INTRODUCTION
Heavy metals that accumulate in the waters of the northern coast of Java has
prevented thousands of fishermen from making their living. Heavy metal contamination
in the coast has led to the level of toxicity in biota living in the sea, down
to the cellular level. The possible impacts of the toxicity also led to the
death of fish, crabs, shrimps (Lestari and Edward, 2004)
and even the green mussels cultivated by fishermen and, of course, this affects
the ecological balance.
The content of metals in aquatic biota usually continues to increase from time
to time. Constant exposures to heavy metals will lead to toxicity in marine
biota. In certain circumstances, organisms have the ability to detoxify heavy
metals entering their bodies but when it is excessive, it certainly can cause
toxicity. Toxicity of heavy metals in the cell caused by the presence of metal
ions that act as oxidants and bind to organic molecules or proteins. The metal
ions bonds are transferred into the cell cytoplasm and subsequently bind to
metallothionein proteins. These bonds will accumulate in the cell. Metal accumulations
tend to occur in the liver (Akoto et al., 2008).
The impact of bioaccumulation of heavy metals in the body of the green mussels
may occur directly or indirectly. One immediate effect of heavy metals is the
disruption in the body's metabolic processes. Early indications of disruption
of metabolic processes in the body is loss of weight (Cordova
et al., 2011).
This study was conducted to determine traces of heavy metals bioaccumulations
in the hepatopancreas, gills, muscles and gonads of green mussels in Panimbang
ponds, Muara Angke ponds and Port of Muara Angke, as well as their impacts on
the mussels weight loss.
MATERIAL AND METHODS
The sample in this study are the green mussels (Perna viridis) obtained from
three places; the port and ponds in Muara Angke, as well as ponds in Panimbang
as control. Testing of heavy metals Cd, Hg and Pb was conducted on marine water
quality in three locations and the hepatopancreas, gills, muscles and gonads
organs, using the AAS method (Atomic Absorption Spectrophotometry) at the Regional
Environmental Management Agency (BPLHD) of DKI Jakarta province. Tests were
also done to trace heavy metals in the tissues.
Observations of the body weight, length, width and thickness of the mussels
were done to test the toxicity of the heavy metals. Measurements were made with
a caliper. The parameter for the length of the body was measured from the tip
of the anterior to the posterior base, the parameter for the width was measured
from the dorsal to the ventral side and the parameter for the height of the
shell (thickness of mussel) was measured from the thickness of the shell in
closed position.
Statistical analysis: Morphometry and weight data were analyzed with
t-test at α 0.05.
RESULTS
Environmental conditions and heavy metals: The study was conducted in
three regions, namely the Port of Muara Angke, Muara Angke ponds and Panimbang
ponds. Port of Muara Angke (Fig. 1a) is located in urban areas
which is very close to the residential area of Jakarta. Environmental condition
in Muara Angke tend to be polluted, in which the waters are dirty, smelly, blackish
brown, with garbage strewn everywhere and a lot of oil waste on the surface
of the waters. It is caused by the hectic human activities in Muara Angke, such
as port activities, industry, commerce and recreation. Muara Angke ponds (Fig.
1b) are located amidst Muara Angke waters. The distance between Port of
Muara Angke and Muara Angke ponds is about 2.5 kilometers (1.6 miles). Compared
to the Port of Muara Angke, the environmental condition of Muara Angke ponds
is relatively cleaner, with its light brown water,
despite some garbage still found floating on the water surface. Panimbang ponds
(Fig. 1c) are located in remote rural areas of Banten, far
away from residential areas and there are minimal human activities in its vicinity.
The environmental condition in Panimbang Ponds are relatively clean and unspoiled,
characterized by clear, odorless and garbage-free water. Based on direct observation
of the environmental conditions above, these three areas are suspected as being
polluted. However, the results of heavy metals analysis by BPLHD showed no heavy
metals were detected in the water (Table 1).
No heavy metals detected in the water does not mean these three areas are free
from them. The highly dynamic nature of water is one of the difficulties in
detecting the presence of heavy metals. Therefore, it is necessary to analyze
heavy metals in the body of marine biota settling in this water, such as green
mussels. The results of the analysis of heavy metals in hepatopancreas, gills,
muscles and gonads of the mussels are listed in Table 2.
The results show that heavy metals Hg, Pb and Cd have been accumulated in the
male and female gonads of the muscles from the Port of Muara Angke and Muara
Angke Ponds. The heavy metals detected in the tissues have already exceeded
the acceptable limit. On the contrary, a minimal content of Hg, Pb and Cd has
been found in gonads of mussels from Panimbang ponds which confirms that Panimbang
ponds are relatively unpolluted.
