1. science
2. ecology
3. pollution

INTRODUCTION
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1.0 INTRODUCTION
Our environment consists of air, water and soil. The air we breathe, water we
drink and soil we use to generate food. Each compartment may be polluted by
undesired or toxic substances. Since the industrial revolution, industries have been
booming and, consequently, millions of anthropogenic compounds have entered our
environment. Persistent organic pollutants have been found even in remote areas of
the world (Ballschmiter et al., 2002). Pollution may be defined as the presence of
undesired natural or anthropogenic substances in our environment or a chemical that
exceeds normal background level and has the potential to cause harm. Harm is taken
to include biochemical or physiological changes that adversely affect an individual,
organism’s ability to breed, grow or survive (Walker et al., 1996).
One of the major public health concerns in recent years has been
Environmental Pollution and its effects on the living organism. Population explosion,
urbanization, industrialization and human apathy have all contributed towards
increasing quantities of pollutants leading to an “ecological disaster”. Pollution of
water has emerged as one of the most significant environmental problem of recent
times. Not only there is an increasing concern for rapidly deteriorating supply of
water but the quantity of utilizable water also fast diminishing. The wide array of
pollutants discharged into the aquatic environment may have physico-chemical,
biological, toxic and pathogenic effects (Goel, 2000).
The Industrial growth and consequent pollution let into the freshwater system
are a challenge for the fragile freshwater ecosystems. The ability of water bodies to
clean themselves has been affected by the sheer quantity of waste generated by ever
increasing population (Ghosh, 1992). The quantity of utilizable water decreases due to
over exploitation and also by pollution. This is a major environmental problem. Today
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people must be educated to understand the need for wise and restrained use of the
earth’s resources, water being the most vital one (Bhosle and Patil, 2001).
Freshwater habitat occupy a relatively small portion of earth’s surface when
compared to marine and terrestrial habitats, but their importance to man is far greater
than their area because they are the most cheaply available water source for domestic
and industrial needs. Freshwater ecosystems provide the most convenient and
cheapest waste disposable systems, over exploitation and misuse of these unique
systems result in environmental degradation, depletion and pollution causing health
hazards. Aquatic systems are mainly polluted through domestic (sewage and
nutrients), agricultural, aqua cultural and industrial wastes, endangering the existence
of aquatic living resource on which millions of people depends for their existence.
The protection of environment is necessary for the existence of living beings as water
is the elixir of life (Kaza and Jafer, 1997).
Rivers are polluted with the addition of discharged lethal waste from domestic
and industrial establishments neglecting the hazards caused to the life that subsist in
the water. Increasing pollution of rivers has become a matter of great concern all over
the world. Moreover, these surface waters are highly sensitive to any change in the
chemical balance or equilibrium due to industrial discharge. Most of the major
industries in India are situated on the banks of the surface water bodies. The
sensitivity or tolerance limits of inland surface waters specifically of transition zones
like estuaries with regard to impact by human interference in terms of
industrialization are to be considered before setting up industries at any one point.
Numerous aspects of river pollution such as physio-chemical properties of
different river water have been reported in India (Motwani et al., 1965; Singh et al.,
1982; Anandavalli, 1986; Sheikh et al., 1997; Sharma and Pande, 1998; and David et
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al., 2005). There are more than one thousand industries discharging their wastes
directly into the river Yamuna without proper treatment, thereby increasing heavy
metal concentration in surface and subsurface water bodies. Discharging of sewage
and industrial effluents into the river water without any treatment causes alarming
pollution. These pollutants cause changes in physiology, behavior, and histology of
aquatic fauna and flora including human beings.
The study of David et al., (2005) on the ecology of south Indian River
Vamanapuram showed the riverine and estuarine habitats were subjected to major
human imposed disturbances, which affects the fauna and flora to a greater extent.
They further indicated that the practices of Coconut coir retting along the bank of the
estuarine habitat and the effluent discharged into the estuary has adversely affected
the health of the estuarine habitat.
