METAL CONTENT IN SEA WATER AND SHELL NACRE OF PERNA I r I R I D I S FROM EAST COAST OF INDIA

2.1. Introduction

2.2. Results 2.2.1. Recovery and reference mntrrinl 2.2.2. Metal concentrations in sea wntcr

and metnl content in shell nacre

2.2.3. Relationship between the metal content in shell nacre and metal concent.ration in sea water

2.2.4. Site-level discrimination 2.2.5. Observations on metal content and

physical parameters of the shell

2.3. Discussion 2.3.1. Metal bioconcentration in shell 2.3.2. Relationship between :

a. The metal content and s h c l l measurfmeo ts

b. Wi thin she1 1 measurements

2 . 1 . INTRODUCTION

The bivalve shell is a complex organic/inorganic system

oonnintinP of two oaloified doroo-ventrnl valvoa O O V H ~ R ~ by an

organic layer. The periostracum's main role in marine

bivalves is to act as a support and substrate for the initial

nucleation and crystal growth of the calcareous shell. This shell

conaists of calcium carbonate crystals and a small amount of

organic matrix organised into two structural components, an outer

prismatic calcitic layer and an inner aragonite layer. The matrix

is structurally associated with shell crystals and is considered

to play an important role in nucleation, growth inhibition,

orientation, size regulation and/or polymorphism of crystal

(Kawaguchi and Watabe, 1 9 9 3 ) . Like the shell, the mantle

epithelium greatly overhangs the body, and it forms a large sheet

of tissue lying beneath the valves. Various cells present in the

mantle edge is responsible for shell secretions. The shell

secretion occurs within the extra pallial space in which the

mantle epithelium secretes the extrapallial fluid. The calcium

carbonate and the organic matrix are deposited from the pallial

fluid excluding where the muscles attach the two valves

to~ether.(Lingard, 1 9 9 2 ) . The actual sequencing of different

structural shell components, i.e., periostracum layer - > Cnlcite

4 5

layer - > nacreous layer is determined by different regions like

mantle matrix, mantle edge, etc., on the epithelium (Bourgoin,

1990). The cost of calcification/formation of this shell would

equal 6% of the total respiratory losses but would be equivalent

to 75% to 410% of energy invested in somatic growth and

reproduction (Palmer, 1992).

Taylor et al. (1969) defined seven main categories of shell

structure in which calcium carbonate crystals differ in their

shape and orientation. These structures occur as distinct

mono-minerallic layers within the bivalve shell. The pallial

myostracum consists of irregular aragonite prisms nnd separates

the calcitic and nacreous layers. The outer layer of the shell is

categorised as prismatic calcites and consists of columnar

prisms, polygonal in section and upto 50 mp long arrhnged in

sheets, like rows. The inner nacreous shell layer consists of

tablet- like aragonite crystals 5,um thick, deposited in regular

layers parallel to the shell interior (Bourgoin, 1988). The size

of the microstructural units is the most significant factor in

determining the mechanical ropert ties of the shell (Taylor and

Layman, 1972). Thus, the prismatic structure consists of small

sheet-like units, where as in nacreous structure the individual

crystals are the largest units present (Bourgoin, 19881.

46

Nacre is distiguished from other molluscan structural

materials both by being stronger and by having a flat topped

stress-stain curve. This feature of the curve gives a clue to

another property of nacre, that is, to some extent tough. The

plates of nacre are bound laterally by other plates, that have

butted up against (Currey, 1988). Cracks developing at the nacre

would have their energy dissipated at many crystal boundaries,

where as in the prismatic layers, there will be a tendency for

cracks to travel along boundaries of the larger units of the

structure (Bourgoin, 1988). In addition the cracks travelling

into nacre from another structural type are bought to halt at the

nacre (Currey, 1988).

The pallial fluid that secretes various components of shell,

which consists the constituents (calcium carbonate and organic

matrices) required for bio-mineralisation, also contains

substances such as trace elements assimilated from the water by

the organism. The metal enrichment in shells normally occurs in

two different processes:

a. Active accumulation of trace metals like zinc, cadmium,

copper, lead, manganese and cobalt, are regulated by

metabolic functions which ultimately result in the

integration of metal into the shell matrix. Such elements

4 7

may be bound directly with various shell structural

components like organometallic pigments, calcium carbonate

crystals or alternatively may be incorporated within the

organic lattice (Lingard, 1992; Struesson, 1976; Fox, 1966;

Babukutty and Chacko, 1992).

b. Passive enrichment is mainly adsorptive and taking place on

surfaces exposed to sea water (Shimizu et al., 1971;

Struesson, 1976). The nature of adsorptive processes, the

complexation capacity of shell proteins, ionic radii of

metals, genetic variability of the organism etc., govern the

uptake of metals into the shells independently or jointly

(Carell et al., 1987; Chester and Elderfield, 1967; Segar et

al., 1971; Bertine and Goldberg, 1972; Struesson, 1984;

Carriker et al., 1980; Al-Dabbas et al., 19841 .

Trace metals passively adsorbed into the shell surface

cannot be differentiated from those actlvely incorporated by the

assimilation of the organism. The periostracum and calcite layers

are exposed to water column and therefore adsorb metals from the

medium. Due to passive adsorption processes, shell as a whole

does not indicate the metabolically deposited trace metals

(Keckes et al., 1968; Romeril, 1971). In addition, Chipman and

Schommers (1968) have attributed the presence and absence of

4 8

metals on periostracum to the presence of micro-organism, showing

the influence of epibiotic organisms on metal content, on the

outer surface of the shell. The apparent variability in metal

composition of shell can often be traced to poor and non-uniform

shell treatment with periostracum (Babukutty and Chacko, 1992;

Rosenberg, 1980). In turn, the extrapallial space is effectively

isolated from the outer environment (Chetail and Krampotz, 1982).

Since the incorporation of trace metals into the shell matrix

accompanies shell formation, they must have been assimilated by

the organism itself (Wilbur and Saleuddin, 1983). Shell

formation being a gradual and continuous process, the

relationship between trace metal concentrations ir~ the nacre and

the environment is more consistent.