Concentrations of heavy metals Hg, pb and Cd in the hepatopancreas, muscles
and gills of green mussels in Panimbang ponds are undetectable, except for Pb
concentrations in the hepatopancreas that was at 0.01. This suggests that the
ponds in Panimbang are relatively uncontaminated.
| Table 1: |
Results of the analysis of heavy metals in the waters of
muara angke, at the port of muara angke and panimbang in 2013, North Jakarta,
Indonesia |
 |
| (*)Undetected |
|
| Fig. 1(a-c): |
Environmental conditions of the waters on the study site (a)
Port of Muara Angke (b) Muara angke ponds and (c) Panimbang ponds |
| Table 2: |
Concentration of heavy metals Pb, Hg and Cd in the hepatopancreas,
gills, muscles and gonads organs of green mussels living in muara angke
and panimbang waters, North Jakarta, 2013 |
 |
|
HP: Hepatopancreas, G: Gonads, *Undetected
|
| Table 3: |
Data of body weight, length, width and thickness of green
mussels (Perna viridis) living in the muara angke and panimbang waters,
North Jakarta, Indonesia, 2013 |
 |
| *: Significant at α = 0.05 |
Concentrations of heavy metals Hg, Pb and Cd in hepatopancreas, muscles and
gills of mussels in Muara Angke ponds shows that all three heavy metals were
found in hepatopancreas and gills, while only Cd was found in the muscles. The
heavy metal content is relatively the same and above the established acceptable
limit. This suggests that Muara Angke ponds are relatively polluted by heavy
metals, such as Hg, Pb and Cd. In general, the organs containing concentrations
of Hg, Pb and Cd the most are the hepatopancreas and gills. Most polluted areas
based on Table 2 is the port area as opposed to the pond areas.
Data of green mussels’ body weight and morphometry: Data from the observations
of the weight and morphometry of the green mussels are listed in Table
3. The average weight of green mussels in Port of Muara Angke and Muara
Angke ponds is 6.20±2.05 mg and 8.14±1.80 mg, less than the weight of green
mussels in Panimbang ponds (3.39±13.89 mg). Statistical test results concluded
that the weights are significantly different.
The average body length measurement results of the mussels in Port of Muara
Angke and Muara Angke ponds are 42.85±5.76 mm and 51.17±3.80 mm, less than the
length of mussels in Panimbang ponds, reaching up to 62.63±6.08 mm. Statistical
test results conclude that there is a significance at α = 0.05. Similarly,
the width and thickness of the green mussels in Port of Muara Angke are on average
of 22.76 mm and 15.70±2.23±1.38 and in Muara Angke ponds are 24.77±2.12 and
±2.3 mm 16.51 which is lower than the average width and thickness of the green
mussels in Panimbang ponds. From the statistical results, it can be concluded
that the difference in width and thickness are significant.
DISCUSSION
The water conditions in the port and ponds of Muara Angke, as well as the ponds
in Panimbang showed a difference in terms of environmental condition. The ponds
in Panimbang waters are located far from urban areas, in the rural areas of
Banten, where the population is still small. Based on direct observation, the
condition of the aquatic environment of Panimbang ponds is relatively clear,
without strewn garbage and odorless. This condition is due to the lack of people
living in the area around Panimbang. Research by Jalius (2008)
also explained that heavy metals were undetected in Panimbang waters. Judging
from the environmental conditions and direct observation, it is suspected that
the water in Panimbang ponds is still uncontaminated. On the other hand, the
condition of the pond and port waters in Muara Angke is a lot different, since
it is located nearer from urban, more densely populated areas with heavier human
activities which greatly affect the surrounding environment. This is indicated
by the dirty, garbage-riddled and malodorous water. It is highly suspected that
the waters in the port and ponds of Muara Angke are already contaminated, with
a condition that gradually worsens from day to day.
Heavy metals analysis by BPLDH reveled that the presence of heavy metals in
Panimbang waters were undetected. Judging from the condition of the waters in
Panimbang area and supported by the data, it is safe to assume that the area
is not contaminated. It is certainly different from Muara Angke waters, where
the environmental condition is thought to be leading to severe pollution levels,
although based on water analysis by BPLDH, contaminants were not detected (Table
1). This does not mean that the waters in the port and ponds of Muara Angke
are free from heavy metals. Heavy metal analysis in this study was also performed
on hepatopancreas, gills, muscles and gonads organs of green mussels (Table
2). This is done to prove that the waters of Muara Angke have indeed been
contaminated, as it is known that the detection of heavy metals in water is
very difficult due to the highly dynamic nature of water, especially sea water,
with its constantly moving currents and waves (Rochyatun
and Rozak, 2007), causing heavy metals to settle in sediments and would
usually be easily found in the bodies of green mussels which live sedentary
lives (Jalius, 2008). Based on the tests of heavy metals
content in hepatopancreas, gills, muscles and gonads of the mussels, the presence
of heavy metals, especially Pb, Hg and Cd was detected. Therefore it is safe
to assume that contaminations have occurred in the areas where Port of Muara
Angke and Muara Angke ponds are located.
