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The study comparatively assessed the level of heavy metals in the tissue of fish sourced from River Niger at Illushi, Esan South East Local Government area of Edo state and River Null at Kiama, Kolokuma/Opokuma Local Government Area of Bayelsa state. Samples of Clarias gariepinus, Momyrops cabalus, Hemisynodontis membranaceous, Momyrops rume, and Parachyna obscura fish were collected from River Niger and Null respectively. Standard biochemical procedures were applied in the determination of heavy metals such as zinc (Zn), copper (Cu), nickel (Ni), lead (Pb) and iron (Fe) present in the tissue, heart, liver, lungs and kidney of the various fish samples. Some selected non-heavy metals, magnesium (Mg), sodium (Na), potassium (K) and calcium (Ca) were also investigated. These heavy metals were assessed with atomic absorption spectrophotometer while sodium and potassium was assessed using flame photometer. Result of this study revealed that three heavy metals (nickel, lead and cadmium) were not detected in the organs of the fishes sourced from both rivers. The level of zinc obtained in all assessed organs of Clarias gariepinus, Momyrops cabalus, and Hemisynodontis membranaceous was higher in fish collected from river Null compared to those obtained from River Niger. However, organs of Clarias gariepinus, Hemisynodontis membranaceous, and Parachyna obscura from both rivers contained lower zinc levels when compared to the WHO recommended permissible limit of 2003. However elevated levels were observed in the heart (0.134mmol/kg), liver (0.107mmol/kg) and kidney (0.134mmol/kg) of Momyrops cabalus  as well as in the liver (0.069mmol/kg) and kidney (0.055mmol/kg) of Momyrops rume both from river Null as they possessed significantly (p < 0.05) higher zinc level compared to the recommended limit. Higher copper levels were also observed in fish from River Null compared to those from River Niger, but these observed values were lower than the WHO recommended for copper standard limits studied. Iron was significantly (p < 0.05) higher in the various organs of the fish, especially those sourced from River Niger. Consequently, the presence of the assessed heavy metals (apart from iron) in the investigated organs of the selected fish from river Niger at Illushi were noticed in concentrations within permissible maximum limits, compared to those obtained from River null. Thus, except for the bioaccumulation of iron above the WHO permissible limit, fishes from river Niger could be better for consumption than those from River Null, based on their heavy metal contents


Content                                                                                                          Page Number

Title page                                                                                                                                i

Certification                                                                                                                            ii

Dedication                                                                                                                              iii

Acknowledgment                                                                                                                   iv

Table of Contents                                                                                                                   v

List of figures                                                                                                                         viii

List of  tables                                                                                                                          ix

Abstract                                                                                                                                  x

CHAPTER ONE: Introduction                                                                                           1

1.1       Justification of study                                                                                                  2

1.2       Aim of study                                                                                                               3

1.3       Specific objectives of study                                                                                        3

CHAPTER TWO: Literature Reviews                                                                               5

2.1       Heavy metals                                                                                                              5

2.2       Sources of heavy metals and toxicity of trace elements                                             8

2.2.1    Sources of heavy metals                                                                                 8

2.2.2    Mode of action and toxicity of trace elements                                               10

2.3       Some heavy metals and their toxicity                                                                         16

2.3.1    Cadmium (Cd) and its toxicity                                                                       18

2.3.2    Manganese (Mn) and its toxicity                                                                    29

2.3.3    Iron (Fe) and its toxicity                                                                                 30

2.3.4    Lead (Pb) and its toxicity                                                                               32

2.3.5    Zinc (Zn) and its toxicity                                                                                37

2.3.6    Nickel (Ni) and its toxicity                                                                             38

2.3.7    Copper (Cu) and its toxicity                                                                           41

2.4       Some Minerals and their Significance                                                                       46

2.4.1    Sodium (Na)                                                                                                   46

2.4.2    Potassium (K)                                                                                                 47

2.4.3    Calcium (Ca)                                                                                                   48

2.4.4    Magnesium (Mg)                                                                                             49

2.5       Anatomical Description of Some Organs                                                                   53

2.5.1    Heart                                                                                                               53