The shell necre consists of two components that are

potential binding sites of metal namely the organic matrix and

crystal lattice of calcium carbonate. The first adsorption onto

the organic matrix is from the pallial fluid, thereby functioning

merely as a sink for second site of metal incorporation. In such

a case, the heavy metals act as a substitute for calcium ions and

are actively incorporated into the crystal structure (Lingard,

1992). Though majority of the metals are bound to crystal

lattice, the concentration depends on the organic-crystal ratio

4 9

(~ingard, 1992). Since majority of the metals are crystal lattice

bound and these crystals are deposited gradually, the shell nacre

should provide a reliable chronological index of metal-exposure

with no significant post-depositional mobility occurring.

Bivalves have the ability to accumulate and concentrate

heavy metal to levels of several orders of magnitude above those

found in their environment. Shells which are preserved in the

geological time-scale may retain a record of environment.al levels

of metals (Koide et al,, 1982; Carrel1 et al., 1987). The shell

analyses can ascertain the metnl concentrations as a consequence

of the anthropogenic activities (Bertine and Coldberg, 1972). In

various studies on radionuclides (Guary and Fowler, 1981;

Miramand et al., 1980; NAS, 1980), the contents wcre observed to

be stored with re'entively from weeks to years.

The utilization of shells as indicators for metal pollution

monitoring in marine waters can offer several advantages over

that of soft tissues. Clearly they are more readily maintained in

the laboratory for longer periods before assay. As a consequence

of longer biological half lives of metals in shell and perhaps of

relatively uniform pumping of metal from soft-tissues to shell

(paralleling shell growth), the shell may be a better recorders

of environmental levels of contaminants (Chow et al., 1976; Koide

5 0

et al., 1982; Bertine and Goldberg, 1976). Besides the obvious

advantages associated with shell analyses such as by-passing

de~uration times and refrigeration of samples, bivalve shell has

already proved useful in reconstructing the historical trace

metal levels over tens (Lindh et al., 1988), hundreds (Carrel1 et

al., 1987) or even thousands of years (Bourgoin and Risk, 1987).

Segar and co-worker8 (1971) have studied elemental

composition in shells of some bivalves and have observed that

there was lesser taxonomic variation in content of some metals in

the shells of various bivalves. The cadmium content was between

0.04 ppm to 0,96 ppm; copper was betweer1 0.38 to 3.0 ppm; lead

was in the range of 0.40 to 2.0 ppm. Zinc (0.04 - 160 ppml,

aluminium (76 - 430 ppm), manganese (2.0 -20 ppm) and iron (15 -

1,600 ppm). Rertitre and Goldberg (1972) in their st.udy on the

shell of Mytilus edulis recorded iron (8.9 ppm), cobalt (0.029

ppm), antimony (0.022 ppm), zinc (0.059 ppm), selenium (0.046

ppm), silver (0,006 ppm) and chromium (0.01 ppm), from ~elgian

coast. Koide et al. (1982) recorded various metals like copper,

cadmium, zinc, lead, silver and nickel along with actinide

elements namely plutonium and americum in mussel shells collected

from east, west and gulf coasts under U . S . Mussel Watch

Programme. 24 and 239t240p~ ratio in M.californianus and in

5 1

~.edulis were in ranges of 0.8 - 5.8 ppm and 0.3 - 1.0 ppm

respectively. There were markedly higher concentrations of lead

(4.65 PP~), copper (2.68 ppm), zinc (7.52 ppm) nickel (1.02 ppm),

cadmium (0.74 ppm) and silver (0.042 ppm) in mussel from marine

sites adjacent to highly industrialized and polluted areas such

as San Francisco Bay and San Diego Bay. Bourgoin (1990) similarly

observed a definite site level discrimination in the lead content

in shell nacre based on gradient of pollution. Lead content in

shell nacre of M.edulis varied from 1.9 pg/g in fnrther. most site

to effluent discharge to 49.1 pg/g in site of discharge at

Belledune harbour, Canada. Metal content in shell of Villorita

cyprinoides from Cochin estuary, India was studied by Babukutty

and Chacko (1992). Along various sites of the estuary cadmium,

zinc, copper, lead, manganese and cobalt showed a range of 3.21 - 3.61 pg/g, 3.46 - 4.64 pg/g, 36.76 - 40.11 /Jg/g, 20.19 -

35.99pg/g and 38.74 - 43.35 pg/g respectively. Observations by Fiacher (1983) and Lobe1 et al. (1991) have

shown that the elemental concentrations in the shell were related

to weight and dimensions (length, weight and width) of the shell.

The applicability of the above variables as indicators of metal

content was also suggested. The measurements (length, width,

height and weight) are of importance in calculating the condition

5 2

indices, a commonly used tool in describing the physiological and

nutritive status of bivalve molluscs (Roper et al., 1991; Lobe1

et a1 . , 1 9 9 1 ) .

Keeping the above observations in view, it was aimed to:

1. Assess the trend in the metal contamination in the four

sites along East coast of India, selected on basis of the

extent of urbanisation and industrialisation. Preliminary

indications from literature has shown high concentrations of

metals in coastal waters in the above areas, the sea water

analyses of the metals of interest (aluminium, lead,

cadmium, copper and zinc) substantiating the same

2 . To assess the applicability of shell nacre as an indicator

of spatial variations in metal contamination. Shell nacre

was used as an indicator because of various advantages

mentioned earlier and shell nacre was selected as a viable

component to indicate the biological accumulation of metals.

3. A study of the relationship between the metal content and

the physical measurements of the shell and the relationship

within the physical dimensions was attempted.

2 . 2 . RESULTS

The metals namely aluminium, lead, cadmium, copper and zinc

53

were estimated in the sea water and shell of perna v i r i d i s along

the four sites of East ooast of India. The validity of the method

used for metal estimation was verified by conducting recovery

studies and certified reference material analysis.