The presence of heavy metals in hepatopancreas, gills, muscles and gonads of
mussels is definitely a concern for other marine lives living around the area,
as it has caused toxicity to the green mussels. These animals have a sedentary
way of life on the sea bed as filter feeders (Barnes, 1974),
causing them to be largely exposed to heavy metals. The constant exposure to
heavy metals will have an impact that leads to growth disorders on the biota.
Heavy metals entering the water will be removed from the body of water through
three processes, namely precipitation, adsorption and absorption by aquatic
organisms (Bryan, 1976). Heavy metals in aquatic environments
are generally in the form of free ions, organic ion pairs, complex ions and
other ionic forms (Palar, 1994).
First entry of heavy metals occurs through the gills. Gills are composed of
a layer of flat epithelial directly related to the gills membrane vessels (that
allows the heavy metals to be) carried by the bloodstream, spreading them to
other organs (Overnell and Sparla, 1990). Although
the heavy metals pass along with the water that goes through the gills, it does
not mean that there is no accumulation of metals in the gills. This study reveals
that there are actually accumulations of Hg, Pb and Cd in the gills of mussels
in Muara Angke as opposed to the controls (mussels in Panimbang). This can be
explained by the fact that gills contain mucus which main constituent is glycoprotein.
Metals will be bound to the metallothionein protein (a glycoprotein) which main
constituent is cysteine. Thus, metal accumulation in the gills is probable.
Heavy metals are absorbed by the body of organisms through a number of cell
membranes, composing of lipid and protein membranes. Entries of heavy metals
can occur through diffusions or active transports, depending on the form of
their compounds. In the body, metals will form complex bonds with ligands. Metal
ions can bind to groups of hydroxyl, carboxyl, sulfhydryl and amino acids in
protein. Metal ions more effectively bound to sulfhydryl groups, such as cysteine
having a nitrogen group. Sulfur and nitrogen group is an active group of an
enzyme. Therefore, the action mechanism of heavy metals always attacks the active
group of an enzyme which is the sulfide bond.
Another organ where heavy metals are accumulated most is the hepatopancreas.
This organ is rich in sulfide bonds, as well as digestive enzymes needed for
the detoxification process. Therefore, the heavy metals test on hepatopancreas
resulted in a very high number, 0.06 (Table 2) compared to
the other organs; gills, muscles and gonads (Prakash et
al., 1994). Ranks of heavy metals accumulation from the highest to the
lowest is in the hepatopancreas, gills, gonads and muscles. The ability of hepatopancreas
to accumulate heavy metals is due to its being equipped with very complex mucus
and has about 80% ability to accumulate heavy metals, related to sulfhydryl
groups within lysosomes. Heavy metals enter the organs by way of active diffusion
through endocytosis vesicles, hence accumulated in lysosomes (Jalius,
2008).
The result of the study by Putri et al. (2012),
was that the waters of Muara Kamal is already polluted by heavy metals exceeding
the acceptable limits. The results of the study stated that the contents of
heavy metals in the body tissues of green mussels in Muara Kamal were found
at 0.92-1.425 (ug g-1) for Pb, 0.46-0743 (g g-1)
for Cd and 0.0017-0.012 (g g-1) for Hg. The study done in Muara
Angke reveals that the contents of Hg, Pb and Cd in the organs of green mussels
there are relatively higher compared to those in Muara Kamal. Therefore, the
relatively high concentration is something to be alert about, for heavy metals
dissolved in water columns and inside the body (of organisms) at a certain concentration
can become a source of poison to aquatic life (Palar, 1994).
Toxicity caused by one type of heavy metals may differ from one aquatic biota
to another but the destruction of a group can break a link in the chain of life.
Even in small amounts, heavy metals can kill living organisms, such as the
green mussels. The process begins by the accumulation of heavy metals which
in the long run may exceed the tolerance of the mussels’ bodies. The impacts
of heavy metals bioaccumulation in the mussels’ bodies can be either direct
or indirect. One of the direct impacts of heavy metals bioaccumulation in the
body of an organism is the disruptions in the metabolic processes in the body.
Early indications of such disruptions is the weight loss, as a result of heavy
metal toxicity. This condition interrupts the growth of the green mussels, resulting
in smaller than normal size and reduced distribution (Cordova
et al., 2011) and can further cause death to the mussels.
CONCLUSION
Due to the accumulated heavy metals in their bodies, the condition of green
mussels in Jakarta Bay is worsening every year.
ACKNOWLEDGMENTS
We thank to DIKTI. This research was performed with support from a Competitive
Research Grant of DIKTI Indonesia 2014.
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