In recent years, because of the importance of heavy metals in human body
(both the essential and nonessential ones) many studies were done with
rats (Musavi et al., 2007).
Metal bioaccumulation can apply to the entire organism, including both
metal adsorbed to surfaces or absorbed by the organism, or to specific
tissue, it is usually expressed on a weight (dry or wet.) adjusted basis
(McGeer et al., 2004).
In contrast, several studies have suggested that dermal uptake contributes
substantially to total uptake of waterborne chemicals by small fish and
juveniles of larger species. Lien and McKim (1993) suggested that dermal
uptake should increase in relative importance in small fish because of
the way in which gill and skin surface areas scale to fish body weight.
Lien and McKim (1993) predicted that skin surface area approaches and
may even exceed that of the gills in fish weighing less than 5 g. Reduced
skin thickness and increased skin visualization, also contribute to relatively
greater dermal uptake in small fish (Di Giulio and Hinton, 2008).
This study was undertaken to investigate the concentration levels of
heavy metals of the selected tissues in the Cyprinus carpio and
the sediments at five stations differing in locations, also determining
fish scale as the most suitable bioindicator for lead and zinc sedimentation
in the environment of the sampling stations.
MATERIALS AND METHODS
Five sampling stations were chosen in different regions of Astara, Hashtpar,
Bandar Anzali, Ramsar and Chalous (Fig. 1). Samples
were collected in the year 2007.
In each station at the fishing area, samples were taken from surface
sediments with the aid of the Eckman grab sampling device and by using
fishing boats (Obasohan et al., 2005). Also, fish samples were
taken with the aid of flapping seine net (Andreji et al., 2006).
Nets at the Stations
The total length and weight of the sample fish were measured at the site
and their scales, livers and gonad were separated. The samples were kept
at a temperature less than 4Â°C until they arrived at the laboratory.
After being transferred to the lab, the samples were prepared for digestion
(Ayse, 2003; ROPME, 1999).
The sediments and tissues were dried at 105Â°C for 24 h. The dried
sediments were passed through a 60 mesh stainless screen to remove larger
particles (Hulya and Erhan, 2000).
Then the samples were dried; their water content was calculated and they
were homogenized in three separate longitudinal groups.
An amount equal to 1 g of the dry powdered homogeneous sample (liver
and scales) was digested by 10 mL of concentrated Nitric acid and 2 mL
of H2O2 (Ayse, 2003; ROPME, 1999).
Sedimental samples from 5 stations were first mixed and heated with Nitric
acid and then 10 mL of HCl was added to them before they were heated again
The volume of the clear solutions obtained from digestion was increased
to 50 mL and then by using the atomic absorption device, the amounts of
zinc and lead were measured (Ayse, 2003; ROPME, 1999).
||Stations of sampling
The highest lead content was measured as 48.27 mg g-1 in the
scales of the small fish belonging to the group < 48 cm, at Bander
Anzali sampling station (Table 1) and the least amount
in the liver of the big fish (> 54 cm) as 4 mg g-1 at Astara
sampling station (Table 2). Also, the highest amount
of zinc was measured in the liver of the medium fish as 174.28 mg g-1
at Chalous sampling station (Table 2) and the least
amount of zinc in the male gonad of the big (long) fish as 6. 79 mg g-1
at Bandar Anzali sampling station (Table 3). Variations
of average lead concentration in fish scales at the sampling stations
Bandar Anzali > Ramsar > Hashtpar > Astara >
Chalous (Table 4
Variations of average zinc concentration in
fish scales at the sampling stations under study:
Astara > Hashtpar > Ramsar > Chalous > Bandar
Anzali (Table 4
The bioaccumulation of lead in the related tissues
was found to be in the following order:
Liver average < Female gonad average < Sediments
average < Male gonad average < Scales average (Table
The bioaccumulation of zinc in the studied tissues
was found to be in the following order:
Male gonad average < Sediments average < Female
gonad average < scales average < Liver average (Table
||Variation of lead and zinc concentration in fish scales
at sampling stations
|| Variation of lead and zinc concentration in fish livers
at sampling stations
|| Variation of zinc concentration in the male gonad of
fish at sampling stations
||Variation of average lead and zinc concentration in
fish scales at sampling stations
||Variation of average lead and zinc concentration in
the studied tissues
Results of correlation tests show that fish scale is a better index of
zinc content than liver and gonad in addition; fish scale is a better
index of lead content than gonad.
As no strong correlation was found between lead pollution level in the
environment and that in fish scales, it was concluded that fish scale
is a weaker index for lead than for zinc.
In the study conducted in the Nairobi River about metal analysis of fish
and water in 2005, the highest bioaccumulation of zinc in fish scales
was measured as 360 mg g-1 and the lowest as 55 mg g-1
in the Female Gonad of the ovaries (Budambula and Wachiro, 2005).
The Zn content of the scales from juvenile fish was linearly correlated
with environmental Zn concentrations. At elevated environmental Zn concentrations,
the fraction of the total Zn body burden contained by the scales increased.