2.2.1. Recovery pcJ reference material

The data (table 2.2.la) on the recovery studies of lead and

aluminium in tiseue and shell nacre of Perna v i r i d i s showed 98 - 100 percent recovery. While in the case of cadmium, the percent

recovery in the above components was about 95 - 96 percent

Table 2.2.1a

Recovery studies of aluminium, lead and cadmium in different tissues and shell nacre of P. v i r i d i s ,

Item Metal original metal added metal percent content (mg/g) content (mg/g) recovery

Shell A1 Pb Cd

Dig. A1 gland Pb

Cd

Gills ~l 0.226 Pb 0.009 Cd 0.005

Mantle ~l 0.120 Pb 0.001 Cd 0.001

The comparison of measured aluminium, cadmium, copper and

zinc in National Institute of Environmental Sciences

(NIES-Japan) Certified Reference Material (CRM) No. 10 B (rice

flour - unpolished) with the certified and reference values

indicated that the method followed was accurate and this data

helped in validating the method followed . The comparative values of certified data and estimated data for reference materials is

represented in the following table (2.2.lb):

Table 2.2.lb

CRM values.

CRM metal CRM values(vg/g) estimated valuea (pg/g)

Rice A1 2.0 + 0.08 2.0 + 0.08 flour Cd 0.32 + 0.02 0.3 + 0.04

C u 3.3 + 0.2 2.9 + 0.6 Zn 22.3 2 0.9 20.8 + 1.2

2.2.2. Metal concentrations in sea water and its content in shell

nBCre

a.Aluminium (Table 2.1; Fig. 2 - 1 1

SEA WATER:

Aluminium concentrations were high in site 2 compared to all

other sites except in the month of December in which aluminium

66

was higher in site 1. In site 1 , the concentrations ranged from

1 0 6 . 5 Pg/l to 3 0 4 . 2 Pg/l. The lowest observed was in the month of

May and highest in January. In site 2 , the concentrations ranged

from 194.5 to 3 7 3 . 5 pg/l with the lowest in the month of May and

higheat in January. In site 3, the range was from 106 pg/l in May

to 2 2 3 pg/l in October. In site 4 , tho lowest concentration

observed was 1 8 7 . 0 pg/l and highest concentration was 2 4 1 . 6 pg/l

observed in October and December respectively. No definite

pattern was observed in the fluctuation in aluminium

concentrations over a period of one year. The background

concentration of aluminium in natural sea water was observed to

be 1 pg/l (Sackett and Arrhenius, 1 9 6 2 ) which was far lower than

the concentrations obtained in the present study.

SHELL:

Aluminium is significantly higher in ahcll tt~or~ i r r sea wutcr

at all sites except site 4 . In site 1 , aluminium was observed to

be the lowest in the month of May and the highest in the month of

January with content ranging from 1 6 7 . 1 pg/g to 4 8 7 . 2 pg/g. The

average concentration was observed to 3 6 2 . 8 pg/g. Aluminium

Content in shells from site 2 ranged from 3 2 5 . 2 ,Ug/g to 5 9 0 pg/g

with lowest in the month of May and highest in the month of

October. The average was 4 7 9 . 1 pg/g in this site. In site 3, the

6 6

range was from 2 7 4 . 4 Pg/g to 6 0 6 . 6 pg/g with an average of 4 0 9 . 9

pg/g. The minimum content of aluminium in shell was recorded in

the month of March and maximum was in the month of October. Site

4 had a range from 1 0 3 . 1 pg/g in the month of January to 2 1 0 pg/g

in the month of December, with an average of 127.3 vg/g. In all

sites, the trend in aluminium content in the shell nacre was

similar to dissolved aluminium concentrations in nea water.

b . L e a d (Table 2.2; Fig. 2.2)

SEA WATER:

Lead concentrations was observed to be very high in site 2

compared to all other sites. In site 1, the concentrations ranged

from 1 . 2 pg/l to 1 3 . 2 ~ g / 1 , with the lowest in the month of

October and the highest in the month of August. In site 2 , the

concentration8 of lead was in the range of 1 3 . 4 pg/1 to 1 9 . 4

pg/l. The highest concentration was observed in the month of

December and the lowest was in the month of October. In Site 3,

the lead concentrations ranged form 2 . 0 to 4 . 0 pg/l. the lowest

being in thc month of March and the highest in the month of

January. In site 4, the concentrations ranged from levels below

the detectable limits ( < 0 . 0 0 9 pg/g) to 4 . 2 1 The

concentration was lowest in the month of Mnrch and higheat irl the

month of December. During this month, it was observed to be at

5 7

higher concentrations than site 3. Schaule and Patterson ( 1 9 7 8 )

observed background concentration of Lead to be of 0 . 0 0 5 pgll -

0 . 0 1 0 pg/1 which is far lower than the observations made during

this study at all the above sites.

SHELL:

In the case of shell also, the metal content was observed to

be higher in site 2 compared to all other sites. In site 1 , it

ranged from 1 . 0 pg/g to 4 . 8 pg/g with an average of 3.6 pg/g. The

highest was in the month of December and the lowest was in the

month of March. In site 2, the lead content was the highest in

month of August and lowest in October with 0.9 pg/g and 5.3 pg/g

respectively. The average metal content was 6 . 9 pg/g in this

site. Lead content in shells from site 3 had a range from 1 . 1

pg/g and 1 . 7 pg/g. The lowest was in the month of May and the

highest was in January and August. The average concentration was

1.4 pg/g in this site. In site 4, the lend content ranged from

levels below the detectable limits ( ( 0 . 0 0 9 pg/g)to 1 . 7 pg/g. The

lowest observation which was non-detectable was observed in the

month of August. The average was 1 . 5 pg/g in this site. At all

sites, there was a close similarity between the lead

concentrations in shell and that of the dissolved metal in sea

water.

5 8

C . Cadmium (Table 2.3; Fig. 2.3)

SEA WATER:

The concentrations of Cadmium was highest in site 1 in the

month of January. The range of cadmium concentrations in this

site was from 1.9 Pg/l to 4.6 pg/l with an average of 2.9 pg/l.