Due to the enormous growth of technology and industry, pollutants have been
dramatically amplified in natural environments. In particular at the urban and
municipal levels, seas, rivers and lakes have become a big eventual sink for man
disposed pollutants. Lakes of Manzala, Borollus, Eduku and Maryut that fringe the
northern side of Nile Delta are not exception. These shallow brackish water lake, that
used to have high fishery production, gradually became loaded with polluted
discharges from the adjacent urban and industrials settlements (El-Rayis and ElSabrouti, 1998 and Adham et al., 2002). Similar studies of the Double Lake, Porur
lake, Puzhal Lake were carried out by several investigators pertaining to pollution
(Mazher Sultana and Dawood Shrief, 2004).
There have been numerous studies of pollution of water ways, which would
not be possible to summarize (Appasamy, 1987; Sharma and Pande, 1998 and Lendhe
and Yeragi, 2004), so many might be useful to illustrate the extent of pollution with
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examples. Coovum river is comparatively uncontaminated when it enters the city; it
becomes severely polluted by the time it reaches the sea since it receives a
considerable amount of sewage, sullage and other urban drainage. Since the terrain is
very flat, the velocity of flow is far below the self cleansing velocity and
sedimentation is heavy (Mohanakrishnan, 1986).
A toxicant is a agent that can produce adverse response or effect in a
biological system, seriously damaging its structure or function or causing even death.
Acute toxicity tests assess the biological effects of chemical toxicant and hence are
used to detect and evaluate the potential toxicological effects of the chemical
toxicants and pollutants on an organism (Rand and Petrocelli, 1985). The heavy
metals mercury, lead, cadmium, copper, zinc and chromium are the most notorious
metallic pollutants, their severity and persistence in water is generally compounded by
the fact that they are generally water soluble nondegradable and strongly bonded to
polypeptides and proteins. Availability and toxicity of trace metal to aquatic biota are
primarily determined by the chemical nature of the aquatic environment (Sajid, 2007).
Heavy metals play a vital role in the growth and development of plants. They
may act as co-factors of some enzymes and help in the formation of intermediate
metabolites. When excess amount of metal are absorbed by the plant toxic effects are
produced resulting in impairment of growth, inhibition of respiration and
abnormalities in cell division (Nakamura, 1994) and the extent of injury depends on
the concentration of the metal present. Naga et al., (2002) have demonstrated that the
toxic metals are capable of causing a reduction in the activities of hydrolases. Sarkar,
(1999) has demonstrated Cd to be more toxic than Pb in plants. Chromium merits a
special mention as it is not only an essential trace element to both plants animals but
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also potentially toxic and tends to accumulate in organisms interfering with the
integrity of the cell affecting many vital functions of the body.
The quantitative study of pollutants in aquatic organisms offers an interesting
challenge to the research. Heavy metals are well known environmental pollutants;
they often persist, circulate and eventually accumulated throughout the food chain,
thus cause a serious threat to non-target organisms (Akhtar and Mohan, 1995).
Many trace metals are also important in animal nutrition, where as
micronutrients, play an essential role in tissue metabolism and growth. Essential trace
metals included Cd, Cu, Cr, Fe, Nn, Ni, Mo, Se, Sn and Zn severe in the imbalance in
the metal micronutrients can causes mortality, where as marginal imbalance lead to
poor health non - essential trace metal such as Pb, Cd and Hg also can be toxic at
concentrations commonly observed in soil and natural waters (Leland and Kuwabara,
1985). Handy (1992) analyzed sediments of pollutants including heavy metals,
petroleum hydrocarbons, monoaromatic hydrocarbons, organic chlorine pesticides,
poly chlorinated biphenyls (PCBS) and poly cyclic aromatic hydrocarbons (PAHS).
Cadmium, Chromium, Cobalt, Nickel, Selenium and Lead present in the raw
materials for cement manufacture were reported to occur in coconut soils and plant
tissues including coconut, collected at distances ranging from 0.1 to 5 km away from
cement factories in Karnataka state, India. Presence of Fe, Cu, Mn, Zn, Cr, Pb, Ni,
Co, Cd and Hg were reported in sewage sludge in an experiment based on water
treatment plants with different effluent origins in Spain, where low level of organic
matter in soils was a predominant problem (Clark, 1992).
