gradual decrease with and to&% alkalinity 143 5 ppm. increase in lime (Fig. 2). En general the increase in

hdysis of heavy metals : Composite water prcerit m o a l i v was related to bath time and metal sampIescolIectedfromthes~ll~lplingsileswerepreserved concentrations. Th: highest mortality occurred

AQUACULT Vol. 3 (2) 1:. 0. Joseph ei a: 145

24 48 72 96

Time (Hours)

Fig. I : Response curve of heavy metals to I? nzonuh.

AQLIACULT Vol. 3 (2) Acute toxicdy of some heavy metals to the shrlmp 1 46

I I

Fig. 2 : Toxiclty c u m of heavy metals to II monodon.

between 48 and 96 hours especially in higher of CU, 0.2 pprnof Zn and 0.5 ppm of Cr for 24,48,24, concentrations of the metals. 48 and 48 hours exposure times respectively. Survival

In the present study, sutvival was observed rates subsequently started declining and after 96 hours, up to 0.005 ppm of Hg and 0.01 ppm of Cd, 0.2 ppm 100% mortality occurred at 0.07 11p111 of Hg and 0.45

ppm of Cd, 3 ppm of Cu, 3 pprn of Zn and 7.5 ppm of Cr respectively.

Copper was found to be more toxic than cadmium to the Australian shrimp Catlianassa australiensis (Ahsanullah et al, 1981). But in the present study, cadmium was found to be more toxic to 19 monodon juveniles than copper. It is to be noted that despite its acute toxicity, a prolonged exposure to 50 ppb of copper actually stimulates the growth of the shrimp I! indkus (Camel et a[, 1983).

Zinc is generally known as a mildly toxic metal as evidenced from the present study, it has been found to be less toxic to II monodon than copper and cadmium (Table 1).

The relative importance of acute toxicity tests with larval bioassay studies to derive soundwater quality criteria has been stressed by NAS/NAE (1973). In order to save the life of marine organisms, maximum permissible levels of the heavy metals were established by applying an application factor of 0.01 to 96 h LC,, values (Ahsanullah et al, 1981). tlccordingll; calculated safe concentrations for Hg, Cd, Cu, Zn and Cr were 0.3, 1.5, 12, 15 and 42 ppb, respectively.

As for mercury toxicity, due to its high toxic nature compared with other metals, there is no infonation avadable on the application factor. The USEPA has recommended the minimal risk concentration of 0.1 ppb, however NASmAE (1973) suggested that the Hg concentration of 0.1 ppb is hazardous in marine environment.

Result of analysis of heavy metals in coastal waters of Andhra Pradesh and Tamil Nadu indicate that only mercury was found in the inflow seawater of Rticodn, Tamil Nado. Heavy metals were beiow detection level in water samples collected from pond and discharge points of shrimp f a m in Tuticorin area of TWJ N d u and inflow, pond and discharge points of shrimp fan11

in Pudiparthi area of Andhra Pradesh. Based on the LC,, values and derived safe concentrations, %ticorin inflow sea water appeared to be safe at present level of

Mercurj at 0.0003 ppm.

Conclusion

The obtained experimental LC,, values provide data on comparative effect of pollutants and are useful in screening potentially toxic substances. From the present study, it may be concluded that among five metals studied, mercury is the most toxic and chromium is the least Studies conducted on assessment of heavy metals in coastal shrimp farm areas of Tuticorin in Tamil Nadu and Pudiparthy in Andhra Pradesh indicates that coastal i d o w water is safe to the shrimp I! monodon. However, further studies are required in the accumulation and depravation of heavy metals in the body of the animal.

Acknowledgement

Authors are thankful to Dr. G. R. M Rao, Director, Central Institute of Brackishwater Aquaculture, Chennai for providing facilities and his encouragement. Financial assistant from ICAR, New D e h (At Cess Fund) is gratefully acknowledge.

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