The lowest concentrations was observed in the month of May. In

Site 2, the concentration ranged from 1.9 pg/l to 3 . 7 pg/1 with

an average of 2 . 8 pg/l. The highest concentration in this site

was observed in the month of December and the lowest was in the

month of May. Site 3 had a range of cadmium concentrations from

0.5 to 1 . 0 pg/l with an average of 0 . 8 pg/l The lowest

observation was both in the month of May and October, the higheat

concentrations was observed in January and December. The

concentrations of cadmium in site 4 ranged from 0 . 6 pg/l to 0.9

pg/1 with an average of 0 . 7 3 pg/l and the highest and lowest

observations in January-December arid March respectively. The

background oorlcentration of cadmium as observed by Boylc et al.

( 1976 ) was 0 . 0 1 pg/l in natural sea water. The concentrations of

cadmium observed in all the sites exceeds the above background

levels.

SHELL :

Cadmium content in shell was observed to be highest in site

59

1. The range in the shells from this site wan between 0.9 to 1.9

Pg/g with an average of 1 . 6 pg/g. The highest wan in the month of

January and the lowest in the month of ~ugust. site 2 had a range

of 0.8 to 1.2 /Jg/g with an average of 0.9 pg/g and the maximum

and minimum in January and August respectively. ~n site 3, the

range was between 0 . 2 pg/g to 0 . 4 pg/g with an average of 0.3

pg/g. the lowest was in the month of May arid the highest wtls in

the month of January. Site 4, had a very narrow range in cadmium

content of shell. The minimum was below detectable limit ( < 0.06

pg/g) in the months of May and October and the maximum was 0.3

pg/g in the months of January, August and December. The average

was 0.28 pg/g. Cadmium also showed no similarity between the

content in shell and the concentrations in sea water.

d. Copper (Table 2.4; Fig. 2 . 4 )

SEA WATER:

Concentrations of copper was observed to be higher in site 1

and site 2 followed by site 3 and 4. copper ranged from 58.8 pg/1

to 83.9 pg/l in site 1 with an average of 7 4 . 6 pg/1. The lowest

Concentration was recorded in the month of May and the highest

was in the month of ~ugust. In site 2 , the concentrations of

copper ranged from 72 to 88.2 /J8/1. The copper was low in January

and high in the month of ~ugust. The concentrations of copper in

6 0

n i t o 2 did nt>t. rollow nny ~ p e o i f i c ~,rlt.t.orrl d u r i t l ~ t . 1 ~ ~ ~ n t . ~ d y

period. Site 3 has copper concentrations in the range of 29.4 to

35.1 pg/1. The highest was observed in the month of January and

lowest was in the month of May. Site 4 has lowest concentration

of copper than all other sites except in the month of December,

in which the copper concentrations were slightly higher than

site 3.

SHELL:

Copper content in shell was observed to be highest in site 2

compared to all sites. In site 1 , the Copper content ranged from

9.3 pg/g to 19.6 pg/g with an average of 13.6 pg/g. The highest

was observed in the month of January and the lowest in the month

of August. It is observed that the trend in the copper content to

ha; not followed the concentrations of dissolved copper in the

medium in this site. In site 2, the range of copper content was

from 17.6 pg/g to 28.1 pg/g with highest in March and lowest in

October. The average was 21.6 pg/g. The trend between shell

content and the concentration in sea water was similar to that of

site 1. In site 3, the copper content in shell ranged from 10.7

?8/g to 5.2 pg/g with an average of 7.7 pg/g. The highest was

observed in the month of January and lowest was in May. he

copper content in shell followed the trend of the concentrations

6 1

in sea water at this site. Site 4 hod rnnge of 2.0 pg/g to 3.5

pg/g with an average of 2 . 7 pg/g, The lowest woe observed In the

month of August and the highest in the month of January. No

similarity was observed between the copper content in the shell

and the sea water.

e , Zinc (Table 2.5; Fig. 2.5)

SEA WATER:

The concentrations of Zinc was observed to fluctuate in wide

ranges at all sites. In site 1, the range of the concentrations

was from 300.5 to 358.1 pg/l with the lowest in the month of May

and the highest in the month of December. The average

concentration was 338.9 pg/l. In site 2, the lowest coriceritratiori

was 100.2 pg/1 in the month of May and highest concentration was

3 ) s pg/l in the month of December. The average concentration was

24.9 pg/l. In site 3, the concentrations were almost equnl to

site 1 and had a range from 300.0 pg/l to 354.0 pg/l and an

average of 333.1 pg/1. The month of May had lowest concentration

and the highest was observed in December in this site. In site 4 ,

the range of the concentrations of zinc was from 137.1 to 182.2

Pg/l with an average of 158.4 pg/l. No definite pattern based on

monsoon was observed in any of the sites.

SHELL:

zinc content was observed to be higher in site 1 compared to

all other sites. The range was from 80.0 to 1 2 5 pg/g with an

average of 9 3 . 6 pg/g. The maximum amount of zinc was in the month

of December. In site 2 , the range was from 10.0 pg/g to 87.1 pg/g

with an average of 6 4 . 9 pg/g. Shell in the month of March had

minimum of zinc content and maximum was recorded in the month of

August. Site 3 had a range from lowest of 13.0 pg/g in the month

of March to highest of 71.8 pg/g in the month of December with an

average of 4 5 . 3 pg/g. Zinc content in shell from site 4 was in

the range of 42 pg/g and 6 9 . 5 pg/g with an average of 5 5 . 6 pg/g.

The maximum was in the month of December and minimum was in the

month of January. There was no similarity between the zinc

co:itent in shell nacre and dissolved zinc concentrations in the

seawater during the study period.

2 . 2 . 3 . Relationship between the metal content in shell nacre 4

dissolved metal concentrations eea w!~..k!l

Correlation analysis on the relationship betwce!~ the allell

metal contcnt with that of Bca wutcr concentrttlioris hnve shown

that there was a definite metal to metal variations in

bioconcentration.

Table 2.6

correlation coefficient values between metal content in shell nacre and the dissolved concentrations of metals in sea water.