The increased accumulation of anthropogenic trace/toxic metals in the north
Chennai harbour, Cuvum and Adyar marine environments is less desirable byproducts of industrialized society of these regions because of their extreme
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persistence, high toxicity and tendency to bioaccumulation (De Santo, 1991). The
study of Palanisamy Shanmugam et al., (2006) revealed the variations in metal
concentrations before and during monsoonal storms. It is observed that copper
concentrations during the monsoonal storm are found to be higher than the allowable
limit (0.02 mg/l). The abrupt increase in copper concentrations is due to surface
runoff and contributions of river and pipeline discharges to the coastal system. In both
periods, the manganese concentrations are within the permissible limit (0.1 ppm) in
all sample locations, though increased levels of magnesium at Annai Sivagami Nagar
can be attributed to the concentrated municipal wastes accumulated before storms
prevailed. It is evident from their results that the concentrations of nickel, cobalt, lead
and cadmium appeared to be very high during September and exceeded the maximum
permissible limit in most of the sample locations. As a result of monsoonal storms
during October, these concentrations were considerably decreased to be within the
permissible limit of the international standards.
It was also observed that the river-influenced areas have high concentrations
of toxic metals such as cadmium and cobalt during above periods. Such high
concentrations of cadmium and cobalt could result in severe health hazards to the
marine biota’s (Selvakumar et al., 1996). Based on the ecotoxicological studies, it has
been suggested that slightly elevated metal levels in freshwaters, estuarine and coastal
waters may cause the following sub lethal effects in aquatic organisms: (1)
histological or morphological change in tissues; (2) changes in physiology, such as
suppression of growth and development, poor swimming performance, changes in
circulation; (3) change in biochemistry, such as enzyme activity and blood chemistry;
(4) change in behavior; (5) and changes in reproduction (Connell and Miller, 1984,
Mazher Sultana and Dawood Sharief, 2004 and Mazher Sultana and Bojarajan, 2007).
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As a result, many fishing communities suffer from serious skin diseases around
coastal city (Balasubramanian, 1999). Among thousands of substance of
anthropogenic origin, several classes of industrial contaminants have gained interest
due to their persistence, toxicity, high levels, etc. These includes PAH, PCBs, dioxins,
dioxin-like compounds, phenolic compounds benzofurans, plasticisers, detergents,
metabolites of all these and many others etc., (Van der Oost et al., 2003).
Water pollution has become a global problem. An increasing number of
organic trace pollutants such as polycyclic aromatic hydrocarbons (PAHs),
polychlorinated biphenyls (PCBs), dibenzo-p-dioxins, and organochlorine pesticides
were produced by the development of chemical industries, resulting in the
environment becoming burdened with foreign organic chemicals. Many of these
contaminants ultimately entered the aquatic environment, either by direct discharge,
hydrologic processes or by atmospheric deposition (Van der Oost et al., 2003).
Physico-chemical characteristics of water reflect the quality of water. Every
human, physiologically requires 2-5 liters per day for proper functioning of vital
organs. Increase in water pollutant leads to the risk of cancer, non Hodgkin‘s disease,
chance of miscarriage, childhoods asthma and even juvenile diabetes. The pollutant in
water damages the inner part of kidney, accordingly accumulation of certain affinity
anions and cations with buffering actions, accumulates calcium oxalate, phosphate,
sulphate as scales inside and adjoining parts of kidney. Such accumulations disturb
the metabolic activities of digestion. Certainly the value of ingredients in the blood
will deviate, e.g. increase in sugar contents, and decrease in the antibodies leading to
uncontrollable diseases. This also deviates the functioning of the pancrease, lungs,
heart, arteries and veins even effects the nerves. Water pollutants of certain hardness
producing cations and anions damage certain organs and continuously damage soft
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organs. It has been found that in certain specific cases digestive system’s potentiality
is decreased (Byod et.al., 1992).