2.5.2    Liver                                                                                                                62

2.5.3    Lungs                                                                                                              67

2.5.4    Kidney                                                                                                                        70

CHAPTER THREE: Materials and Methods                                                                   76

3.1       Source and Identification of Fish Samples                                                                 76

3.2       Reagents Used                                                                                                                        76

3.3       Collection and Preparation of Fish Organs                                                                 76

3.4       Determination of Metals                                                                                             77

3.4.1    Determination of Zinc (Zn) Concentration                                                     77

3.4.2    Determination of Copper (Cu) Concentration                                                77

3.4.3    Determination of Nickel (Ni) Concentration                                                  78

3.4.4    Determination of Iron (Fe) Concentration                                                      78

3.4.5    Determination of Lead (Pb) Concentration                                                      78

3.4.6    Determination of Cadmium (Cd) Concentration                                            79

3.4.7    Determination of Calcium (Ca) and Magnesium (Mg) Concentrations          78

3.4.8    Determination of Sodium (Na) and Potassium (K)                                        79

3.5       Statistical Analysis                                                                                                      80

CHAPTER FOUR: Results                                                                                                 81

4.1       Concentrations of Heavy Metals in Some Organs of Selected Fishes from

River Null and Niger                                                                                                  81

4.2       Concentrations of non-heavy metals in some organs of selected fishes

from River Null and Niger                                                                                          86

CHAPTER FIVE: Discussion, Conclusion and Recommendations                                 92

5.1       Discussion                                                                                                                   92

5.2       Conclusion and recommendations                                                                              95

REFERENCES                                                                                                                    97

APPENDIX I: List of materials and reagents used                                                           112

APPENDIX II: Weights of organs of the fishes                                                                 113





Figures                                                                                                                 Page Number

2.1:      Scheme of signalling induced by trace elements in living systems                             15

2.2:      Scheme depicting Cadmium-induced neurotoxicity and genotoxicity in cell            28

2.3:      Biliary tract                                                                                                                 65

2.4:      Gas exchange in the alveoli                                                                                        69

2.5:      Diagram of the cut surface of a bisected Kidney                                                       71

2.6:      Absorption and excretion in the Kidney                                                                    72




Tables                                                                                                             Page Number

2.1:      Concentrations of Lead in some selected species of fish                                           7

2.2:      Concentrations of Cadmium in some selected species of fish                                    7

4.1:      Concentrations of heavy metals in some organs of selected fish species

from River Null, Bayelsa State                                                                                   83

4.2:      Concentrations of heavy metals in some organs of selected fish species

from River Niger, Illushi, Edo State                                                                           84

4.3:      Concentrations of non-heavy metals in organs of fishes from River Null,

Bayelsa State                                                                                                              87

4.4:      Concentrations of non-heavy metals in organs of fishes from River Niger,

Illushi State                                                                                                                 89

1:         Weights of organs of the different fishes from River Illushi                                   114

2:         Weights of organs of the different fishes from River Null                                        115




Metal contaminations of aquatic ecosystem have long been recognised as a serious pollution problem (Ayandiran et al., 2009). Heavy metal released into the environment find their way into the aquatic environment as a result of direct input, atmospheric deposition and erosion due to rain water which can be attributed to wide use of heavy metals in the environment for a lot of anthropogenic purposes (Kahay and Canli, 2000). This leads to elevated levels of metals in fishes due to uptake of these metals from their environment (Dupreez and Steyn, 1992; Seymore, 1994).

However, not all metals taken up by fishes accumulate due to their ability to regulate their body metal concentration to some extent (Romanenko et al., 1986). Excretion of metals has been reported via gills, bile/faeces, kidney and skin (Heath, 1987). There are five potential routes for pollutant to enter fishes – feed, non-food particles, gills, oral consumption of water and skin (Ayandiran et al., 2009). Subsequently, heavy metals are transported by the blood to either a storage point like the bones or to the liver for transformation and storage (Oronsaye and Ogbebo, 1995). Hence, contamination of fishes with heavy metals is a consequence of pollution of the environment and plays significant role in bioaccumulation of these metals in them.