Site 1 0.93 0.98 0.84 0.4 1 0.56

(>0.005) ((0.001) ((0.2) ((0.5) ((0.5)

Site 2 0.95 0.97 0.34 0.61 0.76 00.01) ((0.001) ((0.5) ((0.2) (<0.1)

Site 3 0.98 0.90 0.74 0.88 N S ()0.01) (<0.01) ((0.1) ((0.02)

Site 4 0.65 0.47 N S 0,77 0.37

((0.2) ((0.5) (<0.11 ((0.51

2.2.4 Site level discrimination

The background values (ppb) in oceanic sea water and fresh

water for the heavy metals (aluminium, lead, cadmium, copper and

zinc) is given in table (Table 2.7).

The site level differences between the highly urbanised and

industrialised sites viz., Vishakapatnam (Site 1) arid Madras

(Site 2); moderately urbanised/ industrialised viz., Pondicherry

(Site 3) and site with low population density viz., Porto Novo

(Site 4) oould be distinguised in thia 8turl.v. Witti mcnn

6 4

concentration values (in parentheses) from different sites for

the metal studied, differences between sites is shown in the

table ( 2 . 8 ) taking the highest value of the each metal content

among the sites as 100 X or maximum effect value.

Table 2.7 .

Background values.

t Metal Fresh watere Sea water Reference

Aluminium < 30 0 .85 Hydea, 1979 Lead 0 . 2 0 .001-0 .15 Schaule and

Patterson, 1980 Cadmium 0.07 0.015-0.118 Romanov arid

Copper 1.8 0 .092-0 .24 Rrulnnd eL al., 1979 Zinc 10 0 .007-0 .04 B K . U ~ ~ I I I ~ trL al., 1979

B - Forstner and Wittmann ( 1 9 7 9 ) ; * - Bryan ( 1 9 8 4 )

In a nutshell, of the two industrialised uit,es, site 2

(Madras) had more amount of dissolved aluminium, lc!ud and copper

i l l scn wat.o~* and also i r i ~ l \ c l l I , w l h i I f . nitc? 1

(Vi~haka~atnom) had higher concentrations of cudmiurn and zinc. Of

the other two sites studied namely Pondicherry (site 3) and Porto

Novo (site 4) lead, cadmium, copper and zinc were observed to be

higher in sea water and aluminium, cadmium and copper in shell

65

nacre in site 3. Though site 4 had no industrial locations,

dissolved aluminium in sea water and lead and einc in shell nacre

were higher than site 3.

Table 2.8

Site level variations (Sh - shell; Sw - sea water).

Aluminium Sh 75.7 100 85.5 26.6

Lead Sh 51.0 100 20.6 20.9 (3.55) (6.96) (1.43) (1.46)

Sw 48.2 100 , 17.4 16.4 (8.63) (17.88) (3.12) (2.94)

Cadmium Sh 100 65.5 20.7 18.9

Copper Sh 62.3 100 05.6 12.3 (13.56) (21.63) (7.7) (2.68)

Sw 92.4 100 38.5 27.5 (74.55) (80.7) (31.23) (27.17)

Zinc Sh 100 69.4 48.4 59.46 (93.6) (64.9) (45.3) (55.7)

Sw 100 73.6 98.5 46.9 (338.9) (249.0) (333.1) (158.9)

2.2.5. Observations on metal content physical parameters of

the shell -- The metal content of aluminium, lead and cadmium of all the

shells correlated with the physical measurements like width,

length, height and weight of the shell. The aluminium content of

the shell was observed to be significantly related to the shell

weight, where as lead and cadmium content were related to the

width:height ratio of the shell (table '2.9). ' The independent

components of shell namely the length, width and height were

correlated with shell weight and it was found that length and

height were related to the weight (r2 = 0.68 p < 0.001 and r2 =

0.57 p < 0.001). However, no relationship was observed between

width and height of the shell.

Teble 2.9

Correlation coefficient values between metal content in shell nacre and physical variables (n = 166) [P ( 0.51.

variable aluminium lead cadmium --

Shell weight 0.54 N 3 N S Width:Height N S 0.65 0.63 ratio

From the above results on the studlea on the metal content

6 7

in sea water and shell nacre from four sites during a one year

period the following observations were arrived at:

I) a. Sea water :

Al: site 2 > site 1 ) site 4 > site 3

Pb: site 2 > site 1 ) site 3 > site 4

Cd: site 1 > site 2 > site 3 ) site 4

Cu: site 2 > site 1 > site 3 > site 4

Zn: site 1 ) site 3 > site 2 ) site 4

b. Shell :

Al: site 2 > site 3 > site 1 > site 4

Pb: site 2 > site 1 > site 4 > site 3

Cd: site 1 > site 2 > site 3 > site 4

Cu: site 2 > site 1 > site 3 > site 4

Zn: site 1 ) site 2 > site 4 ) Site 3

c. All sites:

Shell : A1 > Zn > Cu > Pb > Cd

Sea Water : A1 > Zn > Cu > Pb > Cd

1I)a. A1 < - - - - > shell weight

Cd < - - - - ) width:height ratio

Pb < - - - - ) width:height ratio

b. Length and height < - - - - > weight of the shell

Width < - - - - > weight of the shell

Table. 2.1.

Dissolved aluminium selected deviation)

aluminium concentrations in sea water (pg/l) and content in ahell nacre of Perna vlridls (pg/g) from sites along East coast of India (SD - standard

Sampling Site 1 site 2 site 3 site 4

Period (VZL) (MAS ) ( PDY ) (PNO)

Sea water

Jan 3 0 4 . 2 354.7 115 .6 2 3 2 . 1

Mar 2 3 0 . 1 3 2 6 . 2 1 4 3 . 2 211 .0

May 106 .5 1 9 4 . 2 143 .2 214.9

Aug 1 8 5 . 2 268 .6 1 6 5 . 2 2 0 0 . 1

Oct 2 9 8 . 2 373 .5 223 .0 187 .0

Dec 300.4 265 .4 2 0 2 . 1 2 4 1 . 5

Mean 2 3 7 . 4 2 9 7 . 1 159 .2 214 .4

S D 7 3 . 1 6 1 . 1 42 .7 1 8 . 3

Shell nacre

Jan 4 8 7 . 2 5 3 1 . 2 2 9 7 . 0 1 0 3 . 1

Mar 364 .4 5 0 4 . 0 274 .4 1 1 4 . 0

May 1 6 7 . 1 3 2 5 . 2 3 7 4 . 4 1 2 0 . 0

Aui3 3 0 0 . 2 4 3 6 . 1 4 3 6 . 2 1 1 3 . 2

Oct 489 .9 5 9 0 . 0 5 8 9 . 6 1 0 3 . 4

Dec 373 .0 4 8 8 . 2 4 8 8 . 0 2 1 0 . 0

Mean 362 .8 4 7 9 . 1 409 .9 1 2 7 . 3

SD 110 .1 82 .9 1 0 9 . 1 37 .6

Figure. 2 . 1 .

