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Assessing The Microbiological and Heavy Metal Burden in Some Fresh Water and Marine Fishes in a Segment of the Bight of Bonny, Niger Delta Area of Nigeria.

Favour A. Eyo and Alfred Y. Itah*

Department of Microbiology

University of Uyo, Uyo,

Akwa Ibom State, Nigeria

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Fig. 1: Map of Nigeria showing study area (Bight of Bonny)

BACKGROUND OF THE STUDYThe Bight of Bonny, on the Southern Atlantic coast of Nigeria (4°15’- 4° 35’ N; 7°30’- 8°25’ E) (Fig. 1). This coastal aquatic system is about 100 km long and more than 30 km wide. Its constitutes the eastern flank of the Niger Delta (Ntekim et al., 1992 and Benson et al; 2007 ), spanning the shorelines of Akwa Ibom, Cross River and Rivers States of Nigeria. The entire ecosystem is made up of extensive network of rivers, estuaries, creeks and tributaries which together form a significant commercial hydrographic feature within the region. The estuaries with the major creeks constitute a rich assemblage of fluvial ecohydrological biotopes, dominated predominantly by intertidal mangrove and Nipa forested wetlands. The study area is exposed to significant anthropogenic inputs such as oil spills, untreated sewage and industrial waste waters. Several other smaller fluvial and domestic effluents are also disposed in the shallow marginal estuarine beaches and creeks.

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Background of the Study Area Cont’d

Callinectes pallidus

Fin fishes

The contamination of aquatic ecosytems with a wide range of pollutants has become a matter of concern in

the Niger Delta Area of Nigeria over the last few decades, as a result of rapid human population growth and

industrial output.

Petrogenic and anthropogenic activities, urbanization, industrialization and agricultural practices have

increased the amount of heavy metals in the environment especially in aquatic ecosystem.

Fishes are conditioned by their environment and hence it is obvious that if the growing and harvesting

environment of fish is polluted chemically or microbiologically, the fishes are also polluted. Hence the use of

fish to evaluate the health of aquatic ecosystems because pollutants build up in the food chain and are

responsible for adverse effects and death in the aquatic systems.

It has been established that the microbiological and heavy metal load of fish is a reflection of the

contamination level of their habitat and thus a potential indicator of pollution

This work will therefore establish the contamination level of the aquatic ecosystems in question by

determining the contamination levels of fishes inhabiting them.

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Background of the Study Area Cont’d

Gas flaring

Mangrove oyster (Crassostrea tulipa)

Callinectes pallidus

Fin fishes

Artisanal fishing

Ecosystem pollution

Aquatic resources harvested for human consumption

Figure 2: Evidence of Pollution

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Objectives Quantitative and qualitative microbiological assessment of

sediment, water and fish samples from marine and freshwater ecosystems

Assess the heavy metal concentration and total petroleum hydrocarbon degrading microorganisms in the different samples

Determine the physicochemical characteristics of sediment and water samples

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Materials and Methods

Sample (water, sediment and fish) collection and processing

Physicochemical analysis Culture-dependent microbiological analysis

• Total heterotrophic micro-organisms

• Total coliform bacteria• Heavy metal content

• Total hydrocarbon content

• Petroleum hydrocarbon degrading microorganisms

Temperature, pH, total alkalinity, total hardness, turbidity, electrical conductivity, Total and suspended solids, Dissolved O₂, COD, BOD₅, TOC, NH₄, NO₂, NO, N₂, PO₄, SO₄, Sodium, Potassium,

Statistical analysis performed using Statistica® software with levels of significance maintained at 95% for each test

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Fish Samples and their Local NamesFresh water fin fishes Common name Total weight

Parachanna africana Snake head 105.21g

Malapterus electricus Electric fish 32.78g

Heterobranchus bidorsalis Fresh water cat fish 38.00g

Tilapia zilli Tilapia 35.21g

Oreochromis niloticus Tilapia 34.01g

Fresh water shell fish

Callinectes pallidus Blue crab 14.4g

Macrobrachium vollenhoevenii Brackish water prawn 5.68g

Macrobrachium macrobractiion Shrimp 5.01g

Penaeus notialis Shrimp 4.68g

Callinectes amnicota Crab 4.68g

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Fish Samples and their Local Names Cont’d.

