NACRE OF PERNA IrIRIDIS FROM EAST OF...
Transcript of NACRE OF PERNA IrIRIDIS FROM EAST OF...
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
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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.
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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
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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
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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
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(~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
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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
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~.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
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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
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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
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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
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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
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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.
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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
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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
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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
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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
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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
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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).