When the pollutants enter water bodies they can have direct or indirect
impacts on the biota of aquatic systems. They often interfere with the normal
functioning of an organism and its ability to live in harmony with the environment
(Ashraf, 2005). The changes they cause in behavior, growth, and reproduction of an
organism will eventually result in undesirable effects at higher biological organization
levels.The pollutants present in the water affect not only aquatic organism, but also
public health as a result of bioaccumulation in food chain. The diversity of aquatic
organism becomes limited with the extent of pollution. Therefore, there is a great
need to assess the impacts of pollution in the aquatic environment.
The prevalence of toxic heavy metals in the environment is of increasing
concern to both environmental and medical communities since aquatic animals are
often the first life forms to come into contacts, with these poisons. The detrimental
effects, as well as the mechanism by which these animals cope with such poisons are
of great interest. By such studies it may be possible to establish the biological index
for heavy metal toxicity in the aquatic environment.
The development of biomarkers in the late 1980’s provide enormous
possibilities for using biological responses to assess environmental exposure and
effects. A biomarker can be defined as a xenobiotically induced variation in cellular
or biochemical components or processes, structures, or functions that is measurable in
a biological system or sample (Everaarts et al., 1993). Effects of pollutants are usually
expressed first at the molecular/biochemical level. Changes at these levels can induce
structural and functional change at a higher level, such as hormonal regulation,
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immune system, and metabolism in an organism. These changes may finally impair
the growth, reproduction and survival ability of the organism (Adams et al., 1990). A
variety of changes observable or measurable at molecular, biochemical, cellular, or
physiological level in individuals have been studied as biomarkers for investigating
the present or past exposure of the individual to pollutants (Kaiser, 2001).
The use of biomarkers in environmental monitoring has the following
advantages (McCarthy and Shugart, 1990 and Kaiser, 2001). First, measurements of
biomarkers provide scientific evidence for a link between toxicant exposure and
relevant biological effects on an individual, a population or a community level.
Because changes in biomarkers are often indicates the exposure to a particular type of
pollutant (s), biomarkers help to establish a cause-and-effect relationship between
environmental exposure and their effects. Second, biomarkers can indicate the
exposure of organism to toxic chemicals that do not bioaccumulate or are rapidly
metabolized and eliminated. The change in biomarkers is the integrated consequences
of exposure to the parent compound as well as their metabolites. Third, biomarkers
reflect the integrated effect of exposure to complex mixture of contaminants and other
environmental factors such as water temperature, water velocity, sediment, oxygen,
and food availability. They present the cumulative effect of these factors on the target
organism. Fourth, biomarkers at molecular and biochemical level respond quickly to
change in the environment. The rapid response can offer early warning signals of
environmental deterioration and potential effect of toxicants at sites. Because of these
properties, the use of biomarkers strengthens assessment of the extent and nature of
environmental degradation (Adams et al., 1990).
Although there is legislation dealing with this problem in various countries,
water pollution from toxic chemicals still occurs. Aquatic organisms, such as fishes
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and mollusks, accumulate pollutants directly from contaminated water and indirectly
through the ingestion of contaminated organisms. Genotoxic pollutants contaminate
not only aquatic organisms but also the whole ecosystem and in the end, humans
through contamination of our food (White and Rasmussen, 1998; Avishai et al., 2002;
Rajaguru et al., 2002; Vigan`o et al., 2002; Ohe et al., 2003).
Lipid peroxidation is a well-established mechanism of cellular injury in both
plants and animals, and is used as an indicator of oxidative stress in cells and tissues.
Initiation of lipid peroxidation is caused by an attack of any free radical that has
sufficient reactivity to abstract a hydrogen atom from the polyunsaturated fatty acid
moiety of membrane phospholipids and forms a variety of products, including lipid
hydroperoxides,4-hydroxy-nonenal,conjugated-dienes,isoprostanes
and
alonodialdehyde. These molecules are generally reactive and some, such as
isoprostanes, possess biological activity. Many have been measured as markers of
oxidative stress and used as an indicator of lipid peroxidation. Plasma levels of
malonodialdehyde, a marker of lipid peroxidation was measured as thiobarbituric acid
reactive substances (TBARS) by fluorescence methodology (Yagi, 1976).