~iaeolved eluminium concentrations in sea water (pg/l) and aluminium content in shell nacre of perna viridis (pg/g) from Rrlnot .nd n i t , e ~ n l ~ n l t F.nflt O O R R ~ o f I n d i n ( r v n l u o in parentl~e~es).

Vishakapatnam Madras (slte 1) (site 2)

un nbf eh-I! B l w . nbt m nhsN

Pondicherry Porto Novo (site 3) (site 4)

Table. 2 .2 .

~iesolved lead concentrations in eea water (pg/l) and lead content in shell nacre of Perna v l r i d f s (pg/g) from selected sites along East coast of India (SD - standard deviation; * - non-detectable).

Sampling Site 1 site 2 site 3 site 4

Period (VZL) (MAS ) ( PDY ) ( PNO

Sea water

Jan 11 .9 1 7 . 8 4 . 0 2.9

Mar 1 . 2 17 .8 2.0 ND'

May 5 . 7 1 8 . 9 2 . 1 1 . 5

Aug 1 1 . 2 2 0 . 0 3.5 2.9

Oct 8 . 6 13 .4 3 . 5 3 .2

Dec 13 .2 1 9 . 4 3.6 4 . 2

Mean 8 . 6 17 .8 3.1 2 . 9

Shell nacre

Jan 4 . 8 6 . 9 1.7 1 . 6

Mar 1 .O 6 . 5 1.2 1 . 2

May 2 . 5 7.4 1.1 ND*

AW 4 .6 7.9 1 . 7 1.7

Oct 3.7 5 . 3 1 .4 1 .2

Dec 4.7 7.8 1 . 5 1.6

Mean 3 . 5 6.9 1 . 4 1 . 5

S D 1.4 0 .9 0 .2 0 .2

Figure. 2 . 2 .

~ieeolved lead concentratione in sea water (pg/ll and lead content in ahell nacre of Perna v i r j d i a ( p g / g ) from seleoted sites along East coast of India Ir value in parentheses)

Vishakapatnam Madras (slte 1) (slte 2)

Pondicherr y Porto Novo (site 3) (eft6 4)

Table. 2.3.

Dissolved cadmium concentrations in sea water (pg/l) and cadmium content in shell nacre of Perna viridis (pg/g) from selected sites along East coast of India (SD - standard deviation; i - non-detectable).

Sampling Site 1 site 2 site 3 site 4

Period ( VZL) (HAS) ( PDY ( PNO )

Sea water

Jan 4.6 3.2 1 .O 0 . 9

Mar 2.3 2.7 0 .9 0 .5

May 1.9 1.9 0.5 0 .8

Auii 2.5 2.5 0 .6 0.6

Oct 2.5 2.8 0.5 0 . 7

Dec 3 .8 3.6 1 .O 0.9

Mean 2.9 2.8 0 . 8 0.7

SD 0.9 0 .6 0 . 2 0 .2

Shell nacre

Jan 1.9 1 . a 0.4 0.3

Mar 1.8 1 .O 0.3 0.2 1

May 1.2 0.9 0 . 2 ND

Aug 0.9 0.8 0 .3 0.3

oct 1.2 0.e ND* ND*

Dec 1.7 0.9 0 . 3 0.3

Mean 1.5 0 .9 0.3 0 . 3

SD 0 . 4 1.2 0 . 1 0 .05

Figure. 2.3

Dissolved cadmium concentrations in sea water (pg/l) and content in shell nacre of Perne v i r i d i s (pg/g) from

selected sites along East coast of India (r value in parentheses).

Vishakapatnam Madras (site 1) (alte 2)

0unbm 1am1sh1L I 4

4 * 1

I

I

I I

0 0 Jen Mu M q r u g 0ol Dl0 Jan UDr Mnr *uo 011 D w

Pondicherry (alte 3)

Porto Novo (site 4)

Table. 2.4

Dissolved copper concentrations in sea water (pg/l) and copper content in shell nacre of Perna viridis (pg/g) from selected sites along East coast of India (SD - standard deviation).

Sampling Site 1 site 2 eite 3 site 4

Period (VZL (MA8 ( PDY ) (PNO)

Sea water

Jan 58 .8 7 2 . 0 3 6 . 1 3 5 . 1

Mar 7 5 . 9 8 0 . 2 29 .4 1 5 . 0

May 60.2 8 4 . 3 2 3 . 2 1 2 . 0

Aug 8 3 . 5 8 8 . 2 3 1 . 2 16 .4

Oct 8 5 . 0 8 6 . 2 3 3 . 5 17 .2

Dec 8 3 . 9 7 3 . 1 3 5 . 0 3 7 . 3

Mean 7 4 . 6 8 0 . 7 3 1 . 2 2 2 . 2

SD 11.1 6 . 2 4 . 1 1 0 . 1

Shell nacre

Jan 19 .6 2 5 . 2

Mar 1 4 . 1 2 8 . 1

May 1 0 . 8 20.5

Aug 9.3 18 .3

Oct 13 .5 1 7 . 6

Dec 1 4 . 1 2 0 . 1

Mean 13 .6 21 .6 7 . 7 2.7

SD 3 .2 3 . 8 1.8 0 . 5

Figure. 2 . 4 ,

i is solved copper concentration8 In sea water (pg/l) and copper content in shell nacre of Perna viridis (pg/g) from selected site6 along East coast of India (r value in parentheses)

Vishakapatnam (eke 1)

Madras (slte 2)

Jan UU Uly Ocl Doe I n n Mar Mv h a 001 Dee

Pondicherry Porto Novo (eke 3) (sltcr 4)

Table. 2 .6 .