Marine water fin fish Common name Total weight Ethmalosa fimbriata Bonga fish 128.34gPseudotolithus senegalensis Croacker 128.54g

Pseudotolithus elongatus Croaker 143.80gChrysichthys nigrodigitus Catfish 101.18gPseudotolithus typus Croacker 32.54gMarine water shellfishParapenaeopsis altantica Guinea shrimp 5.70gGeryon maritae West African geryon 4.02gParapenaens congirostris Deep water rose 7.05gAnadara senegalensis Senegal ark 6.70gCardium costatum Costate cockle 8.9g

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Physicochemical Characteristics of fresh and marine water samples

Physicochemical parameters Sample WHO StandardFresh water Marine water

Appearance Slightly cloudy Slightly cloudy with suspended particles

Clear

Colour (H.U) 20.0 73.0 15.0Odour Inoffensive Marshy InoffensiveTemperature (oc) 26.30 27.63 27-28Turbidity (NTU) 2.14 36.18 5.0Total suspended solids (mg/l) 1.50 8.90 <10.0Electrical conductivity (µS/cm) 38.36 2570 1000Dissolved oxygen (mg/l) 2.20 2.70 6.00Total dissolved solids (mg/l) 19.27 126.5 500pH 6.52 6.71 6.5-8.5Biochemical oxygen demand (mg/l) 1.20 1.60 10.00Sodium (mg/l) 1.50 1.80 200Potassium (mg/l) 0.20 0.50 150Sulphate (mg/l) 2.27 62.4 250Nitrate (mg/l) 0.83 5.96 10.0Phosphate (mg/l) 0.08 24.6 3.50Nitrite (mg/l) 0.01 0.01 0.20Salinity as Cl-(mg/l) 9.0 25.0 250

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Physicochemical Characteristics of Marine and Fresh Water FishPhysicochemical parameters Sample WHO

StandardFresh water Marine water

Appearance Slightly cloudy Slightly cloudy with suspended particles

Clear

Alkalinity (mg/l) 1.50 1.00 200Total hardness (mg/l) 23.0 252.0 100Calcium hardness (mg/l) 10.0 150.0 200Magnesium hardness (mg/l) 3.17 36.60 150Aluminium (mg/l) 0.008 4.306 0.20Lead (mg/l) <0.001 0.689 0.01Cadmium (mg/l) <0.001 0.260 0.003Nickel (mg/l) <0.001 1.364 0.07Zinc (mg/l) 0.080 0.763 0.10Copper (mg/l) 0.128 1.085 1.00Iron (mg/l) 0.120 2.068 0.30

HU = Hazen unitNTU = Nephelometric Turbidity UnitµS/cm = Microsiemen per centimetre

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Figure 3: Comparative evaluation and distribution of different physiological groups of microorganisms from marine and freshwater

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Figure 4: Comparative evaluation and distribution of different physiological groups of microorganisms from marine and freshwater sediment

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Figure 5: Comparative evaluation and distribution of different physiological groups of microorganisms in finfishes from freshwater

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Figure 6: Comparative evaluation and distribution of different physiological groups of microorganisms in shell fishes from freshwater

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Figure 7: Comparative evaluation and distribution of different physiological groups of microorganisms in finfishes from marine water

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Figure 8: Comparative evaluation and distribution of different physiological groups of microorganisms in shell fishes from marine water

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Heavy metal concentration in fresh water and marine sediment

Sample Aluminium Lead Cadmium Nickel Zinc Copper Iron

Fresh Water 0.050 0.001 0.001 0.002 0.020 0.200 0.240

Marine Water 7.115 3.431 3.429 4.981 1.832 2.10 9.553

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Figure 9: Level of heavy metals concentration in finfish parts from marine water

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Figure 10: Level of Heavy metal concentration in finfish parts from freshwater

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Figure 11: Level of heavy metal concentration in shell fish parts from freshwater

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Figure 12: Level of heavy metals concentration in shell fish parts from marine water

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Summary and Conclusion

The study on the whole evidenced the microbial and heavy metal status of shell and fin-fishes found in freshwater and marine ecosystems.

The heavy metal concentration in the fish organs vary directly with the concentration values in the water and sediment samples analyzed in this study, pointing to the fact that the heavy metals have their way into the fish organs from the environment through respiratory and feeding activities.

Some microbiological analysis, such as, Total heterotrophic counts; Total coliforms; Petroleum hydrocarbon degraders and Total fungal counts, were performed on different fish organs, water and sediment samples.

The presence of Petroleum hydrocarbon degraders e.g. Chromobacterium violaceum, B. subtilis, Penicillium italicum, C. albicans and Micrococcus varians in the fishes present some ecological advantages in the event of oil spill as the degraders in fish could multiply and biodegrade the pollutant for their survival.

It also confirms the fact that both shell and fin fishes remain a promising option in bio-monitoring and pollution assessment in lenthic aquatic systems.

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