In order to assess exposure to or effects of environmental pollutants on aquatic
ecosystems,
the
following
suite
of
fish
biomarkers
may
be
examined:
biotransformation enzymes (phase I and II), oxidative stress parameters,
biotransformation products, stress proteins, metallothioneins, MXR (multixenobiotic
resistance)
proteins,
hematological
parameters,
immunological
parameters,
reproductive and endocrine parameters, genotoxic parameters, neuromuscular
parameters, physiological, histological and morphological parameters (Van der Oost
et al., 2003).
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Proteins are the most important macromolecule in the cell, as they are
responsible for almost all cellular functions. They play roles that are as diverse from
regulating gene expression, to playing a role in maintaining the proper cellular
structure, sensing the environment, as well as acting to mediate communication
between neighboring and distant cells.
In multi-cellular organisms, as cells
differentiate (take on specific functions), the profile of proteins that they express
become different. For instance, an epithelial cell will express different proteins, than
a neuron, etc. Additionally, certain cell types may contain higher protein content than
others. One such cell type that contains high protein content is muscle cells. For
locomotion to occur, muscles must contract and relax. The contraction and relaxation
is mediated by proteins, specifically actin and myosin. Additionally, several others
are important in controlling the contraction and relaxation cycle (Dong Shi Chen and
King Ming Chan, 2009).
Proteomics is the study of proteins, particularly their structures and functions.
This term was coined to make an analogy with genomics, and while it is often viewed
as the "next step", proteomics is much more complicated than genomics. Most
importantly, while the genome is a rather constant entity, the proteome differs from
cell to cell and is constantly changing through its biochemical interactions with the
genome and the environment. One organism will have radically different protein
expression in different parts of its body, in different stages of its life cycle, and in
different environmental conditions. The entirety of proteins in existence in an
organism throughout its life cycle, or on a smaller scale the entirety of proteins found
in a particular cell type under a particular type of stimulation, are referred to as the
proteome of the organism or cell type, respectively.
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Variations in an organism’s proteins may reflect physiological adaptations to
an ecological niche and environment, but they originate as chance DNA mutations.
Such random mutation events, if favorable, persist through the natural selection
process and contribute to the evolution of new species – with new specialized
functions. The discovery of the chemical structure of DNA by Watson, Crick,
Wilkins, and Franklin and our understanding of how the triplet code of nitrogen bases
leads to the synthesis of proteins (which is the phenotypic expression) convinced us
that adaptations are the result of changes in the DNA code (mutations). However,
current research in the field of proteomics is leading some scientist’s to question
whether or not DNA is the final determining factor in the synthesis of proteins and
thus the determining factor in evolution.
Proteomics was initially defined as the effort to catalog all the proteins
expressed in all cells at all stages of development. That definition has now been
expanded to include the study of protein functions, protein-protein interactions,
cellular locations, expression levels, and post translational modifications of all
proteins within all cells and tissues at all stages of development (Dong Shi Chen and
King Ming Chan, 2009; Bradley, 2002).Among the tests for genotoxicity, the
micronucleus test has been widely utilized in fish to determine exposure to water
pollutants, in the environment as well as under experimental laboratory conditions
(Al-Sabti and Metcalfe, 1995; Minissi et al., 1996; Hayashi et al., 1998). Meanwhile,
the comet assay has been proposed as a tool to monitor genotoxicity in ocean and
continental waters, utilizing fish for the detection of DNA damage induced by directacting mutagens and pro-mutagens dissolved in the water as well as environmental
analysis of water samples (Al-Sabti and Metcalfe, 1995; Minissi et al., 1996; Sasaki et
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al., 1997; Hayashi et al., 1998; Mitchelmore and Chipman, 1998a, b, and Lee and
Steinert, 2003).