Dissolved zinc conoentrations in aea water (pg/l) and zinc content in shell nacre of Perna viridis ( p g / g ) from selected sites along East coast of India (SD - standard deviation).

Sampling Site 1 site 2 site 3 site 4

Period (VZL) (MAS ) ( PDY ) ( PNO )

Sea water

Jan 3 4 9 . 2 123 .5 3 6 1 . 2 1 6 4 . 2

Mar 320 .4 1 0 0 . 2 3 4 8 . 0 1 4 8 . 0

May 3 0 0 . 5 2 9 8 . 2 3 0 0 . 0 1 3 7 . 1

AUK 3 5 6 . 1 3 4 5 . 0 3 3 0 . 1 1 6 4 . 5

Oct 3 4 9 . 2 3 2 9 . 2 315 .4 1 5 4 . 2

Dec 3 5 8 . 1 2 9 8 . 1 354 .O 1 8 2 . 2

Mean 338.9 249 .0 3 3 3 . 1 158 .4

S D 21 .2 9 8 . 6 2 0 . 0 1 4 . 2

Shell nacre

Jan 1 0 7 . 2 7 0 . 0 5 1 . 0 4 2 . 0

Mar 8 0 . 0 1 0 . 0 13 .0 4 9 . 8

May 8 0 . 6 6 5 . 1 4 6 . 5 66 .6

Au% 8 1 . 5 8 7 . 1 4 4 . 1 56 .0

Oct 8 7 . 2 82 .3 45 .4 6 0 . 0

Dec 1 2 5 . 0 7 5 . 2 7 1 . 8 6 9 . 5

- -

Mean 9 3 . 6 64 .9

Figure. 2 . 5 .

iss solved einc concentrations in sea water (pg/l) and zinc oontent in shell nacre of Perna v i r i d i s ( p a / # ) from seleoted sites along East coaet of India (r value in parentheses)

Vishakapatnam (site 1)

Madras (site 3)

380

100 f f l

1 0

IW tw

110

I W t w

80

0 0 Jan MY Ma7 Aul Oot 01. Jnn Mar Ma7 Auq 011 D.0

Pondicherr y Porto Novo (site 3) (site 4)

f f l I60

t W .

t w 10

0 J," M., M* Ivl Dot D.0

2 . 3 DISCUSSION

This study elucidates (a) the relationship between the metal

content in shell nacre and concentrations of dissolved metal in

sea water; (b) pattern of metals accumulated in the shell and

application of shell nacre as a appropriate component for

monitoring of metal content in bivalve indicator systems.

2 . 3 . 1 . Metal bioconcentration in shell

a. Aluminium:

Segar and his co-workers (1911 ) in their studies on metals

in various molluscs from Irish coasts have observed aluminium

around 76 ppm in shells of Mytilus edulis. Aluminium content in

other bivalves were in the range of 71 ppm to 430 ppm (Pecten

maximus - 190 ; Chylamys opercularis - 430; Glycymeris glycymeris- 420; Modiolus modiolus - 150; Cardium edule - 84; Mercenaria

mercenaria - 71). There is no other record on the aluminium

content in shells of marine bivalve to-date. It has been observed

by the above authors that there is lesser taxonomic variability

in aluminium content in shell. The present study, in a duration

o f one year, has recorded the aluminium content in the range of

103.1 pg/g (site 4 ) to 590 pg/g (site 2 ) .

Aluminium has no role involvement in the formation/structure

Of' bivalve shell. It may be presumed that the chemical

69

characteristic8 such as low density, good tensilo strength and

maleability might favour its accumulation in the shell structure.

Aluminium is presumed to compete with and substitute cat2 at the

cell membrane (Exley et al., 1991), and alter the stereochemistry

of accepting membrane for biomolecules (Womack and Colowick,

1979). Significantly high amount of aluminium was also found in

bones of patients with chronic renal failure and osteomalacia

indicating that aluminium substitutes calcium (Smeyers-Verbeke

and Verbeelen, 1988). Therefore, the possibility of the

substitution of aluminium to calcium in the crystal lattice of

the shell may be assumed.

b. Lead:

Lead conte~t in shells of marine bivalves were reported by

Segar et al. (1971) in M. e d u l i s (2.0 ppm), M. modiolus (1.9

ppm), 0 . g l y c y m e r i s (0.6 ppm), P . maximus (2.0 ppm), M.

mercenaria (1.7 ppm), Anodonta sps. (7.6 ppm) and C. e d u l e (3.0

ppm) from Irish coasts. Koide et al. (1982) reported the lead

Content in the range of 0.10 - 4.65 ppm in Mussel shell from U.S .

coasts.. M. e d u l i s shells from Dalhousie harbour was observed to

have lead content of 1.0 pg/g - 49.1 pg/g (Bourgoin, 1990). The

observations from the present study on Perna v i r i d i s shell nacre

has shown the lead content to be in the range of 1.0 pg/g to 7.9

70

pg/g taking all sites into account. Other observations in shells

of marine/estuarine bivalves from coastline of India have shown

that lead content in Villorita cyprinoides var, cochinensis

(shell wt. > 20 gms) was in the range of 38.5 pg/g to 39.0 pg/g

(Babukutty and Chacko, 1990). Studies on P. viridis from

Kalpakkam, east coast of India have recorded lead content of 3.81

pg/g in the shells (Wesley and Sanjeevnraj, 1983).