The results suggest that fish scales may play an important role in the
metabolism and detoxification of heavy metal pollutants. The relationship
between metal uptake and calcification is discussed (Sauer and Watabe,
Lead also accumulation in or adsorbs on scales of fish at considerably
high levels and the absorption ratio of lead may be more than some other
heavy metal like cadmium (Kalay and Canli, 1999).The results obtained
from Nasser Lake study in 2000 showed that of all the fish parts, fish
liver accumulated the highest levels of Cu and Zn. Scales exhibited the
highest levels of Co, Cr, Ni and Sr (Rashed, 2001).
The surface layer of sediments in the east of the Anzali Lagoon was surveyed
for heavy metal contamination during the year 2004 at the National Inland
Water Aquaculture Institute. Concentration of Pb, Fe, Cu and Cd were 7.92,
0.2775%, 25.8 and 1.645 Î¼g g-1 dry weight, respectively.
The Fe and Cu have the highest concentration (Babaei et al., 2007).
The liver, kidney, gill, ovary and muscle tissues of the caught Liza
aurata have been sampled in spring 2002 in the southern Caspian Sea.
The highest concentration of lead in the liver tissue followed by gill,
kidney and. The lowest concentration of lead was seen in muscle tissue
of Liza aurata. The highest accumulation of Ni and Zn was detected
in ovary followed by liver, gill and kidney of the fish. The lowest concentration
of Nickel and Zinc in the muscle tissue and also determined the highest
contamination of the fish with these chemicals to be occurring in the
southwest followed by south center and southeast Caspian Sea (Fazeli et
The results obtained from Nairobi River study were analyzed by using
variance method. No significant difference was found for the following
concentrations at six sampling stations: Manganese, Aluminum, Zinc, Copper,
Cadmium, Lead, Calcium and Magnesium. But for Fe/Na/ and k/a significant
difference (level 0.05) was observed at the sampling stations (Budambula
and Wachiro, 2005). A significant difference at the level of 0.05 was
observed in test results related length comparison of 42 short, medium
and long (large) fish for ANOVA-One Way test and Tukey test. Otherwise,
no significant differences were obtained when comparing lead and zinc
concentrations of the sediment samples between stations. The same lack
of significant difference was observed for lead and zinc amounts compared
in the scales, livers, male gonad and female gonad related to the three
length groups (short, medium and long).
Musavi et al. (2007) found that there was significant difference
of Sexes (male and female) for Zn in their Kidney and bone may be related
to the generating and lactation functions of the female that cause heavy
metals get out of the body. Moreover, the high levels of Pb and Cd in
rat's bone are due to the existence of such elements in their environment.
In the study conducted of the southern coast of the Caspian Sea, the
results were statistically analyzed and mean, one-way ANOVA test, LSD
test, mean of variance were compared. Coefficient Correlation and linear
regression were calculated by Pearson method and figure or curve of Hierarchical
Cluster Analysis, using average linkage, Euclidian distance were drawn.
There was also positive correlation between kidney-liver and Kidney-sediment
for Cu concentration and between liver-sediment, kidney-sediment for Pb
concentration (Amini et al., 2003).
The correlation coefficient was calculated for establishing possible
relations between lead and zinc concentrations found at average sediments
in different stations. Variations in concentrations of these elements
in the scales, liver and gonad of the fish samples (in three groups :
short, medium and long) and also between related tissues.
Relative coefficient factor between lead concentration in sediments and
its concentration in fish scales (in small sized group) showed an average
relevancy for two parameters (r = 0.542) and scale can be an average environmental
indicator for small sized group. However, relative coefficient factor
between zinc concentration in sediments and its concentration in fish
scales (in large sized group) showed a high relevancy for two parameters
(r = 0.703) and shows a positive linear relation between parameters so
that increasing in zinc concentration in sediments, increase its concentration
in scale too. Regarding to zinc concentration changes procedure in sediments
and fish scales (large sized group); scale could be an environmental indicator.
Consideration of relative coefficient factor between sediment lead concentration
in noted stations and its concentration in fish liver (small sized group)
showed a proportional high relevancy for two parameters (r = 0.717) it
means there is a positive linear relation between parameters. Consideration
of relative coefficient factor between sediment lead concentration in
noted stations and its concentration in fish gonads (small sized group)
showed a high relevancy for two parameters (r = 0.961).
Relative coefficient factor between sediment lead concentration in noted
stations and its concentration in female gonads showed an average relevancy
for two parameters (r = 0.564).
Consideration of relative coefficient factor between liver lead concentration
in and its concentration in fish scales (small sized group) showed a high
relevancy in p<0.05 for two parameters (r = 0.939). It means there
is a positive linear relation between parameters and increasing in liver
Considering the studied cases, the following conclusion can be drawn:
Scales can be a more suitable index for showing zinc content than the
liver and female gonad and male gonad and a more suitable index for showing
lead content than male gonad.
Comparison of the present study amounts with the corresponding standards
values Obasohan et al. (2005) shows that they exceed the maximum
allowable Pb level for human beings in food materials.
Therefore, food consumption of Cyprinus carpio gonad should be
avoided in the study areas of Gilan and Mazandaran (Obasohan et al.,
In sediment, mean metal levels were generally higher than pre-dredging
levels in sediment, when compared to available predredging recorded by
Obasohan and Oronsaye (2000) and Obasohan et al. (2005).
The reason could be due to human activity and entering in the area of
organic and mineral pollutants as unnatural pollutions.