Antioxidant enzyme systems are a well developed regulatory mechanism
protecting against oxidative stress. Under normal physiological states, reactive
oxygen species (ROS) are rapidly eliminated by antioxidant enzymes, including
superoxidate dismutase (SOD) and catalase (Yu, 1994; Abele and Puntarulo, 2004;
Mohankumar and Ramasamy, 2006). The SOD catalyses the dismutation of two
superoxide radicals to hydrogen peroxide (H2O2), whereas CAT degrade H2O2
(Holmblad and Soderhall, 1999; Mohankumar and Ramasamy, 2006).
The studies of Farombi et al., (2007) revealed that arsenic treatment to
Oreochromis mossambica increased the activity of antioxidant enzyme superoxidate
dismutase (SOD) and catalase but decreased glutathione deductase activity within the
day of exposure, indicating the generation of oxidative stress in fish at an early stage.
They further concluded that peroxisomal H2O2 metabolizing enzymes are potential
targets of arsenic toxicity in O. mossambica.
Similar studies of Antonova et al., (2009) in Nile tilapia following in vivo
exposure to damoic acid indicated a dose and time dependent increases in the
oxidative parameters, such as SOD, CAT, GPx and GRd. These studies also recorded
that the toxic effects were more pronounced in liver than in gill tissue of Nile tilapia.
The critical tumor suppressor p53 plays important roles in cell-cycle arrest,
apoptosis, senescence, or differentiation in response to various genotoxic and cellular
stresses, including oxidative stress (Mansur, 1997). As a transcription factor, p53
consists of two N-terminal transactivation domains, a core DNA-binding domain and
a C-terminal oligomerization domain (Pavletich et al, 1993). Because of its potent
activity in inducing apoptosis and senescence, the p53 stability and activity are tightly
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regulated by post translational mechanisms. Exposure to acidic environments and
ROS can act synergistically to cause extensive DNA damage leading to apoptosis
(programmed cell death) (Antonova et al., 2009). Oxidative stress is known to play a
role in apoptosis through the products of several cell cycle genes such as p53 (Bonini
et al., 2004; Ito et al., 2004). The principal function of p53 is to promote the survival
or deletion of cells exposed to agents that cause DNA damage, such as hypoxia, UV
radiation, ROS or mutagens (Fujita et al., 1996;Zakaria et al., 2009). Chen et al.,
(2005) suggest that apoptosis is a mechanism used by hepatocytes in response to
microcystin-LR which has documented genotoxic potential and therefore can act as
tumor initiator (e.g. Zegura et al., 2003).
In most animal cells, glucose is transported across cell membranes by
facilitated diffusion mediated by a family of glucose transporters (GLUTs). Several
GLUT isoforms (GLUT 1-5, 8-11) have been identified in mammals, particularly in
insulin-sensitive tissue such as adipose tissue, skeletal muscle and heart (Capilla et
al., 2002 and Diaz et al., 2007), which is responsible for the glucose uptake by
insulin. The studies of Capilla et al., (2002) on Salmonids skeletal muscle and adipose
tissue revealed the expression of a structural and functional GLUT4 homolog, which
can increase the glucose uptake when the transporter is expressed in Xenopus oocytes.
In particular, GLUT4 is expressed predominantly in muscle and adipose
tissue and is responsible for the stimulation of glucose uptake in these two tissues by
insulin. In mammals, insulin rapidly increases the number of GLUT4 molecules at the
plasma membrane through its stimulation of the translocation of GLUT4 from
intracellular storage sites in both muscle and adipose cells (Kahn, 1996). In fish,
insulin is also known to increase the in vivo uptake and utilization of glucose in
skeletal muscle and to regulate the number of specific insulin receptors in muscle as
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well as in adipose tissue. Although the direct effects of insulin on glucose uptake by
fish muscle or adipose cells are not clearly established, it is possible that insulin could
exert its hypoglycemic effect by stimulating glucose uptake mediated by an insulinsensitive GLUT (Capilla et.al, 2002).