In this study, assessment of bioaccumulation of some metals would be carried out in Momyrops rume, Momyrops caballus, Clarias gariepinus, Parachyna obscura, Hemisynodontis membranaceous fishes sourced from River Niger at Illushi, Esan South East Local Government of Edo State and those from River Null at Kiama, Kolokuma/Opokuma Local Government of Bayelsa State. The essence is to assess the level of contamination of the body water/environment of these fishes.

Illushi is an agrarian community. It is along the River Niger and fishes sold in their market are sourced from River Niger while fishes sold at Kiama are sourced from River Null in Niger Delta area where oil prospecting activities are taking place. This in some instances has been associated with oil spillage and other attendant problems. In this study, the level of different metals in different organs or tissue of similar species of fishes sourced from River Niger at the agrarian Illushi community and those obtained from River Null; in industrial or oil prospecting site at Kiama will be assessed. Many researchers have been concerned with the physiological effects and bio-concentration patterns of individual metals in aquatic ecosystems (Senthil et al., 2008).


Heavy metal contamination in our aquatic environment is constantly increasing principally due to industrial discharge of a considerable amount of untreated effluents into our rivers. The bio accumulation of heavy metals in tissues of aquatic organisms have been used as an indirect measure of abundance and availability of such metals in the aquatic environment (Grobler et al.,1991). Furthermore, heavy metals are seen as the most important toxic pollutants for aquatic organisms, as heavy metals are known to bio accumulate and concentrate to toxic levels at different stages of the food chain.  Fish serve as an excellent biomarker of metal pollution in aquatic environment for many reasons; it occupies a higher trophic level in an aquatic ecosystem; therefore, they can normally accumulate heavy metals from food, water and sediments. Metal toxicity adversely affects the physical and physiological behaviour of fish. Heavy metals discharged into our aquatic environment can damage both the biodiversity and ecosystem, due to their toxicity and accumulative tendency in aquatic biota they pose a risk to fish consumers such as humans and wildlife because biomagnifications in tissue can lead to several clinical side effects (Senthil et al., 2008).

Fish is an important constituent of non-vegetarian diet of human, it is eaten to supply high quality protein rich in lysine and sulphur containing amino acids, it also provides calcium, iodine, trace elements (Fe, Mn, Zn, Se, Cu), vitamins and omega-3-polyunsaturated fatty acids.   In a situation where the fish is contaminated, the deleterious health effects that may be associated with the high content of toxic heavy metals in such fish can counteract the beneficial effects of consuming fish (Adeosun et al., 2015)

Oil prospecting activities releases a considerable load of heavy metals into our aquatic environment. The need to provide resource information on the effects of oil prospecting activities on aquatic life in Niger Delta area informs the need for this study. Presently, there is lack of information in this regard. Many researchers have been concerned with the physiological effects and bio-concentration patterns of individual metals in aquatic ecosystems (Villegas-Navarro and Villareal-Trevino 1989, Mohan and Choudhary, 1991; Peres and Pihan, 1991; Pelgrom et al., 1995; Senthil et al., 2008).

Hence, this study is designed to investigate the concentration of some heavy metals in the organs and tissues of Momyrops rume, Momyrops caballus, Clarias gariepinus, Parachyna obscura, Hemisynodontis membranaceous fishes sourced from River Niger at illushi and River Null at bayelsa in Niger Delta area of Nigeria.

1.2       AIM OF STUDY

The overall aim of the study is to provide animal model consequences of oil prospecting on aquatic animal life in Niger Delta.


  • To provide information on some metal/mineral contents in Momyrops rume, Momyrops caballus, Clarias gariepinus, Parachyna obscura, Hemisynodontis membranaceous sourced from River Niger at Illushi, Esan South East Local Government area of Edo State.
  • To provide resource information as above on the same species of fishes sourced from River Null, Niger Delta area; River Null at Kiama, Kolokuma/Opokuma Local Government area of Bayelsa State.
  • Provide comparative assessment report from data obtained from specific objective (a) and (b) above from different organs and tissues.
  • Relate the data obtained above to evidence of pollution or otherwise.





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