It has been observed that the lead in shell of bivalves

undergoes a isomorphic substitution with calcium (Lingard et al.,

1992) because of isoatructural similarity between lead carbonate

and aragonite (Babukutty and Chacko, 1992). Aragonites are known

to take up metal ions like lead which are larger than cat' ions

(Imaly, 1982). Lead is distributed in two components of shell

uacre (Lingard et al., 1992). In Elliptio complanata, a soft

water bivalve, 2.95% was observed in the organic matrix and

62.32% in calcium carbonate crystals. Shell is observed to

assimilate a factor of 0.32 of lead from tissues in the above

organisms, With high toxic nature of lead in the biological

system (Brooks and Rumsby, 1965)) the organism may respond to the

entry into the body by depurating the same towards external

medium or by immobilizing the same through deposition in the

shell structure.

7 1

C . cadmium:

Segar et al. (1971) reported the cadmium content in marine

bivalves P Ma edulis (0.95ppm), P. maximus (0.04 ppm) ,

~.glycymeris (0.03 ppm), M. Modiolus (0.03 ppm), C. edule (0,34

ppm), M. mercenaria (0.8 ppm) and Anodonta spa. (0.43). Mussel

shells from U.S.coasts were observed to consist 0.008 to 0.74

pg/g lead (Koide et al., 1982).

Observations in the present study of cadmium content in

P.viridis was in the range of 0.3 pg/g to 1.9 pg/g from all sites

studied. Bivalve (V. cyprinoides) shells from Cochin estuarine

ecosystem was reported to have 3.21 pg/g to 3.61 pg/g of cadmium

(Babukutty and Chacko, 1992).

Cadmium content in E. complanata is distributed within two

components like lead. Cadmium in organic matrix constitutes about

369 ng/g and in crystal lattice constitutes about 57 ng/g of the

total cadmium present in the shell. The higher partitioning of

cadmium in organic matrix of the shell nacre presumably may be

due to its higher absorption coefficient for oren~~ic molecules

(Campbell and Evans, 1986). Cadmium is assimilated in a lesser

quantity in shell than lead with a factor of 0.01 and substitutes

calcium in the crystal lattice similar to lead (Lingard et al.,

1992). Differences in distribution coefficients between cadmium

7 2

and lead may be explained partially by the fact that lead

undergoes isomorphic substitution for calcium more readily than

0 2 t 0 cadmium. (cdt2 = 1.14 A , Ca = 1.18 A', pb+' = 1.20 A )

(Lingard et al., 1992). In adult human patients, induced

disturbances in calcium metabolism accompanied by softening of

bones, fractures and skeletal deformities were noted showing the

influence of lead on the calcium (Friberg et al., 1974).

d. Copper:

Copper concentrations in various bivalve shells studied by

Segar et al. (1971) did not show any wide taxonomic variations.

The concentrations in P.maximus shells was 1.1 pg/g, C.

opercularis was 0.7 pg/g, C. glycymeris was 0.09 pg/g, M.modiolus

was 1.0 pg/g, M edulis was 2.0 pg/g, C. edule was 3.0 pg/g. M.

mercenaria was 1.7 pg/g and Anodonta sps was 7.6 pg/g. Koide et

al. (1982) has observed the concentrations of copper to be in the

range of 0.39-2.39 pg/g in M. edulis from California coasts.

The range of copper concentrations in the present study was

from 3.5 pg/g to 28.1 pg/g taking all sitea into account. The

presence of copper does not have any significant contribution in

the shell structure or organisation. The copper ions assimilated

into the shell may be due to the elimination of excess of copper

ions absorbed by the biological system.

7 3

e.Zinc:

Segar et al. ( 1 9 7 1 ) in their observations on zinc content in

various bivalve shells have observed 6 . 6 pg/g in P. maximus, 1 1

pg/g in opercularis, 160 Pg/g in G. glycymeris, 6 . 2 pg/g in

C-edule, 5 . 4 pg/g in M. mercenaria and 6.4 pg/g in Anodonta spa.

Bertine and Goldberg ( 1 9 7 1 ) in their observations on mussels and

clams from Belgian coast, noted the zinc content to be of 0 . 0 5 9

ppm. They indicated that carbonate exoskeleton may act as

receptacle for these ions. Koide et al. (1982) observed a range

of 0 . 3 6 to 7 . 5 2 ppm of zinc in shells of mussels from U.S. coasts

The observations have shown the zinc content of 6 9 . 5 pg/g to 125

pg/g in P. viridis shells from the sites studied. Observations on

other coaatal/estuarine bivalves have shown concentrations of

1 9 . 1 2 ug.g in P.viridis from Kalpakkam coast (Wesley and

Sanjeevaraj, 1 9 8 3 ) and 3 . 4 6 - 4 . 6 4 pg/g in V.cyprinoides from

Cochin estuaries (Babukutty and Chacko, 1 9 9 2 ) . With no

significant function of zinc ions in the structural integrity of

the shell it may also be accumulated in the shell as a mode of

removal of excess of zinc from the body of the organism.

The present study has shown that the metals studied namely

aluminium, lead, cadmium, copper and zinc are related to the

concentrations in the ambient medium in majority of the

7 4

observations. Exceptions were observed in zinc concentrations in

site 3 and cadmium concentrations in site 4 , which were not

significantly related.

The observations obtained in this study is in agreement with

the studies of Babukutty and Chacko (1992), Bourgoin (1990) and

Koide et al. (1982) as an index of metnl bioavailability in the

marine environment. Further, this study is of significance as it

represents probably the first data in the temporal variations in

shell metal content in accordance with the variations in the

concentrations on Indian coast.

2.3.2. Relationship between a.& metal content

measurements b.within shell mensurements

An observation on the relationships between the metal

content and shell measurements, and within shell measurements has

shown that aluminium and lead/cadmium were correlated with

respect to shell weight and widththeight ratio respectively. It

is assumed that the chemical characteristics of the metal and

nature of its bioaccumulation in shell might contribute to the

variations in weight and dimensions to some extent. The report on

the relationship within shell measuremets i.e., length, width,

and height vs weight (as mentioned in the results) are of

importance as there is increasing significance on application of

7 6

physical variables in physiological (condition indices, nutritive

status) and ecoloeical (community structure and stability)

observations of marine bivalve (Fischer, 1983; Roper et al.,

1991; Lobe1 et al., 1991).