Teleost fish are widely known to be glucose intolerant and to produce insulin
primarily in response to amino acid secretogogues (Palmer and Ryman, 1972; Ince,
1983; Mommsen and Plisetskaya, 1991; Wright, 1998). This is puzzling in the context
of the observation that tilapia (Oreochromis nilotica) islets, when transplanted into
streptozotocin (STZ) – diabetic athymicnude mice, will induce long-term
normoglycemia and mammalian-like glucose tolerance profiles (Wright et al., 1992;
Morsiani et al., 1995; Yang et al., 1997a). However, the vast majority of earlier
studies which have examined aspects of glucose metabolism in fish were performed in
carnivorous, cold-water species. In contrast, tilapia is omnivorous, tropical fish. The
results of the transplantation studies noted above suggested that, perhaps, tilapia is not
glucose intolerant or, alternatively, that tilapia are peripherally resistant to the
glucose-lowering effects of insulin.
Water is one of the essential factors for the maintenance of the vital functions
of the living beings. With the continuous population growth and a consequent
increase in water consumption, the rational use of this mineral asset has been
encouraged, aiming a conservation of the quality of our waters, since this is a finite
mineral resource (Frederico et al., 2009).
Histology is useful technique for investigating the toxic effect of various
pollutants. Such a study also offers opportunity to locate the effect of pollutants in
various organs and systems of animals. This type of study in fish has been to a great
extent is handicapped because of the lack of adequate histological literature
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concerning various fish organs (Hinton et al., 1997).Considerable interest has been
shown in recent years in histopathological studies while conducting sub-lethal tests
in fish. Tissue changes in test organisms exposed to sub-lethal concentration of
toxicant are a functional response of organisms which provides information on the
nature of toxicant.
Histopathological biomarkers can be indicators of the effects on organisms of
various anthropogenic pollutants and are a reflection of the overall health of the entire
population in the ecosystem.The alterations in cells and tissues in vertebrate fish are
recurrently used biomarkers in many studies.The degree of pathological intensity is
dependent on the dose and duration of exposure. These studies have been conducted
to help establish causal relationships between contaminant exposure and various
biological responses. Histopathological biomarkers embody tissue lesions arising as a
result of a previous or current exposure of the organism to one or more toxins
(Mazher Sultana and Bojarajan, 2007).
There is considerable information indicating that pesticides and heavy
metals are responsible for many adverse effects in fishes and other animals from the
histopathological and histochemical points of view (Mazher Sultana and Dawood
Sharief, 2004; Ashraf, 2005; Vinodhini and Narayanan, 2009).
In this study, the water of Chrompet Lake was submitted to environmental
testing using molecular and biochemical evidence for ecotoxicological impact on
fresh water fish (O. mossambicus). This urban lake receives domestic waste
discharge, storm water and industrial runoff. The study of monitoring the quality of
the water of lake was important and necessary, since it is utilized as a domestic and
recreational area. In addition, the aim was to collect data with respect to the validation
of the oxidative stress related biomarkers in fish.
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A fresh water fish, O. mossambicus was selected for the investigation mainly
because it serves as an important biological indicator of water quality, which is
affected by the global environmental degradation. Also, because fish serve as
experimental models and hypotheses deduced from investigations on them can be
extrapolated to human system to a certain extent. Further fishes form a major link in
the food web of the aquatic ecosystem and their ability to produce large number of off
spring and survive at high population densities, make them suitable for
experimentation.
Overall Aim of the Study:
To study the role of selected physicochemical and intracellular parameters as
risk factors of pollution in a fish is evaluated by sensitive methods using biochemical
and cytological, molecular biomarkers such as oxidative stress and DNA
fragmentation (Comet assay), before more severe morphological alterations occur.
1.1 Specific Objectives
1. To assess the water quality (Physico-chemical parameters and metal
content) of Chrompet Lake for a period of Twelve months from May 2009
to April 2010. To compare observed levels of studied parameters with the
corresponding WHO guidelines values for drinking water quality.
2. To investigate the association of oxidative stress and antioxidant enzyme
activity levels in control fish and pollution affected fish (O. mossambicus).
3. To investigate the molecular evidences in O. mossambicus related to
senescence and resistance mechanism.
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4. To investigate the role of eco-toxicological pollutants on biochemical and
histopathological modulation in control fish and pollution affected fish O.
mossambicus.
5. To create awareness among the locals of the Chrompet area with regard to
the importance of the water quality and its implication.
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